Wood is a natural product and as such expands and contracts with changes in atmospheric conditions. It is for this reason that wooden floors need an expansion gap. Solid wood floors take in moisture when there is a high level of humidity in the air and let that moisture go when the humidity reduces. High humidity in the wood causes it to expand. Low, or reducing humidity causes it to contract. When the wood expands, it may be that any small gaps disappear but when the wood contracts the gaps will typically reappear. This is entirely normal.
Either way, it is absolutely essential to leave an expansion gap around the perimeter of your room when laying a wood floor. Expansion gaps should be around 15mm to allow the wood to expand and contract without suffering any sort of distortion. If you don’t leave this gap, when your floor expands it could well rise, causing damage.
In a domestic setting, particularly in centrally heated homes, floors expand and contract with the seasons. During winter months, when you switch the central heating on, wooden floors will lose moisture and contract. This contraction is caused by the dryness of the air, encouraging the wood to naturally lose its inherent moisture. The contraction which occurs in the wood during these winter months is highly likely to cause gaps to appear in the floor, which, if not properly insulated may give rise to draughts. In order to avoid this, you should make sure your sub floor is well insulated.
In the warmer months, when the heating is switched off, the wood will expand again. This is caused by the rising moisture in the air which is absorbed by the floor. When this happens, if there have been any gaps over the winter months, they are highly likely to disappear. This natural process of expansion and contraction is unlikely to pose any sort of damage or distortion to your solid wood floor as long as it has been well fitted with the requisite expansion gap.
If you don’t allow for an appropriate expansion gap in your flooring project, the effects could be catastrophic. When a floor expands and touches a wall or door frame (known in the trade as a “pinch point”), there is pressure placed on the boards causing them to rise. Like all things flooring, if you’re in any doubt, your flooring supplier should be able to reassure you.