Historically timber frame has not been renowned for quick-fire innovation. But the past decade has seen technological advances that have given it a huge boost in ‘buildability’, durability and performance. The list includes closed panel walls, reverse wall construction, open web joists and I-beams, cassette floors, pre-assembled roofs, factory finished and installed joinery.
The suitability of timber frame in low-rise developments is well proven. For more complex and larger scale developments, however, timber frame has still to command a foothold.
‘Timber is almost always at an immediate disadvantage in such circumstances,’ said Martin Milner, managing director of Chiltern Clarke Bond. ‘Designers are generally much more conversant with the use of the alternatives. Timber engineering is seldom taught at undergraduate level and the construction industry as a whole “understands” steel and concrete..’
Design conversion
More often than not, the starting point for timber frame is not in optimising a new design, but in re-designing a scheme already developed in steel or concrete. Much of the timber frame build costs are therefore in the conversion of the scheme to suit timber frame and in the training of the project’s design team about timber frame construction. ‘Such activities are an unnecessary cost that clients carry – and one that can make timber frame solutions look less competitive,’ said Mr Milner.
Chiltern Clarke Bond was formed in 2000 – as a specialist engineering consultancy dealing only with prefabrication of light frame solutions – to address this issue. Mr Milner believes that the next innovation in timber frame will be to engage timber frame design teams early in the project process.
A good example of the commercial advantages of timber frame is the ground-breaking Ion building at North Woolwich, for which Chiltern Clarke Bond was the timber engineer. The seven-storey apartment building was developed by St James Homes. In this case, said Mr Milner, six storeys of timber frame on an integral concrete ground floor and foundation structure provided the solution to meet the client’s demands for a lightweight building suited to the ground conditions and which combined speed of construction with high performance/high build quality.
Frame fabricator and erector Bedford and Jennings welcomed the closer involvement of Chiltern Clarke Bond’s professional team in the construction process and looks to adopt similar practices in future projects.
Recent material advances with engineering timber components such as super dry graded timber, I-joists and LVL products, together with the structural performance findings from TF2000, the TRADA Technology and BRE six-storey test building project, mean that the timber frame industry is ‘no longer restricted to self-build homes or low rise housing estates,’ he added.
Lifestyle housing
‘The housing market wants lifestyle apartments in high-density residential buildings and timber frame delivers the required in-service performance together with the fast build times demanded by developers. In addition the growth of multi-storey student accommodation is perfect for timber frame, where repeatability of units deliver significant cost benefits with this approach to building,’ said Mr Milner.
A point worth noting is the government’s target to build 60% of new homes on brownfield sites. ‘That means high density schemes are here for the foreseeable future, as developers look to increase the volume of usable building over smaller sites, to compensate for the higher ground work costs. Timber frame can deliver the solutions sought.’
Chiltern Clarke Bond believes that its role should not begin and end with a timber frame design brief. ‘We bring a holistic approach to the project and advocate that the whole project team should meet at intervals throughout, from “build philosophy” right through to the construction process.’
Previously head of TRADA Technology‘s timber engineering consultancy team, Martin Milner has brought experience of troubleshooting with him.
Chiltern Clarke Bond technical director David Barber said: ‘The use of prefabrication techniques offer some significant advantages to the building industry, not least of which are the reduced construction time, leading to reduced site costs and less reliance on large numbers of skilled site labour. Among other benefits are potential reductions in foundation or transfer beam costs as a direct result of the decrease in dead load of the structure, particularly if lightweight cladding systems are adopted.’
The key to a successful project, the company believes, is to adopt process management techniques rather than use a project trade management approach. Mr Barber added: ‘Integration and co-ordination of design issues using the superstructure engineer as a lead consultant, focused on the manufacture of the structure, can eliminate those areas that traditionally cause installation problems, particularly those associated with wall and roof claddings. Bringing together all the parties that have a design responsibility at an early stage to identify the design constraints is necessary to ensure an economic and trouble-free timber frame.’
But Chiltern Clarke Bond does not set out to recommend the use of timber frame for all projects. Mr Milner stated: ‘We do not aim to shoehorn timber frame into every building solution. That can only give timber a bad name. We aim to advise on what we believe to be the best engineering solution for the job, whether in timber frame, steel or concrete.’
The team is now working on a challenging leisure complex in Birmingham for Morrisons Construction and PACE Timber Systems, which will be five timber frame storeys on three storeys of steel frame. A further Chiltern Clarke Bond design is a high density project being manufactured and erected by Pinewood Structures in Wolverhampton, comprising five- and seven-storey timber frame student accommodation. Both projects required design development input and liaison with the main contractor on the impact of using a prefabricated approach to building.
Design software
With its underlying philosophy of innovation and best practice, Chiltern Clarke Bond has adopted state-of-the art design software which it helped to develop. The timber frame drawing environment is based on Auto Cad and Architectural Desk Top. The software provides seamless integration between developers’ drawings and provides tailor-made output for the timber frame fabricator. Software developer COINS intends to launch the software commercially this year.
Architectural Desktop has been widely in use for some time. It allows structural features to be made available in a number of styles and loaded into a 3D drawing as intelligent objects.
As well as the design of modular and prefabricated frames, the company offers scheme evaluation and value engineering, production of fabrication drawings and schedules, component design expertise, product support and independent, authoritative checking of detail across the supply chain.
