Timber Cladding
Timber cladding that is correctly specified can remain attractive for many years, while incorrectly specified timber cladding can become unattractive quickly. Factors that can help timber cladding become unattractive quickly include use of the wrong timber species, use of the wrong timber cladding profile, the timber cladding system being incorrectly installed, placement of timber cladding system, and several others. Compromise in timber cladding with poor specification can actually exceed ones’ expectations.
Timber cladding specification mostly concern timber species, and it is usually where decisions go wrong. There are varying degrees to the to timber cladding durability for cedar, pressure-treated wood, thermal- treated wood, term-treated larch, and others. It is actually preferred that western red cedar becomes a silver-grey. It is interesting to note that this can actually occur without treatment as well. Larch timber is in fact denser and has more impact resistant durability than cedar timber and actually has more durability than treatment of the moisture. Moving to the acetylated timber cladding, it is actually more resilient to moisture than untreated timber. However, it is not as prosperous to impact resistance as the previous.
Thermowood has good placement in today’s market. In the prescribed conditions, all softwoods are heated above 180°C. At these temperatures, the moisture in the wood reaches a critical low point and fungal decay is inhibited. Softwoods are naturally more prone to decay than hardwood. The heat treatment in the prescribed conditions changes the structure of the wood to improve stability. The softwoods do not move as much as hardwood and the gapping and movement of softwoods becomes less of a concern. Additionally, there are no biocides used in the heat treatment process. In the end, there are no potentially hazardous chemicals derived and, for builders and developers of environmentally conservative clients, thermowood is a viable option.
Fire ratings are a required specification that is often overlooked and creates problems down the road. In the Current Documents, Part B of the Building Code, all cladding on external walls of buildings greater than 18m falls under the classification of A2-s1,d0. This is a regulated class. Timber in its natural form does not meet it as that class demands a burn time extinction of less than 30 seconds. In the second, treated and modified classes, the burn time is less than 2 minutes. The claim is that for buildings in which the new regulations apply, the design for the building must firstly be controls compliant. This must be done before building control people ask, not after.
The profiles also impact the aesthetic and the drainage performance. Water moves in a circulation pattern and is less damaging due to the moisture. In the other profiles there is a chance of water damage. The other profiles look good and are less prone to problems, but also do not allow for drainage. Fasteners are hidden and not visible, which eliminates the rust from the fasteners visibly staining the wood.
This section discusses timber species selection, cladding profiles, the fire performance aspects for timber and non-timber materials used in commercial applications, and the maintenance requirements for each material. It is designed for architects, contractors, and developers to aid in their decision of materials to specify, rather than simply pick from a brochure.