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You are permitted to refer to published materials to aid you in your answers

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You are permitted to refer to published materials to aid you in your answers. 2. Published sources must be referenced. This includes all on-line sources. Using Harvard style. 3. Over-reliance on published sources is considered to be poor academic practice. 4. maximum word limit of 500 words per question. Questions: 1. (a) With the aid of sketches, describe the constructional details of cold, warm and inverted flat roofs. (b) Identify the advantages and disadvantages of each of the three types of flat roofs. 2. (a) What are the four main issues which underpin the current Building Regulations? (b) For each issue identified, choose one Part of the Building Regulations which relates to that issue. (You should choose 4 different Parts). Give an example or examples of how that Part relates to achieving objectives related to the issue identified. (c) State the purpose of the ‘Approved Documents’ and state whether the technical solutions provided in these are mandatory for use in the UK. School of the Built Environment GROUND MOVEMENT This Photo by Unknown Author is licensed under CC BY Dr Tabarak Ballal University Teaching Fellow Associate Professor Copyright University of Reading LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT CONTENT OF LECTURE • Ground Movement •Definitions •Causes • Site Investigation 12 LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT LEARNING OUTCOMES By the end of today, you will be able to: • Identify reasons for movement of the ground • Describe the four stages and associated processes of ‘Site Investigation’; • Identify sources of information about aproposed site and its ground conditions; • Explain the importance of conducting site investigations and impact on the design and construction of buildings LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT RECAP LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT What causes the failure of foundations? GROUND MOVEMENT LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT GROUND MOVEMENT The movement of the ground as it compresses, slips/shears, or deforms. Two reasons: • Subsidence • Settlement LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Subsidence v Settlement Subsidence: the soil moves away from the structure and allowing the foundation to move. Settlement: where the structure moves the soil due to application of load. CAUSES OF GROUND MOVEMENT 1. SUBSIDENCE 1. Subsidence • Man- Made • Natural LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT 2. SETTLEMENT Over-loading of soil (! Remember BP and BC !) • Poor design of foundations • Poor workmanship on site LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT 3. LOWERING OF THE WATER TABLE What is a water table? This Photo by Unknown Author is licensed under CC BY-SA LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT 3. LOWERING OF THE WATER TABLE • Pumping water from the ground • Insertion of land drainage • Lack of rainfall • Excavation below water table • Roots of trees drawing water LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT 4. RISE IN THE WATER TABLE • Prolonged periods of rain • Felling of trees LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT EFFECT OF TREES • Foundation design needs to take account of the water-absorbing capacity of nearby trees • Foundations need to be significantly deep to avoid the zone of shrinkage and swelling • Some tree species can affect foundations 20m away LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT PREVIOUS REQUIREMENT BY BUILDING REGULATIONS • Distance to one mature tree should be at least equal to the height of the tree • Distance to a group of trees must be at least equal to one and a half of the height of the tallest tree LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Normal Mature Safe Distance (M) Height (M) Apple / Pear 12 10 Beech 20 15 Birch 14 10 GENERAL Cherry 17 11 GUIDANCE ON Elm 25 30 TREES Hawthorn 10 12 Holly 14 6 Horse Chestnut 20 23 Laurel 8 6 Adapted from Magnolia 9 5 Association of British Maple 21 20 Oak 24 30 Insurers Pine 29 8 Plum 12 11 Poplar 28 35 Sycamore 24 17 Spruce 18 7 Walnut 18 14 White Beam / Rowan 12 11 Willow 24 40 Yew 12 LIMITLESSPOTENTIAL 5 | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Species 5. FROST HEAVE Swelling of soil due to freezing of moisture in the ground LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT 5. FROST HEAVE The Building Regulations states that: …the strip foundations should have a minimum depth of 0.45m to their underside to avoid the action of frost… … this depth would normally be increased in areas subject to prolonged periods of frost in order to transfer the loading onto satisfactory ground… … on clay soils the depth should not be less than 0.75m Normally, the underside of foundations is at 1m depth LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT SETTLEMENT OF SOIL • Degree of settlement • Uniformity of settlement • Differential settlement DEGREE OF SETTLEMENT • Slight settlement of soil is to be expected as it adjusts to imposed weight • Excessive settlement is problematic as it may cause ‘shear failure’ of the soil • Shear means to displace something relative to something else. In this case, the upper portion of soil against that of the lower portion of soil LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT UNIFORMITY OF SETTLEMENT • Settlement of soil must be uniform throughout the building. • Damage may be caused by ‘differential settlement’ - cracks will appear and in severe cases the building may collapse. LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Differential Settlement The damage occurs when the foundation sinks in different areas at different rates. Differential Settlement Leaning Tower of Pisa Degree of settlement Differential settlement Reflections • What are the causes of ground movement? • Why is excessive differential settlement harmful to a building? QUESTIONS? School of the Built Environment SITE INVESTIGATION This Photo by Unknown Author is licensed under CC BY Dr Tabarak Ballal University Teaching Fellow Associate Professor Copyright University of Reading LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT CONTENT OF LECTURE •Site Investigation and Analysis: •Stages; •Sources of Information; • Outcome 12 LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT LEARNING OUTCOMES By the end of this lecture, you will be able to: •Describe the four stages and associated processes of ‘Site Investigation’; •Identify sources of information about a proposed site; •Explain the importance of conducting site investigations and impact on the design and construction of buildings LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT SITE INVESTIGATION Definition: “…isthe gathering of information on ground conditions whichmight be relevant to design andconstruction ona particular site…” LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT The Building Regulations Part C: Site Preparation and Resistance to Contaminants and Moisture • topography of the ground • location of existing services • structural capacity of the soil The Building Regulations Part C: Site Preparation and Resistance to Contaminants and Moisture • The site investigation should consist of a number of well-defined stages: • • • • A. Planning Stage B. Desk Study C. Site Reconnaissance or Walkover Survey D. Main Ground Investigation and Reporting A. Planning Stage Clear objectives should be set for the investigation • Scope and requirements which enable the investigation to be planned and carried out efficiently and provide the required information. LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT B. Desk Study As much as possible is researched in the office • Search of geological maps, memoirs, and local records • Information from local building inspector • Information from local ground investigation specialist firm LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT OBJECTIVES OF ADESK STUDY • The desk study has two main objectives: • to determine the nature, past use, and condition of the site (green, brown or of historical significance). • to determine whether this has any implications for the proposed building and its foundations. LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Archaeological findings An early 19th century wooden boat was discovered adjacent to the Stadium site as part of the archaeological programme across the Olympic Park. (unknown source) One of four skeletons discovered within the Aquatics Centre site during the programme of archaeology across the Olympic Park. (unknown source) Remains of old buildings OTHER OBJECTIVES • filled or contaminated ground • utility services (drains, electricity, gas, telephone, optical cables etc) • quarrying or mining • previous vegetation (i.e. large felled trees) • rights of way • ponds, watercourses, ground water levels and the risk of flooding • landslip • naturally occurring aggressive chemicals (eg sulfates), harmful gases (radon) and landfill gases (methane and CO2). LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT SourcesOf Information for Desk Study • Current Ordnance Survey Maps • Planning Divisions of Local Authorities • Early Ordnance Survey Maps • at the British Library • National Library of Scotland • National Museum of Wales • Archaeological and Historical Maps • Published by the Ordnance Survey • Geological Maps, Memoirs, and Bore- hole Records • Institute of Geological Sciences • Local Records • Libraries • Local Authorities • County Records Office • Public Records Office • Aerial Photographs • County/local authorities • Private Survey Firms • Mining Records • British Coal Mining Record Office • Plans Record Office - HSE LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT C. SITE RECONAISSANCE • Visit the site and see for yourself • • • • • • Vegetation Trees Topography Rivers, streams, canals, or ponds Existing and adjacent buildings Obstructions LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT OBJECTIVES OFAWALK- OVER SURVEY • This is the third stage in t he site investigation. It's a detailed site inspection which: • enables much of the material discovered in the desk study to be confirmed or further investigated • identifies other potential hazards • enables the surveyor to collect photographic records • gives the designer/surveyor/engineer the opportunity to make detailed drawings of all those items (trees, existing buildings, watercourses, etc) which will have implications for the building design LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT C. SITE RECONAISSANCE Example of a Walkover Survey Checklist Report http://www.planningservices.haringey.gov.uk/ portal/servlets/AttachmentShowServlet?Image Name=880777 LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT D. Ground Investigation This is necessary to identify: • Soil Profile • Soil Classification • Soil parameters • Groundwater conditions • Depths of existing or adjacent foundations LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Detailed knowledge of the nature and variability of the sub-soil is essential 1. Taking borehole samples 2. Digging trial pits Boreholes To obtain samples of the soil for laboratory analysis GROUND INVESTIGATION TECHNIQUES • Bore-holes • filled sites • where peat or other soft layers are expected at depth • where clays may be desiccated by trees • where piles will be needed through softer material on to harder soils below Light