Floor Coverings & Underfloor Heating – What You Need To Know

Underfloor heating feet on wooden floor

Most floor finishes, aside from those with high insulation properties, are compatible with underfloor heating (UFH) but depending on the thermal resistance of the material, some transfer heat better than others.

Here’s a detailed guide to help you select the ideal floor covering for your UFH system.

General Guidelines

When choosing a floor finish, ensure that both the covering and adhesive can endure contact temperatures up to 40°C.

Pay close attention to the tog rating of the material; a higher tog rating means greater insulation. For screed systems, it is recommended that the floor covering have a tog rating between 1 and 2.5.

CERAMIC TILES

Ceramic tiles are an excellent choice for UFH due to their high thermal conductivity and low thickness.

Use a quality two-part flexible adhesive, and for screed systems, a de-coupling membrane can prevent contraction cracks in the screed from affecting the tiles.

For floating floors, install UFH over a flat, level surface using high-compressive-strength insulation.

Special substrates like Fermacell are suitable for tiling on floating floors, but always check the manufacturer’s guidance.

SOLID WOOD

Timber floors work well with UFH and can even prevent ‘cupping,’ which often occurs with air convection systems like radiators.

Timber is typically glued or nailed to battens or joists but can also be continuously glued to screed floors.

Do not exceed a board thickness of 30mm, and ensure the timber’s moisture content is around 10% at the time of installation.

ENGINEERED WOOD BOARDS

Engineered wood boards are more stable than solid timber due to their cross-laminated structure and less critical moisture content.

Boards under 20mm need additional support and should be fixed to decking material unless installed over a screeded slab.

If floating the boards over screed, underlays like Duralay Heatflow are ideal.

LAMINATE

Laminate flooring is advantageous for UFH as it is easy to install, stable, and generally not thermally resistive, ensuring good heat output.

Similar to engineered boards, laminates under 20mm thickness require support and fixing to additional decking material, such as plywood, unless laid on a continuous floor like a screeded slab.

CARPET

Most carpets are suitable for UFH, provided the underlay is not a good thermal insulator to allow heat to pass through.

Avoid polyurethane and felt underlays.

The underlay should have a tog rating of 1 or less, and the combined tog rating of carpet and underlay should not exceed 2.5.

VINYL

Vinyl is another suitable option due to its thin structure, allowing efficient heat transfer.

While some vinyl can withstand high temperatures, most can only tolerate up to 26°C.

Thus, the heat output should be limited to around 65W/m², making vinyl less ideal for high heat loss areas like conservatories.

Always check the manufacturer’s guidance to avoid issues like tiles ripping or lifting.

MARBLE/STONE

Stone floors, including marble, are highly thermally conductive, making them a top choice for UFH.

Use a quality two-part flexible adhesive like BAL Fastflex to bond the tiles to the substructure.

However, marble and stone are not suitable for floating floors.

SLATE

Slate floors function similarly to marble/stone, providing excellent thermal conductivity for use with UFH.

By following these guidelines and material-specific recommendations, you can ensure optimal performance and efficiency of your underfloor heating system.

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