The changing face of wood

If you had the opportunity to dream up a new material for building today, I wonder if you would have the audacity to imagine a material that grew itself and, while it grew, absorbed carbon dioxide and produced oxygen; that needed only sunlight, air and water, and that came with a huge range of capabilities, that could be soft and easy to work at first and yet would become harder and stronger the longer it was in service.

It seems almost unbelievable and yet we are so familiar with wood that we forget how incredible it is as a living building material.

It is the sustainability of wood as a building material that is the main driving force behind its increasing use in building. This sustainability has made wood and wood products fashionable and has encouraged the development of new systems and new products that make use of the marvellous range of capabilities of timber in building.

This is particularly brought home to me each year when I act as a judge for the Wood Awards, which bring together the best examples of the use of wood in building in this country each summer.

Range of cladding

Initially, it seemed that the most noticeable use of wood in the projects we saw were those using western red cedar as cladding with its beautiful weathered silver grey surface, but this was soon followed by projects using both seasoned and green oak boarding more locally grown and accepting the problems of the run-off of tannin. In its turn, Scottish larch has become fashionable and, more recently, there has been an intriguing use of coppiced sweet chestnut, finger-jointed to make high quality cladding and joinery, which is very sustainable both in growing and its production.

Of course, this increase in the range of timber used for cladding has been paralleled by the development of modern structures in wood from the extraordinary sweeping curves of the lightweight gridshell structures to geodesic timber structures using poles or elegant glue laminated struts and simpler timber framed housing with exposed frames.

A general theme in this development has been the intelligent combination of sustainable production methods in forestry such as coppicing, together with the best of modern technology in computer design and production systems, the development of adhesives and particularly the development of new composite materials.

One area where these elements have come together is in the development of the use of panel composite products in building. From timber frame using open stick, faced plywood or other composite facing panels to the development of structural insulated panels (SIPs) in various forms and to the development of Kerto, structural ply panels where thicker multiple plys are laminated in parallel to give the greatest structural strength, in a continuous process that can produce very long stable structural panels.

Engineered panels

More recently we have seen the extending use of solid softwood engineered panels. They are made up of softwood battens glue laminated together in layers set at right angles to each other to make up solid stable panels which, through their stability and strength, have enabled timber-framed buildings to take a major leap forward. In fact, these panels are enabling city centre multi-storey timber framed housing to be constructed at eight, nine or even more storeys and at the same time provide for the full integration of services and give all the other advantages of offsite construction. The most striking aspect of this system is the clean, dry building process on site that develops from the use of these panels.

Another development has been in the pre-treatment of timber to extend the life of softwoods in exposed situations. Accoya, using pine impregnated using acetic anhydride, to produce a stable resistant material of very high durability is a specialist example. Thermowood using heat-treated softwood, which again increases stability and resistance to weathering, has produced a new form of timber for cladding, which is now gaining in popularity.

It is in the continuing development of these systems and composite materials that I see the most vibrant and interesting sector of wood futures. The need for greater sustainability will continue to drive the development of better and more subtle systems, combining wood and other natural fibres together with adhesives and within matrices of lime, cement, or others to produce new panels and building systems for the future.