innovative construction & product techniques

Innovative Construction Products and Techniques

BD 2503

www.communities.gov.ukcommunity, opportunity, prosperity

Innovative Construction Products and Techniques

BD 2503

January 2008Communities and Local Government: London

The authors of this report are employed by the Building Research Establishment (BRE). The workreported herein was carried out under contract placed by the Department for Communities and LocalGovernment. Any views expressed are not necessarily those of the Department.

Department for Communities and Local GovernmentEland HouseBressenden PlaceLondonSW1E 5DUTelephone: 020 7944 4400Website: www.communities.gov.uk

© Crown Copyright, 2008

Copyright in the typographical arrangement rests with the Crown.

This publication, excluding logos, may be reproduced free of charge in any format or medium forresearch, private study or for internal circulation within an organisation. This is subject to it beingreproduced accurately and not used in a misleading context. The material must be acknowledged asCrown copyright and the title of the publication specified.

Any other use of the contents of this publication would require a copyright licence. Please apply for aClick-Use Licence for core material at www.opsi.gov.uk/click-use/system/online/pLogin.asp, or by writingto the Office of Public Sector Information, Information Policy Team, St Clements House, 2-16 Colegate,Norwich, NR3 1BQ. Fax: 01603 723000 or email: [email protected]

If you require this publication in an alternative format please [email protected]

Communities and Local Government PublicationsPO Box 236WetherbyWest YorkshireLS23 7NBTel: 08701 226 236Fax: 08701 226 237Textphone: 08701 207 405Email: [email protected] online via the Communities and Local Government website: www.communities.gov.uk

January 2008

Product Code: 07 BD 04986

Executive summary

This report provides information on a range of issues concerning InnovativeConstruction Products and Techniques (ICPT), with particular regard to thefire safety and robustness of new and emerging products and systems.

The overall aim of the project is to assist in ensuring that constructioninnovation is embraced and encouraged in a way that maintains the requiredlevels of fire safety and structural integrity.

This report details the various types of ICPT and considers their comparativeuse by the market.

A steering group of representative stakeholders provided invaluable input tothe project and considered a range of issues including fire spread, integrity ofcompartmentation, cavity barriers, external cladding, structural insulatedpanel systems (SIPS) and workmanship.

This scoping study has identified the need to undertake more detailed workto ascertain the real fire performance of several modern methods ofconstruction utilising ICPT.

A prioritised programme of detailed work needed to resolve these issues hasbeen developed in consultation with the Project Steering Group.

This report will be of interest to key stakeholders including the Fire andRescue Service, national and local authority building control bodies, insurers,mortgage lenders, manufacturers and housing associations.

Executive Summary | 3

Contents

1 Introduction and objectives 5

2 Programme of work 6

2.1 Task 1 Formation of a steering group and associated information 6gathering

2.2 Task 2 Identification of the various different types of ICPT 8(building systems) and their level of use within the marketplace

2.2.1 Definitions 8

2.2.2 Market share 8

2.3 Task 3: Identification of issues of concern in relation to ICPT 10(building systems)

2.4 Task 4: Identification of specific products in relation to ICPT 14and their performance in fire

2.5 Task 5: Consideration of ICPT, in terms of Parts A and B and 18Regulation 7, property protection and sustainability

2.6 Task 6: Robustness and the potential whole-life impact of 21alterations to buildings utilising ICPT

2.7 Task 7: Development and prioritising of a programme of work 32required in support of possible changes to regulatory and design requirements in relation to ICPT

3 Conclusions 35

4 References 37

Appendix A Summary of the research 38

Appendix B Definition of building systems 39

4 | Innovative Construction Products and Techniques

Chapter 1

Introduction and objectives

This is the final report due for the project, Innovative Construction Productsand Techniques (ICPT). This project was commissioned under the Departmentof Communities and Local Government Fire Safety Framework Agreementwith the BRE-led consortium.

The overall aim of the project is to assist in ensuring that constructioninnovation is embraced and encouraged in a way that maintains fire safetyand structural integrity, by providing the Department of Communities andLocal Government with an understanding of the range of issues associatedwith ICPT and to provide recommendations, and priorities, for further workthat might be needed.

It is clear that change is essential if the construction industry is to meet thechallenging requirements of the modern world. It is necessary to ensure thatinnovation does not have a detrimental impact on the safety of those in andaround the built environment.

Many of the issues discussed are concerned with the quality of workmanshipand attention to detail. These are issues that not only impact on ICPT but canaffect all forms of construction, including brick and block.

The specific objectives of this project are:

• To consider ICPT, cavity barriers, fire compartmentation/separation and,where relevant, their respective inter-relationships.

• To produce a prioritised programme of further work needed on the issuesraised above. This should include the possible development of suitablemethods of test and assessment that cover all forms of construction, withparticular emphasis on innovative methods of construction, where adatabase of performance in real fires does not exist.

The programme of work undertaken has met the key objectives of theproject.

Introduction and objectives | 5

Chapter 2

Programme of work

2.1 Task 1 Formation of a steering group and associatedinformation gathering

The programme of work included a requirement for key stakeholderinvolvement to ensure broad representation and consultation. The project isvery wide ranging and covers a number of separate disciplines. For thisreason, a number of experts from within BRE and from the consortium haveprovided input to specific areas. In addition to the project team, a number oforganisations have participated in the project. These organisations representkey stakeholders including insurers, mortgage providers, the Fire and RescueService and building control. Wherever possible, industry groups orassociations were involved rather than individual companies or namedindividuals.

The organisations consulted cover the key stakeholders involved in theprocess of implementing, assessing and validating the performance of ICPT.Three steering group meetings were held over the course of the project, alltaking place at BRE Garston on 28th March, 27th June and 2nd October2006.

The steering group meetings and subsequent discussions andcorrespondence have been a key element in the success of the project. Inparticular, the provision of information from the Fire and Rescue Service andthe insurance industry means that the findings and recommendations fromthe project are informed by current real-life incidents.

The table below shows the constitution of the steering group (excludingmembers of the BRE consortium).


Table 1 Constitution of project steering group

Name Affiliation Representing

Glyn Evans Fire Brigades Union FBU

Andrew Heywood Council of Mortgage Lenders CML

Neil Smith National House Building Council NHBC

Keith Snook Royal Institution of BritishArchitects

RIBA

Simon Hunt Chief Fire Officers Association CFOA

Andy Howard Chief Fire Officers Association CFOA

Alister Smith Norwich Union Association of British Insurers

Mark Newton Royal Sun Alliance Association of British Insurers

Dave Sibert Fire Protection Association FPA

Richard Shipman Department of Communities andLocal Government

Department of Communities andLocal Government

Anthony Burd Department of Communities andLocal Government


Mike Payne AEA Technology Department of Communities andLocal Government

Mike Wood Pilkington Construction Products Association

John Fay Department of Communities andLocal Government


Dave Mitchell Home Builders Federation HBF

Clive Clowes Housing Corporation Housing Corporation

Programme of work | 7

2.2 Task 2 Identification of the various different types of ICPT(building systems) and their level of use within themarketplace

2.2.1 DefinitionsA number of generic definitions have been produced by the Home BuildersFederation (HBF) and the recently formed National House Building CouncilFoundation (NHBCF) established in partnership with the BRE Trust, to coverbuilding systems. These include:

• Volumetric or modular construction

• Panellised

• Hybrid (semi-volumetric)

• Site-based systems

Examples of each of the categories are included in Appendix B.

2.2.2 Market shareInformation on the precise level of use of the various systems is unclear.Individual sectors within the industry produce their own figures. These figuresare frequently quoted without a clear understanding of how the informationwas actually derived. This consequently leads to confusion andmisrepresentation of the true value and size of the UK offsite market.However, although the information available may not be particularlyaccurate, it is certainly able to identify trends in the market.

