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Carpet underlay for underfloor heating

Updated: October 2026

The room already has pipes in the floor, and you are about to add a thick comfort roll because the carpet felt cold last winter. Carpet underlay for underfloor heating is a tog sum, not a millimetre contest. Carpet plus underlay should stay at or under 2.5 tog. Many heat-pump systems want that combined figure under 1.5 tog. Ten of the eleven amazon.co.uk rolls here do not print a tog. The one that does, Plushwalk, prints 3.5 tog as a seller claim, already over 2.5 before any carpet. The product grid is the [carpet underlay comparison](/hub/flooring/carpet-underlay). Products Compared read these listings on 19 October 2026 and did not test them in a lab.

The room already has pipes in the floor, and you are about to add a thick comfort roll because the carpet felt cold last winter. Carpet underlay for underfloor heating is a tog sum, not a millimetre contest.

Our top picks

FloorPro FloorPro 10 mm 5 m²

Best overall

FloorPro FloorPro 10 mm 5 m²
9.6/10about £27.50
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SIXNEA SIXNEA 12 mm PU underlay

Best value

SIXNEA SIXNEA 12 mm PU underlay
9.4/10about £48.99
View offer
Plushwalk Plushwalk 12 mm memory foam

Alternative

Plushwalk Plushwalk 12 mm memory foam
9.4/10about £119.99
View offer
On this page
  1. 1.The limit is tog, added together
  2. 2.What a comfort foam does to that sum
  3. 3.What this set cannot tell you, and how it is fitted

The limit is tog, added together

BEAMA’s floor-covering guide is the industry source behind the 2.5 figure. It defines 1 tog as 0.1 m²K/W, and it says carpet plus underlay under 2.5 tog lets an underfloor system work efficiently. Nu-Heat uses the same combined ceiling, and it prefers under 1.5 tog when the heat source is a heat pump. Uheat repeats that pair of limits. A boiler system and a heat pump are not the same allowance. Thickness cannot stand in for tog. Nu-Heat’s examples of heating-oriented underlay are about 0.56 tog, 0.66 tog and 1.1 tog for a waffle rubber. Homebuilding cites about 0.5–0.6 tog for purpose-made heating underlay. Interfloor asks for underlay at or under 0.8 tog with carpet, which is stricter than the combined 2.5. Keep 0.8 tog as that manufacturer’s target. Nu-Heat’s worked carpet example is Brinton’s Bell Twist at 1.23 tog. Add an underlay of 1.1 tog and you are already at 2.33. Add a normal comfort foam and you are through it. Why some sponge sheets carry a low tog, and why this basket does not include them, is on PU foam vs rubber carpet underlay.

What a comfort foam does to that sum

Plushwalk, ASIN B00EZMX4DY, is about £119.99 for 15 m² of 12 mm memory foam, with 4.7 from 184 reviews. The Amazon bullets claim 3.5 tog, 49 dB, a damp-proof layer and a test to BS 5808:1991. Those lines are seller claims. Wilsons’ specification sheet lists the 12 mm product at 3.5 tog to BS 4745 and 105 kg/m³, and it marks double-stick as no. A shop blog that says 3.3 tog disagrees with the sheet. Prefer the sheet’s 3.5. Either way the underlay alone is over 2.5 tog. There is no remaining allowance for a carpet. Do not buy it for a heated floor. It can still be a comfort roll in an unheated room. One buyer needed three deliveries before an undamaged parcel arrived. Interfloor’s Omega 10 sheet, cited as an example outside this basket, is a 10 mm PU with GD/U, 2.4 tog and 38 dB. At 2.4 tog the underlay has almost nothing left once any carpet is added. Standard PU is described by Interfloor as a barrier over heating. The 8 mm, 10 mm and 12 mm polyurethane rolls here do not give you that 2.4 figure. You cannot assume they are lower because a title says 8 mm. Thickness for a cold, unheated room is the carpet underlay buying guide.
FloorPro FloorPro 10 mm 5 m²

