As a natural material, timber cladding needs a little extra understanding to ensure long term successful implementation, as Tom Barnes of Vastern Timber explains.
The use of timber cladding has boomed in recent decades. In many cases timber cladding still looks beautiful 5 – 10 years later, but in other cases it has not fared as well. The key to successful implementation is a good understanding of weathering – both natural and human influenced – and how species react in modern environments, also the effect of elevation and aspect.
Timber cladding is often used on buildings with numerous elevations and overhangs where panels will face different influencing factors. These can include the weather and differing amounts of UV light and wind. With a huge amount of differential weathering to consider, these effects can be highly noticeable if not enough consideration is given to aspect, elevation, and detailing.
Obviously, when left in its natural state timber will weather more quickly than when protected. Common unexpected changes in appearance can include; extractive staining in woods like oak, sweet chestnut and western red cedar, where soluble organic compounds in the wood migrate in the presence of rain; black and green mould caused by a lack of sunlight or perpetually damp conditions; blackening due to particulates in pollution; and surface greying (bleaching) which, while an attractive feature, can be undesirable if uneven due to different levels of exposure to rain and sunlight.
Canadian cedar is the most popular cladding species. In unpolluted rural areas and on designs that have considered weathering factors, uncoated Canadian cedar will develop a beautiful silver/grey colour. However, its inappropriate use in the wrong environment and a failure to consider weathering factors can result in an unattractive patchy appearance.
Oak and sweet chestnut are heavy in tannic acid, which is very reactive and brown in colour. In some cases these species have been used to clad the top storey of buildings while the lower storey features white render. Rain can cause tannins and oils to leach out from the wood, often resulting in staining on the render. Similarly, ferrous particulates in urban road pollution will react with these extracts causing unattractive blackening of the surface.
The correct approach for designers looking to successfully use timber cladding is to take a broad view of the project and the specific influencers that will affect the timber used, including; aspect of the elevations; the environment (is it rural or urban?); proximity of other buildings or trees that might provide shade; design and management of water run-off; and consideration of the reactivity of different species.
As seen in Specification Magazine