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Floor Coverings

Underfloor heating can work successfully with a wide range of floor coverings, with some offering a better heat transfer than others.

When you choose Nu-Heat, you are choosing an underfloor heating solution that is designed by experts specifically for the project. We will design the UFH system to offset any difference in performance of your chosen floor coverings.

What are the best floor coverings for underfloor heating?

Stone and ceramic surfaces
The best floor coverings for use with underfloor heating are hard surfaces such as stone and ceramic tile as they have the least resistance and transfer heat effectively. As the most thermally conductive of all floor coverings, energy from the heating tube array can transfer quickly to the surface of the stone/tile. Increasing the thickness will have little effect on power output, but will slightly increase heat-up times.

It is always advisable to use a de-coupling membrane and flexible adhesive with solid floor finishes to reduce the potential for hairline expansion cracks; large areas will also benefit from expansion joints, especially through doorways. The flooring supplier will be able to offer advice on specific coverings.

Ceramic tiles

Due to their high thermal conductivity and slim profile, ceramic tiles are one of the best floor finishes for use with underfloor heating. In all cases, a quality 2 part flexible adhesive such as BAL Fastflex should be used. When laid on screed floor heating, a de-coupling membrane should be used. This prevents contraction cracks in the screed being transmitted through the floor covering.

Polished screed

Polished screed is by its nature very conductive and although unusual, is well suited for use with a Nu-Heat warm water underfloor heating system.

Limestone

Limestone has been used as a building material for many generations and is gaining popularity as a sophisticated flooring material offering the timeless qualities only possible with natural materials. Of all stone floor coverings, limestone requires the most care and attention during installation.

Slate

An extremely conductive natural finish, ideal for use with underfloor heating. The durability of slate is a byproduct of its origin. Most rocks have a medium or coarse texture. Slate is very smooth, somewhat like plastic laminate. Very small silt and clay particles bonded together under high temperature and pressure give slate this monolithic texture. This ultra fine texture makes it tough for liquids (stains) to penetrate slate. Tiles and flags should be bonded to the substructure using a quality 2 part flexible adhesive such as BAL Fastflex.

Flagstones

A thicker stone finish that exhibits very good thermal conductivity. Tiles and flags should be bonded to the substructure using a quality two part flexible adhesive such as BAL Fastflex.

Marble

An excellent heat conductor available in varying thicknesses. With a naturally elegant appearance, marble tiles and marble slabs are a beautiful flooring choice. Marble tile flooring and marble slabs can be a subtle or a bold feature in your home.

Timber flooring
Engineered timber is the best option for use with underfloor heating as its structural stability allows it to perform well with fluctuating temperatures. Solid hardwoods and soft woods also transfer heat well but care should be taken when specifying board width and thickness.

Engineered timber

Engineered hardwood flooring is the natural progression from laminate flooring, offering the beauty of a real wood finish. An engineered board features a top layer of real wood combined with a cross-ply base laminate for stability. This is a more stable product than solid timber as it is cross laminated, like plywood, with a natural timber upper layer, and its moisture content is less critical. It can be laid directly over the underfloor heating as a ‘floating floor’ or secret nailed to battens or joists. Unless installed over a screeded slab, engineered boards of less than 20mm thickness should be supported and fixed to additional decking material to lend suitable structural support. Underlays such as Duralay Heatflow by Interfloor are particularly suitable when floating the boards over screed.

Solid hardwood

If a rustic look is preferred, solid wood boards will give the right effect. Despite common misconceptions, these floors work very well with underfloor heating. They are gently heated so that the surface temperature usually doesn’t exceed 27°C and because the surface of the floor is not dried out in the way it would be using air convecting systems like radiators, underfloor heating can actually prevent timber floors from ‘cupping’. Of more importance is the control of the moisture content of the timber such that it is maintained at around 10% at the time of laying. Beech and Maple are more prone to movement due to moisture than other boards. It is standard practice to screw or glue and nail the timber to battens or joists. Alternatively timber can be continuously glued to screed floors using products like Sikabond. Boards should not exceed a thickness of 25mm (1″).

Solid hardwood flooring is not recommended for use with LoPro™ retrofit UFH floor constructions due to the higher heat outputs generated.

Soft woods

Most softwoods can be used with underfloor heating, but it is better to avoid using timbers wider than 125mm (5″ and thicker than 25mm (1″).

