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BUILDINGS & CONSTRUCTION PROCESSES


Demonstrating benefits of prefabricated housing Although prefabrication has been widely promoted as a way of improving construction processes, its use in the UK


housing market has been very limited. BRE research, as part of a Government-sponsored, industry-led project, has assessed the design, construction, cost and appeal of prefabricated housing.


T


he project included two case studies of prefabricated social housing developments – the Peabody Trust’s Murray Grove development (30 one- and two-bedroom apartments – see picture) in London, and the Joseph Rowntree Foundation’s CASPAR II development (a five-storey building of 45 flats) in Leeds. The two cases indicate that, through good design, aesthetically appealing, practicable and flexible buildings can be achieved with modular construction. They also show that prefabrication is not synonymous with low quality, badly insulated, damp and noisy units, as its current image suggests.


both developments showed tenants to be very happy living there, that all tenants found their flats to be warm and comfortable and that they had not needed to make much use of their heating systems.


For further information please contact Cecilia Bagenholm at BRE (01923 664317;


fax: 01923 664084; E-mail Bagenholmc@bre.co.uk).


TIMBER & CONSTRUCTION PROCESSES


New flitch brings added value ‘Timber 2005,’ the research and innovation strategy developed through the UK


Government for timber in construction, stressed that added value, ease of fabrication and guaranteed performance in use are all vital issues to drive forward the British timber sector. ‘Best value from UK timber’ was identified as a specific Priority Area. The Partners in Innovation Competition 2000 and ‘Roots for Growth,’ the Action Plan of the Scottish Forest Industries Cluster, also identified the creation of specific innovative products, together with the sharing of knowledge about them, as vital stages in their future strategy.


T Murray Grove development under construction


On construction processes, the case studies showed that prefabrication can reduce construction time significantly – it is easier to predict and meet the completion date, less time is needed for snagging (ie putting right faults before handover to the client) and it is not so weather-dependent as conventional construction. However, more time needs to be spent on planning for a prefabrication project, as it is vital that the timing and logistics of the project are well thought out early.


While both projects were slightly more expensive than conventionally built social housing, the additional costs can largely be attributed to their prototype nature and higher than normal specification.However, the faster construction time enabled the client to collect rental income at a much earlier stage, this being roughly equivalent to the price of an additional flat. Finally, any concerns that tenants might object to prefabricated construction – equating it with poor quality – proved unfounded, as the clients had no difficulty in letting the flats. Satisfaction surveys on


he aims of a recent, small, but highly successful ‘New Age Flitch’ Partners in Innovation


project were to:


• demonstrate the transfer of innovation into practice within the UK timber supply chain;


• develop a specific, new, value- added use for UK-grown softwoods, within the construction sector;


• disseminate the results during and after project completion, to provide a Case Study for further such commercial and technical ventures.


The initial phase of work on the new flitch beams has been completed by TRADA Technology and a group of forest products and timber industry partners. The intention is to drive forward the concept into the market, and to continue with further improvements and extensions. Future Europe-wide consortia are also being considered, since value- addition from the basic products of the plantation softwood supply chain is a common theme throughout NW Europe.


The new flitch system shows the potential for utilising simple, dried, strength-graded, solid softwood members. Abundant production facilities for these exist at modern UK sawmills. Having invested more recently than competitors elsewhere in the temperate globe, UK producers have some of the best and most up-to-date sawing, grading and drying equipment anywhere.


Conventional plain carbon steel strip, in structural grades, is used for the central flitches. A manufacturing innovation is the use of ballistically-fired fasteners and tooling. These enable accurate assembly by driving fasteners through both the timber and the steel without the need for pre-drilling.


Research Focus NO. 48 FEBRUARY 2002


Footbridge using the new flitch system Courtesy of Trada Technology Ltd


Investigations have so far included:


• viability of products incorporating the new flitch technology;


• specific applications and likely costs; • fixing developments; • durability evaluations, covering a range of applications and environments;


• preliminary determination of long-term performance;


• development of a simple design method.


As part of the continuous dissemination strategy, a footbridge was built, recorded, and described in a feature in View Point, the TRADA Membership Newsletter.


For further information contact Pia Larsen of Trada Technology Ltd, Stocking Lane, High Wycombe, Bucks, HP14 4ND (01494 569600; fax: 01494 565487; E-mail: plarsen@tradatechnology.co.uk). Project website: www.ttlchiltern.co.uk/ research_projects/pif284/index.htm


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