Expansion or control joints
Expansion or control joints are required to allow for the potential movement of timber floors (caused by fluctuations in moisture content) during normal service condition.

Generally, for floors up to 6m in width (measured at right angles to the boards), simply leaving a clear gap of 10mm between the floor edge and any structure will suffice. For continuous floor widths over 6m, intermediate expansion joints (parallel with boards) should be provided in addition to the minimum 10mm perimeter gaps. These joints can be either a single 10mm wide gap potentially located under a wall or across a doorway leading to a hallway and the like, or smaller gaps with closer spacing to give an equivalent total gap, for example a series of 1mm gaps at 1m spacings.

Where expansion joints occur in timber floors spanning between supports, it is recommended that a nogging be installed under the tongued and grooved joint to provide support.