Can You Put Carpet on Underfloor Heating?

Underfloor heating (UFH) and carpet get on fine when they're matched properly, and badly when they're not. The problem is never the heating itself. It's insulation: every layer you put on top of the pipes or cables slows the heat coming up, and carpet plus a thick underlay can slow it a lot. Get the combination right and you keep warm floors and sensible heating bills. Get it wrong and the room stays cool while the system works harder to compensate.

What Is Tog, and Why Does It Matter for Underfloor Heating?

Tog is a measure of thermal resistance: the higher the number, the more a material insulates. It's the same unit used on duvets. For UFH, what matters is the combined tog of everything on top of the heating, which means the carpet and the underlay added together.

Industry guidance puts the ceiling at a combined 2.5 tog for most systems, and many heat pump installations aim for 1.5 tog or lower because heat pumps run at lower water temperatures and suffer more from over-insulation. Always check the figure your heating installer or manufacturer specifies, because it overrides any general rule.

How to Work Out Whether Your Carpet Will Work

You need two numbers, and both are normally on the product's technical sheet or label: the carpet's tog and the underlay's tog. Add them up.

Those figures are examples to show the method, not ratings for any particular product. Use the real numbers for the carpet and underlay you're considering. In general, deep, dense and wool-rich carpets carry a higher tog than a short-pile or loop carpet, so the carpet you choose has as much effect as the underlay.

Which Underlay to Use Over Underfloor Heating

Use a thin, UFH-specific underlay, typically 0.5 to 1.0 tog and often a perforated or waffle design that lets heat pass through. The thick 9 to 11mm PU foam we'd normally recommend for a bedroom or lounge is usually too insulating for UFH, so it gets swapped for a thinner, lower-tog product. If you already have a luxury carpet in mind, pair it with the lowest-tog underlay that still supports it, and check the maths above.

For how underlay choice works in general, see our carpet underlay guide.

Fitting Carpet Over Underfloor Heating: What a Fitter Does Differently

• Gripper rods: on a screed over UFH, rods are usually glued rather than deep-nailed, so there's no risk of a nail hitting a pipe or cable underneath.
• Switch the heating off: we turn it off for around 48 hours before and after fitting, to avoid thermal shock to the carpet and adhesive.
• Bring it back up gradually: after fitting, raise the temperature in stages rather than switching straight to full heat.
• Stretching still applies: the carpet is still power-stretched to stay taut, which matters more when heating cycles expand and contract the floor slightly.

Carpet fitted straight onto UFH screed is one of several subfloor situations covered in our guide to what you can and can't fit carpet over.

What to Check Before You Buy

1. Ask your heating installer for the maximum combined tog for your system.
2. Find the tog rating of each carpet you're considering.
3. Choose an underlay rated for UFH and check its tog.
4. Add the two and make sure the total is at or below the limit.
5. Confirm the manufacturer's warranty isn't affected by fitting over UFH.

If you're budgeting the job, our carpet fitting cost guide covers what a typical job costs.

Frequently Asked Questions

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