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InterfaceEngineering

Publications is aCo-Construct

initiativesupported by

Screeds withUnderfloor Heating

Guidance for a defect-free interface

Edited by Roderic Bunn and Dick Roberts

What is Co-Construct?Co-Construct is a network of five leading construction research and informationorganisations - Concrete Society, BSRIA, CIRIA, TRADA and SCI - who areworking together to produce a single point of communication for constructionprofessionals.

BSRIA covers all aspects of mechanical and electrical services in buildings,including heating, air conditioning, and ventilation. Its services to industry includeinformation, collaborative research, consultancy, testing and certification. It also hasa worldwide market research and intelligence group, and offers hire calibration andsale of instruments to the industry.

The Construction Industry Research and Information Association (CIRIA )works with the construction industry to develop and implement best practice,leading to better performance. CIRIA's independence and wide membership basemakes it uniquely placed to bring together all parties with an interest in improvingperformance.

The Concrete Society is renowned for providing impartial information andtechnical reports on concrete specification and best practice. The Society operatesan independent advisory service and offers networking through its regions andclubs.

The Steel Construction Institute (SCI) is an independent, international, member-based organisation with a mission to develop and promote the effective use of steelin construction. SCI specialises in providing advanced internet-based solutions forthe construction industry.

TRADA provides timber information, research and consultancy for theconstruction industry. The fully confidential range of expert services extends fromstrategic planning and market analysis through to product development, technicaladvice, training and publications.

For more information on Co-Construct visit www.construction.co.uk.

Screeds with Underfloor HeatingCopyright of all material is this publication rests with the Concrete Society andBSRIA. Guidance appearing in the green text boxes is copyright Concrete SocietyLtd, while all guidance in blue text boxes is copyright BSRIA.

All photographs and illustrations in this publication were provided by BSRIA andThe Concrete Society.

Authors: Dick Roberts is with The Concrete Society, and Roderic Bunn is withBSRIA.

Cover Illustration: Jason Harris.

This publication was part-funded by the Department of Trade and Industry underthe Partners In Innovation (PII) collaborative research programme. The viewsexpressed in this publication are not necessaily those of the DTI. Final editorialcontrol and publishing responsibility of this publication rested with BSRIA.

©BSRIA/The Concrete Society IEP11/2003 August 2003 ISBN 0 80622 627 1 Printed by The Chameleon Press Ltd

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system,or transmitted in any form or by any means electronic or mechanical including photocopying,recording or otherwise without prior written permission of the publisher.

1SCREEDS WITH UNDERFLOOR HEATING

Underfloor heating is an established technology. However, while the design andoperating principles are well known to building services engineers, the finerpoints of design and installation may not be known by other specialists such asstructural engineers, concrete contractors, installers and facilities managers.

Disputes commonly occur on-site where particular items of work were assumedto have been carried out by another party, and as a consequence the work wasnot completed. With water-based underfloor heating, a common interfaceproblem is between the heating element installation and the screed. If theseinterface problems are not understood, failures in system performance and/orfailure of the screed may occur.

This publication, the first in a series of similar guidance notes called InterfaceEngineering Publications, has been compiled by BSRIA and The ConcreteSociety. The objective of this publication is to provide building servicesengineers and screed specialists with consistent, interlocking advice on howwater-based underfloor heating systems and screeds fit together technically, andin relation to the work programme.

This guide largely contains material repackaged from existing BSRIA andConcrete Society guidance. Where possible this has been done word-for-wordto avoid giving conflicting or ambiguous guidance. Details of the originalpublications, relevant European and British standards and other references forfurther reading are provided at the end of this publication.

All reputable underfloor heating suppliers will provide detailed guidance onthe application of their products, and the correct ways to interface thoseproducts with screeds and floor coverings. This interface publication shouldtherefore be considered as providing the minimum requirements, with thedetailed requirements for the installation being provided by the underfloorheating supplier.

Finally, the design of a floor should be considered a top-down activity, not abottom-up activity. The choice of floor type will affect the position of joints inthe screed and therefore the positioning of the pipework. Flooring type istherefore very much a client briefing issue - not just for reasons of aesthetics,but also for reasons of system performance.

In this guide

Introduction

2 SCREEDS WITH UNDERFLOOR HEATING

How to use this guide

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Key mechanical watchpoints

� Essential mechanical engineeringmessages from the guide

Key screeding watchpoints

� Essential screeding messages fromthe guide

Also see

Links to m&e sectionsLinks to screeding sectionsLinks to common sections

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Standards for screeds and m&e design

Further reading to support this guide

Glossary for terms and definitions

Advice about the screeding requirements ofunderfloor heating systems will be found ingreen-tinted boxes. Comments marked by� link to mechanical engineering sectionslisted under also see. Comments marked by denote a link common to bothspecialisms.

Advice about the mechanical engineeringrequirements of underfloor heating systemswill be found in blue-tinted boxes.Comments marked by � link to screedingsections listed under also see. Commentsmarked by denote a link common to bothspecialisms.


Contents

Introduction 1

Client briefing 4Client briefing advice: servicesClient briefing advice: screeds

Outline design 6Services design information needed

Design inputsWarranty and guarantees

Screed information neededDesign inputs

Detailed design: services 8Mechanical information needed

Design inputsDesign outputsDesign checksDesign information for contractorsInsulation details

Detailed design: screeds 10Screeds design information needed

Design inputsDesign outputsScreed materialsSand/cement screedsCalcium sulfate and anhydrite screedsPumpable screedsDrying the screedFloor constructionFinishes

Screeds: services design issuesPre-installation issues

Installation 16Services installation issues

Pipework fixingScreed installation issues

Pressure testing and drying

Commissioning 18Services commissioning issuesScreed finishing issues

Cost model 20

Standards and further reading 21

Glossary 22


Full client briefing is crucial if an underfloor heating system is to meet users’ needs. Issues thatmust be addressed include seemingly prosaic but vital topics such as flooring type and anticipated hours ofoccupation. The response time of underfloor heating will be different for a thick carpet than for clay tiles.Irregular and/or transient occupancy may mean that a radiator-based heating system is more suitable, asfaster response may be more important than higher comfort conditions.

Client briefingIssues to address during

Client briefing advice: services

Client briefing advice: screeds

Water-based underfloor heating and coolingsystems became common in the early 1980s.They use the entire floor area of a room or azone, such as a reception or atrium, as the heatemitter (figure 1).

