Underfloor Heating Guide
Installation of Engineered Wood over Underfloor Heating
Good underfloor heating (electric or water-borne) is an ideal heating method, and underfloor heating
combined with a wood floor gives optimal domestic comfort.
The laying instructions for each floor type also apply when laying over underfloor heating.
The following instructions summarise what is specific to wood floors laid over underfloor heating.
Choice of wood floor
An ideal choice is engineered flooring. This reduces the risk of cracking.
Engineered flooring can be laid over underfloor heating, which must distribute the heat efficiently and
evenly across the floor.
The surface temperature of the floor must never exceed 27°C. This also applies near radiator pipes and
under any rugs, etc.
Beech and Hard Maple engineered floors expand and contract more than other wood species. Underfloor
heating causes the wood to dry out more, which results in additional shrinkage. In a cold, dry climate (e.g.
in Sweden), cracks between strips and slightly concave boards are to be expected.
The Crown range is compatible with underfloor heating (both water and electric).
However, Crown recommends that checks are made with underfloor heating supplier to
ensure the heating system selected is suitable for use with wooden floors.
Concrete or anhydrite subfloors laid over heating ducts should be at least 30mm thick.
The concrete subfloor must be sufficiently dry. A newly poured subfloor requires a
drying time of about 1 week per cm depth up to 5cm and 2 weeks per cm after that.
For example, an 8cm subfloor requires 11 weeks of drying time prior to installation of
an engineered wood floor. As before, readings should be taken with an appropriate
meter. The moisture content of concrete subfloors with underfloor heating must not
exceed 1.8% and the moisture content of anhydrite subfloors must not exceed 0.6%.
With water systems, prior to flooring installation, the heating must be run and checked
for leaks and appropriate pressure. The temperature should be increased by 5ºC each
day up to its maximum and then down by 5ºC each day to 20°C.
Acclimatise the wooden floor boards for at least 5 days, still in their packaging, laid
flat in the centre of the room. During acclimatisation the room temperature must be
between 18°C and 20°C and relative humidity between 45% and 60%.
When installing with underfloor heating, it is recommended to stick direct to the
subfloor. However, it is also possible to use a floating installation provided that a low
tog underlay is used.
3 days after installation, run the underfloor heating, increasing the temperature at a
rate of 5ºC each day to the required level.
The maximum water temperature of the heating installation may not exceed 45°C.
The surface temperature (which is different from the air temperature) of the floor may
never exceed 27°C.
Maintain a steady relative humidity between 45% and 60%.
Temperature levels should be kept stable with no large fluctuations.
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