Timber is a natural, renewable substrate with a long history of use in New Zealand. Results are often excellent, however certain expectations need to be tempered. Timber often will have small amounts movement, which is usually caused by changes in moisture levels in the timber. Timber is hygroscopic, meaning it will be in an equilibrium state, always absorbing and releasing water depending on the surrounding environmental conditions. As the moisture level increases timber will swell, or contract as moisture is then released — this is timber movement.

When timber is first milled, it is saturated and needs to be dried out prior to use. Equilibrium moisture content is usually in the range of 14-18%, and so timber should be dried to this level prior to use, otherwise excessive timber movement might be experienced (as well as other problems such as tannin bleed). Even when timber is properly dried prior to use, small amounts of timber movement are likely. When a timber weatherboard is installed during the cooler months of the year, the equilibrium moisture content will be at the upper end of the range, but as the weather warms up the timber will lose moisture and shrink. Environmental conditions and the colour of the paint will also play a role — darker colours will heat the timber up more, leading to more water loss.

While timber movement problems are more likely with new timber, this seasonal expansion and contraction is a permanent reality for all timber. Weathershield X10 has Maxiflex technology, so it is able to move with the timber for the seasonal changes. When the initial contraction is too much, or if timber has been repainted with a darker colour, gaps of unpainted timber may appear where different timber planks meet, and this will require touching up.