The UK offsite market makes up 2.1% of the construction market as a whole,including new build, refurbishment and repair, and civil engineering projects2.When new build only is considered and civil engineering works excluded, thisfigure rises to 4.1%.

The largest markets are education and healthcare. It is expected that thesemarkets will continue to grow, with a combined market size anticipated to bein excess of £1 billion. Housing is anticipated to become the third largestmarket by 2009, with military establishments and hotels also showingsubstantial growth. These three sectors provide a combined market sizeprojected to be £777 million3.

The modular construction market in the UK was £1.84 billion in 2005. Thismarket can be further divided between portable buildings (£1.06bn) andpermanent buildings (£0.78bn). As a percentage of the new-build market,this represents a current take up of only 2%. The situation is illustrated inFigure 1.


In total, the market has achieved a growth rate of 7% between 2000 and2005 and is forecast to grow at 12% between 2005 and 2009. However,there is a significant difference between the portable and permanent market.Portable buildings have shown a flat rate of growth between 2000 and 2005and are forecast to remain static to 2009. The growth in permanent buildingshas been 20% compound annual growth rate (CAGR) between 2000 and2005 and is forecast to grow at 24% CAGR between 2005 and 2009.

This can be further broken down by material. Materials used in modularconstruction are timber, steel and concrete. Currently, timber and steel areused at an equivalent level. However, steel is forecast to have the greatergrowth rate from 2005 to 2009 of 23%. The relative position of eachmaterial is illustrated in Figure 2 below.

The offsite market for permanent new-build projects using a steel solution iscurrently £377.7 million and is expected to rise to £854.2 million by 2009, anabsolute growth of 226% or 23% CAGR3.

Innovative Construction Products and Techniques (ICPT) will have a significantrole in meeting the current and future levels of demand for housing. TheGovernment’s large new-build programme in this area is worth more than£1.2 billion. The Government will commit to 1600 affordable houses in ruralareas and 8000 key worker accommodation units.

Figure 2 UK market for permanent prefabricated buildings by material

0

200

400

600

800

1000

2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

£m

Timber

Steel

Concrete

Figure 1 UK market for portable and permanent prefabricated buildings

0

500

1000

1500

2000

2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

£m

Portable

Permanent


2.3 Task 3: Identification of issues of concern in relationto ICPT (building systems)

A number of recent initiatives have attempted to identify and address theconcerns of key players in the supply and procurement of ICPT. In general,such initiatives have concentrated primarily on the housing sector. Forexample, a number of influential bodies have contributed to the developmentof a new certification standard for innovative housing systems – LPS 202010.Two of the principal organisations involved in developing the scope of thestandard were the Council of Mortgage Lenders (CML) and the Association ofBritish Insurers (ABI). However, the concerns of insurers and lenders extendbeyond housing to cover all other sectors. Also other key stakeholders, suchas the Fire and Rescue Service, were not part of the consultation processleading to the development of LPS 202010.

The principal identified concerns of the various sectors of the industry aresummarised below. These are taken from the consultation process to developLPS 202010. These opinions are based on individual experiences and not frommajor independent studies. The research focused on UK experience and didnot include evidence from Europe.

Mortgage lendersThe principal concern for mortgage lenders is based on experience of post-war system-built houses using non-traditional forms of construction. Thepost-war situation in terms of demand for dwellings and shortage of skilledworkers in many ways mirrors the current situation, “Experiences in the pastmay well affect lenders’ willingness to lend on new construction types whichare unfamiliar and which may appear to exhibit some of the samecharacteristics as those they have had problems with in the past.”4. Anumber of housing systems were designated as defective under the 1984Housing Defects legislation. Problems were also identified with Large PanelSystem (LPS) buildings used to construct many of the high-rise towers builtduring the 1950s and 1960s. Although the vast majority of these systemswere originally built as public sector dwellings, many entered the privatehousing market through the right-to-buy legislation. An excellent source ofinformation on non-traditional housing in the UK is available through theCML website5.

Based on the experience gained from the previous generation of non-traditional forms of construction, the key issues for lenders in relation to ICPTare:

• Durability – what is the track record of the ICPT? Has experience beengained in the UK or elsewhere where environmental conditions may besignificantly different?

• Whole life costs – will they affect demand over the longer term?


• Repairability – how easy is it to repair defects? Will costs be comparablewith traditional construction types?

• Projected life span – is the life span sufficient for the property to maintainadequate security over the term of the loan?

• Adaptability – will it be possible to modify or extend the initialconstruction?

• Availability of insurance – both for new build and over the longer term

• Maintenance of demand – in order to maintain security over the term ofthe loan the design must be such that demand is sustained over time.

A number of these issues will affect the future value of the property and aretherefore of particular interest to lenders. The CML has been active in anumber of forums considering the issue of ICPT in the residential sector. Itsees the development of a certification standard and accreditation scheme asa crucial step in providing the reassurance required to overcome theconcerns.

InsurersWhile lenders’ concerns are based on past experience of non-traditionalforms of construction and associated defects, insurers are concerned aboutthe absence of an appropriate risk profile to apply to the various forms ofICPT. “The risk profile of a property – number and cost of expected claims – isthe key piece of information that insurers need to underwrite the risk”6.Information on risks to ICPT properties is currently anecdotal. Insurers wouldlike to see equivalent performance to conventional build against a range ofcommon risks.

Insurers may require higher standards to compensate for the absence of a“track record”. Such requirements may be seen as unfair by manufacturers asthey are asked to provide evidence of performance over and above thatrequired for traditional products.

Many of the specific issues raised are similar to the concerns of the lenders.The key areas identified by the ABI are resilience and repairability. Theinsurance industry has identified a range of perils that affect buildings; theseare:

• Flooding

• Driving rain

• Fire

• Subsidence

• Windstorm


During discussions with BRE as part of the focus groups to develop the LPS2020 standard10, the ABI, in discussion with loss adjusters, produced specificdamage and repair scenarios to provide a more objective way to measure thekey performance indicators of resilience and repairability. Resilience is definedas the ability of a system, element or component to resist damage resultingfrom accidental events. In relation to resilience, the relevant scenarios forcomparison against conventional buildings are:

• Storm with wind speeds exceeding 80 km/h on average for eight hourswith occasional gusts of more than 120 km/h

• Leak of 1000 litres of water from an upstairs room due to a burst pipe

• Single room fire breaking out through the window, damaging the internallinings and external cladding above the window

• 1 m deep dirty water flood lasting two days

• Subsidence event resulting in a 5 cm drop on one corner of the building

• Gas explosion in kitchen area

• Vehicle impact on exterior corner, resulting in a 1 m deformation

• Internal impact damage that exposes building insulation material (e.g.moving furniture or DIY)

• Attempted theft by forcing doorframe to gain access

The most significant consequence of any of the events identified above is thecost of repair. There is concern among insurers that even relatively minordamage could result in extensive repairs to a whole series of inter-relatedcomponents or localised repair requiring specialist skills and/or components.Available experimental evidence suggests that disproportionate collapse isunlikely (see Section 2.6). The key features to consider in relation to repairare:

• Costs and availability of replacement parts

• Costs and availability of labour – can local labour be used or only specialistcontractors? If local labour is used is there a danger they will notunderstand the system, so the repair is not carried out to adequatestandards?

• Extent and speed to which a building could be dried out in a flood andthen made good

• Degree of inter-connection between structural elements – particularlyimportant for modular construction


The resilience scenarios defined above were informed from discussions withloss adjusters. The specific perils were ranked in terms of frequency and cost.This information is summarised in Table 2.