Percussion Drilling Rig LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT An example of a borehole log GROUND INVESTIGATION TECHNIQUES • Trial Pits • assessment of made ground above subsoil • confirmation of expected depth to subsoil • confirmation of type of sub- soil expected • assessment of sub-soil t o ascertain allowable bearing pressure • assessment of ground- water level • assessment of variations across the site • assessment of existing and adjacent foundations and obstructions A JCB digging trial pits LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT DATA GENERATED BYASITE INVESTIGATION Asite investigation provides information concerning: • The nature of soil; • The thickness of the layers of different types of soil at the test location; • The strength of the soil; • The existence of contaminants in the soil; • The degree of moisture present; • The location of existing services. LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT What do we do with all of this data? PRODUCE FOUNDATION ENGINEERING REPORT What is the content of the foundation engineering report? • Introduction • General description of site • General geology of area • Description of soil conditions found in boreholes and trial pits • Laboratory test results • Discussion of the results of the investigation in relation to foundation design and construction • Conclusions/recommendations. The report will conclude with a recommendation of a suitable foundation system based on all of the factual data. Example Report http://planning.breckland.gov.uk/OcellaWeb/v iewDocument?file=dv_pl_files%5C3PL_2017_0 775_F%5CYE3134+-+Report.pdf&module=pl LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT The Word Cloud Reflections • Why is excessive differential settlement harmful to a building? • What are the causes of ground movement? • What are the stages of site investigation as set out in the building regulations? • What information is reported following a site investigation? School of the Built Environment Foundations Dr Tabarak Ballal University Teaching Fellow Associate Professor 1 Copyright University of Reading LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT LEARNING OUTCOMES By the end of this lecture, you will be able to: • Differentiate between different types of foundations • Understand when each might be used LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT CHOICE OF FOUNDATIONS The choice of foundation for a building depends mainly on three factors: • The total loads of the building; • The nature and bearing capacity of the subsoil; • The amount of settlement produced by the loading. LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT The Purpose of Foundations The foundation is required to: • safely transfer the loads carried by a building to the ground; • ensure that these loads are appropriately distributed through the ground where the building rests; • resist the forces set up by settlement, differential movement, subsidence and other possible ground movements (e.g. earthquakes). LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT TYPESOF FOUNDATIONS • Shallow Foundations • Transmit loads on or close to t he surface of the ground • Deep Foundations • Transmit loads at depths of more than 1.8m from the surface of the ground LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT SHALLOW FOUNDATIONS • Pad Foundations • Strip Foundations • Raft Foundations LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT PAD FOUNDATIONS Reinforced Concrete Framed Structure • Used as foundations for framed structures • Suitable for most subsoils except loose sands and filled areas • Footings act in an independent manner but designers should ensure that loads imposed on different footings are not substantially different to minimise likelihood of differential movement • Independent pad footings are usually tied together using ground beams LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT PAD FOUNDATIONS Courtesy: Science Photo Library\UIG Steel Framed Structure LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT STRIP FOUNDATIONS • Traditional Strip (Horizontal) • Trench Fill (Deep/Vertical) • Stepped Foundations LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT TRADITIONAL STRIP FOUNDATIONS • Most common type for low-rise buildings • The load-bearing walls transmit all loads from floors, roof, and walls to foundations Also known as Horizontal Foundations • Foundation uniformly distributes loads onto soil • The foundation has uniform width and thickness WHY? • Minimum thickness (150mm) • Working space (450-500mm) LIMITLESSPOTENTIAL | LIM ITLESS OPPORTUNITIES | LIMITLESSIMPACT REFLECTIVE LEARNING • Why should the depth be at least equal to the projection of the foundation from the face of the wall? Shear Failure LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT TRADITIONAL STRIP FOUNDATIONS Types of Soils [Bearing Capacity of 600 kN/m 2]: Sands and Gravel Solid Chalk LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT TRENCH FILL FOUNDATION • Firm grounds “shrinkable clay” • Laid to width of the excavated trench (300mm) • Trench filled to about 225mm (3 courses of brickwork) below finished external ground level AlsoknownasDeep/VerticalFoundation • Light loads • Not reinforced with steel bars LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Trench Fill Foundation LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Typesof Soils [BearingCapacity of >150 KN/m 2]: Firm, Stiff &ShrinkableClay wherevegetationis insignificant LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT TRENCH FILL V TRADITIONAL • Advantages • width can be reduced (less excavation) • trench open for less time • Disadvantages • More concrete (but less brickwork) • difficult to inspect bottom of trench and clean out • no difficult brick or block-work in a confined space • less time on site by skilled tradesmen • less backfill LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT STEPPED FOUNDATOINS • All foundations must bear horizontally to t he soil • What happens on a sloped ground? • Slight slope – 1:50 – CUT & FILL • Steep slope – 1:10 – Stepping down foundations LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Stepped Foundation LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT STEPPED FOUNDATIONS • Steps should be: • Uniform in height Used on sloping grounds saves on excavation saves on brick-work • Length to match brick sizes • Building Regulations minimum requirement for lap: Thickness Height • Traditional strip • thickness of foundation, or twice height of step, or 300mm • Deep fill • twice the step, or 1 m Lap LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT RAFT FOUNDATION • A continuous reinforced concrete slab under a whole building • Used where there is a likelihood of subsidence or differential settlement • Soft clays, soft silty clays • Manmade “compressible” ground Raft Foundation • Very common in mining areas BC< 75KN/m2 LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT FLAT RAFT FOUNDATION • Rafts are designed by an Engineer on a one- to- one basis • No ‘deemed to satisfy’ provision in the Building Regulations LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Wide Toe Raft Foundation • Reinforcement (top and bottom) • Expensive Tabarak Ballal LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Wide Toe Raft Foundation Slab is projected 300mm beyond wall perimeter. WHY? Tabarak Ballal LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT RAFTS ON FILLED SITES • Cost effective alternative • Can be used in sloped ground instead of stepped foundations • Fill and raft must be designed by specialist soil and foundation engineers LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT TYPICAL DIMENSIONS FOR RAFT FOUNDATION LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT ADVANTAGES OF RAFT OVER STRIP FOUNDATIONS • No trenching is required; • Less interference with subsoil water movement (water table); • No risk to people working in trenches LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Terminology… LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT RECAP… Reflective Learning • What are the three alternative forms for strip foundations? • When would a raft foundation be used? • What are the advantages and disadvantages of each of the foundation systems? LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT School of the Built Environment Deep Foundations Dr Tabarak Ballal University Teaching Fellow Associate Professor 1 Copyright University of Reading LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT DEEPFOUNDATIONS Piles are used to transmit loads through soft soils or made- up ground to firmer sub- soils LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Traditionally used when there is • Shrinkable clay • Considerable numbers of trees and vegetation • Ground obstructions • Firm stratum at depth > 1.8m below ground level • High water table LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT WHY SHORT- BORED PILES? • The increased pressure to re- develop 'brownfield' sites, where strip foundations may not always be appropriate • Increased costs of 'carting away' and tipping surplus excavation from foundation t renches (particularly in cities) • The development and easy availability of smaller piling rigs and piling systems which are, nowadays, cost effective for house foundations • Greater understanding of piling in general (partly through better building education). LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT TWO TYPES OF PILES • Deep Piles – High rise buildings • Short- bor ed piles – Low rise buildings LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT SHORT- BORED PILE FOUNDATIONS LOAD • Friction Piles • In- situ concrete • Short lengths of 20mm reinforcing bars should be set in the top of the pile Friction Pile LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT SHORT- BORED PILE FOUNDATIONS LOAD • End bearing Piles Weak Stratum • Pre- cast concrete • Load is transmitted by end bearing over the area of the pile base Bearing Stratum End Bearing Pile LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT FRICTION PILES - REPLACEMENT LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT END BEARING PILES - DISPLACEMENT LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT QUESTION? Why do Friction and End-Bearing Piles behave differently when transmitting loads? LOAD LOAD Weak Stratum Bearing Stratum Friction Pile End Bearing Pile LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT COMPARISON Friction/Replacement Piles End- bearing/ Displacement Piles • Cohesive soils • Arisings (excavated soil) • Vibration free • Noise free • Granular soils • No arisings • Vibration of ground • Noisy LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Track mountedcontinuosflight auger (CFA)pilling rig. LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Pilingcontractorcleaningthe accumulated debrisandearthoff the continuos flight auger aspart of routine maintenance. LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT REINFORCEMENT BARS LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Short- bored Piles: Length 2.0- 3.5m Diameter 250- 300mm LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT GROUND BEAMS Reinforced ground beams supported on piles are a very efficient method of providing foundation support to new structures built on poor ground. LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT GROUND BEAMS LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT ANIMATION CLIP ON END-BEARING PILES LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT ADVANTAGES OF SHORT- BORED PILES OVER STRIPFOUNDATION • Speed of construction • Reduction in quantity of surplus soil • Reduction in quantity of concrete used • Ability to continue work in bad weather LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Economic and construction considerations when selecting an appropriate foundation system The selection of the most appropriate system is a bit of a ‘balancing act’. All of the engineering options can be juggled until an optimum is identified. Terminology… LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT RECAP… LEARNING OUTCOMES • What are the three alternative forms for strip foundations? • When would a raft foundation be used? • What is the difference between friction and end-bearing piles? • What are the advantages and disadvantages of each of the foundation systems? LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT School of the Built Environment EXTERNAL ENVELOPEAND SOLID WALL CONSTRUCTION Dr Tabarak Ballal University Teaching Fellow Associate Professor 1 Copyright University of Reading LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT CONTENT OF LECTURE • External Envelope: Functional and Performance Requirements • Solid Wall Construction: • Brief History • Meeting Building Regulation Requirements • Principles of Bonding 12 LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT LEARNING OUTCOMES By the end of this lecture, you will be able to: • Describe the functional and performance requirements of t he external envelope; • Identify different types of Bonding arrangements for Solid Walls; • Appreciate the challenges of Solid Walls in meeting UK Building Regulation requirements; LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT EXTERNAL ENVELOPE Exterior shell of a building including Walls and Roofs LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT External Loadbearing Walls Has two basic functions: 1. To transfer the loads from suspended floors and the roof to the foundation; 2. To provide environmental protection for the building. LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT FUNCTIONAL REQUIREMENTS OF EXTERNAL WALLS • Strength and Stability • Weather protection • Good thermal insulation Superimposed Load • Good acoustic control • Fire protection • Durability LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT FUNCTIONAL REQUIREMENTS OF EXTERNAL WALLS • Strength • Resistance to stresses applied by the live, dead and wind loads • Resistance to stresses applied by lateral loads from the surrounding soil below ground level Superimposed Load LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT FUNCTIONAL REQUIREMENTS OF EXTERNAL WALLS • Strength of a wall is determined by: • Its thickness; • Compressive strength of the material from which it is constructed Superimposed Load • Below ground level, typical bricks or blocks with compresseive strength of 5-7 N/mm2 will be used LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT FUNCTIONAL REQUIREMENTS OF EXTERNAL WALLS • Stability • Buckling: due to excessive slenderness of the wall Superimposed Load • Slenderness Ratio • Overturning: due to the application of lateral forces LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT FUNCTIONAL REQUIREMENTS OF EXTERNAL WALLS • Weather exclusion • the sponge principle • the impervious skin principle Superimposed Load • the cavity principle LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT FUNCTION OF EXTERNAL ENVELOPES • Thermal insulation • barrier to passage of heat • Measured by the air-to-air transmittance coefficient (Uvalue) LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT FUNCTION OF EXTERNAL ENVELOPES • Sound insulation/acoustic control • Mass/Density of material • air-borne sound – mass/density • Structure-borne or impact sound – physical breaks within wall LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT FUNCTION OF EXTERNAL ENVELOPES • Durability - affected by three main weathering effects: 1. Frost action when clay bricks are saturated (Spalling); 2. Crystallisation of soluble salts caused by evaporation of moisture (Efflorescence); 3. Expansion of mortar when brickwork is wet for a prolonged period LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Spalling of Brickwork Efflorescence of Brickwork FUNCTION OF EXTERNAL ENVELOPES • Fire resistance • Time • Surface spread of flame • Appearance • Size, shape, colour & texture of materials • Feasibility • Resources • Legislation LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT EXTERNAL WALLS • Materials • Natural stone • Artificial stone • bricks • blocks • Timber LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT SOLID WALL CONSTRUCTION • Used until 1920s • Natural Stone walls • Artificial Stone walls • Bricks LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Types of Bricks • Common Bricks: • Acceptable in terms of performance characteristics: • • • • strength (5-9 N/mm2), water absorption (12-26%), durability (frost damage causes SPALL), thermal movement • Cheaply produced • Appearance is poor… • Not used in modern house construction COMMON BRICK LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Types of Bricks • Facing Bricks: • Similar to common brick in terms of performance characteristics • More expensive to produce than common bricks • Appearance is good… • Used for external walls of houses FACING BRICK LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Types of Bricks • Engineering Bricks: • • • • • Stronger than common and facing bricks (9-25 N/mm2 ) Have lower moisture absorption characteristics (4.5-7%) More expensive to produce Appearance is not great… Used below ground for their enhanced strength and low porosity • Used in civil engineering structures ENGINEERING BRICK FOOTINGS LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Standard Brick Size 102.5mm 65mm 215mm Stretcher Face Header Face LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT SOLID BRICK WALLS Two Headers + 10mm mortar joint = One Stretcher Face Three Course Height (+20mm) = One Stretcher Face 102.5mm 65mm 215mm Stretcher Face Header Face LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Types of Blocks • Dense Concrete Blocks: • Made from cement, sand and crushed gravel • Suitable for foundation walls - below ground level • Have high density and therefore are good conductors of heat – not used for external walls without additional insulation Dense Concrete Blocks • Suitable for ‘Party Walls’ and ‘Loadbearing Partitions’ LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Types of Blocks • Lightweight (Aerated) Concrete Blocks: • Made from cement, lime, sand, pulverised fuel ash and aluminium powder • High levels of thermal insulation Aerated Concrete Blocks • Light in weight and easy to cut and handle • Used for internal leaf of modern cavity walls • Low density – not good for sound insulation LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Standard Block Size 100mm 440mm 215mm LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Blocks V Bricks • Light in weight, enabling their greater bulk to be handled easily when constructing a wall • Sized to correspond to multiple bricks, enabling work requiring corresponding course levels to be undertaken – MODULAR CO-ORDINATION • They are comparatively cheap to produce, giving economical wall construction in comparison to brickwork • Better thermal resistance values than bricks • Accept nail and screw fixings more readily than brickwork • They have a keyed or textured surface for the application of plaster or render LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT BONDING • Stack bonding • Stretcher bond • Header bond • English bonding • Flemish bonding • English garden wall bonding • Flemish garden wall bonding LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT TYPES OF BONDS • Stacked • Continuous vertical joints “perpends” • Never used LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Reason for Bonding Tabarak Ballal LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT STRETCHER BOND • Stretcher face visible • Ahalf brick wall • Quickest and most economical method for wall construction • Not suitable for loadbearing walls Acourse of bricks? APerpend? ABed? HEADER BOND • Header face visible • Aone brick wall • Unattractive ENGLISH BOND • Alternating layersof headersandstretchers Queen Closer? Quoin? • Onebrickwallthick • Thicker wallscanbeformed, e.g. oneandahalf brick thick ENGLISH BOND FLEMISH BOND • Alternating bricks laid as headers and stretchers in each course • One Brick Wall (thicker walls were accommodated for) • More economical than English Bond FLEMISH BOND I l l University of W Reading Flemish bond Section een closer I . 5 brick thick I LIMITLESS OPPORTUNITIES I LIMITLESS IMPACT ENGLISH GARDEN WALL BOND • Has three stretcher courses to one header course • Quicker to build than English Bond but not as strong ENGLISH GARDEN WALL BOND FLEMISH GARDEN WALL BOND • Has three stretcher bricks to one header brick in each course • Quicker to build than Flemish bond FLEMISH GARDEN WALL BOND SHORTCOMINGS OF SOLID WALL CONSTRUCTION • For adequate resistance to moisture penetration, thickness should not be less than 350mm – more than one and half brick thick • For adequate thermal insulation, thickness should not be less than 450mm – more than two-brick thick LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT SOLID WALL CLOUD LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Learning Points • Functional requirements of external walls • Solid wall construction methods • Bonding of brickwork School of the Built Environment WALL CONSTRUCTION: CAVITY WALLS Dr Tabarak Ballal University Teaching Fellow Associate Professor Copyright University of Reading LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT LEARNING OUTCOMES By the end of t his lecture, you will be able to: • Describe constructional details of cavity walls; • Differentiate between cavity wall construction above and below DPC ; • Understand importance of lintels in redistribution of loads above openings. LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Cavity Wall Construction • The Cavity Principle Cavity Wall Construction • Cavity prevents passage of moisture • Materials with high thermal insulation properties can be used effectively LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT EARLY CAVITY WALLS – 1920 • An outer leaf of brickwork would be built in facing bricks and usually in stretcher bond • The inner leaf was usually formed in common bricks LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT EARLYCAVITY WALLS – 1930- 1950 • By the 1930s some developers were using concrete blocks for the inner leaf. • However, the use of blockwork was slow to catch on and even as late as the 1950s bricks were still used for internal leaves of cavity walls. LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT MODERN CAVITY WALLS • Modern brick/block cavity walls vary in thickness depending on the nature of the cavity and the nature of the inner leaf. LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT COMPONENTS OF ACAVITY WALL • Outer skin/leaf of brickwork in stretcher bond (half brick thick) LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT COMPONENTS OF ACAVITY WALL • Inner skin/leaf of blockwork 100mm aerated concrete blocks • They are quicker to lay than bricks • They have low thermal conductivity values (U-value). • However, they have high water absorption levels… CONCRETE BLOCK INNER LEAF LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT