PU foam vs rubber carpet underlay
Updated: October 2026
You are comparing a light foam roll with something a fitter called rubber, and the amazon.co.uk basket in front of you is foam only. PU foam vs rubber carpet underlay is three materials, not one product with two nicknames. Polyurethane is the light cushion most of these listings are. Crumb rubber is the heavy sheet trade floors use under furniture and on many stairs. Sponge rubber is a third type, and some sponge sheets are the low-tog products used over heating. This comparison stocks neither crumb nor sponge. The 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.
You are comparing a light foam roll with something a fitter called rubber, and the amazon.co.uk basket in front of you is foam only.
You are comparing a light foam roll with something a fitter called rubber, and the amazon.co.uk basket in front of you is foam only. PU foam vs rubber carpet underlay is three materials, not one product with two nicknames. Polyurethane is the light cushion most of these listings are. Crumb rubber is the heavy sheet trade floors use under furniture and on many stairs. Sponge rubber is a third type, and some sponge sheets are the low-tog products used over heating. This comparison stocks neither crumb nor sponge. The grid is the carpet underlay comparison. Products Compared read these listings on 19 October 2026 and did not test them in a lab.
Our top picks
| Badge | Product | Material | Thickness | Coverage | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  FloorPro FloorPro 10 mm 5 m² | PU foam | 10 mm | 5 m² | 9.6 | about £27.50 | View offer |
| Best value |  SIXNEA SIXNEA 12 mm PU underlay | PU recycled foam | 12 mm | 15 m² | 9.4 | about £48.99 | View offer |
| Alternative |  FloorPro FloorPro PE foam 15 m² | PE foam | 6 mm / 7 mm | 15 m² | 7.8 | about £25.99 | View offer |
On this page
Three materials, not one underlay
Trade descriptions often call polyurethane underlay rebonded foam, chopped from furniture foam and pressed into a sheet. It is light and it feels warm under a bedroom carpet. Queen Street’s buying guide puts recycled foam as light and warm, and not the first choice when a flight needs a harder feel. Carpet Flooring Supplies makes the same split: PU for bedrooms and lounges, crumb where granules need to stay firm, sponge as the springy cellular sheet that sometimes includes a low-tog product. A PU roll with no class is not “the bedroom one” merely because it is foam.
Crumb rubber is granules, often from tyres, bound into a heavy roll. Trade pages start with it for halls, stairs and chairs. Interfloor describes the type as having strong recovery under load, including a line it phrases as full recovery. That is Interfloor’s description of the type, not a test of a crumb roll that is not in this set. Do not invent a price or a density for one. Sponge rubber is not crumb. It is cellular rubber, flat or waffle, and heavier than a furniture-foam rebond of the same area. Nu-Heat’s waffle example at about 1.1 tog sits in the heating group. Others are thick comfort rubbers. “Sponge” does not mean safe over underfloor heating. Only a printed tog does. Those checks stay on carpet underlay for underfloor heating.
What this set actually is
Nine listings are polyurethane or an unnamed foam in the same comfort band. SIXNEA is recycled PU, 12 mm, 15 m², about £48.99, with 4.7 from 1,686 reviews. The FloorPro 8 mm and 10 mm rolls are PU at 5 m², about £25.95 and about £27.50. 247Floors is 10 mm polyurethane, 15.07 m², about £54.95. Those are the rolls you can order if a light cushion matches an unheated room. They do not become rubber because a review says the floor feels bouncy. Room picks inside that foam grid stay on best carpet underlay.
FloorPro B08JKMM5GY is easy to misread as a cheap PU. It is polyethylene, about £25.99 for a stated 15 m², with a 7 mm title and a 6 mm catalogue thickness, and 3.9 from 83 reviews. Reviews describe a ribbed sheet. Polyethylene is still a foam. It is not polyurethane, and it is not crumb or sponge. Buying it because the ticket matches a 5 m² PU roll is a material mistake. Plushwalk is memory foam, 12 mm, 15 m², about £119.99. Wilsons’ sheet describes that range as polyurethane and viscoelastic foam, with 3.5 tog on the 12 mm line. Memory foam is not rubber, and that tog takes it out of the heating column.