The large floor area means that the meanwater temperature can be reduced below thatin a radiator-based system, thus providing therequired heat output for less energy. Thetechnique gives the beneficial comfortconditions of warm feet and a cool head, aneven distribution of heat in the room, and noradiators to impinge on floor area.

Underfloor heating can also be used in acooling mode in summer. In heating mode,the maximum heating output is around100 W/m2, which generally provides adequatespace heating for buildings meeting thecurrent Building Regulations.

Most underfloor heating systems use cross-linked polyethelene (PE-X) pipework. Othermaterials used include Polybutelene (PB),polypropylene and copper. A metal/plasticsmulti-layer composite pipe is also available.Plastic pipes are used because of their ease of

Underfloor heating pipework is generally laidon top of insulation to prevent downwardthermal losses. In turn the insulation is laid onthe upper surface of the structural concretebase slab. To protect the pipes in which hotand cold water is circulated, the underfloorheating system is embedded in a sand andcement (fine aggregate) or proprietarycementitious-based levelling or wearingscreed (figure 1). A final surface such as a floorcovering of thin pvc sheet or tiles must be laidon a levelling screed. Alternatively, a wearingscreed can be used without a flooring.

The three most common types of floorconstruction are:� a solid ground floor (figure 1)� a floating floor (figure 2), which should notbe confused with a floating screed.

installation, though copper pipes have the bestthermal characteristics.

Designers should advise clients that spacesheated by underfloor systems have certainconstraints. For example, if the space is goingto be used as a library, the client must ensurethat the library bookshelves are not fixed tothe floor using shot-fired fixings. Forwarehouses, underfloor heating can be a veryeffective method of providing backgroundheating. However, it would be inappropriate tostore foodstuffs such as sugar or grain close tothe floor as the heat may damage the goods.

Designers should make clear to the clientthat an underfloor heating system has a slowresponse time, and that it requires a differentcontrol strategy to conventional heating.

Figure 1: Use this image in briefing documentation to show atypical underfloor heating construction. ©BSRIA.

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Key m&e watchpoints


Ensure all briefing documentsinclude clear and well annotateddiagrams showing the specificnature of the basic system

Ensure the client is made fullyaware of the specificcommissioning and maintenancerequirements of all options

Discuss how different floorcoverings can affect thermaloutput

Ensure guidance is available thattestifies to the reliability of thepipework, and of the controls

Ensure all briefing documentsinclude diagrams showing how abasic underfloor heating systemrelates to the screed and floorcoverings

Ensure that the client briefingdocuments cover the choice offlooring, that the screed type isappropriate to the flooring, andthe movement joints are required

Discuss how different floorcoverings can affect thermaloutput and the joint layout

Ensure the client is made fullyaware of the specificcommissioning and maintenancerequirements of all the options

Also see

Figure 8, page 16Screeding installation, page 17Figure 3, page 9Screeding advice, page 10

Standards on page 21

Further reading on page 21

Glossary on page 22

� a timber suspended/intermediate floor(this type has a sand/cement infill as opposedto a screed – figure 3, page 9).

The installation approach is the same for allsolid floor types. A layer of insulation onwhich the pipework is placed is laid on top ofthe concrete slab to reduce heat loss and tosatisfy the Building Regulations. A layer ofscreed is then laid on top of the pipework toact as the heat transfer medium, and to leveland strengthen the floor ready for theflooring, such as carpet, tiles or stone.Alternatively, the structural slab, withunderfloor heating pipework cast within it,can be laid directly onto the insulation. Thisdoes away with the need for a screed.

Floating floor installations are generallyconstructed by laying a pre-formed high-density polystyrene profiled panel on top ofthe floor slab. Pipework is laid into thepreformed profile, the screed placed, andfloor decking – chipboard or finished timberor laminate – is laid on top (figure 2).

Note that the decision to opt for anunderfloor heating system may force a changein the height of the building to accommodatethe additional depth of the screed.

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Mechanical engineering issues

Screeding issues

Figure 2: A underfloor heating system using screed over pre-formed insulation panels. ©BSRIA.

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Above: An example of timber flooring used to cover anunderfloor heating and cooling installation. The nature ofexpected pedestrian traffic will directly influence the choice ofscreed. The heavier the traffic, the stronger the screed.

The outline design stage is the point at which the main strategic decisions will be made. Thearchitect will be liasing with the client over a wide range of issues – such as floor layouts, space plans andfinishes – that will directly affect the design and construction of the underfloor heating scheme. The servicesdesigners, system supplier and specialist contractors need to get access to (and influence) this information.This is also the time where all engineers can make a valuable contribution to a discussion on floor finishes.

Outline designIssues to address during

Services design information needed

At the outline design stage the buildingservices engineer needs to get access to thefollowing information. The list is not definitive(read BSRIA AG 1/2002 Design Checks forHVAC for the full range of design checks), butgives the specific information required toensure a satisfactory interface with thescreeding specialist.

Design inputs� Architectural drawings for all zones� details of the structural frame� space plan and layout� floor to ceiling heights� position of partitions, glazing and doors� details of desired floor finishes� space uses� hours of occupancy

� transient occupancy details� desired internal design condition� target building air leakage rate (inaccordance with Building Regulations Part L2).

Note that all materials based on cementshrink as they dry; this is aggravated byunderfloor heating systems. It is important todesign for this movement with the addedcomplication that expansion and contractionmovement is associated with heated screeds.

In terms of coverings, carpet tends to be apoor choice of floor covering as it can act asan insulant. Its structure can also be adverselyaffected by heat over time.

Parquet flooring may be used, but manypeople advise against it, due to the need foran insulating felt underlay. When anunderfloor heating system is run in coolingmode, there is also the risk of condensationforming under the floor covering.

Linoleum (or similar) is considered a goodfloor covering, as are the various types ofrigid and non-rigid floor tile.

Warranty and guaranteesWarranty and guarantees need to be lookedat very closely at the outline design stage, asall sorts of claims can be made. The designerneeds to look very closely at exactly what isbeing guaranteed. For example, if a 20 yearguarantee is being claimed for the pipe, theengineer needs to know whether that wouldinclude the cost of breaking out the floor andreinstating it, as well as the costs for anydamage caused by pipework failure.

Where the underfloor heating specialist hasdesigned the complete system, any guaranteesshould include the complete system, althoughplant such as pumps and boilers willnormally have a shorter guarantee period.


Key m&e watchpoints

Also see

Detailed screed design, page 10Figure 7, page 14Commissioning of screeds, page 18



Glossary on page 22

At the outline design stage the underfloorheating supplier and screeding specialist needaccess to the following information. Nodecision should be taken on the type orthickness of the screed until this informationhas been gathered and shared with the otherpartners in the design process.

