According to TRADA (The Timber Research and Development Association), in recent years, timber in construction has undergone something of a renaissance, led by the desire to use more environmentally-friendly materials. While timber is at risk to biological decay, a combination of appropriate design and material selection will mitigate this risk.
reSAWN provides several designs on modified timbers that enable it to resist decay and increase durability. Accoya utilizes a process called acetylation, a cutting-edge patented technology, enabling it to it resist rot, defy the elements and stay strong for decades. Guaranteed for 50 years above ground and 25 years in ground or freshwater, its performance and properties are remarkable. Kebony is impregnated with furfuryl alcohol, which improves the durability and performance of the wood. The process permanently modifies the wood cell walls giving Kebony premium hardwood characteristics and a rich brown color.
The performance or service life of wood products is based on a combination of the design of timber components and structures, life cycle analysis and biological durability. Each of these factors plays a key role in ensuring a satisfactory service life for timber products.
The service life increases when the design calls for avoiding ground contact, covering end grains and avoiding moisture traps. Life cycle analysis addresses the entire life cycle of a product and a wide range of environmental impacts, avoiding ‘problem shifting’ – for example from one life cycle stage to another or from one environmental compartment to another.
Biological durability is the key factor determining performance for wood in different use classes. The robust laboratory and field test methods that exist make it possible to assign a durability rating (from non-durable to very durable) to timber linked to the intended use class and assuming a worst-case scenario.
The use of heartwood from more durable timber species, wood preservatives or modified wood can also improve the service life of outdoor products. Despite these, better design must also play a part in ensuring their satisfactory service life.
While work is ongoing in these areas, it is hoped that developments will continue to advance opportunities for timber, and in particular engineered wood products, to meet modern construction needs.