Adrian Young, Technical Editor, Exova BM TRADA hails the release of TRADA’s new National Structural Timber Specification – providing best practice guidelines for timber buildings…
The UK Government’s chief construction adviser called it a “milestone” but what exactly does TRADA’s new National Structural Timber Specification (NSTS) mean for those at the coalface – the engineers tasked with using it?
Nearly four months after the NSTS was launched at a high profile event at Arup’s London headquarters, what are engineers, specifiers and the timber industry’s leading lights saying about it?
Both the steel and concrete industries have had a specification document for some time; timber had lagged considerably behind in this area with engineers cobbling together specification documents literally on the job and tweaking them from project to project.
Not anymore. By providing a framework and information on minimum standards, the NSTS simply makes it easier for engineers to specify timber.
“Our clients want reassurance that they are using tried and tested methods of construction,” says Andrew Lawrence, Arup timber specialist. “The very existence of the NSTS alongside the growing body of large timber structures in the UK is helping clients realise that modern engineered timber is now a standard method of construction that can compete with steel and concrete on equal terms.”
Essentially, the NSTS gives the construction industry a set of best practice guidelines against which timber buildings can be erected. Some of the timber industry’s leading lights have been instrumental in helping TRADA put together the NSTS, which is now available to download free to those who register ( www.trada.co.uk/nsts ).
The NSTS project was driven by a group of TRADA members who have taken the lead in specifying timber. Most have their own bespoke specifications that they have shared with BM TRADA to enable this new specification to evolve.
Nick Milestone of B&K Structures chaired the steering group, which included representatives from Kingspan, Arup and Exova BM TRADA. Peer reviewing was provided by representatives from Smith and Wallwork, BAM Construct UK, Ramboll, Waugh Thistleton, NHBC, KLH, and Cullinan Studio, followed by a wider consultation among TRADA members.
Working with this group, TRADA developed a recognised comprehensive specification that covers information exchange, materials, fabrication, erection, protection and quality assurance. It’s a real game-changer for an industry that has – to this point – relied on using documentation from previous projects to fit the latest one.
“The NSTS is a game changer for the UK structural timber industry,” says Nick Milestone. “Architects, contractors, clients, specifiers and structural engineers have all embraced the NSTS as it is seen as what the industry has been missing in terms of acceptable tolerances in the design, manufacture and construction of structural timber components.
“The NSTS gives much needed confidence and reliance when specifying structural timber.”
Arup’s Andrew Lawrence agrees: “Clients are realising that to get high quality fast construction, timber is the ideal choice. We need to make timber easier for people to use; having a standard specification is part of that.”
The NSTS focuses on structural uses of kiln-dried softwoods for use in three main areas. The first is light-frame construction – usually known as ‘timber frame’ – the main application for this being housing. These can be ‘open panel’ and ‘closed panel’ as well as floor cassettes.
It also includes heavy-frame construction – typically glulam and other engineered timber post and beam structures – as well as panel construction (typically cross-laminated timber and structural insulated panels).
These systems establish methods of erection and tolerances. It is conceivable that the specifier might choose to adopt a ‘different’ system from that normally expected. For example, a closed panel timber frame could be installed to ‘panel’ standard.
The design of NSTS has deliberately followed Eurocode 5. There has been no provision for BS 5268 because it has been withdrawn. In future editions, it may be possible to create further modules to cover non-structural uses of timber – joinery, decking, cladding, flooring, etc. Other areas for future consideration will be hardwoods and also hybrid construction (where timber is combined structurally with other materials).
TRADA wants to make it easier for structural engineers to specify timber and that has inspired the development of the NSTS. Further, to ensure that the take-up of timber is successful and that learning is as seamless as possible, the NSTS includes links to essential best practice guidance from TRADA, much of which is contained in Wood Information Sheets.
The NSTS also helps engineers choose the right materials for the job. The section on timber materials details European harmonised standards, before delving in to various structural timber types that could be used in modern buildings, for example glulam, OSB and cross-laminated timber. There are also sections on connections, adhesives and workmanship, everything an engineer needs, in fact, to be able to specify timber.
TRADA has developed a recognised comprehensive specification that covers information exchange, materials, fabrication, erection, protection and quality assurance. It’s a real game-changer for an industry that has – to this point – relied on using documentation from previous projects to fit the latest one.
With the NSTS, TRADA has developed a recognised comprehensive specification that covers information exchange, materials, fabrication, erection, protection and quality assurance. It’s a real game-changer for an industry that has – to this point – relied on using documentation from previous projects to fit the latest one.
“Timber construction has the potential to change the face of the built environment and create a new form of sustainable urban design,” says David Hopkins, director Wood for Good.
“The details and information in the NSTS means professionals can specify timber with confidence making it a first choice material for all future design.” ■
To download a copy of the NSTS, please visit http://www.trada.co.uk/nsts
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Adrian Young
Technical Editor
Exova BM TRADA