Design inputs� Architectural drawings for all zones� details of the structural frame� space plan and layout� position of partitions, glazing and doors� details of desired floor finishes; for exampletimber, tiles (stone, ceramic or clay), carpettiles (and their flexibility)� space uses� nature of pedestrian traffic (heavy or light)� the desired internal design conditions.

Note that all materials based on cementshrink as they dry; this is aggravated byunderfloor heating systems as heated screedswill dry more than non-heated screeds, andwill therefore shrink and crack more. It isimportant to design for this movement andensure that the drying process is very carefullyplanned and tightly controlled.

Cracks and joints in heated screeds will belive owing to expansion and contractionduring system operation.

Flooring choice depends on the context. Athick flooring material (high thermal inertia)is recommended for buildings where therewill be no abrupt changes in latent loads.

A thin flooring (low inertia) allows a fasterresponse time, which is advantageous inhouses, for example, where there can beabrupt changes in loads from people enteringand leaving rooms, or from changes in solarloads.

Screed information needed

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Read BSRIA AG 1/2002 DesignChecks for HVAC for the full rangeof design checks

Read BSRIA 30/2003 StandardCalculations for Building Services forguidance on calculating thermalrequirements

Design for the movement ofdrying cementitious materials, andaccount for expansion andcontraction during system use

Gather product information fromunderfloor heating suppliers andcross-check their system designrequirements

Gather a full set of architecturaldocumentation before deciding onthe type or thickness of screed

Design for the movement ofdrying cementitious materials, andthat required by the flooring, andaccount for expansion andcontraction during system use

Cross-check with the mechanicaldesign engineer on the screedingrequirements for all theproposed underfloor heatingsuppliers

Advise on a flooring system thatwill be able to cope withexpansion and contraction of theheated screed

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Screeding issues


Detailed design: servicesIssues to address during

Mechanical engineering information

The detailed design stage is where all the building services, structural and screedinginformation must come together in a coherent manner. The building services engineer must sharethe operational requirements of the underfloor heating system – either wholly or partially supplied by theunderfloor heating supplier – with all the specialists involved on the project. Full communication of all systemrequirements is the key to a successful interface between the building services and the structure.

The following mechanical design informationis required at the detailed design stage (inaccordance with BSRIA AG1/2002 DesignChecks for HVAC).

Design inputs� Zone heating loads� design flow and return temperatures� the internal design condition.

Design outputs� A schedule of zones giving outputrequirements, flow rates, maximum floortemperatures, and connection and valvesa statement of a commissioning strategy� relevant specification clauses.

Design checks� Check that the floor surface temperature issatisfactory for the space� specify adequate insulation under the entiresystem to reduce casual heat loss to the floorbelow� specify an insulating strip around theperimeter of concrete floors to reduce coldbridging, as per the supplier’s instructions� check that the depth of floor screed issufficient to accommodate pipework and thatit meets the requirements of the relevantBritish Standard. BS 8402 recommends notless than 75 mm for a cement/sand screed and50 mm for a pumpable screed� check that the system suppliers’ materials,such as plastic or multilayer pipe, will not beadversely affected by the concrete� check that the chosen flooring is suitablefor underfloor heating, such as carpetstypically with an insulation value less than0�15 m2K/W, adhesives suitable for up to 40�C,and timber with moisture content below 10%.

Design information for contractorsAll the contractors involved in an underfloorheating installation need to understand thebasic principles of the technology in order tointegrate it properly and efficiently into theoverall construction process.

The main contractor needs to avoid damageto the pipework by arranging for the screed tobe laid as soon as possible after the pipeworkis installed and commissioned.

The main contractor should also beinformed that the heating must not be used todry out the structure. A lengthy running upperiod will be needed to bring the systeminto use. This needs to be accommodated inthe programme and explained in the detaileddesign documents. It should also be clearlyexpressed in the instructions to the contractor.

The respective responsibilities of therelevant contractors and the underfloorheating specialist also need to be made clear atthe tender stage, and written into all tenderdocumentation to ensure that tenders can beevaluated on the same value and cost basis.

Insulation detailsInsulation is generally applied beneath thecircuit pipework to stop downward heat lossin excess of the maximum permitted loss of10% as stated in BS EN 1264-2.

Three insulating materials are available:expanded polystyrene, extruded polystyrene,and polyurethane. Polyurethane andpolystyrene are available in a number ofdensity grades, each providing different levelsof mechanical strength and resistance topressure. For commercial and industrialsituations, the heavier grades may be required.This should be discussed with the architect.

Most manufacturers propose expanded

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Commissioning, page 18Finishes, page 19Screed installation, page 17Commissioning, page 19Figure 2, page 5



Glossary on page 22

The main contractor needs to avoiddamage to the pipework by ensuringthe screed is laid as soon aspossible after the pipework isinstalled and commissioned

All persons involved in the contractshould be informed that the heatingmust not be used to dry out thestructure

A lengthy running up period will beneeded to bring the system into use

Key m&e watchpoints


Also see

Check that the temperature of thefloor surface is satisfactory

Specify adequate insulation underthe entire system to reduce casualheat loss to the floor below

Specify an insulating strip aroundthe perimeter of concrete floorsto reduce cold bridging

Check that the depth of floorscreed is sufficient toaccommodate pipework

Check that the heating materialsare not adversely affected by thescreed

Check the type of flooring to seeif it requires movement joints asthis will affect the layout of thepipework. Reflective cracking inthe flooring may otherwise occur

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Figure 3: A sand/cement infill, in this case within an intermediate/suspended floor construction. ©BSRIA.

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polystyrene as the insulating material, eventhough polyurethane has a lower thermalconductivity (0�021 W/mK for polyurethaneand 0�033 W/mK for expanded polystyrene).Expanded polystyrene is cheaper and hasbetter acoustic properties. The thickness of theinsulating layer is generally 20-40 mm. Abarrier should be provided over the insulationto prevent moisture and fresh screed materialspenetrating the joints between the insulation.This can also act as a secondary vapour barrier.

Insulation can be supplied with pre-formedprofiles to hold the pipework. This isgenerally used for floating-floor installations(figure 2). Pipework is laid into the pre-formed profile and the floor decking –chipboard or finished timber or laminate – islaid on top.

Alternatively, flat sheets are used and thepipework secured to the insulation by a clipsystem. A sand/cement screed is laid over thepipework to a depth of about 75 mm to forma solid floor on which flooring can be placed.