Stairs, furniture, and a rug pad
A class or a tog still beats the material name. Floorwise’s LD/U mark means light domestic, and it is not for stairs. None of these eleven pages prints LD/U, GD/U, or any other BS EN 14499 class. The FloorPro titles say the small PU rolls are suitable for stairs. That is seller text. If the flight is the job, a crumb roll with a printed stair class is the trade starting point, and you will not find that roll here. Leaving the set is the honest recommendation.
Heavy furniture is the same gap. A 10 mm PU such as 247Floors can dent: one review warns of deep indentations under movable furniture. That is what a soft foam does. It is a reason to buy rubber, from a shop that sells it, if the chairs move every day. A felt pad with a rubber back is a different product again. It stops a loose rug creeping. One felt pad, about 180 by 280 cm, was removed from this set as a misfit. Do not lay it under a fitted carpet and expect the gripper to work. The carpet has to slide on the underlay face while you stretch it. Thickness, coverage and class for an unheated room are on the carpet underlay buying guide. A qualifying purchase through our links can earn a commission at no extra cost to you.
Common questions
What is PU foam underlay made of, and why is it light?
Trade guides describe it as rebonded polyurethane, often from recycled furniture foam. A 15 m² roll such as 247Floors can list 10 kg, and SIXNEA lists 14 kg, rather than the heavy lift of a rubber roll of the same size. Light does not mean it has a stair class.
What is crumb rubber, and is it in this set?
Crumb is rubber granules bound into a firm, heavy sheet. Fitters start with it for halls, stairs and furniture that would dent a soft foam. It is not in this Amazon set. Interfloor’s “full recovery” line describes the type, not a roll we can link from this page.
How is sponge rubber different from crumb?
Sponge is cellular rubber, flat or waffle. Some sponge sheets are low-tog heating underlays, including examples around 1.1 tog. Some are not. The word sponge is not a heating approval. This comparison does not stock either kind.
Is polyethylene foam the same as PU?
No. The FloorPro roll at about £25.99 for 15 m² is polyethylene, with a 7 mm title and a 6 mm catalogue figure, and 3.9 from 83 reviews. The other FloorPro rolls are polyurethane. PE is not a cheaper version of the 10 mm PU roll.
Is memory foam a kind of rubber?
No. Plushwalk is a 12 mm foam at about £119.99 for 15 m². The seller claims 3.5 tog. That tog is a heating problem, not a sign that the sheet is rubber. A crumb roll would be specified for firmness, which is the opposite reason to buy memory foam.
Can I use a felt rug pad under a fitted carpet?
No. A rug pad grips a loose rug. The removed 180 by 280 cm felt pad is that object, and it is not in the staged set. Fitted carpet needs underlay inside the gripper. A rubber back meant to stop sliding works against that stretch.
Related pages
Sources
Public UK sources listed in the research digest. Listing prices, stars, and review counts are from amazon.co.uk on 19 October 2026.
- BEAMA underfloor-heating guide — floor covering and the 2.5 tog combined limit (retrieved 19 October 2026)
- Nu-Heat — carpet and underfloor heating (retrieved 19 October 2026)
- Approved Document E — resistance to the passage of sound (retrieved 19 October 2026)
- NBS — BS EN 14499:2024 textile floor coverings, classification of carpet underlays (retrieved 19 October 2026)
- Floorwise recommendation guide — end-use class labels (retrieved 19 October 2026)
- Interfloor Omega 10 specification — example PU underlay (retrieved 19 October 2026)
- Carpetshire — thickness by room as a rule of thumb (retrieved 19 October 2026)
- Homebuilding — 8 mm, 10 mm, and 12 mm comfort map (retrieved 19 October 2026)