1. The end user customer should obtain from the under floor heating supplier written confirmation that the system is operational with controlled temperatures so that the surface of the subfloor does not exceed 27* centigrade. This requires flow control valves and floor temperature probes in addition to room stats. We strongly recommend the installation of several floor temperature data loggers such as the Fidbox, as this will prove the floor has not overheated in the unlikely event of a warranty claim.

2. Check the following before laying : -

  • The moisture content of the concrete screed must not exceed 1.8%
  • Air relative humidity must be between 40% and 65%
  • The maximum deviation in flatness does not exceed 3mm per linear metre
  • The sub floor must be a closed and self supporting surface
  • The sub floor must be clean and dust free
  • If plywood or chipboard are used as an additional sub floor, they must be of good quality.

3.The installation of the UFH must be carried out by qualified installers recognized by the UFH manufacturer so that : -

  • Hot water pipes must be sufficiently below the top surface of the screed to ensure even heat distribution and to avoid hot spots. This would normally be approx 40mm.
  • There must be sufficient insulation below the UFH and a functional DPM to prevent moisture being drawn up through the screed
  • No attempt should be made to force dry the screed using the UFH - such action will destroy the integrity of the cement screed

4. The UFH should be commissioned by the installer so that : -

  • On day one the pipe water temperature should be set to 20*C and then increased 5*c each day to achieve a maximum of 45*C which should be maintained for 8 days. This temperature should then be reduced 5*C per day over 8 days. Total commissioning period is therefore 21 days.
  • Good ventilation should be provided over the commissioning period.
  • The installer should provide certification of the commissioning including records of the temperatures achieved at the sub floor surface.

5. Before the flooring is fitted the UFH should be turned off and left off during the fitting process. After the floor is fitted and finished, the heating should not be turned on for at least 48 hours and where the floor has been oiled, the oil manufacturer’s instructions must be followed so that the oil does not dry out. In some cases this may require a waiting period of 14 days. After this the floor temperature may be increased by 1*C or 2*C per day.

6. It is imperative to avoid subjecting the wood flooring to extreme changes of temperature and/or humidity IN A SHORT PERIOD. Such action will shock the wood flooring and can cause delamination. Ideally the UFH should never be turned off completely but should be allowed to remain at a low temperature. If the UFH is turned off and the floor gets cold as may happen in the Summer time, when the UFH is turned on again, then the water pipe temperature increase must be controlled as in paragraph 4 above. Air humidity in the building should always be kept between 40 and 65% RH to ensure that the wood does not get too dry. This may mean that air humidifiers are required.

SUMMARY
The following floor situations should be avoided:-

  • Rapid changes in the surface temperature
  • Insufficient adhesive is used to stick down the wood floor causing hot spots and uneven heat distribution
  • Low or High room humidity
  • Surface temperature over 27*C
  • Cleaning the floor with too much water
  • Thick rugs or carpets laid on the wood ( these will increase the wood temperature)
  • Turning the heating on and off


If allowed these situations will cause the following floor failures:-

  • Warped boards
  • Delamination of the top layer
  • Gaps appear between boards
  • Lack of heat transfer through the boards
  • Cracks appear in the wood surface