Intermediate/suspended floor constructionalso uses flat insulation sheeting on which thepipework is secured. Either a sand/cementinfill is placed around the pipework or thespace between the flooring (timber productsupported on floor joists) and insulation left asan air gap. While this provides a degree ofthermal mass similar to a solid floor and raisesthe floor’s heat transfer, the implications of theextra weight must be considered (figure 3).

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Detailed design: screedingIssues to address during

Screeding design information needed

The detailed design stage is where all the building services, structural and screedinginformation must come together in a coherent manner. The screeding contractor must share theinstallation requirements of the screed with the services consultant and the underfloor heating supplier. Fullcommunication of all system requirements is the key to a successful interface – and zero defects – betweenthe structure and the building services.

The following screeding design information isrequired at the detailed design stage. It is vitalto agree the consistent use of terminology(such as levelling or wearing screed) with them&e design engineer and underfloor heatingsupplier/contractor (Table 1).

Design inputsThe designer should provide and describe thetype of flooring, whether it is flexible, ormade of tiles, carpet tiles, stone or clay tiles.

The locations of protrusions through theslab and the location of any columns andinsets should be identified and described tohelp define the location of joints. Thisinformation should be transferred onto thedrawings used by the underfloor heatingsupplier/sub-contractor, and the m&econsulting engineer.

The screeding specialist should obtaininformation from the m&e designer about thepipework fixing details - whether it is to theinsulation or to the concrete base. Thescreeding specialist should also obtaininformation about services access points, suchas required for pipework manifolds.

Design outputsIn addition to the m&e design outputs, thefollowing design outputs should be providedby the architect/specifier to all partners:� Floor construction, thicknesses, jointlocation and shrinkage characteristics� details of the proposed (or choices of)screed material, such as cementitious, calciumsulfate or other proprietary screed� the proposed flooring material� the screed surface finish in relation to theflooring� relevant standards and codes of practice.

Screed materialsA screed is defined as a layer of well-compacted material applied to a structuralbase or other substrate, finished to adesignated level.

There are differences in screed terminologythat are commonly used both within the UKand abroad. It is therefore important that anyinformation generated by the design teamrelating to screeds fully conveys the intendedend use.

BS 8204-1: 2002 defines the followingscreed types:� Levelling screed: screed suitably finished toobtain a defined level and to receive the finalflooring and� wearing screed: screed that serves as aflooring.

In this guide the term screed relates to alevelling screed. Additionally, as the majorityof heated screeds are laid on an insulatinglayer, the term floating screed is used, whichis a screed laid on an acoustic and/orinsulating layer and completely separatedfrom other building elements, such as wallsand pipework.

Other definitions relate to the materialitself. Fine concrete screeds consist of sand/cement material that contains a proportion ofaggregate of nominally 10 mm single size,while a sand/cement screed contains a sandof up to a nominal 5 mm in size.

The use of proprietary products may nowreduce the risk of cracking, curling, andhollowness.

Sand/cement screedsThe majority of heated screeds are madewith cement and sand mix. A semi-dryconsistency is necessary to enable the screed

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Glossary, page 22; Table 1 aboveMechanical information, page 6Glossary page 22Figure 5, page 13



Glossary on page 22

Agree the consistent use ofterminology (such as levelling orwearing screed) with the m&edesign engineer and underfloorheating contractor

Define the location of joints. Thisinformation should be transferredonto the drawings used by theunderfloor heating supplier/sub-contractor

Provide details of the proposedscreed material to the heatingdesigners

Specify whether a levelling orsmoothing compound may berequired


Also see

to be finished to a degree of accuracy. A semi-dry consistency of screed demands goodcompaction and high levels of workmanshipto ensure soundness. However, a high surfaceaccuracy may be difficult to achieve, and afurther levelling or smoothing compound maybe required.

For floating screeds a minimum thickness of75 mm is required for commercial installations(65 mm for domestic installations), with aminimum thickness of 25 mm over the pipes(BS 8204-1).

Fine concretes are commonly used inscreeds thicker than 50 mm. They can easecompaction effort and potentially reduceshrinkage. For floating screeds a minimumthickness of 75 mm (for commercialapplications) is required (table 1). Theproportion of aggregate incorporated in thescreed is necessarily low.

Although the thermal insulating propertiesof no-fines screeds are three to four timesbetter than a cement/sand screed, it is notsufficient to use a no-fines screed as aninsulation layer without the use of additionalinsulation. Its thermal efficiency is notsufficient to replace polystyrene insulation in aheated floor.

Calcium sulfate and anhydrite screedsCalcium sulfate (anhydrite and semi-hydrite)screeds are traditional hand-laid screeds.

Synthetic anhydrite is a by-product of thechemical industry. When processed it forms abinder similar to gypsum that can be usedwith aggregates and admixtures to form adense screed material. Its advantages are:� A low drying shrinkage� the free water content is chemicallycombined and therefore the drying time is less �

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Screeding issues��

Table 1: The properties of different screedmaterials used with underfloor heatingsystems. Domestic measurements are inbrackets. ©The Concrete Society.

lairetaMmuminiMssenkciht

mm

revorevoCkrowepip

mm

dradnatS

lanoitidarTsuoititnemectnemec/dnas

)56(57 52 1-4028SB

muiclaclanoitidarTetaflus

04 53AIRIC

481tropeR

elbapmuPgnihtooms-flesetaflusmuiclac

)53(04 52 7-4028SB

elbapmuPgnihtooms-fles

suotitnemec)53(04 51 7-4028SB

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Detailed design: screeding 2Issues to address during

than sand/cement screeds� good density and low coefficient of thermalmovement.

A major disadvantage of synthetic anhydriteis its intolerance to moisture. However, theability to lay large areas with little risk ofcracking or curling, and with relatively lowthermal expansion, makes synthetic anhydritea suitable material for heated screeds.

For floating screeds the minimum thicknessis 40 mm. Ferrous reinforcement should notbe used due to the risk of corrosion.

Pumpable self-smoothing screedsPumpable screeds are covered in BS 8204-7:2003. As these are proprietary systems, it isessential that the advice of the manufacturer orsupplier is sought. Pumpable screeds are basedon special cementitious or anhydrite/semi-hydrite binders with selected aggregates,additives, polymers and admixtures which,when mixed with water, produce a workableflowing material which has self-levelling orself-smoothing properties. The consistencyallows the materials to be pumped.

Cement-based pumpable screeds tend tohave a restriction on thickness due to the heatof hydration emitted and are generally notused for floating screeds. The minimumthickness of a calcium sulfate-based screedmaterial is 40 mm for commercial use, and 35mm for domestic applications (see table 1).