COMPONENTS OF ACAVITY WALL • Cavity minimum 50mm and maximum 100mm Building Regulations Requirement LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT COMPONENTS OF ACAVITY WALL • Walls connected by ties LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT PRIMARY FUNCTIONS OF WALL TIES • Securesinsulation board against inner leaf • Transferlateral loads • Permits in- plane movement to accommodate differential material movement • Providesstructural reinforcement around openings LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT WALL TIES • Material • Stainless steel • PVC: 2- storey housing • Galvanised butterfly steel • Coated butterfly wire LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT WALL TIES • Staggered Spacing • 900 mm horizontally • 450 mm vertically • extra around openings (300mm) LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT WALL TIES • Moisture • Should be allowed to fall freely to DPC outlet • Should not be allowed to travel to inner leaf • Cleanliness CAVITYBRIDGE? LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT WALL TIE FAILURE LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT CONSTRUCTION PROCESS • Commences after ground floor is cast • Height limited to 1.5m per day – WHY? • 2 leaves raised together • Clean cavity LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT OPENINGS IN CAVITY WALLS • Inner leaf returned to outer leaf • Problem with Cold Bridging? LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT OPENINGS IN CAVITY WALLS • Inner leaf returned to outer leaf • Vertical DPC must be inserted LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT OPENINGS IN CAVITY WALLS • Temporary timber windows and door frames to be built in as work proceeds – WHY? • Self- finished windows to be placed after construction of wall is complete • Lintels provided above openings LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT WHAT IS ALINTEL? Asupporting member positioned above a ‘door’ or ‘window’ opening to carry and support the walling above that opening. LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT EARLY LINTELS • Single Reinforced Concrete beams to carry both inner and outer leaf • PROBLEMS? • Cavity bridge • Cold bridge LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT EARLY LINTELS • Cavity trays were introduced • Tell tale signs: usually a few new courses of brickwork over the lintel. LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT EARLY LINTELS • To overcome problems of moisture penetration ‘Boot Lintels’ were introduced. • The top of the lintel was usually coated in t ar (from coal) or bitumen (from oil) to prevent water soaking into the lintel itself. • However, problem of condensation still persisted – caused by cold bridging LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT DEVELOPMENTS IN LINTELS • RC to carry inner leaf and soldier course to carry outer leaf • Stainless steel LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT MODERN LINTELS Galvanised Steel Lintels LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT LINTELS • A separate Cavity Tray provided • Bearing of 150mm; • Weepholes provided; • Soffit covered with galvanised mesh. LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT CAVITY WALLS BELOW DPC • 2 leaves of 100mm thick dense concrete • Levels adjusted by use of a course of cut bricksor blocks • Holes left for cables; pipes; other services • Cavity filled with fine concrete LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Cavity Wall below DPC • The base of the cavity wall is being built off a solid concrete block footing. Note that the perforations in the brickwork have been filled in with mortar to add strength to the wall. BASE OF CAVITY WALL CAVITY WALLS BELOW DPC Indents provided for bonding of internal loadbearing walls LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT DPC? • Impermeable barrier LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT EARLY FORMS OF DPC • By 1920s most walls included DPCs • In early cavity walls large pieces of slate were used which bridged the cavity • Other materials included: lead, copper, asphalt and bitumen felt LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT DAMP PROOF COURSE MATERIALS • Flexible • Semi-rigid • Rigid Semi-Rigid DPC Bitumen felt is a traditional material used for damp proof courses. It may extrude under pressure when loaded and can become brittle if exposed to ultra violet light for long periods. BITUMEN FELT DAMP PROOF COURSE LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Flexible DPC Polyethylene is an inexpensive DPC material that does not extrude under load or suffer from ultra violet embrittlement. POLYETHYLENE DAMP PROOF COURSE LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT DAMP PROOF COURSE (DPC) • Should not project into cavity; • Minimum distance of 150mm from finished ground level; • Should be provided around openings LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT DAMP PROOF COURSE - DPC LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Online Test 2 Week 11 • Test 2 will cover: General Introduction to Building Soils and Site Investigation Foundations • There are 40 questions • Timed tests – 50 minutes • Test will open at 15:00 and close at 23:59 on Thursday 14 November 2019 (Week 11) • 10% of final mark Wall Cloud Final Reflections • Constructional details of cavity walls; • Cavity wall construction above and below DPC ; • Construction details of openings including lintels and their importance in redistribution of loads above windows and doors. School of the Built Environment PITCHED ROOF STRUCTURES Dr Tabarak Ballal University Teaching Fellow Associate Professor 1 Copyright University of Reading LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT LEARNING OUTCOMES By the end of this lecture, you will be able to: • Describe the construction of traditional timber pitched roofs; • Describe the construction of modern timber pitched roofs; LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT BASIC ROOF FORMS • Degree of Inclination to the Horizontal • Structural Form • Single Roof • Double Roof • Triple Roof • Flat Roofs • Where the slope in any one plane does not exceed 10 degrees to the horizontal • Pitched Roofs • Span • Where the slope in any one plane exceeds 10 degrees to the horizontal • Short Span • Less than 7.6m • Medium Span • 7.6m - 24.4m • Long Span • More than 24.4m LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT TIMBER PITCHED ROOFS LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT Roof Shapes LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT PITCHED ROOF TERMINOLOGY LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT SINGLE ROOFS LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT MONOPITCH ROOF (LEAN-TO-ROOF) • Used for rear “Extensions” of houses, and for garages • Limited span (2 - 3 m) wall plate • Made of a series of sloped timber boards (Rafters ) • Ends of rafters were built into walls Rising damp • Traditionally, the rafters were placed directly on the wall PROBLEM? • In modern construction, the roof rafters are supported on a “Wall Plate” - ADVANTAGES? LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT COUPLE ROOF • Pairs of Rafters connected to a “Ridge Board” • Ridge Board runs from gable to gable to provide lateral restraint • Rafters rest on a “Wall Plate” LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT COUPLE ROOF • Problem • Under loads of tiling and snow, rafters tend to spread, this causes walls to overturn Span limited to 3.5m LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT CLOSED COUPLE ROOF • A ceiling joist acts as a tie which connects feet of rafters: • Prevents rafter feet from spreading • Span limited to 6.10m (most economical upto 5.5m) • Joint between tie and foot of rafter should be adequately nailed (inadequate fixing was a common cause of roof failure) • Ceiling joists (ties) also support ceiling finish LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT CLOSED COUPLE ROOF • Ties may sag due to weight of roof Hanger • Deeper section of timber boards Binder • More economical solutions is to use • Use a series of hangers (50mm*38mm) and binders (75mm*50mm) LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT COLLAR ROOF • Ties are raised upto 1/2 rise of roof. • Used to economise in walling. • Less effective in solving problem of spreading rafters. • Connection between tie & rafter is of more importance. LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT SIZES OF ROOF TIMBERS • Rafters: • are usually 38-50mm thick, and 100-150mm deep • Spacing between rafters is 400-600mm centre to centre • Depth and spacing of rafters depend upon: • Type of roof covering • Weight of roof covering • Unsupported length of roof • Imposed loads of wind and snow LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT • Ceiling Joists (ties): • are usually 38-50mm thick • 75-225mm deep • spaced at 400-600mm (similar to rafters) • Collars: • are 44mm thick • 100-150mm deep LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT • Wall plates: • 100mm wide • 25, 50,or 75mm deep • Wall plates are bedded in mortar and rest on inner leaf of a wall • Ridge boards: • 25-38mm thick • Depth depend on size of splay cut ends of rafters LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT DOUBLE ROOFS LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT STRUTTED PURLIN ROOFS • Spans upto 7.5m • Purlins require support provided byPurlin struts (struts 75*75) • Struts require central support provided by “loadbearing party walls” • Ends of purlins are built into Gable end or party walls LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT ADDITIONAL DETAILS LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT TRIPLE ROOFS LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT TRIPLE ROOFS • Prefabricated trusses comprising rafters, struts and ties, joined together by toothed plate or split ring connectors, replace every fourth set of rafters and provide support to the purlins without the need for a loadbearing spine wall. • The components to the truss can be delivered loose and assembled on site. KING POST TRUSS ROOF LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT Modern Roof Construction TRUSS RAFTERS • Used for the last 3 decades • Prefabricated (factory made) timber roofs • Pitch; Span; Rafter spacing; Type of coverings; • Supported by inner leaf of external walls • No internal support is required by loadbearing (party) walls • Special connector plates are used to join roof members LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT DIFFERENT TYPES OF TRUSS RAFTERS LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT ADVANTAGES OF USING TRUSSED RAFTERS • No internal support is required • Faster form of construction • Relatively cheap • Erection does not require skilled labour • Prefabricated LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT Braces should be formed in at least 22mm by 97mm softwood and should be fixed to every trussed rafter with 2 No. 3.35x65mm galvanised wire nails. BRACING • To avoid damage of roof and subsequently of roof coverings bracing is required • Damage occurs as a result of: • Imposed and wind load • Compression • Without the bracing the roof could twist or buckle resulting in damage to the roof coverings or potential structural movement of the gable ends. LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT TO AVOID UPLIFTING OF THE ROOF STRUCTURE Wall plates must be strapped down using galvanised metal strap positioned at 600mm intervals. AS