Under-floor Heating
Despite the concerns sometimes expressed by those with less experience in this area, with the right preparation and the right product, it is possible to successfully lay solid wooden flooring over all types of under-floor heating.
Broadleaf have developed the following basic guidelines as a result of considerable experience over recent years and, if you do plan to fit a solid wooden floor over under-floor heating, we would recommend that you take 5 minutes to study them:
1) Ensure the correct system temperature
The first and most important step is to ensure that the under-floor heating supplier is aware that a wooden floor is to be fitted over the system so that the system itself can be correctly specified. It will need to be set to ensure that the surface temperature does not exceed 27 degrees centigrade. If possible, to help ensure that this is the case, we also recommend that a floor thermostat is specified as a supplement to the standard air thermostat and that this is set as the master control .
2) Choose a flooring product that is suitable for use over under-floor heating.
In our opinion traditional solid Oak can be used successfully, but must be re-kilned below 9% humidity. Drying the timber to this level prevents the close proximity of the heat from the under-floor heating shrinking / warping the boards once the floor has been laid. (Normally boards are kilned to 9 – 12%).
Re-kilning takes place prior to the machining of the timber into boards, so can generally only be offered by manufacturers of timber flooring. Some suppliers therefore suggest that their Oak flooring to be used over under-floor heating without being re-kilned, but they will normally require it to be loose laid (spread across the floor without fixing) for anything from 6-8 weeks before fitting. The idea is that any shrinkage takes place during this time, but this process is not 'scientific' and 'acclimatisation' is often inconsistent.
We also consider our Strata Oak and Chestnut boards suitable for use over under-floor heating. Due to their particular structure and dimensions these products will remain stable in close proximity to under-floor heating without the need for re-kilning or loose laying.
Suitable Broadleaf products are detailed in our brochure or can be recommended by our staff, but currently include most of our Traditional Oak, Vintage and Nuances ranges in traditional solid boards up to 150mm wide and Strata up to 200mm, our Loft Oak or Brushed & Limed Oak from the contemporary collection, any of our parquet blocks and Byron Squares. The product specifications for each product on the website also provide this information.
3) Ensure that the site is correctly prepared.
As with any other installation, the site and subfloor must be prepared in line with our basic recommendations (see Fixing Issues)
The heating must then be run for 3 weeks. This should be at normal room temperature, unless the ambient room temperature is too high to activate the thermostat in which case you will need to overide it so that the heating comes on to warm the screed. Although this may cause some discomfort in summer months, it is vital to ensure the evaporation of latent humidity. Once heated, the concrete loses a further 5% of its latent humidity and it must be given the chance to do so before the floor is laid over it.
Once this has been done, check that the water temperature at the manifold is set to the specfied temperature (normally 40 - 45 degrees centigrade for wood floors) and that any floor thermostat is set to 27 degrees centigrade.
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