How to lay laminate underlay
Updated: 20 October 2026
The roll is in the hall and you want the floor down this weekend. How to lay laminate underlay, for these 5 mm gold rolls and XPS boards, comes down to a dry flat base, butt joints, tape on a vapour layer, and a gap at the wall that matches the plank sheet. Overlaps become a ridge you can feel. Missing tape leaves a path for moisture. No gap at the skirting lets the floor press the wall and lift. This page starts once you have accepted the subfloor. The product table is the [5mm acoustic underlay comparison](/hub/flooring/5mm-acoustic-underlay). If you buy through our amazon.co.uk links, we may earn a commission at no extra cost to you. We used the listings plus Wickes, EGGER’s GB guide, and the DEFRA steps hosted by Sandwell Council. We did not fit a floor in a lab.
The roll is in the hall and you want the floor down this weekend.
The roll is in the hall and you want the floor down this weekend. How to lay laminate underlay, for these 5 mm gold rolls and XPS boards, comes down to a dry flat base, butt joints, tape on a vapour layer, and a gap at the wall that matches the plank sheet. Overlaps become a ridge you can feel. Missing tape leaves a path for moisture. No gap at the skirting lets the floor press the wall and lift. This page starts once you have accepted the subfloor. The product table is the 5mm acoustic underlay comparison. If you buy through our amazon.co.uk links, we may earn a commission at no extra cost to you. We used the listings plus Wickes, EGGER’s GB guide, and the DEFRA steps hosted by Sandwell Council. We did not fit a floor in a lab.
Our top picks
| Badge | Product | Format | Foil on the listing | Seam tape | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  Royale Royale Sonic Gold 5 mm | Roll, 15 m² | Not stated | Not stated | 8.3 | about £29.34 | View offer |
| Best value |  AcuStick AcuStick sonic gold 15 m² | Roll, 15 m² | Stated | Not included | 8.1 | about £29.50 | View offer |
| Alternative |  FloorPro FloorPro XPS 5 mm boards | 21 boards, 9.79 m² | Not stated | Not included | 7.7 | about £24.77 | View offer |
On this page
Before the first strip
Sweep until the concrete or the boards are free of grit. A single plaster crumb under 5 mm foam prints through as a bump, and it can puncture a foil. Check flatness with a straight edge. These underlays copy the shape underneath. Contract Flooring Journal’s point is blunt: underlay does not level hollows. If you can see a dip the plank maker would reject, stop and sort the floor. Doubling the foam to fill that dip is how click joints start to rock. The support check is on the buying guide.
Buy the tape before you open the roll. AcuStick and the FloorPro XPS pack both tell you to use Barrier Pro X tape, and neither puts it in the box. A vapour layer with untaped seams is a film with a gap every metre. Measure the room and add a cutting margin. Do not treat a 15 m² label as 15 m² of finished floor. UK reviews include short rolls, one measured under 12 m² and about 40 cm short on a 3 m by 4 m room. If the roll looks short on the first unroll, photograph it against a tape measure before you cut. Let the flooring acclimatise as the plank sheet says. You cannot butt a seam you cannot see.
Direction and which face goes down
Roll the underlay out flat. EGGER’s GB guide puts the foil towards the subfloor, with butt joints and taped seams. That matches the usual gold-roll picture: the film on the concrete or screed, the foam against the laminate. If your plank sheet says otherwise, the plank sheet wins. Follow a vapour-layer method only when the product you bought actually states a membrane. Royale’s bullets do not state a foil, even though reviewers describe a gold face. On the XPS boards there is no stated foil, so gold side down does not apply. Lay the boards flat, in the direction the flooring instructions prefer, and tape the joints because the listing tells you to.
Wickes, writing about a fibreboard alternative, runs that board at 90 degrees to the floor planks. These XPS sheets are not that fibreboard, but stagger the board joints so you are not building a long seam under a long plank joint. Reviews say the sheets snap. Support a board on a flat offcut and cut away from the edge you still need. Keep the run in one direction. A patchwork of offcuts in the middle is where ridges start.
Seams, tape, and the wall
Butt the edges. Do not overlap them. An overlap on 5 mm foam is a 10 mm ridge, and the laminate will rock on it or refuse to click. Sandwell’s DEFRA appendices say the same thing: no overlap, turn the layer up at the perimeter if that is the method you are following, keep the floor off the wall, and do not nail through the underlay. A floating floor stays floating.