Heating pipes should be secured firmly toprevent flotation in the wet screed. Theflowing material must also be prevented fromgetting between the insulation boards. Theminimum thickness above the pipes should be35 mm for calcium sulfate screeds, 25 mm forpumpable calcium sulfate screeds, and 15 mmfor cement-based pumpable screed (table 1).

Drying the screedHeating should only be applied accordingthe instructions supplied by the underfloorheating system. For a cement-based screedthis should be after it has cured and dried;for calcium sulfate, heating should only beapplied seven days after laying.

In all cases the screed should be heatedvery slowly to their operating temperatureand maintained for several days beforecooling to room temperature, but not below15�C, before installing flooring.

Note that the usual operating surfacetemperature is 27-29�C but can be as high as35�C. Higher temperatures can adverselyaffect the floor covering and the stability ofcalcium sulfate screeds.

Floor constructionWhile the design of a floor should be a top-down process, rather than bottom up (figure5), it is vital that the concrete base is notuneven. If it is uneven, the insulation maycollapse causing cracking of the screed(figure 6).

All materials based on cement shrink asthey dry – a characteristic that is aggravatedby underfloor heating systems. Materials alsotend to expand and contract with changes intemperature, and this is also aggravated byunderfloor heating systems. This drying,shrinkage and thermal movement causes thescreed to crack. The specifier must think ofthis at the design stage.

Due to this shrinkage and movement,wearing screeds are generally specified withmovement joints at set positions. Thespecifier should detail these joints at the startof the contract.

The type of flooring will affect the

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Services installation, page 16Services commissioning, page 18Services design, page 8



Glossary on page 22

Also see

Figure 6: If the concrete base is uneven,the insulation may bridge undulations.When the screed load is applied theinsulation may collapse causing crackingof the screed. The revision to BS 8204will require the level to be better than3 mm under a 2 m straight edge.Tamped bases may need levelling or aregulating layer prior to the insulationbeing placed. ©The Concrete Society.

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positioning of joints in the screed andtherefore the positioning of the pipework.Guidance for the installation, positioning andspacing of joints in screeds is specified inBS 8204-2.

FinishesLevelling screeds, which are specified to BS8204-1 are either jointed or unjointeddepending upon the flooring to be laid onthem. Thin flexible floorings such as vinylsheet, tiles or carpet are usually laid on screedswithout joints.

With some floorings such as natural stoneand clay tiles, the flooring itself requiresmovement joints. These movement joints,detailed in BS 5385, must be to a depth onethird the screed thickness and must also passthrough the levelling screed. In such cases theposition of the movement joints in theflooring and levelling screed will affect thelayout of the underfloor heating system.

Where the flooring itself does not normallyrequire joints, such as vinyl sheet, problems

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Screeding issuesBe familiar with the propertiesof the screed and understandtheir limitations

For pumpable screeds, be awareof the minimum screed cover topipework – 40 mm forcommercial, and 35 mm fordomestic premises

Scheduling should take accountof the timing for pipeworkcommissioning, screed curing,screed drying and flooringrequirements


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Figure 5: Cement/sand or fine concrete construction. ©The Concrete Society.

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Detailed design: screeding 3Issues to address during

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Screeds: services design issues

Figure 7: Cracks caused by drying shrinkage may be live due toimposed thermal movement, and may cause ripples in thinflooring. This could be exacerbated by heat concentrating locallythrough the crack, softening the sheet flooring. ©The ConcreteSociety.

The choice of flooring depends on theunderfloor heating application.

A thick flooring (high thermal inertia) isrecommended in buildings where there areno abrupt changes in latent loads. A thinflooring (low inertia) allows a faster responsetime, which is useful in houses, for example,where there can be abrupt changes in loadsfrom people entering and leaving the rooms,or from changes in solar loads.

The generally recommended sand/cementscreed cover over pipework is 25 mm. Thisassumes an overall screed depth of 65 mm fordomestic use and 75 mm for commercial use.This will vary depending on the size ofpipework, but should meet the relevant BritishStandards for screed thickness (see Table 1).

The following measures are needed tocontrol expansion:� A peripheral joint of expanded polystyreneall around the slab� reinforcement can help to reduce the widthof cracks and prevents lipping. It should beplaced across pipework within the 25 mmcover thickness and extend at least 150 mmeither side (figures 5 and 7).� movement joints – definitive guidance onlocation of joints (whether expansion,contraction or induced) is difficult as itdepends on the structural layout of thebuilding, the flooring joint pattern, and theheating circuit layout. BS 1264-4 recommendsjoints in stone and ceramic finished screedsevery 40 m2, of a maximum length of 8 m andan aspect ratio of 2:1.

To avoid fractures, a specific joint must beplaced every 8 m across the floor, but this jointneed only be cut into the screed to a depthone third its thickness. It should therefore notaffect the pipe circuit. Regarding the circuit

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arise due to the cracks which occur withinthe screed being live cracks (in other wordsopening and closing) due to the imposedthermal movement.

The movement in the cracks created bythermal expansion and contraction can causedistress and usually stretching and rippling ofthe flooring over the cracks (figure 7).

To prevent such disturbance to the flooringsystem, movement joints must be detailed inthe levelling screed. Again, these joints, theflooring joints and the layout of the panels ofunderfloor heating must coincide.

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Base slab

Screed

Insulation


Pumpable screeds, page 12Table 1, page 11Figure 5, page 13



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pipes, only the supply and return pipesshould pass through movement joints.

The position of all joints must be definedat the project stage and shown in thedrawings. The planner can therefore designthe pipe circuits in a way that only involvessupply pipes crossing movement joints.

BS EN 1264 Floor heating – systems andcomponents, Part 4: Installation states:

In the case of heating screeds of type A and C,movement joints and perimeter joints shall only becrossed by connecting pipes and only in one level.In this case, the connecting pipes shall be coveredwith a flexible tube of some 0�3 m in length.

In other words, the pipe is debonded for300 mm on either side of the joint.

Pre-installation issuesIt is easier and cheaper to resolve as manyissues as possible at the design stage ratherthan on site. For example, the entire floorarea must be free of operatives from all othertrades while the pipework is installed.The building should also be wind and water-tight before installation of the underfloorheating begins. The contract administrator orarchitect will have to develop a programmethat allows other trades to work in other areasduring pipework installation, but this mayrequire the programme to be extended.

