Acclimatisation Of Timber
In order to produce timber mouldings and profiles to be used in any construction, the product goes through a number of processes such as sawing, kiln drying, treating, planing and cross cutting. All these processes can cause twist, warp, shrinkage and expansion of timber. It is imperative that all timber be allowed to adjust naturally to the environment in which it will be installed.
Case 1: Tongue and groove flooring manufactured at 12% moisture content is immediately installed into a new building with fresh plaster walls. For example the moisture content of the building is approx 15%. Once installed the flooring is exposed on all sides to this moist air and will expand as it draws in moisture causing lifting of the flooring if insufficient gaps have been left on the edges. As the building dries out over a period of time, the flooring dries and shrinks causing gaps ! This also happens with insufficient under floor ventilation and high water tables in winter.
Case 2: Timber cladding is installed shortly after CCA treatment (based in water i.e. high moisture content). As the cladding dries, poorly fastened nails pull out and boards cup and pull away from the wall. The exposed side of the cladding dries and shrinks at a quicker rate (exposure to sun/wind) than the inside (no sun/air movement) of the board causing excessive movement. The timber is behaving in a completely natural way.
Structural sizes are generally sold as “Sized”. These products have been planed slightly to a consistent size to allow accurate truss manufacture and exact framing of buildings. Some skip marks may occur from the planing process.