What Lies Beneath
Most wood floors suit UFH but they need to be conditioned (acclimatised) to the correct moisture content. If the timber is too dry, moisture will be absorbed and the timber will swell and warp; if the timber is too damp shrinkage occurs, leaving gaps between the boards.
Another factor to consider is thickness - finishes must be less than 22mm thick.
There is no need to cover the floor beforehand with plywood because this acts as an insulating layer. Likewise fixing battens onto a heated floor leaving an air gap between the floor and the underside of the floor covering is inadvisable because air is an excellent insulator.
Laminates
Generally a laminate floor is laid as a 'floating floor' i.e. it is not fixed down and has an expansion gap aground the perimeter and doorways. In non-underfloor heating properties laminate is often laid on a 3mm combined vapour barrier/foam insulation. With UFH insulation can be dispensed with although the vapour barrier is still needed. Some people do still choose to keep the insulation.
Hardwood Veneers
These are becoming more popular. They have good stability and work well with UFH. They are often laid as a floating floor onto builder's paper.
Hardwood Floors
Often these are kiln dried to too low a moisture content, so they have to condition back to the ideal. An extra five days conditioning should be allowed.
Softwood Floors
Generally these have a high moisture content and extra care should be taken in checking with the supplier that they suitable for suitable for UFH. Conditioning needs to be carried out diligently. An extra five days of conditioning should be sufficient.
Conditioning Wood Floors
We recommend kiln-dried timber sourced from a reputable manufacturer for use with UFH. The kiln drying process removes moisture from the wood, but it is not ready for use straight away because moisture can be absorbed during storage and transportation. For centrally heated properties the moisture content of kin-dried wood is approximate 10 - 12%. For underfloor heating it needs to be 7 - 10 %.
Timescale and Technique
Before the flooring is laid the concrete and screed must be allowed to fully cure and dry. Curing times vary dependent on the type of screed so please check with the contractor/specifier.
After the concrete and screed have cured it still needs to dry out. The generally accepted figure for natural drying is 1mm per day. There should be a moisture content in the floor of not more than 5%, or a relative humidity of 75% which is measured using a hygrometer.
The UFH system can be used to assist with the drying out but the water flow temperature must be increased to operating level (50°C) slowly. The system should be started at 30°C and then increased by 5°C each day. With a Continental Underfloor heating system this is easily adjusted at the manifold.
Finally the timber can be conditioned. The wood should be loosely laid over the floor heating area with the underfloor heating system running at operating temperature and the room thermostat set to the householder's usual preference. The wood should be allowed to condition like this for a period of five days or longer before being fitted following the manufacturer's instructions.
Always check with your flooring supplier that it is suitable for UFH and for laying and conditioning requirements.
If you require further advice when it comes to recommending flooring to partner UFH contact Continental Underfloor Heating by logging on to www.continental-ufh.com or calling on 0845 108 7001.
