Lay underlay for a floating floor on a concrete floor
Lay underlay and a damp-proof membrane over a concrete floor so your new floating floor sits flat, dry and quiet underfoot.
UL-01Clear the roomRemove all furniture, rugs and any old flooring down to the bare concrete. Pull out old gripper rods, tack strips or adhesive residue with a scraper. Sweep the room out so you can see the floor clearly.
UL-02Check the concrete for dampTest the floor with a damp meter in several spots, including corners and the centre of the room. A reading over the meter's dry threshold, or a floor that's been recently laid or screeded, means you need a damp-proof membrane before the underlay goes down. If you're at all unsure, treat the floor as damp — it's cheap insurance against a ruined floor later.
UL-03Fill and level low spotsAny dip, crack or hollow deeper than about 3mm needs filling with floor levelling compound, mixed and poured per the bag instructions. Feather it out with a trowel so there's no ridge. Leave it to cure fully — usually 24 hours — before you walk on it or lay anything over it.
UL-04Sweep and vacuum thoroughlyAny grit or debris left under the underlay will show through as a lump once the floor's finished. Vacuum the whole floor, including edges and corners, right before you start laying anything.
UL-05Lay the damp-proof membrane, if neededRoll out the polythene DPM across the whole floor, overlapping each sheet by at least 200mm. Run it up the walls by about 50mm — this gets trimmed off later once the skirting or scotia moulding goes back on. Tape every overlap and seam so there are no gaps for moisture to creep through.
UL-06Roll out the underlayLay the underlay in strips across the room, butting the edges together — never overlapping them, as this creates a ridge under the flooring. Use the underlay's own manufacturer tape along every joint to stop it shifting while you work.
1 roll · Combination foam underlay with integrated DPM (roll, ~15m²)
UL-07Trim to fit around edges and obstaclesCut the underlay to fit neatly against skirting, door frames and any pipes with a sharp utility knife. Take your time around awkward shapes — a snug fit stops the floating floor rocking or squeaking once it's down.
UL-08Tidy up and check you're readyBin all offcuts and packaging, and give the room a final vacuum. Walk the whole floor checking for any lifted tape, gaps at seams, or debris trapped underneath before you start laying the flooring itself.
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