A recent Technical Claims Forum held by the Chartered Institute of LossAdjusters7 identified fire and flood as areas of specific concern andhighlighted the issue of disproportionate damage. Available experimentalevidence suggests that disproportionate collapse is unlikely (see Section 2.6).A number of issues arose which have already been discussed in relation to theconcerns of insurers and lenders, including the availability of replacementmaterials and the availability of labour with the necessary expertise toundertake repairs. Composite panel systems used in inappropriateenvironments were cited as a specific example where the costs of repair weresignificantly different to those for alternative traditional materials.

Fire and Rescue ServiceOne of the principal concerns for the Fire and Rescue Service is that whenattending a fire, they are, in many cases, no longer aware of the nature of thebuilding and the key structural elements. Cultural and aestheticconsiderations mean that many innovative structural forms “mimic”traditional forms of construction. This can lead to mistaken assumptionsregarding committing fire fighters into the building. The Fire and RescueService has expressed concern over the increasing use of polymeric materials

Table 2 Summary of perils identified by loss adjusters

Peril Frequency CostOverallranking

Rating Rank Rating Rank

Fire 0.5 4 1.32 2 1

Water leak 1.86 1 0.14 6 2

Storm 1.45 2 0.18 5 2

Flood 0.18 6 1.64 1 2

Subsidence 0.36 5 0.55 4 5

Vandalism ortheft

0.64 3 0.09 7 6

Gas explosion 0 7 1 3 6

Vehicle impact 0 7 0.09 7 8

Internal impact 0 7 0 9 9

Lightning 0 7 0 9 9


in building construction. From fire investigation reports it is clear that anumber of serious fires have occurred as a consequence of a small ignitionsource leading to extensive fire spread within concealed cavities. Manymodern building systems contain polymeric insulation sheets in order toreduce thermal losses. In general, thermal insulation is protected from theeffects of a fully developed fire by fire-resistant plasterboard. However, wherethe ignition source is within the cavity itself there is no intrinsic fire resistance.Melting of the thermal insulation can also provide an effective route for fireto spread by bypassing any cavity barriers or fire stopping present. This issueis relevant to external walls, cladding systems, internal walls and cavitiesbetween floors. It is particularly significant where multi-occupant residentialbuildings are concerned, where phased evacuation would be the normalprocedure.

During the course of the study BRE had access to a number of fire investigationreports. One particular feature of these incidents was the number of seriousfires occurring in the construction phase. There is some concern that specificforms of construction are particularly vulnerable to the effects of a fire duringconstruction. This is particularly so where light framing systems rely onsheathing boards for their fire protection. These are often not fixed until theentire superstructure has been erected, meaning that large building frames areoften completely unprotected for a short period of time. This issue is not dealtwith through the Building Regulations Approved Documents which apply onlyto completed buildings. Fire safety on construction sites is addressed by theConstruction (Health, Safety and Welfare) Regulations 1996 and theRegulatory Reform (Fire Safety) Order 2005.

Recent fires, such as occurred in the Beaufort Park development in Colindalein July 2006, have also brought into question the practice of allowing partialoccupation of a partially completed building to provide the income streamsrequired to complete the project.

2.4 Task 4: Identification of specific products in relationto ICPT and their performance in fire

Alongside off-site manufacture (OSM) and site-based systems a number ofnew innovative products have emerged over the last few years. In relation tothe classification system discussed in the context of building systems, theseare generally referred to as sub-assemblies and components. This category isintended to cover approaches that fall short of being classified as systematicOSM but which utilise several factory-fabricated innovative sub-assemblies orcomponents in an otherwise traditionally built structural form. Typically,schemes incorporating the use of floor or roof cassettes, precast concretefoundation assemblies, preformed service installations etc. would fall into thiscategory. Traditionally constructed schemes utilising manufactured units suchas windows, door sets, roof trusses etc. which might otherwise be part of thefabrication process in the other OSM categories should not be included assub-assemblies or components in this category.


Solid timber joists are increasingly being replaced by engineered productssuch as timber “I” beams and lattice joists which are lighter and stiffer thansolid timber. Deep joists (up to ~ 0.5 m) up to 12 m long can be producedallowing much larger distances to be spanned without the need forintermediate structural support.

Figure 3 Engineered floor joists

Floor cassettes are prefabricated framed units which are delivered to siteready-assembled. The floor joists may be timber, light gauge steel orcomposite. Floor cassettes provide the benefits of off-site quality control andmay be used as part of a panellised system to produce framed structures.Floor cassettes may be formed using the engineered joists described above.

Figure 4 Floor cassette as part of steel-framed system


Roof cassettes comprise panels that span from eaves to ridge. They oftenrequire no intermediate structural support, although in some cases purlins areused. Both faces of the panel are normally finished with a sheet material, andinsulation is included within the structure of the panel.

A number of innovative façade systems are available including rainscreensystems, composite panels and render systems. External cladding may beused to provide the weatherproof façade to new buildings or as a means ofrenovating existing buildings. A number of systems (particularly claddingsystems) are generally integrated with various forms of modern methods ofconstruction (MMC). Prefabricated lift shafts may fall into this category. Somecladding systems would incorporate traditional materials such as brick andblock but there are a large number of lightweight systems designed for easeand speed of construction. Many of these systems have been developed inEurope and the United States specifically for application on MMC systems.Some of the more commonly used cladding systems (in relation to domesticdwellings) are described below:

Brick slips – may be used as an alternative façade to traditional brickwork.They are attached to panels using either an adhesive or a clip-on fixingsystem. Much thinner than a conventional brick (approx. 15-30 mm), brickslips may be applied directly onto insulation or onto another backing board orsheet. They can be combined with insulation in prefabricated compositepanels.

Tile hanging – used as an alternative cladding to bricks and applied in thesame manner as roof tiles with an overlap. Insulation may be applied to theframe and timber battens fixed to the insulation from which the tiles can behung.

Terracotta cladding – rainscreen terracotta cladding provides a fast,effective and durable means of cladding buildings constructed using MMC.The system can be applied to buildings with concrete, steel or timber frames.The tiles are clipped onto a metal frame and are open jointed with nopointing or grouting required.

Timber cladding – can be manufactured in the factory producing a high-quality finish that can be applied easily and quickly on site. A number ofdifferent finishes are available in terms of colour and texture. Timber grainweathering board is often used as a cladding for composite panels. Timbercomposite panels are manufactured combining timber with other materialsunder high pressure and heat to produce a durable end-product. Plasticsystems are also available which attempt to replicate the appearance oftimber boards.

Renders – two types of render system are currently used, cement-based andpolymer-based. Both systems can be applied to traditional masonryconstruction or framed construction. However, when applying render to aframed structure it is generally recommended that a drained and ventilatedcavity is provided. Insulated renders are also available.


In traditional masonry construction, renders are generally cement-based andapplied directly to the masonry. Renders are applied to timber frame systemsusing a steel mesh that bonds the render to the frame. Detailing is generallystandardised with the use of bell-cast and other stop beads whereappropriate. Cement-based render results in a thicker construction thanpolymer-based render.

Polymer cement renders provide an alternative to sand and cement rendersand can be applied to a concrete block or framed construction forming aweatherproof composite wall. These systems are relatively thin with the renderapplied onto a layer of insulation. Application of the render often involves theuse of a premixed dry powder with water and applying the mixture usingtraditional plastering techniques. Some renders require the application of onlyone coat while other systems may require up to three coats.

A number of innovative jointing systems are available for precast concreteconstruction. These allow for full continuity of reinforcement with short laplengths through the use of high-strength cementitious materials such as CRCJointcast.

Figure 5 Cruciform connection between precast units using CRC Jointcast

Insulating formwork derives its name from the fact that an insulation material(often expanded polystyrene) is used as permanent shuttering for a cast-in-situ concrete wall. A number of systems are available, some of which rely ontwo sheets of insulating material tied together while others are in the form oflarge building blocks. This type of construction has been popular in the self-build sector due to the ease with which an energy efficient, airtightconstruction can be produced.


