LVT and vinyl on underfloor heating: temperature limits, adhesives and fitting

Luxury vinyl tile (LVT) and sheet vinyl are thin and conduct heat well, so they let almost all the warmth from underfloor heating (UFH) through. The catch is that vinyl and its adhesive soften as they warm. Too much heat, or heat that changes too fast, can make tiles move, open joints, or let the adhesive fail. Strong sun through glass can do the same.

This guide sets out the figures from LVT, vinyl and adhesive makers: the temperature limit, which adhesive to use, screed moisture, the switch-off and warm-up routine, conservatories and electric heating. For all floor finishes compared, see underfloor heating under tiles, LVT, laminate, wood and carpet.

Can you put LVT or vinyl on underfloor heating?

Yes. Vinyl has very little thermal resistance. In the CIBSE figures published by one UFH maker, 2mm vinyl tile is 0.0 tog, the same as 5mm ceramic tile. LVT maker C lists its vinyl floors with underlay at about 0.01 to 0.06m²K/W, well under the 0.15m²K/W limit that applies to laminate.

So vinyl does not block much heat. What limits it is temperature. BEAMA's floor covering guide for heating makers says most vinyl and linoleum makers set 27°C, and most vinyls should not be heated above 26°C. BEAMA also says linoleum suits UFH well.

The rules from LVT makers are consistent:

• Keep the floor at or below the maker's limit, usually 27°C.
• Commission the heating and dry the screed before the floor goes down.
• Turn the heating off around fitting, then raise it slowly.
• Use an adhesive approved for UFH, and a temperature-tolerant one where the sun hits the floor.

What is the maximum temperature for LVT on underfloor heating?

27°C for most LVT, and 26°C for some vinyls. Check the exact product, because the warranty depends on it.

Source	Limit	Measured at
LVT maker A	27°C	Floor surface
LVT maker B	27°C	Floor surface and subfloor surface
Adhesive maker	27°C	Bond line, under British Standard guidance
BEAMA	27°C for most, 26°C for many vinyls	Not stated
Generic rigid core click guide	27°C	Floor surface

The bond line is the layer of adhesive under the vinyl. That is where heat reaches the floor first, so it is the safest place to think about the limit. A thermostat with a 10K floor probe fitted between the pipe runs lets you cap the floor temperature. See floor probes and floor limits for where to fit it.

The limit does reduce what the floor can give. BS EN 1264 allows 29°C in occupied areas, and BEAMA notes that a two-degree difference in floor temperature makes a great difference to heat output. In a well-insulated room this is rarely a problem. In a room with high heat loss it can be.

Which LVT is best over underfloor heating: glue-down, click or loose-lay?

All three can work. The difference is in what holds the floor down and how it copes with heat.

• Glue-down (dryback) LVT: fully bonded to a smoothed subfloor. The adhesive choice matters most. It is the usual choice in conservatories, because LVT maker B recommends dryback with a high-temperature adhesive where there is high temperature variation, including direct sun through glass.
• Rigid core click LVT: a stiff core with a pre-attached underlay, laid floating. One generic rigid core guide says no separate underlay is needed, the surface must stay under 27°C, and the floor needs at least 18°C during acclimatisation.
• Loose-lay LVT: held by weight and friction, sometimes on a self-adhesive underlay. LVT maker B says some infrared heating panels may be suitable with its loose-lay underlay, but care is needed with sudden heat gain.

If you add an underlay under click vinyl, use one the flooring maker approves. LVT maker C's vinyl underlays are rated at 0.01 to 0.045m²K/W.

Which adhesive should I use for LVT on underfloor heating?

The one the LVT maker names for UFH. LVT maker A's guidance says universal, high-temperature (HT) or epoxy adhesives must be used. Its commercial guidance says all its own adhesives are approved for radiant heat.

One UK flooring adhesive maker says its whole adhesive range can be used over all types of UFH. It adds that temperature-tolerant adhesives are needed mainly in heavily glazed areas, because solar gain in a conservatory can cause temperature swings of 60°C, much faster than any heating system.

• Wet-lay temperature-tolerant adhesive: for LVT in areas exposed to high temperatures, such as conservatories.
• Hybrid pressure-sensitive adhesive: one adhesive maker rates its own from minus 20°C to 60°C.
• Check the match: one adhesive maker's compatibility guide lists more than 6,000 floor coverings from over 200 makers.

How do I prepare the floor for LVT over underfloor heating?

Dry the screed, prime it and lay a smoothing compound, so the LVT has a flat, firm, bonded surface. Thin vinyl follows every bump under it.