Soft wood flooring is not recommended for use with LoPro™ retrofit UFH floor constructions due to the higher heat outputs generated.

Traditional parquet

Hardwood flooring blocks are a traditional material which can be laid in several different patterns, the most popular of which are Herringbone and Brick. Floor blocks are bonded directly to the sub floor and are then repeatedly sanded and then oiled or sealed to give the required finish. These flooring blocks can be laid in a number of different ways, but should be continuously glued onto the screed or timber deck for good heat transfer.

Bamboo

Usually similar in construction to engineered timber, making it very suitable for UFH. Bamboo is usually available as a laminate or engineered board. This is a more stable product than solid timber as it is cross laminated, like plywood, with a bamboo upper layer, and its moisture content is less critical.

Laminates, vinyl and rubber
Laminates and vinyls also perform extremely well with underfloor heating. These products heat up and cool down quickly in comparison to stone and timber.

It is advisable to check the manufacturer’s recommended maximum floor surface temperature to ensure the product is suitable for use with UFH. Most manufacturers state 27°C, which equates to approximately 75W/m2 of heat output, which is more than adequate in most situations. For sensitive floor coverings and high heat output floor constructions, Nu-Heat can supply a floor temperature sensor to limit the heat output from the floor.

Vinyl

Vinyl floors work very well with underfloor heating. Heat can easily permeate the relatively thin layer. However, as most vinyls should not be heated to above 26°C, the floor heating power output needs to be restricted (in normal living rooms to around 65W/m2). This means that these vinyls should not be used in high heat loss areas such as conservatories. Alternatively, some vinyls are available that can tolerate higher floor temperatures.

Amtico

Amtico floors offer practicality, durability and individuality. Amtico is more hardwearing than most wood, much more forgiving than ceramic or marble and, importantly, an Amtico floor in the home is guaranteed not to wear out for twenty years. This a very practical and highly versatile flooring. As with linoleum and some timber floors, there is a surface temperature limit (in this case 27°C) which the underfloor heating should not exceed. However this translates to about 75W/m² which is more than adequate in most situations. Amtico recommend the use of their own two part flexible adhesive to fix the product in place.

Linoleum & marmoleum

These are thin natural products that are very well suited to use with underfloor heating. Marmoleum is different from most floors. It is made from natural materials, is bacteriostatic, biodegradable, and provides no hiding place for dust mites. It is also easy to clean, hardwearing and comes in a vast range of colours and designs. Marmoleum is the ideal floor for a healthy home.

Laminate tiles

Laminate tiles are very stable, easy to lay and usually not thermally resistive, so allow greater heat output through the floor. Unless supported on a continuous floor, such as a screeded slab, laminates of less than 20mm thickness should be supported and fixed to additional decking material such as plywood. Underlays such as Duralay Heatflow by Interfloor are particularly suitable when floating the boards over screed.

Rubber

Rubber tends to be relatively thermally conductive resulting in high thermal output and quick heat-up times.

Other popular floor coverings

Carpet and underlay with a combined Tog value of up to 2.5 can be used effectively with underfloor heating. Thicker carpets act as an insulator and stop sufficient heat reaching the room. Nu-Heat’s comprehensive system design will factor in the extra heat output that will be needed if carpet is specified.

Carpet

Underfloor heating can be used with most types of carpet. As long as the underlay is not a good thermal insulator, heat will easily pass through this layer into the carpet itself. The overall Tog value of carpet and underlay combined should not exceed 2.5 with the underlay itself not exceeding 1 Tog. Felt and polyurethane underlays are best avoided as they are good thermal insulators.

Cork

Cork is highly abrasion resistant, resists humidity and dampens sound, making it an ideal choice for both residential and commercial uses. This natural floor finish may be used with underfloor heating but its thickness must be kept below 10mm as it is an efficient insulator.

Coir

A natural product similar to carpet that is subject to a maximum recommended Tog value of 2.5.

Suitability
Some flooring manufacturers stipulate a maximum floor temperature for their product; please advise Nu-Heat if this is the case so it can be factored into the system design. Nu-Heat adheres to BS1264, which states that underfloor heating surface temperature should not operate at more than 29°C.

As part of our complete design service, Nu-Heat is happy to advise on suitability. If you are planning on using a floor covering not listed, please contact us for advice.