Figure 6 Insulated concrete formwork

Many of the concerns expressed regarding the performance of individualproducts mirror those discussed in relation to system performance. Oneparticular aspect relates to the anticipated larger deformations associatedwith long span engineered floor joists. This has implications for fire fighterswho may rely on experience with traditional flooring systems to decide whenstructural stability is a problem for access to floors above fire floors.

2.5 Task 5: Consideration of ICPT, in terms of Parts Aand B and Regulation 7, property protection andsustainability

Schedule 1 of the Building Regulations sets down functional requirements forthe design and construction of buildings. Part A of Schedule 1 deals withstructural safety and Part B deals with fire safety. Regulation 7 provides thatmaterials and workmanship used in the construction should be such that therequirements in Schedule 1 are achieved in the completed building andthroughout its design life.

The current locus of Parts A and B of the Building Regulations is limited byRegulation 8 to the health and safety of people (including the Fire and RescueService) in and around buildings.

In respect of Parts A and B it is not possible to test a completed building toestablish if these requirements have been met. In most cases this wouldinvolve destructive testing of each and every building. Instead, the design andconstruction of a building are assessed against guidance set out in ApprovedDocuments and in associated test and design standards which, in turn, arebased on pre-existing knowledge of how construction systems tend tobehave as a whole.

Where ICPT is used, there is the potential that the tests and standards thathave been developed using experience of conventional construction may beinappropriate for an innovative product or system where modes of failuremay exist that had not previously been envisaged.


In principle building control bodies (BCBs) could reject a proposed buildingdesign even where it meets the guidance given in the relevant ADs if the BCBconsiders that the nature of the construction system is such that functionalrequirements would not be met. However, in practice a BCB is unlikely to beable to do this without considerable resources.

In most situations the guidance in Approved Document B has been found toprovide acceptable levels of safety in relation to the performance in fire ofconstruction products and systems. However, there is evidence that theassessment methods commonly used to show compliance with theRegulations may not always take into account the key performance criteria inrelation to systems such as modern building envelopes and modularconstruction.

A number of products, systems and techniques apparently capable ofmeeting the requirements of the Building Regulations, through achieving asatisfactory performance in either bench-scale reaction to fire tests or isolatedelement fire resistance tests, may still be inappropriate in relation to the enduse and the interconnection with other parts of the building. This issue couldbe covered to some extent by Regulation 7.

Workmanship issues in construction are a function of training and supervisionon site. It is not possible to replicate the variety of standards of workmanshipwithin a test and assessment scheme. Some materials, systems andtechniques are, however, more vulnerable to poor workmanship than others.This is particularly true of the fire situation where many of the protectivemeasures are not visible or accessible in the completed building. Whilstsensitivity to workmanship can be considered, in specific circumstances,through research projects such as the effects of damage to passive fireprotection in offshore structures undertaken by the Health and SafetyExecutive (HSE), it cannot form part of a standardised test and assessmentregime. However, the test methods described in Section 3 do considerworkmanship issues to a limited extent in that they incorporate somefeatures associated with system behaviour and the interaction betweencomponents. However, the extent to which poor workmanship is replicated ina test will always be a matter of some debate.

In paragraph 0.2 of the Approved Document supporting Regulation 7 it isstated that materials chosen to minimise the environmental impact ofbuilding work “must not have any adverse implications for the health andsafety standards of the building work”. This has been an issue throughoutthis scoping study in relation to both test evidence and the results from realfires, where measures to enhance the thermal performance of buildings haveled to the creation of voids or cavities which, in practice, can be difficult tofire stop adequately. The test procedures outlined in Section 3 would allowsuch a situation to be identified prior to construction.

The Building Regulations set baseline standards to ensure the safety andhealth of those in and around buildings. In certain instances, materials orproducts are controlled in terms of performance. One specific example would


be the limiting of the rate of heat release or fire growth for internal linings(walls and ceilings) where the guidance refers to performance againststandard test procedures.

Concerns have been raised by some stakeholders that the rapid increase inthe interest and use of modern systems, materials and techniques used ininnovative construction projects could result in future fire-related problemswhich were not foreseen.

A number of initiatives are currently underway to develop test andassessment procedures which more accurately represent performance underrealistic scenarios. This includes the development of performance testing ofbuildings as a tool for demonstrating compliance with the BuildingRegulations and involves a trend towards larger-scale system tests. However,imposing this type of approach on all ICPT systems and sub-assemblies wouldbe difficult given the lack of any clear definition.

From a consideration of the concerns of key stakeholders, a review ofavailable research and an assessment of test and assessment methods, anumber of specific points can be made.

• There is a gap between the test and assessment procedures used to showcompliance with the provisions for health and safety in the BuildingRegulations and the requirements of those with an interest in the long-term investment in property and for meeting the costs of repair andessential maintenance.

• For the non-regulatory stakeholders, the development of industrystandards may help to bridge this gap and offer an alternative approachfor showing compliance with statutory requirements.

• Evidence from some research projects8 and real fire incidents has tended toshow that, in certain cases, the inappropriate use of materials intended tominimise the environmental impact of building work has compromised thefire performance.

• The involvement of key stakeholders including product manufacturers willbe essential in developing future research and development strategies inrelation to ICPT.

This report has investigated current and developing methods of test andassessment in relation to performance in fire. A number of test methods areavailable that more accurately reflect the end-use condition in relation toboth the choice of materials for construction and the issue of workmanship.


2.6 Task 6: Robustness and the potential whole-lifeimpact of alterations to buildings utilising ICPT

This section of the project focused in particular on the effect that‘misinformed’ alterations to buildings constructed using ICPT may have onthe subsequent structural integrity of those buildings. Clearly the danger ofsuch events increases when building components and systems are new andtherefore potentially not understood.

Before considering the implications of alterations, it is, however, worthrecalling information that was presented in an earlier report. Work by theSteel Construction Institute (SCI) and BRE has shown that, in their originalstate at least, typical examples of steel and timber frame construction providehigh levels of ‘robustness’. Figure 7 shows a light steel-framed houseproduced using the Surebuild system, which was tested by SCI in the 1990s.Key elements were removed including the brick cladding and a number ofstuds on the front elevation. The house showed no signs of distress and theframe was clearly capable of redistributing the load from the absent studs.The disproportionate collapse tests on the TF2000 building (Figure 8)included the removal of an internal timber frame load-bearing wall andseparate removal of a 4 m length of brickwork and timber framing in theexternal wall. The external wall was breached near the corner of the structureat ground level, reducing the corner buttressing effect. This test, theequivalent of a major accident, such as a large vehicle impact, resulted in nocollapse, excessive deflection or even minor cracking of the brickwork. Bothof these examples give reassurance that the systems involved may also havesufficient ‘robustness’ (achieved through load-sharing between numerouselements) to overcome misinformed alterations during their service life. Asimilar member removal scenario was undertaken on the concrete framedbuilding at Cardington (Figure 9). However, none of these experimentsadequately simulate the dynamic response of an impact scenario. Strain ratemay play a crucial part in providing the alternative load paths required toenable load shedding. Very high strain rates such as those associated withexplosions or vehicle impacts may have more serious consequences.


Figure 7 Robustness test on Surebuild steel-framed house

Figure 8 Six-storey TF2000 timber-framed structure at Cardington


Figure 9 Cutting out concrete from column by hydro-demolition

However, whilst there have been robustness studies on framed construction,BRE research shows that the UK construction industry embraces andincreasingly uses a number of ‘second generation’ lightweight constructionsystems, such as structural insulated panels (SIPs). These systems build on theadvantages and groundbreaking developments achieved by theirpredecessors and exploit new techniques of manufacturing and materialtechnology.