BUILT! LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT TO AVOID LATERAL MOVEMENT OF GABLE WALL LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT LEARNING OUTCOMES This is what we have learnt today: • Describe the construction of traditional timber pitched roofs; • Describe the construction of modern timber pitched roofs; LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT School of the Built Environment PITCHED ROOF COVERING Dr Tabarak Ballal University Teaching Fellow Associate Professor 1 Copyright University of Reading LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT LEARNING OUTCOMES By the end of this lecture, you will be able to: • Identify different materials used in roof coverings; • Understand differences in laying roof tiles; • Gain knowledge of special arrangements for weather protection. LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT PITCHED ROOF COVERINGS •Materials and Principles •Details and Methods of Positioning •Problems LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT LAYERS OF ROOF COVERINGS • Two layers: •External Layer • Roof Covering (slates and tiles) •Internal Layer • Sarking felt membrane, battens LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT DEVELOPMENT OF ROOF COVERINGS • Roof Coverings in the 17th and 18th Century LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT MATERIALS AND PRINCIPLES • Plain Tiles • CLAY tiles vary in colour from red to deep purple • Small size : 265mm* 165mm (10-15mm thickness) Plain Clay Tiles • Expensive form of construction (labour & material) • Must be laid to steep pitches 40º - why? LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT MATERIALS AND PRINCIPLES • Natural Slate • Formed from metamorphic rock with laminar structure • Rock can be split into 3-11mm thickness (slates) • Dense, very fine-grained material • Virtually impermeable • Highly resistant to chemical attacks • Early use confined to areas where it naturally occurred. • Early 19th century saw rapid growth in use. • Larger than tiles: 600mm*300mm DURABILITY? LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT MATERIALS AND PRINCIPLES • Stone Slate • Sandstone or Limestone • Are permeable to water • Thick slates with steep pitch • Heavy covering and rarely found in modern construction. Example of slipped stone slates caused by deterioration of the nail heads LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT DEVELOPMENT OF ROOF COVERINGS • Roof Coverings in the 19th Century LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT ROOF COVERINGS IN THE 19TH CENTURY • Interlocking Tiles (Roman) • Popular in the late 19th century • Less expensive than plain tiles • Single and Double Roman tiles LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT MODERN ROOF COVERINGS 20TH CENTURY Concrete Plain Tiles • Was extensively used in modern construction •Early concrete tiles were dull in colour and had a rough surface (around 1950s) •Modern concrete tiles vary in colour and shape •Largely replaced both Clay and Roman tiles LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT MODERN ROOF COVERINGS 20TH CENTURY • Synthetic Slate • Introduced in the early part of 20th century • Made from Asbestos and Cement • Asbestos replaced by Synthetic Fibres. • Significantly cheaper than natural slate but less durable. LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT FIXING OF ‘SLATES’ • Double-lap Coverings • Two layers of slate at any one point on the roof to prevent water dropping into the roof space • Each slate laps two others below LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT FIXING OF ‘SLATES’ • Double-lap Coverings • Every slate is nailed to batten using 2 nails at the head (danger in high wind) or centre (preferred) • Synthetic slates are always fixed in the centre LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT FIXING OF ‘PLAIN TILES’ • Also, Double-lap Coverings, but with two main differences: • Tiles are slightly cambered and thus there is less chance of capillary action • Tiles have nibs and it is therefore unnecessary to nail every tile in position • Tiles (265mm*165mm)are much smaller than slates (600mm*300mm) • Pitch should be at least 40 degrees and headlap at least 65mm. LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT HEAD LAP LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT FIXING OF ‘INTERLOCKING’ TILES • Single-lap Coverings • One layer of tiles on the roof • ‘Double Roman Tiles’ have curved surfaces to provide the overlap • Have 2-3 small projections at the back “nibs” • Perimeter tiles are nailed • Intermediate courses of tiles are not nailed • Used for shallow pitches - less than 30 degrees LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT ADVANTAGES OF SINGLE-LAP OVER DOUBLE-LAP Ability to interlock and overlap allows a much shallower roof pitch which leads to: • Less material used • Overall weight of the covering is reduced • Reduced amount of timber used in the supporting structure • Quick and easy construction LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT ADVANTAGES OF TILES OVER SLATES • Light in weight • Available in a range of thickness and sizes • Have nibs which assist in fixing • Have factory made nail holes LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT Internal Layer 2. UNTEARABLE SARKING FELT • Function • Prevents driving rain or snow entering roof structure • Materials • Bituminous felt • Plastic sheeting • Fixing • Galvanised broad-headed nails @300mm c/c • Vertical joints - minimum lap of 150mm • Horizontal joints - minimum lap of 75mm LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT …EXTRA PRECAUTIONS! • Felt must be dressed up over • ridge board, gable end, and fascia board • must extend into the gutter • An extra full width layer is fixed under the felt in valleys and hips LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT BATTENS Normally cut from softwood • Size • • • • 38mm*19mm (Plain Tiles) 50mm*25mm (Double & Single Roman) 50mm*25mm (Slates) At least 1.2m long • Fixing Fixings must be compatible with preservatives! • Gauge (Length of tile - lap) / 2 LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT SPECIAL TILES • Hip Tiles • Ridge Tiles • Dry Verge Tiles LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT HIPPED ENDS • Special tiles are used • Angular tiles • Bonnet tiles • Rounded tiles • Tiles are bedded in mortar • Hip iron prevents tiles from slipping LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT RIDGES • Material • Clay ridge tiles • Fixing • Tiles have no holes for fixing, instead, they are held in place by the adhesive effect of their mortar bed • End tiles must be mechanically fixed LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT DRY VERGE TILES • The dry verge tiles are made from glass reinforced plastic (GRP) and are laid over the roof tile at the verge. • They are nailed to the tiling batten. • They replace cloaking the underside of the roofing tile with mortar at the verge. LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT WATER PROTECTION FEATURES • Valleys • Gutters • Soakers • Flashings LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT Plywood boards have been fixed to the trussed rafters to form a valley. VALLEYS • Sheets of lead, zinc, or glass fibre were traditionally used to form valleys • Modern valleys are formed using Glass Reinforced Plastic (GRP) Preformed Valley Gutter LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT GUTTER • Rainwater guttering is fixed to the facia board at the eaves. • The timber sprockets fixed to the base of the rafters provides support for the soffit board. Fascia Board fixed to roof rafters • NOTE: Connection between wall plates – scarf joint Rainwater Gutter LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT SOAKERS & FLASHINGS • Required at • joints between roof and wall • around chimneys • Soakers are made from lead • fit on top of tile (single-lap) • fit underneath tile (double-lap) • turned up wall LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT FLASHINGS & SOAKERS • Required at • joints between roof and wall • around chimneys • Soakers are made from lead • fit on top of tile (single-lap) • fit underneath tile (double-lap) • turned up wall • Flashings are made from lead • stepped to reduce material used • slotted into the mortar joint of wall • turned down over soaker LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT RECAP… LEARNING OUTCOMES • Traditional and Modern Pitched Roof Coverings • Materials: Natural and Synthetic • Details and Methods of Positioning • Problems: Uplifting, Water Penetration LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT School of the Built Environment INSULATION OF WALLS AND PITCHED ROOFS Dr Tabarak Ballal University Teaching Fellow Associate Professor Copyright University of Reading LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT CONTENT OF LECTURE • Insulation of Solid Walls • Insulation of Cavity Walls • Insulation of Pitched Roofs 12 LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT LEARNING OUTCOMES By the end of this lecture, you will be able to: • Describe alternative arrangements for insulating solid walls. Describe alternative arrangements for insulating cavity walls. Describe alternative arrangements for insulating pitched roofs. LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Thermal Insulation of Walls LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT HEAT LOSS FROMABUILDING • 35% through external walls • 25% through roof • 15% through ground floor • 15% through doors • 10% through windows LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT BUILDING REGULATIONS - PART L • Conservation of fuel and power “Reasonable provision shall be made for the conservation of fuel and power in buildings…” LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT INSULATION - DEFINITION • Abarrier to the natural flow of heat from an area of high temperature to anarea of low temperature. LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT INSULATION OF SOLID WALLS • Thermal insulation can be applied to existing solid external walls. • Insulation may be applied to either the Internal or External face of the wall. LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT EXTERNAL INSULATION • The entire building is surrounded by insulation therefore ‘cold bridging’ is unlikely • When the heating is turned on, the inner surface temperature rises at a slow pace which is undesirable • When the heating is turned off, the surface temperature drops off slowly so condensation is unlikely to occur LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT EXTERNAL INSULATION • The insulation needs to be protected from water penetration, usually by a coat of render (external finish for wall) • Insulation board is held against the wall by retaining clips • Note actual mechanical fixing (nail) • Note reinforcing mesh to provide suction for render LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT EXTERNAL INSULATION • Advantages: • Dimensions of rooms are maintained • Minimum disruption to occupants • Walls stays at a high temperature so frost attack is unlikely • Condensation is unlikely to occur • May improve the appearance of a building • Disadvantage: • Bad weather restrictions • Thermal insulation performance may be adversely affected over a period of time • Minor failure of DPC may prove significant. Why? • Preferred when: • External facing is used • Building is occupied • Application: • Extent below ground floor to avoid cold bridges • Taken down to 300mm below DPC LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT INTERNAL INSULATION • When the heating is turned on, the inner surface temperature rises very quickly • When the heating is turned off, the surface temperature drops very quickly too so condensation may occur LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT INTERNAL INSULATION • Advantage: • Provides a surface which warms up quickly and results in heating economies in buildings which are only heated intermittently. • Alteration to appearance not permitted. • Disadvantage: • Building is not occupied. • Can cause disruption to occupants. • Application: • Risk of condensation… a vapour control layer is • Directly to internal face. essential. • Separated by an air space. • Preferred if: • No external facing. LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT INSULATION OF CAVITY WALLS • Application to interior face of the wall (as per solid walls) • Filling cavity with suitable insulating material • Application to cavity face of inner leaf 31 LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT FULLY- FILLED CAVITY Cavity insulated during construction: • Semi- rigid slabs in sizes suited to cavity tie spacing should be used • Made from mineral wool (glass or rock) • Renewable materials? • 1200mm long, 450 mm high, and of various thicknesses • Flexible and resilient LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT WALL ACTING AS HEAT STORE LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT CONSTRUCTION OF FULLY- FILLED CAVITY WALL • The external leaf of masonry is built to just above the first row of wall ties. • All mortar is cleaned from the masonry, ties or cavity tray. • Insulation batt is positioned against the wall, so that the wall tie drips are halfway acrossthe top edge of the batts. • The inner leaf is then built to the top level of the insulation batt. • The successive stages of the wall can then proceed. LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT INSULATION AROUND BENDS AND CORNERS • Insulation batts that are 50mm, 65mm, & 75mm thick should be bent around corners to ensure that no gaps are left between batts into which mortar could fall. • Insulation batts of more than 75mm thickness may be butt however it is important to ensure that the joints are closely butted. LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT GABLE WALLS • Insulation should be taken to the highest point of the wall, for example to the ridge level on gable walls LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT PROTECTION WITH CAVITY TRAY • If the insulation batt is to terminate in the height of the wall it should be protected by a DPC Cavity Tray. • If insulation starts at a high level and terminates part way down the walls, it should be protected on the underside by a Cavity Tray. LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT DON’TS • Battsshould never be positioned on top of mortar droppings. • Batts should not be pushed into the cavity. • When small off- cuts are used, the face of the batts and not the edge should be positioned against the wall surface. • Batts should not be teared or impaled. Laminated face – batts are treated with a water repellent LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Insulation of Existing Walls CAVITY WALL INSULATION LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT CAVITY INSULATED AFTER CONSTRUCTION • Blown- in insulatants made from a variety of materials: • Granulated rockwool • Urea-formaldehyde foam • Expanded polystyrene beads Expanded polystyrene beads LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT CAVITY INSULATED AFTER CONSTRUCTION • The Process: • 18mm or 25mm holes are drilled at 1.5m centres in a staggered pattern • Insulation blown into cavity • Holes made good with mortar as work proceeds LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT CAVITY INSULATED AFTER CONSTRUCTION Internally Externally LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT BLOWN- IN INSULANTS • The final product Urea- formaldehyde foam Granulated rockwool LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT PARTIALLY- FILLED CAVITY • Used when the preservation of a cavity is desired • Insulation boards are attached to t he cavity face of the inner leaf • Made from: • expanded or extruded polystyrene • mineral wool (glass or rock) • Aminimum of 50mm clear cavity should be maintained (Building Regulations) LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT SECURING INSULATION BOARDS • The boards are normally supported between t wo rows of t ies - to do this properly requires ties at greater frequency than those required in t he Building Regulations. • Plastic retaining washers clip over t he wall tie. LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT AT THE TOP OF ACAVITY WALL • The top of all cavities should be closed with a non- combustible board “Cavity Closer” LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT SOME PRACTICAL PROBLEMS OF INSULATED WALLS • Fully filled cavity insulation can increase the risk of rain penetration. • When insulation is applied to the inside surface of walls dampness could result possibly causing degrading of the thermal insulation [VAPOUR CONTROL LAYER: VAPOUR CHECK] LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Thermal Insulation of Roofs Insulation at Rafter Level ‘Warm Attic’ Insulation at Ceiling Level • ‘Cold Attic’ - All tanks and pipes in the loft should be insulated to prevent freezing. Insulation of Pitched Roofs LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Room-in-the-Roof Design LEARNING OUTCOMES You are now able to: • Describe alternative arrangements for insulating solid walls. • Describe alternative arrangement for insulating cavity walls • Describe ventilation of pitched roofs LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT QUESTIONS? LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT School of the Built Environment FLAT ROOFS: STRUCTURE & COVERINGS Dr Tabarak Ballal University Teaching Fellow Associate Professor 1 Copyright University of Reading LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT OBJECTIVES OF LECTURE FLAT ROOFS Structure & Materials Design Covering LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT LEARNING OUTCOMES By the end of this lecture, you will be able to: • Describe the constructional details of flat roofs • Distinguish between cold, warm and inverted roof structures • Identify types and defects in flat roof coverings LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT LOADBEARING PRIMARY STRUCTURE Timber Concrete: • insitu concrete slab • precast concrete beams and blocks Profiled Metal Decks LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT PRINCIPAL FUNCTIONAL PARTS Loadbearing Primary Structure Deck Insulation Waterproof Memberane LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT Components of Timber Flat Roofs • Joist – size depends on span and loading 225mm*50mm • Firrings • Wedge-shaped timber joists • Decking (Boarding) • Softwood • Plywood • Chipboard • Strutting LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT Eaves detail of Timber Flat Roofs The fascia may be built flush with the external face of the wall or the eaves may overhang the wall. This provides extra protection to the wall immediately beneath the eaves. LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT COMPONENTS OF METAL DECKING ROOFS • Metal Deck • Profiled Steel Sheets • Profiled Aluminium Sheets • Corrugated Zinc Sheets • Underlay • To support insulation board over the deck troughs LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT CONCRETE DECKS Concrete Deck • Insitu concrete slab • Precast beams and blocks • No decking is required LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT Design Consideration • Flat roofs are divided into 2 main categories: • Cold Roofs • Warm Roofs LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT COLD ROOF DESIGN • Insulation immediately above the ceiling • Deck and roof covering are substantially colder than the interior of the building ‘High Risk of Condensation’ LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT HOW COULD CONDENSATION BE AVOIDED? 1. Moisture entering the roof space should be eliminated. Vapour Control Layer 2. Moisture that does enter should be allowed to escape freely and not cause serious problems. Ventilation LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT WARM ROOF CONSTRUCTION Sandwich Construction With warm deck design the insulation is placed above the decking and must therefore be rigid and strong enough to support foot traffic across the roof. LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT WARM ROOF CONSTRUCTION Sandwich Construction • Less risk of condensation • Vapour barrier is required to eliminate any potential risk of condensation in the insulation LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT Warm Roof Construction Inverted Construction • Waterproof membrane is positioned between the insulation and roof deck • Insulation must be weatherproof and needs to be weighted down with ballast – why? LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT Warm Roof Construction Inverted Construction • There is no risk of condensation • There is no need for a vapour barrier LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT COLD ROOF DESIGN • Advantages 1. Waterproof membrane readily accessible. 2. Membrane replaced without sacrificing insulation. 3. Insulation does not need fixing unless there is a risk of high ventilation rates. 4. Ventilation of water vapour leaking from the occupied spaces below. Disadvantages 1. Effective ventilation difficult to achieve. 2. Increased joist depth to accommodate extra insulation. 3. Snow may enter ventilation openings. 4. Over areas of high moisture hazard, the cavity must be ventilated by pressurised, fresh, unheated air. 5. Effective vapour barrier at ceiling level may be difficult to achieve. LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT WARM SANDWICH CONSTRUCTION Advantages Disadvantages 1. Vapour control layer required 1. Waterproof membrane is accessible for repair and inspection. 2. Insulation can be secured without damage to the waterproof membrane. 2. Water may be trapped in the insulation. 3. The insulation must support the membrane against maintenance traffic and equipment. 4. Membrane exposed to a considerable temperature range. 5. Membrane ages faster. LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT INVERTED ROOF CONSTRUCTION Advantages Disadvantages 1. The waterproof membrane is fully protected against sunlight and extremes of temperature. 1. Membrane not immediately accessible for inspection and repair 2. Insulation must be ballasted by paving stones to prevent uplifting by wind suction forces. 2. There is no requirement for a separate vapour barrier. 3. Insulation must resist frost attack and retain its thermal resistance after prolonged exposure to water. 