Acclimation of timber flooring

Acclimation is the process of allowing new timber flooring to adjust towards the moisture conditions of the building in which it will be installed.

Timber naturally absorbs and releases moisture. If flooring arrives significantly drier than the existing timbers within the property, it may absorb moisture after installation and expand. Conversely, if the new flooring contains considerably more moisture than the surrounding building, it may dry out, shrink and create gaps between the boards.

For example, flooring kiln-dried to around 6–7% moisture content may expand if installed immediately into a property where the existing timber averages closer to 10–12%. Equally, flooring measuring 14–16% could contract noticeably if introduced into a much drier building environment.

The objective is not simply to leave the flooring inside for a set number of days. It is to bring the new hardwood into a suitable equilibrium with the established timbers and normal environmental conditions of the house, allowing them to live more harmoniously together.

Acclimation should therefore only begin once the property is dry, enclosed and operating under normal living conditions. Fresh plaster, recently laid screeds, open windows or doors, residual construction moisture and ongoing wet trades can temporarily raise humidity and give a misleading impression of the building’s long-term environment.

The moisture content of the flooring, existing timber elements, subfloor and surrounding conditions should be assessed before installation. Flooring should only be fitted once the building is stable and the moisture relationship between the new timber and the property is considered suitable.

Correct acclimation cannot eliminate all natural movement, but it greatly reduces the likelihood of excessive expansion, shrinkage and seasonal gapping after installation.