SIPs are increasingly being used in the UK and throughout Europe, mainlybecause of their energy efficiency, and ease and speed of construction. In theUK, it is estimated that more than 2000 homes have been built with SIPs todate. There are around ten SIPs manufacturers in the UK and double thatnumber of contractors trained and skilled in SIPs construction. The number ofhomes built using SIPs is predicted to increase dramatically throughout thenext decade.

The requirement in the Building Regulations with respect to disproportionatecollapse is particularly relevant in relation to the perceived concerns of keystakeholders. Requirement A3 states that:

The building shall be constructed so that in the event of an accident thebuilding will not suffer collapse to an extent disproportionate to the cause9.

Although this provision arose from the progressive collapse which occurredfollowing a relatively small gas explosion in a large panel system tower blockin 1968, the principle applies to many of the concerns of the key stakeholders


expressed during the course of the project. Whether the accidental event isan explosion, vehicle impact, fire or a minor alteration to the existingstructure, there is concern that the event may lead to disproportionatecollapse or disproportionate damage.

Approved Document A classifies buildings according to categories based onoccupancy type and height of structure. Of particular concern are thosebuildings falling into Class 2A or 2B, particularly in relation to medium-riseresidential buildings.

Problems can arise regarding the structural integrity of any building as a resultof alterations. For traditional buildings, it is assumed that sufficientknowledge is widely available for the people involved in the alterations tomake an informed decision. For buildings constructed using ICPT, theknowledge regarding the structural behaviour of new building componentsand systems might not be available or well understood by all parties involvedin the alterations or repair of buildings. This lack of understanding wouldmake the buildings constructed using ICPT more prone to loss of structuralintegrity as a result of alterations and repairs.

The important information about the building and construction processwhich needs to be known for an informed decision-making process is:

Load-bearing Components: The load-bearing components in a buildingneed to be identified so that during alterations and repair, the integrity of thebuilding can be assured. For residential buildings, where inexperiencedpersonnel might undertake the alterations, this is more important. Themethod used for identifying load-bearing components could be to provideguidance in the ‘Home Owners’ Manual’, and to mark the load-bearingcomponents.

Detailing Requirements: For buildings using ICPT, the detailing can becritical in providing integrity to the building. For example, a connectionbetween a wall panel and a floor slab would be designed to provide therequired transfer of loads. If the connection details are required to bechanged owing to alterations or repairs, the new connection should be ableto transfer the required loads.

Proper Use of Components: Certain components of a building have theirparticular functions and may not be replaced by components that look similarbut might structurally behave in a different manner. For example, the steelstuds in a wall panel should only be replaced by studs with similar strengthand deflection characteristics.

Many of the issues that would impact on the long-term integrity of ICPTbuildings have been highlighted in discussions with various stakeholdergroups during the development of LPS 202010. The issues raised in terms ofalterations are:


• Some of the components/materials used in innovative construction are of aspecialist nature. This gives rise to the issues described below:

• The availability of specialist components/materials for alteration or repairpurposes is a concern raised by the lenders and insurers. If damageoccurs to the building, occupants would generally demand like-for-likerepair. With some forms of ICPT, this may not be always possible. Onemeans for controlling this is to ask manufacturers to provideinformation on approved methods of repair when using differentcomponents/systems than those originally used, as required in LPS2020.

• The need for evaluation of the adaptability of systems/components. Theadaptability would determine how well the system and its design wouldcope with potential change of use or demand over time. For example,in LPS 2020 the manufacturers have been asked to specify how thesystem/component can cope with the insertion of an opening such as adoor or window. The change of use can also be due to requirements towithstand additional loads, for example, hanging of loads oninternal/external faces of walls.

• Some alterations or repair procedures may require specialist/certifiedtradesmen or other specialist services (such as design by a structuralengineer). LPS 2020 asks the manufacturers to provide details of theseso that the building owners are aware of the requirements.

• The components used in alterations or repairs may interact with theexisting components and may degrade or cause the existingcomponents to degrade over the long term (e.g. bi-metallic corrosion).

• The practicability of installation (buildability) for buildings constructedusing ICPT has to be assessed in accordance with LPS 2020 to confirmthat the procedures provided in the manufacturer’s instructions arepractical and adoptable. The repairs and alterations need to be carriedout using the manufacturer’s instructions used for the originalconstruction to achieve the same standard as the new-built building.This implies that if the construction of the original building required theinvolvement of a trained or qualified workforce, similar would berequired for satisfactory repairs or alterations.

LPS 2020 also identifies issues that, even without alteration, may affect long-term structural integrity. These issues include:

• Long-term consequences of damage during transportation/storage/erection. For example, damage to layers that protect structural membersfrom corrosion/rot will affect the durability and, consequently, the load-bearing capacity of the structural members. The impact of such damagemight only be clear some time after the building has been in operation.


• Where the buildability for buildings constructed using ICPT has not beenconsidered adequately, the consequent lack of inherent buildability maylead to improvisation on site, which would impact adversely on theintegrity of the building. For example, use of welding when bolts will notfit can lead to corrosion problems at the location of welding, cracking inthe heat-affected zone close to the weld, or an inadequate weld if thereare problems of access etc.

• Inadvertent use of components that, through choice of materials, interactand degrade over the long term (e.g. bi-metallic corrosion) would result ina building with durability and potentially integrity problems. Identificationof such possibilities should be carried out at the design stage.

• A maintenance regime should be planned for all components. Lack ofmaintenance of one component/system could affect the integrity of othercomponents. For example, degradation of seals may lead to façadeleakage, which in turn may lead to durability and consequent integrityproblems with structural components.

Buildings constructed using ICPT in the residential sector are most vulnerableto the issues raised above as there is a higher possibility of residentsundertaking alterations without the involvement of sufficientlyknowledgeable and/or experienced professional advisors.

The main forms of ICPT used for residential buildings include:

• Light steel frame – this includes frames constructed using sticks, panelsand modules using light gauge (cold-formed) galvanised steel.

• Steel frame – construction using hot-rolled steel components.‘Traditionally’ used in commercial applications but now increasingly usedfor apartment buildings when height exceeds say, six storeys. Often usedwith composite steel-concrete floor slabs.

• Timber frame.

• Structural insulated panel systems (SIPS).

• Sheathing board used in the light steel and timber panels may provideboth fire protection and racking resistance. If the sheathing board needs tobe altered or replaced this could affect the performance of the panels.

• Different types of boards have substantially different performance but maynot look that different, or be properly understood by laymen carrying outrepair or alterations. Figure 10 shows failure of a brittle sheathing boardduring a racking test.

• Cutting holes in the sheathing board will significantly affect theperformance of the panel.


• Replacement of sheathing board with a ‘wrong’ alternative may affect theperformance of the panel, both structurally and in a fire.

• Fixings (number, type and positions) are also very important as they enablethe performance of the sheathing boards to be exploited. During repairs,appropriate fixings should be specified and installed correctly.

Figure 10 Tensile failure of brittle board in racking test

Other important issues for consideration include:

• Bracing may be used to provide lateral resistance to the panels used inframe construction. The actions that might give rise to loss of performancecould be:

• Cutting of bracing

• Moving the bracing away from node points (which can seriously reducestructural efficiency)

Figures 11 and 12 show two panels, one with no bracing and one withbracing. The unbraced frame had almost no stiffness whereas the doublecross-braced panel showed good stiffness and strength. The differencebetween these represents an upper bound to the loss of performance thatwould occur if bracing were cut or removed.


Figure 11 Panel without bracing in the racking test rig

Figure 12 Panel with diagonal strap bracing on both faces.

• Noggins may be present in the frame to provide lateral restraint to studs;these should not be removed, e.g. to provide an opening. This couldreduce the axial capacity of the studs by, say 50%.

• When new openings are introduced in the frame, the adequacy of existingstructural support should be assessed. For example, studs may needdoubling up around openings to cope with gravity load, or additionalmembers might need to be added if retrofitting a Velux-type window in aroof.