It needs to be impressed upon the clientthat there will come a point in the designprocess – earlier than they are used to onmore conventional projects – when no morechanges to the general structure and floorplan layout can be accommodated with theunderfloor system design. Once the floorscreed is laid, it is difficult and expensive tomake major changes and still expect theunderfloor heating system to work effectively.


Screeding issues

The position of all joints must bedefined at the project stage andshown on the drawings. Thisplanning should involve themechanical planner and screedingcontractor as well as the architectto ensure continuity. Note that itis not possible to providedefinitive guidelines for jointfrequency

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Ensure that the chosen floorcovering is suitable for thedesired response time of theunderfloor heating system

Check that the edge insulation isof the correct specification to actas an expansion element

Provide design details (movement-absorbing materials and joints)that control expansion

Ensure the client is aware that anymajor building alterations late inthe project may compromise theeffectiveness of the underfloorheating system

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InstallationIssues to address during

Services installation issues

The quality of the installation will ultimately determine the performance of the system.It is very important for all the contractors involved in an underfloor heating installation to understand theprinciples of the technology, so it can be integrated properly and efficiently into the construction process.The m&e and screeding contractors will need to give extra thought to the sequencing of other works on-site to avoid delays and lost production while the pipework is being laid.

Careful thought is needed as to who will beresponsible for issuing instructions to theunderfloor heating specialist. It is in everyone’sinterest to make sure that this is clearlyunderstood before any work starts on site, asinstructions from the wrong source can beexpensive and lead to delays.

Once the order has been placed, theunderfloor heating specialist should provide adetailed programme covering the entireunderfloor heating installation works,including adequate notice periods for testing,witnessing, inspection and commissioning.

The main contractor will need to give extrathought to the sequencing of other works on-site to avoid delays and lost production whilethe pipework is being laid.

Before the works begin, the tenderer/contractor should provide full sets of workingdrawings for approval by the client, architect,project manager, quantity surveyor orengineer, and no works should begin untilapproval for such drawings has been obtained.

The entire floor area must be free ofoperatives from other trades while thepipework is installed. The building should beboth wind and watertight before installation ofthe underfloor heating pipework begins.

The main contractor needs to avoid damageto the pipework once it is installed, byarranging for the screed to be laid as soon aspossible after installation of the pipework.

Pipework fixingThe pipework can be fixed by a number ofmethods, such as the use of a rail onto theinsulation, with securing clips at set distancesinto which the pipework is laid out.

Another method is to lay the pipework outin the desired pattern and simply push a clip

Figure 8: Incorrect and correct ways to apply meshreinforcement. Note that the mesh is not used to anchor thepipework. ©The Concrete Society.

over the pipe into the insulation. A thirdmethod is to fix the pipe to a steel mesh. Thisprovides flexibility, but can take longer toinstall. The screed may be specified as needingreinforcement by means of steel mesh. Thiswould not be a pipe-fixing steel mesh (figure 8).

A layer of screed is then laid on top of thepipework to act as the transfer medium, and tolevel and strengthen the floor ready for thefinal flooring of carpets, tiles or stone.

Note that pipework fixings must be carefullyselected to ensure that they do not endangerthe integrity of the insulation or othermaterials. The contractor will also need to betold that the heating must not be used to dryout structure as a lengthy running up period isrequired to bring the system into use. Thisneeds to be allowed for in the programme.

After the underfloor heating pipe has beenlaid, it should be subjected to a pressure test attwice the working pressure (BS EN 1264-4).While BS EN 1264-4 requires testing at aminimum of 6 bar, underfloor heatingsuppliers recommend testing up to 6 kg/cm2,maintained for 24 h. This pressure should alsobe maintained during laying of the screed.

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Screeding installation issues

Any irregularities in the base must also belevelled as necessary in order to ensure thatthe insulating panels sit flat. This will preventthe insulation bridging a depression and thefloor collapsing under load (page 12, figure 6).If reinforcing mesh is required, it should beinstalled as shown in figure 8 opposite.However, it is very unlikely that reinforcementwill be necessary.

A screed is generally finished with a woodfloat, with the level assessed under a straightedge (3 mm in 2 m as in BS EN 8204amended in 2003).

The surface finish required of a screed isdependant on the flooring to be applied.Many floor coverings are fixed with adhesiveor primer. These must be compatible with thescreed especially calcium sulfate or proprietarytypes of screed.

Pumpable screeds tend to find their ownlevel, but are sometimes agitated with a specialtool to assist the smoothing.

The internal partition walls and anydrainage system must be completed. The zoneunder the distribution manifolds must befinished. It is also advisable for the exteriordoors and windows to be installed if the workis being done during a season where there is arisk of frost.

Pressure testing and dryingAfter the underfloor heating pipe has beenlaid, it should be subjected to a pressure test attwice the working pressure. This pressureshould be maintained during the laying of thescreed.

The screed should be protected from rapiddrying by curing for at least ten days. It shouldalso be protected from draughts and directsunlight.

BS 1264-4; timings, page 19Figure 6, page 12Screed finishing, page 19Services commissioning



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Screeding issuesEnsure the underfloor heatingsystem supplier provides adetailed programme covering theunderfloor heating installation,including testing, witnessing,inspection and commissioning,including screed drying time.

Ensure the contractor providesfull sets of working drawings forapproval

Ensure that the building is windand watertight before installationof the underfloor heatingpipework begins

Ensure that pipework fixings donot endanger the integrity of thevapour barrier

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Level the base to ensure that theinsulating panels sit flat. This willprevent the insulation bridging adepression

Ensure the screed is protectedfrom rapid drying by curing for atleast seven days.

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CommissioningIssues to address during

Services commissioning issues

The commissioning period is a critical to the success of an underfloor heating system.Commissioning not only involves testing the heating system, pipework and the connections, but isalso the process by which the screed is dried and cured. Timing, temperature and measurement arevery important to the process. It is not simply a case of switching the system on and walking away.

With a screeded floor system it is essential thatthe screed is allowed time to dry outthoroughly, and that such time is allowedwithin the construction process. Failure ofscreeds due to insufficient moisture controlcan result in very expensive and disruptiveremedial works. The amount of time requiredfor screed to dry out thoroughly will dependon the type and thickness of screed to be used.

After the underfloor heating pipe has beenlaid, it should be subjected to a pressure test attwice the working pressure. Underfloorheating suppliers usually recommend testingto a minimum of 6 kg/cm2, maintained for 24 h.

The screed should be protected from rapiddrying (it must be cured) for at least threedays. It should also be protected fromdraughts and direct sunlight. After this period,there are several drying-out options given inthe current guidance.

