How to lay laminate underlay
Updated: 23 October 2026
The roll is in the room, the laminate is still boxed, and two fitting sheets do not describe the same edge. How to lay laminate underlay, for the foil foams in this set, comes down to a flat dry subfloor, the foil face on your packet, butt joints, tape if you rely on that film, and one wall detail. The [underlay comparison](/hub/diy-supplies/underlay) holds the five prices and scores. This page does not rank them. We used maker sheets and the amazon.co.uk files from 19 October 2026, not a floor we laid. A qualifying purchase can earn us a commission at no extra cost to you.
The roll is in the room, the laminate is still boxed, and two fitting sheets do not describe the same edge.
The roll is in the room, the laminate is still boxed, and two fitting sheets do not describe the same edge. How to lay laminate underlay, for the foil foams in this set, comes down to a flat dry subfloor, the foil face on your packet, butt joints, tape if you rely on that film, and one wall detail. The underlay comparison holds the five prices and scores. This page does not rank them. We used maker sheets and the amazon.co.uk files from 19 October 2026, not a floor we laid. A qualifying purchase can earn us a commission at no extra cost to you.
Our top picks
| Badge | Product | Foil face | Seam tape | Thickness | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  FloorPro FloorPro silver, 3 mm, 15 m² | Reviews: foil to the floor | Named, not in the box | 3 mm | 8.0 | about £19.88 | View offer |
 AcuStick AcuStick Sonic Gold, 5 mm | Not printed | Named, not in the box | 5 mm | 7.4 | about £29.50 | View offer | |
| Alternative |  Grandismo Grandismo heating underlay, 10 m² | No foil line | Not named | Not printed | 7.0 | about £33.50 | View offer |
On this page
Flat, dry, and empty
Sweep the subfloor until grit is gone, and punch down any nail proud of a timber deck. A small ridge can telegraph through 2 mm or 3 mm of foam. A hollow you can rock a straightedge in wants compound, not a thicker roll. On a new slab, check moisture first. A silver face does not tell you the slab is dry. Those checks are on the laminate underlay buying guide. If the boards already have a pad, stop.
Foil face and butt joints
EGGER’s UK guide says the foil faces down, the edges butt, and the seams are taped, with about a 10 mm gap at the wall for the boards. FloorPro reviews on the 15 m² silver roll say foil to the floor on concrete. AcuStick and the Smoothfit files do not print which face goes down. If your roll is silent, use its packet, not a sentence from another brand. Follow a manufactured flap if the roll has one. Do not invent a 50 mm overlap the file never states.
Grandismo has no foil instruction. Where you rely on a foil barrier, butt the edges and tape the seam. An open join is a gap in the film. Three listings name Barrier Pro X and do not include it: the 15 m² FloorPro, AcuStick, and the 2 mm FloorPro. The 7.5 m² 3 mm file and Grandismo do not name a tape. We do not have a saved price for Barrier Pro X.
The wall: 10 mm or a 10 cm upstand
Leave one edge detail. Do not average the two numbers. EGGER, and several UK board-fitting sheets, keep about a 10 mm expansion gap, with the underlay stopping inboard of that gap. Harrow Council’s noise note, for impact through a separating floor, tells you to turn the underlay up the wall by at least 10 cm, stop the boards 2 cm short, then wrap and trim. Basingstoke’s leaflet sits in the same family. Ten millimetres and ten centimetres are not a range.
Follow the 10 mm gap when nobody lives underneath, and trim the sheet so it does not pinch under the skirting. Upstairs, if the lease allows a hard floor, use Harrow’s upstand and trim it after the boards are in. Do not nail through the sheet. The lease is on the laminate underlay in flats page.
Where you stop
A Saturday lay is a dry, flat, unheated room, a roll inside the board maker’s thickness, and tape you have already bought. Stop when the slab is wet, when a hygrometer reading is above the figure your flooring sheet allows, or when the deck bounces and needs a joist repair. Stop when an electric mat or a wet pipe is in the floor. Some mat manuals forbid any underlay on that mat, and only one roll here prints a tog. Stop when the lease says the floor stays carpeted. A careful seam does not vary a covenant. Call a fitter for a glue-down floor or a heating mat you have already damaged.
Common questions
Which side is the foil?
EGGER’s UK guide says foil down, and reviews of the FloorPro 15 m² roll say foil to the floor on concrete. AcuStick, the Smoothfit files, and Grandismo do not print a face. If the roll in your hand has a printed arrow, that arrow beats a general article, including this one.
Do the edges overlap or butt?
Butt them. EGGER’s method is a close butt, then tape, not a wide lap. A FloorPro review describes a fiddly foil flap, so use the flap on your roll and do not add a second overlap of your own. Do not leave a gap under a board joint.
What gap do I leave at the wall?
Follow one published detail. For the boards themselves, UK fitting sheets, including EGGER, use about a 10 mm expansion gap. Harrow’s noise note turns the underlay up at least 10 cm and stops the boards 2 cm short, then trims. Those are different jobs. Use the 10 mm board gap when nobody lives underneath. Use the upstand when a council noise note applies and you are allowed to lay a hard floor.
Do I tape every seam?
Tape the seam if you are relying on the foil as a damp-proof film. An untaped butt is a slot for vapour. Three listings name Barrier Pro X and leave it out of the box. The 7.5 m² 3 mm FloorPro file does not name a tape, so do not assume masking tape will do.
What if the roll has a foil flap?
Lay the flap over the neighbouring sheet the way the fold is pressed, and tape along the join. The listing does not print the flap width, so measure the one on your roll. A flap you leave untaped is still an open edge.
Can I lay this over a timber floor with a vapour film?
Not by default. EGGER’s UK guide says you do not add a vapour barrier on a timber subfloor that needs to breathe. A foil underlay is itself a vapour film. On concrete, that film is often the point. On boards over a ventilated void, sealing the top can trap moisture in the timber. Call a fitter if the slab is damp, the floor moves, or the lease forbids a hard floor.
Related pages
Sources
Public UK sources and the amazon.co.uk listings compared on this page. Listings captured 19 October 2026. Updated 23 October 2026.
- BSI, BS EN 16354:2018 (retrieved 23 October 2026)
- EPLF underlay bulletin, December 2022 (retrieved 23 October 2026)
- Approved Document E (retrieved 23 October 2026)
- Quick-Step UK heating FAQ (retrieved 23 October 2026)
- Karndean UK glue-down guide (retrieved 23 October 2026)
- BEAMA floor-covering note (retrieved 23 October 2026)
- Leasehold Advisory Service (retrieved 23 October 2026)
- EGGER how to lay underlay (GB) (retrieved 23 October 2026)
- Basingstoke laminate leaflet (retrieved 23 October 2026)