• Steel members need to be ‘warm frame’ (insulation present on outside) toavoid condensation leading to possible corrosion. The insulation should bemaintained so that any damage is rectified. Furthermore, the insulationshould not be removed as a result of alterations.


• Notching of frame elements to enable the passage of new services etc maycause a significant reduction in structural performance. Whilst ‘traditional’notching of solid timber elements may be acceptable, applying the sameprocess but removing the flange of a timber I-joist, or steel joist, could bedisastrous.

• Durability of holding-down provisions is a concern for the long-termintegrity of the structure. Any alterations/repairs which would affect thisshould be avoided.

• Important issues relating to on-site construction practices during erectionand after completion/maintenance schedules have not been independentlyreviewed. There is no clear industry/independent guidance on how thesesystems are to be maintained, adapted or altered. When handling panelsdamage can occur, especially when the internal core is recessed to includeinternal horizontal and vertical jointing. Protruding, unsupported boardedges can be prone to impact and tend to break off, especially whenbrittle materials are used as face veneers. This type of damage has thepotential to reduce the structural performance of the wall assembly. Asecond cause of damage can be over-tight tolerances in the dimensioningof the recesses, causing the cracking, breaking and sometimesdelamination of boards along its length/height upon insertion of thejointing section. This has potential to markedly reduce the structuralperformance of the wall SIP units as the breakage destroys the continuitywithin the wall. Both types of damage are difficult, if not impossible, torepair and broken panels should be replaced since, if the continuity in thefacing board is irreversibly damaged, its function as a load transferring andshielding connection between the panel and the next level of constructionis weakened. Damage occurring within the wall area is equally difficult torepair especially when damage occurs within the central part of the panel.Any damage to the facing veneers should be assessed carefully even ifsacrificial lining is hiding the panel surface in the final wall assembly.Sandwich wall manufacturers provide repair kits, allowing for cosmeticremedial action to be undertaken. However, large damage (greater thanabout 30%) is likely to impact on the panels’ load-bearing behaviour andcannot be restored, so the damaged panel should be replaced.

• The SIPs act as diaphragms to provide resistance to (primarily) wind loads.Cutting holes in the panels may significantly affect their diaphragm actionor weaken the panel joints.

• Damage to SIPs during construction/maintenance/change of use: Rewiringof buildings needs to be monitored as timber frame practice is oftenadopted as panels look similar. The load-bearing function of the skins inSIPs is often not appreciated by structural engineers and on-siteprofessionals, and wiring has been observed to be recessed into the facingmaterials. This destroys the continuity of the face layers and impacts onthe load-bearing performance and fire performance of the panels.


• Performance of SIPs after fire damage: A generic method of establishingthe fire performance of SIP buildings (beyond fire resistance requirements)is needed. Most currently available SIP systems have been independentlycertified by notified bodies such as the British Board of Agreement (BBA).This includes (amongst other testing) fire-resistance testing which must becompleted successfully to obtain a certificate. However, the damagesustained by a structure after this compliance period is not assessed. Thepost-fire stability of structures is not addressed directly through fire testing.In a real building, for example, residential apartments, fire damage can beextensive, and spread beyond the fire compartment. The extent of damagesustained by SIPs in realistic fire scenarios is not known. These issues didnot have major implications in the past because most traditional forms ofconstruction have extended fire resistance through redundant load paths,for example, and are likely to remain structurally load-bearing after the firehas died down in the compartment. In SIPs this cannot be assumedwithout verification as the load-bearing mechanism is fundamentallydifferent.

• Some SIP systems use larger section timber to transfer localised loadsthrough the building. However, there is no unified industry practice anddesign concepts vary considerably. In some cases, no solid members areused in the wall sections as all loads are transferred through the panelskins. This needs to be considered by structural engineers when assessinga change in load-transferring structure, due to changes in room layout, ornew openings or extensions.

• As with all novel forms of construction, the long-term performance of SIPsis unknown. How and when degraded panel components should beinspected and assessed is not considered. Supporting information in theUSA, where SIPs have been used since the 1950s, could probably beassembled and examined but no strategic, generic study has beenundertaken. A maintenance schedule needs to consider the agingbehaviour of the glued connections within the panel, and the long-termperformance of the foamed core. The behaviour of the board materials isthought to be well understood and researched, but knowledge needs tobe extended to cover the various core materials and glue bonds used in SIPconstruction. The reliability of the structural performance of all panelcomponents over time requires investigation and quantification. Similarly,the repairability of SIP structures when damaged in use needs to beexamined. Maintenance schedules and requirements need to beformalised and referenced in generic guidance documents.

• Design may rely on load sharing between the cladding and the frame:

• British Standard BS5268-6.1: 1996 allows this between timber frameand masonry cladding.

• Similar guidance for light steel frame construction is provided in SCIP30111.


The structural integrity of the building may be compromised if the originallyused cladding is replaced, as a result of either alterations or repair, withsomething which has an inferior structural performance (stiffness and/orstrength) or reduced fire resistance. The same would be true for claddingremoved to provide significant openings such as patio doors.

• A ‘known’ problem with composite steel-concrete construction is cuttingholes in the slab (e.g. for passage of services). The cutting has to be carriedout by trained specialists as, unless the cutting is done carefully (i.e. usingdiamond drilling), the profiled decking separates from the concrete andcomposite interaction is lost. Additionally, if the hole is near the beam(which is often the case), the concrete flange of the composite beam willbe affected and this (depending on position within the span) can seriouslyaffect both the strength and stiffness of the beam. Guidance on carryingout this operation is provided in SCI P30012.

• Substitution of heavier materials than those originally used could cause aproblem, for example, replacing a lightweight roof covering with heavier,more traditional, construction.

• Widespread adoption of standards such as LPS 2020 would result in theprovision of adequate information from manufacturers of newcomponents/systems. With the help of available information, the apparentunquantified risk of the different ICPT can be targeted and resolved.

• The issues resulting from the use of specialist materials/components/skillscan be resolved to a certain extent by minimising their use wherepracticable.

• Adequate and clear marking of components would ensure that correctchoices are made when alterations or repairs are carried out. The markingshould include information about:

• the type of component, e.g. type of sheathing;

• the purpose of the component, e.g. load-bearing or non load-bearingmember.

• Issuing of a building handbook and homeowners’ manual would result indissemination of relevant knowledge to parties involved in makingalteration/repair decisions for buildings constructed using ICPT.

• The essential skills which would be required for supporting growth in theICPT building sector should be identified. Training in these skills should beorganised so that the ‘population’ that understands the new systems andtechniques grows.

• Regulatory changes should be brought in to ensure that somebody withsufficient knowledge/experience is always consulted where thealteration/repair decisions could impact on the integrity of the building.


The ‘dumbing down’ of systems, however this might be achieved, is not asensible option as the new methods provide numerous benefits thatoutweigh the potential issues noted here (assuming the latter are controlledthrough the measures proposed herewith).

The new methods of construction provide numerous benefits for theconstruction industry. It is essential that these innovative methods areembraced without having a negative impact on the structural integrity ofbuildings. In order to achieve this, there is a need to provide sufficientinformation (where lacking) to the users of the ICPT so that informeddecisions can be made when alterations and repair are carried out.

Adoption of standards such as LPS 2020 is the right way forward for resolvingmany issues related to the use of ICPT. The other important area would bechanges in the regulations to ensure that somebody with sufficientknowledge/experience is always consulted where the alteration/repairdecisions would impact on the integrity of the building.

