A growing number of architects have chosen to use timber cladding for both domestic and non-domestic buildings. While this increase has been noticeable in the UK, it is worth noting that the phenomenon is far from confined to Great Britain with overseas examples becoming more common as architects and developers begin to recognise the green benefits of using timber as a viable building material.
One of the many advantages of using timber as opposed to other more traditional materials is the relatively small amount of energy needed to produce it, as well as its reduced level of toxic pollution. It is, however, worth considering other factors when choosing a timber. Transportation, drying, preserving and machining the wood, and maintaining its finish all take their toll on the environment and add to the energy consumption required to produce the cladding. These downsides can be reduced by carefully selecting the species of wood and the finish of the final product to reduce the environmental impact when produced and on a long term basis.
Timber cladding is often created using a softwood from the coniferous forests in the Northern and Southern hemispheres because of its wealth of renewable building material. The trees more commonly used are Red Cedar, European larch or Douglas fir, which are robust and durable woods, but if treated with additional preservatives European redwood or whitewood can also be used.
Tropical hardwoods or durable temperate hardwoods such as European oak or sweet chestnut are also becoming more common. This applies in particular to European oak, commonly used in the UK in its unfinished form which weathers to an attractive silver grey. This wood is incredibly hardy and can last for centuries without any additional maintenance, making it a desirable choice for those who prefer a fuss-free home. Wood from these trees is also readily available to those in Europe and the British Isles. Extensive oak forests stretch over these regions, after recovering from widespread deforestation even as late of the 18th century. These rich woodlands would benefit from thinning out and could provide the necessarily sized wood for cladding. Used in its undried state, this would reduce the cost of production and the amount of energy required to produce the timber. As with many untreated timbers, once installed, an allowance must be made for shrinking.
Another benefit of opting for timber cladding is the amount of construction time it takes to install. Cladding is a ‘dry’ process which is simple in its application. The wood can also be arranged into prefabricated panels, which again further reduces the time spent on the site.
The increased interest in wood cladding has also extended to use on timber and steel framed buildings, as well as using wood to clad blockwork and concrete constructions. This option is mainly an aesthetic choice but benefits the homeowner by providing additional protection from the rain. Builders can also install additional external insulation between a masonry wall and the cladding which can improve thermal performance and reduce heating bills.
History of Use
There are two traditional ways of using timber cladding in construction. It can be utilised as a primary form of structure in external walls, or can be used to enclose another structural frame as mentioned above. Structural timber walling can be produced using debarked logs stacked together and overlapping in the corner, which is a construction originally found in the Alps, and later adopted by Scandinavia and North America. Alternatively, solid timber walling can be produced using the stave or palisade construction where thick boards are set directly into the ground to support the roof eaves, and a post structure or framed wall takes the burden of internal loads.
Non-structural timber cladding on the other hand was used to protect the inner frame which supports the major roof trusses. These trusses would have rafters between them, supported by purlins. Between the posts of the internal frame, the cladding would be supported by rails, smaller posts and figs. Examples of this type of construction can be seen in early barn buildings, more common in East Anglia where often the cladding would conceal the posts and wall framing rather than being exposed to the elements. This construction model became the go to for builders in New England until deforestation led to the deciduous trees of the region becoming scarce, and therefore more expensive. It was then that a more modern method of construction using load bearing posts and small section softwood stud walls to support roof rafters and cladding was used.
This new form of construction was buoyed by the development of water power. Previously, boards would be sawn by two men by hand in saw pits. This was a timely and exhausting process. However, with water power, the process could be quicker and less strenuous, increasing production. Saw mills were built alongside rivers near coniferous forests which made it possible for excess timber to be harvested and kept as stock, rather than just cut down for individual constructions. To ensure that the wood was used in the most economical way standard measurements were used when cutting the planking, cladding boards and frames. Sawn boards became more common for urban buildings, as well as the other commonly used split shingles and shakes for cladding. In North America, this became known as ‘clapboard construction’. The other new development in the construction industry at this time was the mass production of steel nails, which made traditional carpentry joints a thing of the past and allowed for smaller, cheaper sections of timber to be used as framing. The use of softwood framed timber clad construction has already been utilised in Scandinavia for hundreds of years and have successfully stood the test of time. There are still buildings of this type in Norway, which have survived since the 13th century.
In those parts of the world where this timber frame construction has become standard, frame buildings are clad in timber boards, shakes or shingles. The materials used often last the life of the building despite the extreme climates they are located in, and this is also the case in the milder weather of the British Isles. The durable softwoods such as western red cedar were historically used much in the way that the European oak is used now in the UK – as unfinished shingles or boards. However, those less durable softwoods, such as European redwoods and whitewoods were more often stained or painted. This became royal decree in 17th Century Sweden, where it was ordered that all wood clad buildings had to be finished with a coating of Falun, which consisted of oil, rye and wheat dust which was mixed with ferrous oxides. This resulted in the traditional red colour of Swedish timber buildings and provided hardwearing long-term protection to the wood, which required very little repainting.
In the 18th century where classical and Renaissance architecture came into fashion, countries which used timber cladded buildings were forced to refine their construction to adhere to these new stylings. Architectural features and motifs such as columns, cornices, pediments and quoins which were more commonly found in stone or stucco were replicated using wood. Gone were more traditional colours of wooden buildings to be replaced with white, grey and pastel colours. This style of architecture is still seen commonly in the United States in New England where the Colonial style of mansions and large town houses have stood the test of time.
Another peculiar example of wood cladding can be found in North America, where small panels of unfinished hardwood were used to simulate individual blocks of ashlar stone and mounted directly on to the timber framing. As these untreated panels weathered naturally, they would fade to grey, creating a convincing appearance of classical stone.
Timber Framed Buildings
Despite existing in the UK since the 18th century, timber framed buildings have never garnered the same level of popularity as the more traditional brick buildings found on our shores. Those that did exist were often faced with plain or mathematical clay tiles to simulate brickwork, or else were faced with an additional brick skin or lime render to conceal the original construction of the building and raising the ‘status’ of the building.
However, some rare original examples of the earlier form of timber cladding do still exist in the UK in the south of England where old farm buildings can be found faced with either tarred or creosoted softwood boards; wide ‘waney’ edged elm boards or unfinished oak.
In the 1930s, there was a small insurgence of timber-framed buildings, which were imported and erected in the British Isles. Despite their age, these have lasted very well and have suffered from little physical deterioration. Sadly, some have been coated with unsuitable paints since their original production which has caused trapped moisture in the wood and decay. Some of the other properties have also been poorly maintained, giving them an overall shabby appearance. Nowadays with correctly designed rainscreen cladding and modern paints and stains, these problems can be avoided.
Not only is timber cladding attractive and easily maintained, but it is also an economical and environmentally friendly way for designers and those wishing to build their home to enclose buildings. With construction regulations and other UK legislation changes in the UK aiding the popularity of sustainable development and increased prefabrication for more efficient building, the popularity of timber cladding is sure to continue to rise.