BS 8204-1 recommends that the screedshould be allowed to dry out as slowly as

practicable after curing to reduce the risk ofcurling. Accelerated drying must not be used.

Waiting for the screed to dry out dependson the ambient conditions. For sand/cementscreeds to BS 8204-1, it is suggested as oneday for each millimetre of thickness of the first50 mm, followed by an increasing time foreach millimetre above this thickness.

BS EN 1264-4: 2001 suggests that sand/cement screeds should not be heated for atleast 21 days after laying. Although Anhydritescreeds should not be heated for at least sevendays after laying, the screed manufacturer mayindicate otherwise. The temperature of thewater entering the circuits should be not morethan 25�C (or 15�C above the temperature ofthe unheated floor screed) for at least threedays, and then raised to the maximum designtemperature and maintained for a further fourdays.

Once the screed has dried and the heatinghas been tested, the flooring system may belaid. Floorings need to be acclimatised to siteconditions prior to laying, and such treatmentdepends on the material. Manufacturers’instructions should always be followed.

The possibility of damage to the flooringover joints and cracks, such as the rippling ofthin sheet, can be caused by the reversal ofcurling as the moisture redistributes once theflooring is laid. This can be reduced bycovering the screed with impermeablesheeting for seven days before laying flooring.

The services contractor should resist anyattempts by other contractors to subject thescreed to integrity testing, such as crushingresistance as laid down in BS 8204-1: 2002.The integrity test could cause damage tounderfloor heating pipework if the test iscarried out on a very poor screed.

Above: An effective way of checking the quality of the installationis to carry out a thermographic survey. Thermographic surveysare available from BSRIA. ©BSRIA.

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Screed finishing issues

A screed needs to be cured for at least threedays to prevent it drying out rapidly as themoisture within the screed is required for thehydration of the cement to ensure that thescreed reaches its full strength. BS 8204-1recommends that the screed should beallowed to dry out as slowly as practicableafter curing to reduce the risk of curling.Accelerated drying must not be used.

Clause 6.1 in BS 8204-1 suggests anapproximate drying time, as drying isinfluenced by ambient conditions, screedquality, thickness and surface finish. Thisperiod for sand/cement screeds is suggestedas one day for each millimetre of thicknessfor the first 50 mm, followed by an increasingtime for each millimetre above this thickness.A screed of about 50 mm could be expectedto dry under good conditions in about twomonths. A 75 mm thick screed wouldprobably take around three months.

It has been suggested that when a screed isfirst heated it drives off water in the top of thescreed, but moisture remains trapped belowthe pipes. The screed must be allowed to coolto room temperature (not below 15�C)before flooring is laid.

During this period of lower temperature,the moisture migrates to the drier regions.Consequently when the heating is nextswitched on, this residual moisture is drivenoff, possibly disrupting the flooring. This isespecially true if the flooring is impermeablesuch as vinyl flooring. This could result inbubbling of the flooring. It is recommendedthat further cycles of heating and cooling arecarried out before laying the flooring.

Before a flooring can be laid, the screedmust be at a moisture level compatible withthe chosen floor covering and its adhesive.

BS EN 1264-4 cl. 4.3 (see Standards)BS 8204-1 cl. 6.1(see Standards)



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The specialist contractor/commissioning contractor shouldprovide one complete and accurateset of as fitted drawings. For thescreed interface, these shouldcover:� the position of all items of plantand equipment that are associatedwith the installation� the routes and sizes of allpipework, including that buriedwithin the floor� the position of all items ofequipment including thermostats,manifolds, valves and controls, anddetailed diagrams of each manifoldclearly identifying each circuit, andwhich areas are served by each

The temperature of the waterentering the circuits should beraised slowly to between 20�C and25�C for three days, and then raisedslowly to the maximum designtemperature and maintained for afurther four days

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Calculate the required drying timefor sand/cement screeds based onone day for each millimetre ofthickness for the first 50 mm,followed by an increasing time foreach millimetre above this thickness

Proprietary screeds dry at differentrates - see manufacturers’instructions

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The actual costs associated with an underfloor heating system and screeddepends on the context. However, the fixed costs of the heating system and theinstallation works are relatively straightforward. The following cost model has been preparedby the cost research departments of Mott Green & Wall and Davis Langdon & Everest,specialists in the cost planning and cost management of building services installations.

Cost model

Costs provided by underfloor heatingcompanies need to be carefully examined tofind out exactly what is included. In somecases insulation will be provided by theunderfloor heating contractor, whereas inother installations it may be provided by thebuilder.

The following costs are indicative currentcosts for underfloor heating and screedsbased upon medium sized projects with anunderfloor heated area of between 300 m2

and 2000 m2.The rates shown are applicable to

competitively tendered commercial contractsin Outer London in July 2003.

The underfloor pipework installation ratesinclude for the mechanical and electricalcontactor’s preliminaries. Main contractor’spreliminaries are also included at 12%.

Excluded costsThe cost rates for the underfloor heating andscreed cost model exclude the followingelements:� Final flooring finish or wearing screed� acoustic or rubber sound absorptionmatting� any allowance for above average floorloadings� part-load charges for small quantities ofpumpable screed� main items of mechanical and electricalplant and primary distribution� any interface with a computerisedbuilding management system� builder’s work in connection with theunderfloor heating system (for example,cutting holes and cupboards for pumpcontrol units)� contingencies� VAT.

The following mechanical and electricalunderfloor heating system data are presentedper square metre area of screed.

Mechanical and electrical cost dataUnderfloor pipework installation: £19.50/m2

Pump control unit with localcontrols (manifold): £8.50/m2

Electrical involvement fromlocal power supply: £3.50/m2

Sub-total underfloorheating cost £31.50/m2

Main contractor preliminary coston m&e underfloor heating (12%): £3.80/m2

Screeding cost dataThe following screeding cost data arepresented per square metre area of screed.

Cement sand screed (cement/sandratio 1:3) 75 mm thick: £17.00/m2

Reinforcement (D49/98): £3.00/m2

Underfloor insulation deck(80 mm thick): £12.50/m2

Separating layer (500 g polythenesheet): £0.50/m2

Tamped finish to concrete base: £0.70/m2

Sub-total for cement andsand screed £33.70/m2

Total system cost (inclusive of abovem&e and screeding costs) £69.00/m2

Alternative screed ratesFine concrete screed (75 mm thick): cost ascement sand screed.Pumpable screed, anhydrite orhemihydrite (75 mm thick, reinforcementnot required): £32.70/m2

Total using pumpable screed £68/m2


Mechanical engineering standardsConcrete screeding standards

Standards

Further reading

BS 7291-1: 2001. Thermoplastic pipes and associated fittings forhot and cold water for domestic purposes and heating installationsin buildings. General requirements.