2.7 Task 7Development and prioritising of a programme ofwork required in support of possible changes toregulatory and design requirements in relation toICPT

The main objective of this project has been to develop a programme ofpotential further work which emerges from the study of ICPT and which isrelevant to the Building Regulations and to other parties concerned withproperty protection and business continuity. Of the issues addressed withinthe project, the following have been highlighted as worthy of further study:

• More information is required on the performance of ICPT in service. Ofparticular concern is the degree of damage resulting from specific events.In the absence of a historical database of performance, recourse should bemade to existing methods of collecting data to identify specific areas ofconcern. The database of real fire events held by the London Fire Brigademay be one area which could play a part in identifying particular areas ofconcern. This could be a useful starting point in developing subsequentresearch priorities in this area. A web-based database would provide auseful and accessible means of information for key stakeholders.

• System performance – for many forms of construction, particularlyengineered solutions, the interaction between members and the ability ofconnections to withstand the large forces and deformations presentduring and immediately after a fire are a critical factor. For many largeframed systems the benefits of structural continuity can lead to loadredistribution from heated areas to cooler undamaged areas. However,these benefits do not necessarily apply to light framed systems where


connections are principally designed to resist shear force. Brittleconnections may not be able to transmit the large tensile and prying forcesgenerated during a fire, and premature failure of the connections wouldprevent the individual members attaining their anticipated fire resistanceperiod. Large-scale fire testing, such as that outlined in emerging national,international and industry standards, would allow a proper evaluation ofsystem performance. This issue of the integrity of the joint betweencompartment walls and floors was identified in a previous research project,BD2413 – The Integrity of Compartmentation in Buildings During a Fire.

• Cavity barriers and fire stopping – the existing requirement assumes a fireon the protected inner face of external or internal panel systems. Theexisting guidance should be reviewed in relation to a more realisticassessment procedure that would consider the effect of an ignition sourcewithin the cavity itself. Evidence from real fire investigations shows thatsuch a scenario is of practical concern. The vulnerability of certain designsolutions to poor workmanship or poor site supervision could also beinvestigated, as there is evidence that critical fire barriers are not alwayscorrectly installed or indeed always present.

• Facade performance should be investigated with reference to Regulation 7dealing with material suitability and workmanship issues. The traditionalmeans of complying with the Building Regulations requirement to limit therate of heat release of external facades has been to rely on small-scalereaction to fire tests which deal principally only with the surface spread offlame. Modern systems are dependent on supporting framework,connections and the presence or otherwise of a ventilated cavity. As wellas vertical flame spread, there is a possibility of burning through thecladding to provide a route back into the building. A large-scale testmethod has been developed to consider these issues. Considerationshould be given to encouraging the greater use of this test method.

• Throughout the project key stakeholders and technical experts have raisedquestions about the performance of SIPS. Of particular concern is the issueof potential disproportionate collapse following a fire. It is stronglyrecommended that a research project is initiated in collaboration withmanufacturers to establish the relationship between the results fromstandard fire tests and performance under realistic conditions.

• There is a need to evaluate the performance of engineered floor joists infire under realistic conditions in relation to loading and clear span.Information on deflection under fire conditions and residual load-bearingcapacity would be of great benefit to key stakeholders, notably the Fireand Rescue Service.

• It is generally assumed that concrete is an inherently fire-resistant material.Fire design normally extends no further than ensuring compliance with“deemed to satisfy” provisions from British Standards covering overalldimensions and cover to reinforcement. The tests on which theseprovisions are based are many years old and the results are not directly


applicable to the modern cements used particularly in ICPT products,where cement replacement materials and fillers are often used to improveservice performance. The relationship between these mix designs usingmodern cements and the traditional reliance on outdated test resultsneeds to be established.


Chapter 3

Conclusions

The research has identified three broad areas for action:

• Use of new materials or permutations of materials (engineered timberproducts, new concrete mixes and structural insulated panels).

• Developing a more robust database for collating information.

• Exploring the impact of new techniques and processes (cavities and firestopping, connections between elements and the risk profile associatedwith different stages in the construction process).

The principal objective of this project was to develop and prioritise aprogramme of further work in relation to ICPT. Specific actions in thecategories above have been prioritised according to the volume of use, likelyimpact and scale of study required. On the basis of contribution andfeedback from the steering group, Table 3 overleaf identifies and prioritisesareas for further research.

Conclusions | 35

Table 3 Prioritised topics for further research work

Topic Comments Ranking

The performance in fireof structural insulatedpanel systems (SIPS)

Large-scale testing required to ascertain residualstrength, possibility of disproportionate collapse andeffect of different filler materials and adhesives. Industrysupport required.

1

Database of real fireincidents

Information required related to form of construction andindividual products. Require input from all keystakeholders. Web-based system preferred. Would haveto manage the interests of insurers, manufacturers andavoid impinging on legal cases.

2

Cavity barriers/cavityfires/fire stopping

Experimental study required to investigate relativeperformance of materials/products/systems where seatof fire is within the cavity. Reference to Regulation 7.Some inherent fire performance required.

3

Fires in theconstruction stage

Guidance is required on measures to minimise the risk ofa serious fire occurring during the construction phase.Many of the real fire incidents brought to the attentionof the project team during the course of the study haveinvolved fires during the construction phase. The risk offire initiation is often very high at a time when thebuilding has little or no inherent fire protection. Thisoften leads to substantial economic losses, particularlywhere ICPT are involved. In terms of life safety, the issueof partial occupation of incomplete residential schemesshould also be addressed.

4

Performance ofmodern concretematerials

Experimental programme to investigate the performanceof a range of modern concretes, including cementreplacement materials, in relation to long-termdurability, strength and fire performance.

5

Performance ofengineered timberproducts

This could be extended to cover long span beams ingeneral. Structural performance likely to be verydifferent to conventional floor joists.

6

System performance infire

Series of large-scale fire tests undertaken with industrialsupport to demonstrate best practice in relation to thedesign of connections and fire stopping.

7


Chapter 4

References

1. Modern methods of construction in Germany – playing the off-site rule,Report of a DTI Global Watch mission, March 2004

2. Chris Goodier and Alistair Gibb, The Value of the UK Market for Offsite,Buildoffsite report, 2004, Loughborough University

3. Market Transformation Programme, Modern Methods of Construction,BRE Draft Report, 2006

4. Council of Mortgage Lenders, Modern Methods of Construction,www.cml.org/cml/policy/issues/107

5. Non-traditional housing in the UK – A brief review, BRE/Council ofMortgage Lenders, July 2002

6. www.abi.org.uk

7. Post Magazine, 29th May 2006, pp. 8, 16-17

8. Fire safety of light steel framed houses (CC2318), Closing report forODPM, BRE report 203-001, March 2003

9. Approved Document A, Structure, The Building Regulations 2000, Officeof the Deputy Prime Minister

10. LPS 2020: 2006, Loss Prevention Standard – Standard for InnovativeSystems, Elements and Components for Residential Buildings, BRECertification

11. Grubb P J, Gorgolewski M T and Lawson R M, Building Design UsingCold Formed Steel Sections – Light Steel Framing in ResidentialConstruction, SCI Publication No. P301, Steel Construction Institute,Ascot, 2001

12. Couchman G H, Mullett D L and Rackham J W, Composite Slabs andBeams Using Steel Decking: Best Practice for Design and Construction,MCRMA Technical Paper No. 13 – SCI Publication No. P300, published bythe Metal Cladding and Roofing Manufacturers Association inpartnership with the Steel Construction Institute, 2000 Edition

References | 37

Appendix A

Summary of the research

The overall aim of the project is to assist in ensuring that constructioninnovation is embraced and encouraged in a way that maintains fire safetyand structural integrity. The report provides information on a range of issuesconcerning Innovative Construction Products and Techniques (ICPT) withparticular regard to fire safety and robustness of new and emerging productsand systems. A prioritised programme of further work has been developed inconsultation with the Project Steering Group. The issues considered by theProject Steering Group include fire spread, integrity of compartmentation,cavity barriers, external cladding, structural insulated panel systems (SIPS) andworkmanship.The specific objectives of this project are:

• To consider ICPT, cavity barriers, fire compartmentation/separation and,where relevant, their respective inter-relationships.

