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Wood Flooring over under floor heating

Manufacturers Specific Guidelines:



General Information: (not to be used in lieu of manufacturers recommendations


  • Generally Solid Wood Floors are not suited to underfloor heating, Most Engineered & Laminate Floors are suitable, however please check with your specific product manufacturer to confirm suitability.
  • Ensure that Heating Systems are tested and commissioned prior to the installation of new floor coverings.
  • New Screeds must be tested for residual construction moisture and must be dry to receive floor coverings, refer to screed and UFH suppliers instructions regarding new screeds, underfloor heating and drying processes.
  • Underfloor Heating should be turned off during any moisture testing procedures.
  • Flooring should be acclimatised on site prior to installation (as usual).
  • Heating should be gradually brought up to an operating temperature avoiding hot spots, or rapid changes in temperature. 


Underfloor heating with Kährs flooring:



UNDERFLOOR HEATING IS IDEAL FOR ENGINEERED WOOD FLOORS

Today, wood floors and underfloor heating are often combined and work well together. Both electrical and hot-water underfloor heating can be used with Kahrs hardwood floors. It is, however, very important to follow both our specially designed installation instructions, as well as the instructions and recommendations given by the supplier of the underfloor heating system. If properly installed, you will achieve a beautiful and long-lasting wood floor with the increased comfort of pleasant warmth. Here you will find instructions and advices on what to consider when choosing underfloor heating for your engineered wood floor.

TEMPERATURE OF THE SURFACE

The surface temperature of the floor must never exceed 27°C. This also applies to areas next to radiators and elements, under furniture and carpets, etc. With good furnishing and without too many carpets, or carpets that are too thick, it is reasonable to achieve a temperature of 23°C over the entire floor area, for a room temperature of around 21°C. Of course, this is assuming that the room requires a normal amount of heating. This means that your sealing, insulation, windows, etc., must be of regulation standard quality. Extra precautions should be taken to ensure the temperature at the feeding of the hot water never exceeds the maximum level, and that installation instructions provided by the supplier of the heating system are followed correctly.

SUSCEPTIBLE TO MOISTURE

Floors with underfloor heating are more susceptible to moisture than those without. This is because the difference in moisture content between the driest and dampest parts of the floor will increase over time. Underfloor heating can cause extensive drying, which makes the wood contract and shrink. In a cold, dry climate, you can expect to see gaps between strips and slightly concave boards from time to time. We recommend Kährs Original 15 mm parquet flooring or Kährs Linnea 7 mm with Woodloc® or Woodloc® 5S joints for floors with underfloor heating. Both Kährs Original and Kährs Linnea reduce the risk of gaps forming.

It is worth bearing in mind that parquet flooring made from Beech and hard Maple expands and contracts more than other wood species and is therefore not recommended for use with underfloor heating.

INSTALLING OVER UNDERFLOOR HEATING

Your wood floor must be laid close to the subfloor and without an air gap, as air gaps can cause the wood to dry out very quickly.

When laying a floor over underfloor heating loops, the working temperature should be at least 18°C. This is applicable to boards, subfloors and room temperature. The relative humidity (RH) of the air must be between 30 and 60% before, during and after laying the floor.

Cardboard is preferred for the intermediate layer, as polyethylene cellular plastic and cork particleboard have a higher thermal resistance.

Find out more about installation over underfloor heating in our guide Subfloor Requirements and Underfloor Heating.

SPECIAL REQUIREMENTS WHEN INSTALLING UNDERFLOOR HEATING

  • The floor construction must have a heat-distributing layer that gives an even temperature over the entire surface of the floor area, in order to prevent high temperatures in certain spots.
  • It must be possible to control and limit the surface temperature with a high degree of accuracy.
  • The entire floor area must be heated. However, this does not apply to comfort heating systems, which complement normal heating. In this case, the temperature should be considerably lower than the permitted 27°C floor surface.
  • The laid floor - including the intermediate layer - must have a low thermal resistance.
  • A vapour barrier must be built into the floor construction, positioned as close as possible to the wood floor. It is particularly important to have the vapour barrier near to the wood floor if the joists are thick or heavy. Under no circumstances may the vapour barrier be placed on the opposite side of the joists.

An underfloor heating system should provide efficient and even heat distribution over the entire floor area. The surface temperature of the floor must never exceed 27°C, including areas next to radiators and heating elements, under furniture and carpets, etc. With good furnishings and without too many carpets (or carpets that are too thick), it is reasonable to achieve a temperature of 23°C over the free floor area, giving a room temperature of around 21°C. This assumes that the room requires a normal amount of heating and that seals, insulation, windows, etc. are all of a regular standard.

A few recommendations

Floors with underfloor heating are more susceptible to moisture than floors without. This is because the difference in moisture content in the driest and dampest parts of the floor will increase over time. Underfloor heating causes more extensive drying, which makes the wood contract and shrink. In a cold, dry climate, like the one we have in Sweden, for instance, you can expect to see gaps between strips and slightly concave boards from time to time.

We recommend Kährs Original 15 mm flooring or Kährs Linnea 7 mm flooring, with Woodloc® joints, for use with underfloor heating. Using either of these products reduces the risk of gaps forming.

It’s worth bearing in mind that beech and hard maple wood floors expand and contract more than other wood species. Underfloor heating increases drying, which causes additional contraction.

Installing over underfloor heating

Your wood floor must be laid close to the subfloor, without an air gap. The wood may dry out very quickly if you leave an air gap.

When laying your floor over underfloor heating ‘loops’, the working temperature should be at least 18°c. This is applicable to boards, subfloors and room temperature. The relative humidity (RH) of the air must be less than 60% before, during and after laying the floor.

Cardboard is recommended for the intermediate layer, as polyethylene cellular plastic and cork particleboard have a higher thermal resistance.

Requirements when installing underfloor heating

  • The floor construction must have a heat-distributing layer that gives an even temperature over the entire surface of the floor area, in order to prevent ‘hot spots’.
  • It must be possible to control and limit the surface temperature with a high degree of accuracy.
  • The entire floor area must be heated. However, this doesn’t apply to comfort heating systems, which complement central heating. In this case, the temperature should be considerably lower than the permitted 27°C at the floor surface.
  • The installed floor, including the intermediate layer, must have a low thermal resistance.
  • A vapour barrier must be built into the floor construction and be positioned as close as possible to the wood floor. If the joists are thick or heavy, it is particularly important to have the vapour barrier close to the wood floor. Under no circumstances must the vapour barrier lie on the opposite side of the joist.

Always check with the product manufacturer or supplier to ensure compatibility prior to ordering your new floor.

Please ensure that you check the product manufacturers website for the most recent guidelines on underfloor heating prior to installing your new wooden floor. 


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