Underfloor Heating and Solid Wood Floors
Solid wood floors present the greatest challenges where underfloor heating is to be used 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 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 drying out. This process never stops and cannot be halted. Underfloor heating will exacerbate this effect for the obvious reason that it is in direct contact with the floor. For this reason, we usually recommend an engineered wood floor if it is to be used 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. Firstly, 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. This involves laying the floor but not fixing it to the subfloor either with glue or nails and also not gluing the boards together. The floor can then be finished with oil or lacquer and used as normal. You might 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 lifted, a few at a time and fixed 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 130mm. 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 absorbtion and loss of moisture that is the real culprit when it comes to movement in wooden floors rather than the temperature directly.
Underfloor Heating with Engineered Wood Floors and Laminate Flooring
Engineered wood flooring and laminate flooring are both far less susceptible to the issues mentioned above that apply to solid wood flooring so can be used with underfloor heating successfully. 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 applicable to solid wood floors such as using as narrow a board as is practical, ensure thorough acclimatisation and avoiding drastic changes in the temperature levels of the underfloor heating