• To produce a prioritised programme of further work needed on the issuesraised above. This should include the possible development of suitablemethods of test and assessment that cover all forms of construction, withparticular emphasis on innovative methods of construction, where adatabase of performance in real fires does not exist.

The programme of work undertaken has met the key objectives of theproject.

This report will be of interest to key stakeholders including the Fire andRescue Service, national and local authority building control bodies, insurers,mortgage lenders, manufacturers and housing associations.


Appendix B

Definition of building systems

Off-site manufacture (OSM) – volumetric

Volumetric construction (also known as modular construction) involves theproduction of three-dimensional units in controlled factory conditions prior totransportation to site. Modules may be brought to site in a variety of differentforms, ranging from a basic structural shell to one where all internal andexternal finishes and services are already installed. A family-sized dwellingmay typically be manufactured as four modules plus an additional roofmodule.

Figure A1. A volumetric construction unit being fitted

Volumetric construction can have many benefits over other forms ofconstruction including improved quality, reduced defects and snagging onsite, rapid assembly, less disruption, better working conditions, increasedpredictability and control, and efficiency in the production process with thepotential benefits of economies of scale. This approach is particularly suitedto areas where there are large amounts of services, such as kitchens andbathrooms.

Definition of building systems | 39

Off-site manufacture – panellised

Flat panel units are produced in a factory and assembled on site to produce athree-dimensional structure. The most common approach is to use openpanels or frames which consist of a skeletal structure only, with services,insulation, external cladding and internal finishing occurring on site. Morecomplex panels – typically referred to as closed panels – involve more factory-based fabrication and may include lining materials and insulation. They mayalso include services, windows, doors, internal wall finishes and externalcladdings.

Steel-framed panels are most commonly “open” and do not includeinsulation, lining boards etc. Such panels may also be referred to as “sub-frames”. Insulation to external walls is normally applied to the outside of theframe and often supplemented by additional insulation placed between thestuds. This creates a “warm frame” construction that is very effective inreducing cold bridging across steel members.

Figure A2. Steel panels used to form the structural frame

Timber frame panel systems have been used for many years. Such“conventional” panels would normally arrive on site with the sheathingboard (generally oriented strand board – OSB) fixed but without insulation orinternal boards. Experience in use has allowed some to view these systems ashaving a satisfactory “track record” of performance. They therefore can beclassified as established or traditional construction. With modern systems,service conduits, linings and window frames can all be fitted in the factory.


Figure A3. A panellised timber frame system

Concrete panels have been used since the end of the Second World War innon-traditional construction, particularly for flats. Bespoke housing systemsare being developed for both single owner/occupier premises and multipleoccupancy flats and apartments. Such applications are very common incontinental Europe, particularly in Germany1.

Floor and wall units are produced off-site in a factory and erected on-site toform robust structures ideal for all repetitive cellular projects. Panels caninclude services, windows, doors and finishes. Building envelope panels withfactory fitted insulation and decorative cladding can also be used as load-bearing elements.

Structural insulated panels (SIPs) are prefabricated lightweight building units,used as principal load-bearing components in domestic and light industrialconstruction. They are essentially a sandwich construction comprising twolayers of high-density sheet material bonded to a low-density cellular corestructure. SIP panels have been widely used in North America for a number ofyears. The face layers of the panel may be cement or gypsum-based buildingboards or oriented strand board (OSB). The materials used as core substrateare diverse and range from synthetic, rigid foam cores, such as extruded andexpanded polystyrene (EPS and XPS) or polyurethane (PUR) and its derivativepolyisocyanurate (PIR), to inorganic mineral fibre. Self-adhesive syntheticfoam cores, such as PUR and PIR, are suited to a continuous productionprocess. Foams such as EPS, XPS and mineral fibre wool have to be glued tothe faces in an additional manufacturing step. They have no internal studswithin the panels and rely on the bond between the foam and the sheetmaterial to form a load-bearing unit; studs may, however, be used at cornersand around openings. In a SIP structure the insulating layer is morecontinuous than in other systems, leading to better thermal performance for


a given thickness of panel due to the absence of thermal bridges associatedwith the presence of studs.

Figure A4. A timber SIP system (these joints are typically nailed together)

Panellised systems are more flexible and can more easily accommodatevariations in form and design. Spaces such as bedrooms and living spaceslend themselves to panel construction systems, providing greater choice forthe client and designer, with fewer restrictions on room size and layout.Furthermore, panellised systems can be stacked flat, enabling more efficienttransportation to site. However, compared to volumetric construction, thelevels of finish and services which can be accommodated are lower.

To obtain the maximum benefit from panellised systems the following pointsshould be taken into consideration:

• Providing a factory-made kit of parts delivered to site for fast erection toform the building frame

• For maximum economy the panels should follow a common designincorporating repeatable sizes from which the building can be formed

• Use of a standard library of components will reduce costs

• Increasing the amount of finishing within the factory will optimiseconstruction efficiency but may have implications for transportation costsand damage to units in transit

• Panels may be in the form of roof, wall or floor panels. Complete cassettesincorporating sheathing, boarding or panelling are commonly used


Off-site manufacture – hybrid

A hybrid method, also referred to as semi-volumetric, combines bothpanellised and volumetric approaches. Typically, volumetric units (oftenreferred to as “pods”) are used for the service-intensive and standardisedareas such as kitchens and bathrooms, with the remainder of the dwelling orbuilding constructed using panels. The hybrid approach is sometimes used toprovide added flexibility on complex sites and those requiring additionalcommunal areas (such as student accommodation). As with both volumetricand panellised approaches, the degree of prefabrication is variable.

Transport is reduced compared to volumetric construction but the quality ofoff-site manufacture is maintained for areas where specific performancerequirements must be met. Such an approach combines the benefits of massproduction, factory production and standardisation with flexibility of options.

Semi-volumetric/hybrid is focused on providing the benefits of volumetricconstruction for heavily serviced areas.

Site-based systems

This category is intended to encompass schemes utilising innovative buildingtechniques and structural systems that fall outside the OSM categories. Thepresence of innovation is an essential feature that might be present in a non-OSM building. This may take the form of a technique familiar in other sectorsbut not generally used in construction (technology transfer) or throughtraditional components being combined in an innovative manner. Exampleswould include “TunnelForm” or aerated concrete systems.

The “TunnelForm” system utilises L-shaped steel shutters to cast concretetunnels. The moulds are heated overnight to accelerate the cure of theconcrete and allow the moulds to be removed and reused on a 24- hourcycle. Reinforcement and service conduits can be placed within the moulds asnecessary prior to pouring the concrete, and openings for stair wells andinterconnecting doors can also be formed.


Figure A5. TunnelForm construction

Figure A6. Aircrete block and plank system

Aerated concrete products

There are two types of aerated concrete products on the market, thin jointblockwork and aerated concrete planks. Thin joint blockwork is constructedusing a special mortar bed of approximately 4 mm. The mortar is mixed onsite to produce a smooth, free-flowing adhesive. The blocks may be largerthan normal blocks and dimensionally more accurate. The blocks can be usedas a direct substitute for conventional blockwork or in conjunction withaerated concrete planks.

A site-based system using reinforced aerated concrete slabs in standard sizescan be used for floors and roofs. It is similar in principle to beam and blockfloors. The slabs are joined together using a tongue and grooved joint along


their length to ensure a good mechanical joint. The floor joints are thenfinished using a bonding grout and a self-levelling bonded screed.

The product can be used as a direct substitute for conventional blockwork orin conjunction with aerated concrete planks. The planks are used to form thefloor and roof elements of buildings.


innovative construction & product techniques

Documents

local government website

local authority

copyright licence

emerging products

range of issues

ascrown copyright

executive summarythis

project steering group