4. Rainwater drains less rapidly than from sandwich roofs. LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT WHICH DESIGN? • Cold roof designs should be avoided • Sandwich roof design can be used for lightweight roofs - timber/profiled metal • Inverted roof design can be used for heavyweight construction - concrete LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT FLAT ROOF COVERINGS • Waterproof Membrane • Bitumen Felt • Mastic Asphalt • Metal Sheets LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT BITUMEN FELT • Bitumen sheets are made of a reinforcement such as glass fibre or polyester coated with bitumen • 2 - 3 layers of bitumen sheets • Sheets are laid in broken joints LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT APPLICATION OF BITUMEN FELTS • Pour-and-Roll • Torch-on LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT Mastic Asphalt • Consists of asphaltic cement combined with mineral (coarse and fine) aggregates and an oil base • Properties of mastic asphalt • High thermal conductivity • High resistance to spread of fire • 2 coats of 10mm thickness are applied LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT Mastic Asphalt • Although mastic asphalt is a jointless covering, it needs to be laid in bays to enable the material to be trowelled level before it cools. • This roof is being laid in two coats on an isolating membrane which separates the covering from the roof structure. Mastic asphalt roof LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT POTENTIAL DEFECTS • Bitumen felt is adversely affected by direct exposure to sunlight • Mastic asphalt hardens and shrinks in direct sunlight LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT POTENTIAL DEFECTS • Ponding • Rainwater does not freely flow to guttering • Blisters • Expansion of entrapped air or moisture by solar heating • Crazing • Overheating of roof covering LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT PROTECTION OF ROOF COVERINGS • Solar Protection • Stone Chippings • Paving Stones • Solar Reflective Paints LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT Satisfactory Performance of Flat Roofs • Design • Materials • Workmanship LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT WHAT HAVE I LEARNT TODAY? • Flat roofs are NOT horizontal; • A variety of materials can be used in the design and construction of flat roofs; • The position of the insulation board in relation to other flat roof components determines the type of flat roof; • Three types: cold, warm and inverted roofs; • Bitumen felt and Mastic asphalt are typical roof coverings; • These must be well protected against solar radiation, variation in temperatures and moisture penertation. LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT QUESTIONS? LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT School of the Built Environment GROUND FLOOR CONSTRUCTION Dr Tabarak Ballal University Teaching Fellow Associate Professor Copyright University of Reading LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT CONTENT OF LECTURE • Floor Structures • Functional requirements • Types • Ground Floor Construction • Hardcore • Alternative design and construction techniques • Thermal insulation LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT LEARNING OUTCOMES By the end of this lecture, you will be able to: • Understand the functions of Hardcore; • Describe alternative methods for Ground Floor construction; • Describe insulation arrangement for ground floors; • Compare and contrast construction methods for solid and suspended ground floors LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT TYPES OF FLOOR STRUCTURES • Form of construction • Material • Concrete • Solid floors • Timber • Suspended floors • Steel LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT FUNCTIONAL REQUIREMENTS • Strength and stability • Damp resistance • Thermal insulation • Prevent the growth of vegetable matter within the building • Support wearing surface LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT PRE-GROUND FLOOR CONSTRUCTION LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT REMOVAL OF TOPSOIL 150mm - 230mm LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT WALL IS RAISED TO DPC LEVEL Remember! DPC must be positioned at least 150mm above finished ground level LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT PROVISION FOR SERVICES • Service pipes and ducts have to be placed and checked for defects. LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT PROVISION FOR SERVICES • Drains must be tested for water tightness LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT HARDCORE LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT FUNCTION OF HARDCORE • Bulk filler which raises floor level to the required level without excess concrete • Provides a clean, dry and firm working platform • Helps prevent contaminated soil or soft ground affecting the concrete ground floor • Provides a consistent material under whole floor area • Helps eliminate the passage of moisture from the ground LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT HARDCORE MATERIAL • Cheap • Durable • Chemically inert • Not affected by water 13 LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT HARDCORE • Best hardcores are by-products from the aggregate industry • Gravel/stone aggregate • Quarry waste • Chalk LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT HARDCORE • Other materials • Brick rubble (Caution: could containsulfates from gypsum plaster) • Concrete rubble (Caution: too large) • Ash from furnaces (Caution: sulfates) • Blast furnace slag (Caution: sulfates) LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT LAYING THE HARDCORE • If thickness is over 200mm then hardcore should be laid in layers of 150mm thick • Should be well compacted Mechanical vibrating plate or roller LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT FINISH TO HARDCORE • For ‘Solid Ground Floors’ Blinded with a layer of sand (25mm thick) if floor is reinforced • For ‘Suspended Floors’ Should be covered with a layer of concrete (100mm thick) LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT GROUND FLOOR CONSTRUCTION • Solid Ground Floors • Suspended Ground Floors LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT SOLID CONCRETE GROUND FLOORS LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT INSITU CONCRETE SLAB • Minimum thickness 100mm, usually 150mm thick LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT REINFORCEMENT OF CONCRETE SLAB • Heavy floor loads • Upward pressure from the soil LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT REINFORCEMENT OF CONCRETE SLAB • Heavy floor loads • Upward pressure from the soil What are these and why are they used? LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT FINISH TO INSITU CONCRETE • Tamping of wet concrete • Levels the concrete • Removes surplus water • Removes surplus air LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT FINISH TO INSITU CONCRETE • Power-Floating • Gives very smooth finish • Protected with a layer of sand until construction work is completed LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT DAMP PROOF MEMBRANES (DPM) • Sheets of polythene (either over or under slab) • Cold-applied bitumen solution (applied to top surface of slab) • Hot asphalt (applied to top surface of slab) LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT DAMP PROOF MEMBRANES (DPM) • Prevents capillary action and not direct water pressure • Polythene are very popular nowadays • Minimum thickness of 0.3mm LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT DAMP PROOF MEMBRANES (DPM) • DPM must be lapped with DPC • Slab must dry out LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT 15% of heat is lost through ground floor THERMAL INSULATION • Insulation below slab is a common practice • Insulation is also below DPM • Must be impervious to water (closed-cell insulation such as XPS extruded polystyrene) • Note insulation on the edge of the floor LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT 15% of heat is lost through ground floor THERMAL INSULATION • Insulation below slab but above DPM • If insulation material does not have closed-cells (such as expanded polystyrene) LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT 15% of heat is lost through ground floor THERMAL INSULATION • Insulation is above slab (cold slab construction) • A wide choice of insulation materials • Screed is thicker than normal – 65-75mm • A thin slip layer can be placed between insulation and screed LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT 15% of heat is lost through ground floor THERMAL INSULATION • Insulation placed over concrete slab • Note an additional vapour control check to prevent condensation and damage to T&G chipboard LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT THERMAL INSULATION And DPM – alternative scenarios Insulation Below Floor Insulation Above Floor LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT FINISH TO SOLID CONCRETE FLOOR • Screed • To provide a level surface for tiles, carpets or thin wood flooring • 38mm thickness (thicker if spread over insulation 65-75mm) • 1:4 (cement:sand) • Must dry out completely before final finish is applied LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT FINISH TO SOLID CONCRETE FLOOR • Floating floor • Tongued and grooved chipboard • No delays as no drying time is required • Laid over 50mm insulation board • If DPM is under slab then a vapour control layer is required LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT CONSTRUCTION PROCESS Solid Ground Floors LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT MERITS OF SOLID FLOOR CONSTRUCTION • Advantages • Disadvantages • Floor completely damp proof • Damage to DPM causes damp • Floor and raft foundation can be penetration – expensive to locate the same unit and rectify • No underfloor draughts • Construction is expensive on sloping sites due to large amounts • Good fire resistance qualities of fill • Heat losses can be reduced to • Alterations to services after acceptable levels construction are difficult and very • Relatively cheap form of expensive construction on level sites • Floor is cold unless insulated LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT QUESTIONS? LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT NEXT SESSION: SUSPENDED GROUND FLOORS 38 LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT School of the Built Environment GROUND FLOOR CONSTRUCTION Dr Tabarak Ballal University Teaching Fellow Associate Professor Copyright University of Reading LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT CONTENT OF LECTURE • Floor Structures • Functional requirements • Types • Ground Floor Construction • Hardcore • Alternative design and construction techniques • Thermal insulation LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT LEARNING OUTCOMES By the end of this lecture, you will be able to: • Understand the functions of Hardcore; • Describe alternative methods for Ground Floor construction; • Describe insulation arrangement for ground floors; • Compare and contrast construction methods for solid and suspended ground floors LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT SUSPENDED GROUND FLOORS 14 LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT WHEN IS A SUSPENDED GROUND FLOOR COMMONLY USED? • When soil heave is likely. Tensile Stresses LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT WHEN IS A SUSPENDED GROUND FLOOR COMMONLY USED? • When soil heave is likely. • When hardcore is more than 600mm. • Above aggressive soils. • On poor bearing ground. • Where there is a high water table. • On steep or difficult slopes. LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT SUSPENDED GROUND FLOORS • Pre-cast concrete construction • Timber floor construction LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT TIMBER GROUND FLOORS • Supported on foundation walls ‘sleeper walls’: • Load is uniformly distributed by means of ‘wall plates’ LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT MODERN TIMBER FLOORS LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT VENTILATION • Height of the under-floor space above the surface of concrete must be at least • 75mm to the underside of any timber wall plate, • 150mm to the underside of the suspended timbers • Cross ventilation must be provided • air brick or sleeved vents must be provided in all external walls • sleeper walls must be of a honeycomb construction LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT VENTILATION LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT 15% of heat is lost through ground floor THERMAL INSULATION Suspended Floors • Boards are inserted between timber joists • Quilts are draped over timber joists • Boards are placed on pre-cast concrete floors LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT THERMAL INSULATION Suspended Floors LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT PRE-CAST CONCRETE FLOORS • Beam and Block Floors LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT PRE-CAST CONCRETE FLOORS • Beam and Block Floors LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT PRE-STRESSED CONCRETE BEAMS 16 LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT PRE-CAST CONCRETE FLOORS • The infill blocks are usually concrete blocks with a strength of 7N/mm2 • Floor is grouted with a 1:4 cement to sand to tighten up the floor and help spread load across the floor area LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT PRE-CAST CONCRETE FLOORS • A lightly reinforced concrete topping is applied to finish off the floor • This can be power-floated to provide a finish smooth enough for carpets. LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT PRE-CAST CONCRETE FLOORS • Beam and Polystyrene Floors Advantages? LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT PRE-CAST CONCRETE FLOORS • Beam and Polystyrene Floors The risk of cold bridging is avoided by producing an insulation profile which protects the bottom of the beam LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT PRE-CAST CONCRETE FLOORS • Beam and Block Floors LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT VENTILATION OF SUSPENDED FLOORS Up until 2004 underfloor ventilation was required in specific circumstances: • to remove sub-floor moisture, or • to vent toxic or combustible gases. Since 2004 it has been a requirement to ventilate all new suspended floors. LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT VENTILATION OF SUSPENDED FLOORS • Air bricks are required to ventilate the stale air from beneath the floor and also to ventilate any gas that may collect under the floor if there is a gas leak. AIR BRICK IN EXTERNAL WALL LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT VENTILATION OF SUSPENDED FLOORS • Periscopic vents do a similar function to air bricks PERISCOPIC VENT IN EXTERNAL WALL LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT MERITS OF SUSPENDED FLOOR CONSTRUCTION • Advantages • Disadvantages • Unlikely to be affected by • Deterioration will occur if dampness, ventilation is cut off, • Any deterioration can be treated and remedied, • Deterioration will occur if • Services are easy to locate and excessive dampness is present, adapt, • Floor can flex and take up small • Timber construction does not have ground movements, good fire resisting qualities, • Floor will readily accept other fixings – no time waste, • Construction is more expensive on • Relatively cheap form of level sites although economies of construction on sloped sites. scale can be achieved on large developments LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT GROUND FLOOR CONSTRUCTION • Points to remember: • Why is solid floor construction generally the preferred method? • When is suspended floor construction used? • What are the advantages and disadvantages of each - in terms of: Damp Penetration, Provision of Thermal Insulation, Construction. • How are timber joists supported? • What provisions are made to ensure adequate ventilation and crossventilation of suspended timber floors? LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT QUESTIONS? LIMITLESS POTENTIAL | LIMITLESS OPPORTUNITIES | LIMITLESS IMPACT Schoolofthe Built Environment STAIRS, INTERNAL WALLS AND FINISHES Dr Tabarak Ballal University Teaching Fellow Associate Professor 1 Copyright University of Reading LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Lecture Outline • • • Functionalrequirements Design requirements Terminology LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT KEY LEARNING OUTCOMES •To understandthe constraints imposed by the BuildingRegulation on the design and constructionof stairs and internal walls •To learn some modern types of internal and external finishes LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT STAIRS: FUNCTIONAL REQUIREMENTS Strength and Stability Fire Resistance Sound Insulation LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT TECHNICALTERMINOLOGY& DEFINITIONS • Step • Flight • series of steps between • two floors • a floor and a landing • two landings • TREAD • RISER • Rise – Vertical Dimension • Rise of a STEP • Rise of a FLIGHT LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT TECHNICALTERMINOLOGY& DEFINITIONS • Nosing • Line of Nosing • Going – Horizontal Dimension • going of a STEP • going of a FLIGHT – Also known as ‘Travel’ LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT TECHNICALTERMINOLOGY& DEFINITIONS • String (or Stringer) • Wall string • fixed to wall and housesthe inner edgesof tread and riser • Outer string • supports the outer edges of treadand riser - acts as an inclinedbeam LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT TYPES OF STAIR LAYOUT Straight Flight • Max 16 steps • 12 steps - comfortable maximum • Problem • dangerous for young and elderlyLIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT TYPES OF STAIR Where all the steps cannot be accommodated in a single straight flight, half space or quarter space landings are used. Tapered treads also enable the required number of steps to be accommodated in a confined space. LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT TYPES OF STAIR Tapered treads are used to enable steps (called winders) to turn through 900. LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT TYPES OF STAIR LAYOUT • Open Well • Landing allows • greater flexibility on planning flights • shorter flights LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT STAIRDESIGN Reduction of Impact Sound COMFORT IN USE Landings;handrails ‘Provisionof soundabsorbent finishes SAFETY IN USE Trips and falls; Incorrect fitting of treads and handrails; Headroom, rise and going. LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT SOUND INSULATION A layer of glass fibre insulation has been added to the underside of the stairs to provide sound insulation. This will be covered by plasterboard to the soffit. LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT BUILDINGREGULATIONS REQUIREMENTS • Purpose groups • Treads and risers • Rise and going • Nosing • Tapered treads • Pitch • Headroom • Flight • Landing • Handrail • Balusters LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT FACTORS AFFECTING DESIGN • Purpose groups Private Stairs Common Stairs Regular use Minimumpitch • maximum 42 degrees maximum 38 degrees Limited to 35 degrees 25 degrees Width[2 personsto pass] Domestic stairs Other building disableduse 865mm 1015mm to 1065mm > 1000mm LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT DESIGN CONSIDERATIONS For safe natural movement • Treads wide enough to comfortably house a foot • Nosing should project sufficiently > 19mm • All steps must be uniform to allowregular movement LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT FACTORS AFFECTING DESIGN • Rise and Going - Assumptions About twice as much effort is required to ascend as to walk horizontally Pace of an average person measure about 585mm LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Example • Design a stair arrangement for the following details: • Total rise = 2.280m • Total going = 2.925m NOTE: 1. Assume number of steps is 14; 2. Calculate rise of a step; 3. Calculate going of a step; 4. Check Building Regulation requirement 2R + G = 550mm - 700mm 2.28m 2.925m Courtesy: tkstairs.com FROM THE BUILDING REGULATIONS Formula 2R + G = 550mm - 700mm Permitted combinations of going and rise are given in graphs… Going:254mm - 305mm Rise: 140mm - 178mm LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT FACTORS AFFECTING DESIGN • Flights • If the number of risers between any consecutive flights exceeds 36 THERE MUST BEACHANGE IN DIRECTION OF THE STAIR BETWEEN FLIGHTS OF AT LEAST 30 DEGREES! LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT FACTORS AFFECTING DESIGN • Headroom • This is the vertical distance between the line of nosing and any obstruction over the stair LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT HANDRAILS • Should be placed at a height of 900mm to 1000mm, measuredvertically from the line of nosing to the top of the handrail • Must be provided to both sides if width exceeds 1000mm • Should be of size and shape suchthat they are easyto grip LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT AESTHETICV BUILDING REGULATIONS If children under the age of 5 are likely to use the staircase: • Vertical balustrade tubes shall be designed such that a 100mm diameter sphere cannot pass through; • Open risers should also NOT allow a 100mm diameter sphere to pass through LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Construction of Straight Flight Timber Stairs ? Connection of treads and risers to strings ? Connection of inner string to loadbearing wall ? Connection of outer string to newel posts ? Connection of newel posts to floors ? Connection of treads to risers ? Support by rough brackets and bearers ? Finishing at top of stairs ? Soffit enclosure LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Joining the Treads and Risers to the Strings A groove is formed in the strings to the profile of the treads and risers. These are tightened by a wedge and glued into place. The treads and risers are joined together by tongued and grooved joints and strengthened at the back by a triangular glue block. LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Fixing of Inner String to Wall The inner string is fixed to a loadbearing wall. Note the temporary plywood boards fixed to the treads to protect them during the construction operations. LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Joining of Outer String and Handrail to the Newel Post The outer string and handrail are morticed and tenoned into the newel post at the head and foot of the stairs. LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Outer String fixed to the Newel Post The outer string is fixed to the newel post at the foot of the stairs. The newel post is fixed to the ground floor. Note the temporary handrails which have been fixed for health and safety purposes during the construction operations. LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Outer String fixed to the Newel Post Triangular blocks are used to join the treads and risers together on their underside. Additional support is provided to the carriage of the stairs by a bracket on the centre line of the stairs and bearers to each side. The joints between the risers, treads and strings can also be seen. LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT Soffit to Underside of Stairs On completion, the underside of the stairs is enclosed by plasterboard. LIMITLESSPOTENTIAL | LIMITLESSOPPORTUNITIES | LIMITLESSIMPACT KEY LEARNING OUTCOMES • To understand the constra...