Underfloor Heating and Solid Wood Floors

Solid wood floors present the greatest challenges where underfloor heating is concerned but this does not mean that they need to be ruled out altogether.

Wooden floors and particularly solid wood floors will expand when they absorb moisture, typically this occurs during the summer months when windows are open and central heating systems are turned off. Conversely, they will contract, during the winter when heating is on and the wood loses its moisture, gradually making it dry out.

This process never stops and cannot be halted. Underfloor heating will exacerbate this effect because it is in direct contact with the floor. For this reason, we usually recommend an engineered wood if it is to be installed over underfloor heating.

However, if it is a requirement to lay a solid wood floor over underfloor heating, the following measures will help to minimise any adverse effects:

• Ensure that the flooring has been properly acclimatised in the room with the heating on at a level that would be normal during the winter months. This can be taken a step further by having your fitter loose-lay the boards ensuring they are not fixed to each other or the sub-floor.
• The floor can then be finished with oil or lacquer and used as normal. You might however find that the joints will creak a bit.
• Then, over a period of a couple of months, gradually raise the temperature of the underfloor heating until it reaches what will be its normal operating temperature. At this stage, with the boards fully acclimatised, they can be fitted according to the appropriate method.
• Also, the wider the plank, the more expansion it will be subject to so, it is recommended to use as narrow a board as possible with an absolute maximum of 130 mm. If at all possible, your underfloor heating should remain on a low constant heat rather than coming on and going off at regular intervals as would be the case if controlled by a timer or thermostat.
• It can also be a good idea to use a humidifier to maintain the room's relative humidity (RH) to between 40% and 60% as it is the absorption and loss of moisture that is the real culprit when it comes to movement in wooden floors rather than the temperature directly.

Underfloor heating using Engineered wood floors and Laminate flooring

Engineered wood and laminate floors are both far less susceptible to the issues mentioned above, engineered wood floors are still subject to a certain amount of expansion and contraction so it is wise to try and adhere to some of the advice like using narrow boards, ensuring thorough acclimatisation and avoiding drastic changes in the temperature levels of the underfloor heating

For further information check out our guide to fitting floors - it includes lots more detail about acclimatisation and if that's not enough please give us a call!