©Titan Wood A Sound Choice
The increasing popularity of external timber cladding as a contemporary design solution is something that many UK house builders and developers are familiar with, but with both consumers and politicians focusing on green issues, it is important to understand why timber cladding is a sound choice and how it can enhance your home. Hal Stebbins, Worldwide Sales & Relationship Management Director of Accsys Technologies, takes a look at timber cladding.
Wood has perennially been the most popular choice for external cladding on residential builds and renovations, combining contemporary style, elegance, simplicity and natural warmth. Low in weight, environmentally friendly and with high density and excellent thermal properties, wood is an excellent match for the demands of both existing and proposed new building regulations. A choice of natural, modified and engineered woods is available for cladding, each offering its own characteristics. So, how do you decide what will be best for your project? The most important factors to bear in mind when choosing a cladding timber are the effect that you require both in terms of finish (light or dark wood, painted, stained or oiled) and style of cladding, the wood’s service life, whether preservatives are required, how frequently you are prepared to maintain it and the environmental credentials of the wood used. From an environmental perspective wood is an excellent choice as it is
low carbon compared to other materials such as plastics. It is also a naturally renewable resource that may be recycled or used as fuel at the end of its service life. To ensure that you are doing your bit for the planet, choose certified sustainable wood, such as Forest Stewardship Council (FSC), PEFC or another regional certification as reassurance that it derives from well managed forests. A well designed external timber cladding system forms a protective and decorative weathering envelope for walls, whether made of brick, concrete or timber. Used in combination with insulation materials, it keeps walls frost-free and will help conserve energy in your home which is another good reason for choosing timber. The fact that wood can be susceptible to deterioration should not be seen as an insurmountable problem, particularly given recent developments in the fields of wood modification and treatments. Different woods have different levels of durability and it is important to specify a wood that is ‘durable’ or ‘moderately durable’ and suitable for Use Class 3 (above ground, regularly exposed to moisture) according to BS EN 335.
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Each species has its own characteristics, life expectancy and maintenance requirements. Western Red Cedar and European Oak are classified as durable
woods, with Western Red Cedar giving an anticipated 60 year service life. European Larch and Douglas Fir from North America are both ‘moderately durable’. UK grown Douglas Fir is considered ‘slightly durable’ (BRE Digest 494). Species that may also be considered, but will require preservative treatment, include Spruce, Fir, Lodgepole Pine from Canada and European whitewood. In this case it is important to consider the environmental impacts of the treatment to be used. A dimensionally stable wood is also highly desirable as wood naturally
tends to swell and shrink in response to variances in moisture levels and which may result in gaps forming or boards warping. The more dimensionally stable the wood the longer it will last and the less coatings and other maintenance it will require. Broadly speaking, the life expectancy of cladding is determined by the species chosen, the method by which its performance is improved (chemical preservatives, organic solvents or thermal or other modification technique), whether it is left unfinished to silver naturally, stained, painted or oiled and whether it is maintained at the appropriate intervals. Traditionally wood has been treated with finishes that are toxic, thus
removing some of its natural benefits. However, more environmentally compatible alternatives are now available, as are new products that do not require additional treatments or preservatives to enhance their performance.
Thermally modified woods are softwoods that have been modified
by heating it to temperatures up to 215?C to change their chemical structure. This reduces the moisture, sap and resin levels by up to 50% and initially produces a dark coloured wood that offers a 30 year service life.
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