Tape every seam if this layer is your vapour control. Press the tape onto a dry, dust-free film. Where the gold rolls have a built-in overlap flap, reviewers on Royale call those flaps awkward. Lay the flap flat and tape it. Do not fold it back into a bump. The XPS pack has no flap. The boards meet edge to edge, and the tape is the whole joint.
At the wall, leave the expansion gap your flooring instructions give. EGGER’s guide uses about 10 mm. Sandwell’s DEFRA steps mention a 2 cm floor gap. Do not average them. The plank sheet is the one that protects the warranty. Underlay that runs tight under the skirting, with the laminate jammed against it, transfers movement into a buckle. Cut the underlay so it does not climb so far up the wall that the skirting cannot cover the edge, unless the method you are following turns the vapour layer up and the skirting hides it.
When to stop
Stop if the floor moves, if a straight edge shows a hollow you are tempted to pack with a second layer of foam, or if a moisture reading has failed. A second layer of 5 mm foam feels like a fix and then lets the clicks open, especially under a thin plank or under click vinyl. That failure is on the laminate or vinyl page. Packing a hollow is a levelling job, with a compound the flooring maker allows, once the slab is dry.
Stop and call a fitter or a damp specialist when the screed is over the moisture limit, when the floor is too far out of level for a floating lay, or when underfloor heating is in the slab and you cannot show a combined thermal resistance at or under about 0.15 m²K/W. The XPS boards, at up to 2.2 tog, fail that sum before the floor is added. A bedroom of ordinary laminate over a dry, flat screed is a weekend job if you can tape a straight seam. A flat conversion that needs a sound test is not. If the roll tears while you walk it, patch only if the plank maker allows a taped repair that stays flat. A bunched repair is the same as an overlap.
Common questions
Which side of a gold roll faces the floor?
EGGER’s GB guide puts the foil towards the subfloor, foam towards the laminate, then butts and tapes the joints. Use that when your own plank sheet does not say otherwise, and only when the listing states a foil. Royale’s bullets do not state one. The XPS boards have no foil face to choose.
Do the seams overlap?
No. Butt them. Wickes, EGGER, and the Sandwell DEFRA steps all keep the layer flat, without a double thickness at the joint. An overlap of 5 mm foam is a ridge the click has to climb. Tape the butt if the layer is your vapour control.
Is tape included with these listings?
Not on the AcuStick rolls or the FloorPro XPS pack. Both name Barrier Pro X tape as a separate buy. Smoothfit and Network do not put tape in the listed contents either. Order it with the underlay so you are not taping with whatever is in the drawer.
How much extra cover should you allow?
Measure the room, then add a cutting margin, and do not assume a 15 m² roll covers a 15 m² room. Reviews in this set include rolls short of the label, one of them under 12 m². A 3 m by 4 m floor is already 12 m² before waste. Photograph a short roll before you cut it.
Can you double the foam if the floor feels hollow?
No. A second layer copies the hollow at a new height and adds give under the clicks. Level the floor with a method the plank maker allows, after the moisture reading has passed. Underlay keeps a constant thickness. It does not fill a dip.
What gap do you leave at the wall?
The gap on the plank instructions. EGGER’s guide is about 10 mm. Sandwell’s DEFRA steps mention about 2 cm. Those are different documents. Use the figure your flooring brand prints, and keep both the underlay and the planks off the wall so the floor can move.
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.
- Approved Document E, GOV.UK (retrieved 19 October 2026)
- East Lindsey Guidance Note 53, resistance to the passage of sound (retrieved 19 October 2026)
- Scottish Technical Handbook 2022, section 5.1, noise separation (retrieved 19 October 2026)
- Technical Booklet G 2012, Northern Ireland (retrieved 19 October 2026)
- SITMA, sub-floor testing requirements under Approved Document E (retrieved 19 October 2026)
- BSI, BS EN 16354:2018 laminate floor underlays (retrieved 19 October 2026)
- EPLF underlay materials bulletin, December 2022 (retrieved 19 October 2026)
- Quick-Step UK, vinyl with underfloor heating or cooling (retrieved 19 October 2026)