Testsieger

FloorPro FloorPro 10 mm 5 m²
9.6/10about £27.50
View offer

What this set cannot tell you, and how it is fitted

Only the Plushwalk seller bullet prints a tog, and that number fails the heating limit on its own. Grandismo, 12 mm and 10 m² at about £39.50, has a customer question about underfloor heating and no answer. The FloorPro polyurethane rolls claim insulation and do not print a tog. SIXNEA, Royale, SnugStep, 247Floors, both Flooring Online rolls and the polyethylene FloorPro sheet are the same silence. A missing tog means you do not buy the roll for a heated floor. A decibel figure would not rescue the gap. Sound reduction is not heat transmission, and it is not evidence of Approved Document E. Do not nail into a heated screed. A staple that finds a pipe is a leak under a new carpet. Gripper on underfloor heating is a call-a-fitter point. The laying sequence for an ordinary dry timber floor is how to fit carpet underlay. Do not copy that nail pattern onto a heated slab. Homebuilding’s 48-hour note, heat off before and after a double-stick installation, is a fitter’s instruction. Wilsons’ sheet marks double-stick as no for the 12 mm Plushwalk. A qualifying purchase through our links can earn a commission at no extra cost to you.

Common questions

What tog can carpet and underlay add up to?
Keep the combined figure at or under 2.5 tog if you want the system to work in the way BEAMA and Nu-Heat describe. One tog is 0.1 m²K/W. A carpet at 1.23 tog plus an underlay at 1.1 tog is already 2.33. A comfort foam at 2.4 tog, the Omega 10 example, leaves almost no carpet allowance.
Is the limit lower with a heat pump?
Nu-Heat prefers the combined carpet and underlay under 1.5 tog on heat-pump systems, against 2.5 as the general ceiling. A roll that only just scrapes under 2.5 with the carpet can still be too much. Ask which of the two numbers your system uses before you order cushion.
Can I use 12 mm foam if the room feels cold?
Not as a fix for underfloor heating. The cold room is often the stack blocking the pipes. Twelve millimetres is a comfort thickness for an unheated floor, once the doors clear. These 12 mm listings do not print the 0.5–0.8 tog figures heating firms quote.
Does Plushwalk’s 3.5 tog work over heating?
No. The Amazon bullet claims 3.5 tog, and Wilsons’ sheet lists 3.5 tog for the 12 mm product. That figure alone is over the 2.5 combined limit, before any carpet. The 49 dB line does not change the tog. At about £119.99 it is a soft unheated-room roll, not a heating underlay.
What if the Amazon listing has no tog at all?
Do not buy it for a heated floor. Grandismo leaves the heating question unanswered. The other PU and PE rolls in this set do not print a tog either. Silence is not a pass. Choose a sheet whose own page states a tog you can add to the carpet.
Are any of these eleven rolls a low-tog heating underlay?
No. The heating-oriented examples in the trade guides sit around 0.56, 0.66, 0.8 and 1.1 tog. This basket does not print those values. Sponge products that sometimes carry a low tog are not stocked here.

Related pages

Best carpet underlay

Carpet underlay

Carpet underlay buying guide: thickness and cover

How to fit carpet underlay inside the gripper

PU foam vs rubber carpet underlay, side by side

Sources

Public UK sources listed in the research digest. Listing prices, stars, and review counts are from amazon.co.uk on 19 October 2026.

  1. BEAMA underfloor-heating guide — floor covering and the 2.5 tog combined limit (retrieved 19 October 2026)
  2. Nu-Heat — carpet and underfloor heating (retrieved 19 October 2026)
  3. Approved Document E — resistance to the passage of sound (retrieved 19 October 2026)
  4. NBS — BS EN 14499:2024 textile floor coverings, classification of carpet underlays (retrieved 19 October 2026)
  5. Floorwise recommendation guide — end-use class labels (retrieved 19 October 2026)
  6. Interfloor Omega 10 specification — example PU underlay (retrieved 19 October 2026)
  7. Carpetshire — thickness by room as a rule of thumb (retrieved 19 October 2026)
  8. Homebuilding — 8 mm, 10 mm, and 12 mm comfort map (retrieved 19 October 2026)