1. Commission the heating. Run it through its warm-up before fitting. LVT maker C says to start at least two weeks before laying and to wait at least 21 days after a new screed before starting. See commissioning underfloor heating.
2. Test the screed. LVT maker B asks for less than 1.8% CM, or 75% RH in the UK, for a heated cement screed, and less than 0.3% CM for an anhydrite (calcium sulphate) screed. Our guide to screed drying times explains how long it takes.
3. Prime. Use the primer the smoothing compound maker specifies, such as Ultra Prime IT.
4. Smooth. LVT maker A asks for a compatible smoothing compound at least 3mm thick over pipes set in concrete.
5. Acclimatise. Bring the room and flooring to a steady temperature. LVT maker C asks for at least 18°C in the room for vinyl.

Over dry overlay boards, ask the LVT maker what base it needs. Most will want a flat, rigid surface with no grooves or joints showing through.

When do I turn the heating off and on around fitting LVT?

Off for 24 to 48 hours before and during fitting, then back on slowly after a wait. The makers' routines differ, so follow the one for your floor.

Maker	Before and during	After fitting
LVT maker A	Off 48 hours before and during	Off 48 hours, then raise about 3°C an hour
LVT maker B	Off at least 24 hours before and during	From 72 hours, raise 5°C a day to a 27°C maximum
LVT maker C vinyl	Off at least 24 hours before, room above 18°C	Wait 48 hours, then raise 5°C a day

If the room is cold on fitting day, LVT maker C says to switch the heating on just enough to reach 18°C. Once the floor is in service, avoid sudden large changes at the start and end of the heating season.

Can I have LVT in a conservatory with underfloor heating?

Yes, with care. One manufacturer says vinyl floors are not recommended in high heat loss areas such as older conservatories, because the floor would need to run hotter than the vinyl allows. BEAMA makes the same point about rooms with high heat losses.

The other risk is the sun. Direct sun through glass can heat the floor far beyond 27°C, whatever the heating is doing. LVT maker B recommends glue-down LVT with its high-temperature adhesive for direct sunlight through glass, and adhesive makers recommend temperature-tolerant adhesives for heavily glazed rooms. Blinds help too.

If the conservatory has a lot of glass, check its heat loss first. Tiles may be a better choice. Our guide to UFH in an extension or conservatory covers the design.

Can LVT go over electric underfloor heating?

Only if the LVT maker approves it, and usually only with the cables fully buried in levelling compound. The vinyl must never sit directly on the wires.

• LVT maker A: mesh or wire systems must be bedded in a base coat of reinforced fibre smoothing compound, then a second coat of primer and compound.
• LVT maker B: wired electric systems are not recommended unless encased in at least 9mm of suitable levelling compound.
• Generic rigid core click LVT: at least 10 to 12mm of levelling compound over the electric system.
• LVT maker C: output limits for LVT over electric heating range from 80 to 140W/m², depending on the build-up.

Our electric mats and loose cable are sold for tile and stone floors, so we do not recommend them under LVT. Water UFH is the simpler match. If you do fit electric heating anywhere, a qualified electrician must make the final connection, to Part P and BS 7671. Our guide to adhesive, levelling and decoupling for electric UFH covers levelling compound over cables.

Frequently asked questions

What temperature should underfloor heating be under LVT?

The floor should not go above 27°C, or 26°C for some vinyls. Set the thermostat's floor limit at or just below the LVT maker's figure.

Do I need a special adhesive for LVT on underfloor heating?

Use one the LVT maker approves for UFH. LVT maker A names universal, high-temperature or epoxy adhesives. In conservatories, use a temperature-tolerant adhesive.

Why switch underfloor heating off before fitting LVT?

Adhesive and vinyl need a steady, moderate temperature while the bond forms. LVT maker A says off for 48 hours before, during and 48 hours after.

Can click vinyl go on underfloor heating?

Yes, if the maker approves it. Keep the surface under 27°C, use only an approved underlay, and raise the heating gradually after fitting.

Is LVT better than laminate over underfloor heating?

LVT has lower thermal resistance, so it passes heat better. Both are usually limited to 27°C at the surface.

Can I put LVT on a heated anhydrite screed?

Yes, once it is dry. LVT maker B asks for less than 0.3% CM in a heated calcium sulphate screed. Prime and smooth before laying.

Will LVT lift on underfloor heating?

Not if the floor stays under its limit, the adhesive is right and the heating is brought up slowly. Lifting usually comes from overheating, strong sun or the wrong adhesive.

Sources: Interiors Monthly: adhesives and temperature, BEAMA: choosing your floor covering for UFH