BS 7291-2: 2001. Thermoplastic pipes and associated fittings forhot and cold water for domestic purposes and heating installationsin buildings. Specification for polybutylene (PB) pipes and associatedfittings.

BS 7291-3: 2001. Thermoplastic pipes and associated fittings forhot and cold water for domestic purposes and heating installationsin buildings. Specification for cross-linked polyethylene (PE-X) pipesand associated fittings.

BS EN 1264-1:1998. Floor heating – Systems and components.Definitions and symbols.

BS EN 1264-2: 1998. Floor heating – Systems and components.Determination of the thermal output.

BS EN 1264-3: 1998. Floor heating – Systems and components.Dimensioning.

BS EN 1264-4: 2001. Floor heating – Systems and components.Installation.

BS EN 1264-4: 2001. Floor heating – Systems and components.Installation.

DIN 4725-4. Hot water floor heating systems – Design andconstruction (plus Amendment A1).

SANDS J. Underfloor heating systems, the designers’ guide AG12/2001 BSRIA 2001. ISBN 086022 5288.

SANDS J. Underfloor heating systems, an assessment standard forinstallations AG 13/2001 BSRIA 2001. ISBN 086022 5836.

Energie Guide: Floor heating and cooling systems, applications oflow temperature heating and height temaperature cooling.Thermie project DIS/1522/97/FR. BSRIA 2002.

BS EN 1264-4: 2001 Floor heating. Systems and components.Installation.

BS 5385-3: 1989 Wall and floor tiling. Code of practice for thedesign and installation of ceramic floor tiles and mosaics.

BS 5385-4: 1992 Wall and floor tiling. Code of practice for tilingand mosaics in specific conditions.

BS 5385-5: 1994 Wall and floor tiling. Code of practice for thedesign and installation of terrazzo tile and slab, natural stone andcomposition block floorings.

BS 8203:2001 Code of practice for installation of resilient floorcoverings.

BS 8204-1: 2002 Screeds, bases and in situ floorings – Part 1:Concrete bases and cement sand levelling screeds to receivefloorings – code of practice.

BS 8204-2: 2002 Screeds, bases and in situ floorings – Part 2:Concrete wearing surfaces – code of practice.

BS 8204-3: 1993 Screeds, bases and in situ floorings – Part 3:Code of practice for polymer modified cementitious wearingsurfaces.

BS 8204-4: 1993 Screeds, bases and in-situ floorings. Code ofpractice for terrazzo wearing surfaces.

BS 8204-6: 2001 Screeds, bases and in-situ floorings. Syntheticresin floorings. Code of practice.

BS 8204-7: 2003 Screeds, bases and in-situ floorings. Pumpableself-smoothing screeds. Code of practice.

Gatfield M J, Screeds, flooring and finishes – selection, constructionand maintenance Construction Industry Research andInformation Association (CIRIA) 1998, ISBN 0 86017 496 4.

Pye P & Harrison H W, Building Elements: Floors and flooring –performance, diagnosis, maintenance, repair and the avoidance ofdefects BRE 1997, ISBN 1860811736.

Chaplin R G, Floor levelling screeds, British Cement Association(BCA) 1997, ISBN 0 7210 1506 9.

Designers and contractors should always follow the guidance laid down in prevailing standards.The standards governing screeding and underfloor heating are generally compatible, but variations in adviceexist, especially where the timing of operations are laid down. Such discrepancies should be identified andresolved in discussion between the screeding specialist and the underfloor heating supplier.


Glossary

Building services terms

Screeding terms

Screed Layer of material laid in-situ directly onto a base or intermediate layerfor one or more of the following purposes

� to obtain a defined level (levelling screed)� to provide a wearing surface (wearing screed)� to carry the final flooring.

Floating screed Screed laid on an acoustic and/or separating layer and completelyseparated from other building elements (not a floating floor).

Pumpable, self-smoothing Proprietary screed that is mixed into a fluid consistency, that can bescreed transported by pump and will flow sufficiently (with or without some

agitation of the wet material) to give the required accuracy of leveland surface regularity.

Curing The process of preventing the loss of moisture from the young screedwhile maintaining a satisfactory temperature regime, so that thecement hydration process can be maximised.

Curling Vertical distortion at the edges of a two-dimensional flooring due todifferences in temperature or moisture content throughout itsthickness.

Drying The process of losing excess moisture from a screed, after asufficient curing period, through evaporation.

Underfloor heating A system of metail or plastic pipes laid in circuits, in a floor screed orbelow a timber floor system, through which hot water is passed. Someunderfloor heating systems use electric elements.

Cross-linked polyethelene Cross-linked polyethelene (PE-X) comes in three forms, each using adifferent method of manufacture for the cross linking. Three types arePEX-a (peroxide cross-linked polyethylene), PEX-b (silane cross-linked polyethylene) and PEX-c (radiation cross-linked polyethylene).

Polybutelene Polybutelene (PB) is typically a multi-layer co-extrusion, with theoxygen barrier enclosed between the Polybutelene inner and outerlayers to minimise the ingress of oxygen into the pipework system.

Insulation Insulation is generally positioned beneath the circuit pipework toprevent downward heat loss. Insulation around the perimeter of anunderfloor heating system also accommodates a certain amount ofslab expansion when the underfloor heating is in use.

An Interface Engineering Publication

What are Interface Engineering Publications?Interface Engineering Publications (IEP) are a series of guides that aim tobridge the gaps in technical knowledge at the interfaces betweenconstruction packages. The publications involve reformating existingprofessional knowledge, developed independently by Co-Constructmembers, into a single source of guidance.

The objective of IEPs are to reduce failures on site, to create greaterunderstanding of shared processes by clients, designers and contractors, andto improve the construction quality and in-use performance of underfloorheating systems.

Screeds and Underfloor Heating has been jointly researched, edited andproduced by BSRIA and The Concrete Society in order to providecomprehensive guidance in a single publication. All the information hasbeen drawn from current research and existing publications, and cross-referenced with the latest regulatory requirements.

For more information on Co-Construct visit www.construction.co.uk.

Co-Constructc/o BSRIA, Old Bracknell Lane West, Bracknell, Berkshire, RG12 7AH, UKTel: +44 (0)1344 426511www.construction.co.uk

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