Laying laminate flooring in uneven rooms

Why a Little Unevenness Causes Big Problems

Laminate flooring is a floating floor. The boards are not nailed or glued down, they simply click together and rest on the subfloor, held in place by their own weight and the skirting boards around the edge. That is what makes it so quick to fit, and it is also why the surface beneath it matters so much more than it does with tiles or glued-down engineered boards.

If the floor dips or rises, the joints take the strain. You will hear it before you see it: a hollow click as you walk across a low spot, or a creak where two boards are rocking against each other. Over a few months those joints can open up, the locking tongues can snap, and the whole run may need lifting. The fix is not expensive, but it has to happen before the first board goes down.

Most laminate manufacturers ask for the subfloor to be flat to within about 3mm over a 2m length. That is a gentler tolerance than most people assume, and older UK houses rarely meet it straight away. The good news is that a room only slightly out of true is usually straightforward to sort.

Checking the Subfloor Properly

Get hold of a 2m straight edge, or use a long spirit level as a straight edge if you have one. Drag it across the room in a grid pattern, in both directions, and look for daylight underneath. Where you see a gap, slide a tape measure or a set of feeler gauges in to judge the depth. Anything over 3mm is worth addressing.

• Concrete or screed: check for dust, loose patches and moisture. Tape a square of polythene down overnight, and if condensation forms underneath, deal with damp before you go any further.
• Chipboard flooring panels: look for swollen edges or movement between sheets. Screw any squeaky or springy panels down firmly, and replace any that have been water damaged.
• T&G floorboards: these are the most common culprit. Run a handheld sander over any high spots, then lay 6mm plywood over the whole floor, screwed down at 150mm centres, to flatten the surface and stop the boards moving independently.

Small dips can be filled with a patching compound or a self-levelling compound, feathered out well beyond the dip itself. High spots are best sanded or planed down rather than filled around. Work patiently — this stage is unglamorous, but it decides how the finished floor feels underfoot for the next fifteen years.

Choosing Underlay That Helps, Not Hinders

Underlay does two jobs at once: it softens the slight imperfections left in the subfloor and it deadens the drum-like sound of a floating floor. The right choice depends on how flat you have managed to get things.

• 2–3mm foam is cheap and fine over a genuinely flat surface, but it does nothing to bridge dips or disguise unevenness.
• 5–6mm fibreboard or wood-fibre underlay is the better bet in older rooms. It takes up small variations, feels warmer underfoot and noticeably reduces noise.
• Combination underlay with a built-in damp-proof membrane is the sensible pick over concrete, saving you a separate DPM layer.

Lay the underlay in overlapping runs, and tape the seams so it does not creep as you work across the room. Never double up on underlay to fill a dip — it compresses unevenly and makes the problem worse.

Acclimatise the Boards Before You Start

Laminate expands and contracts with the room, so it needs to settle at the temperature and humidity it will live in. Bring the packs into the room at least 48 hours before fitting, ideally a little longer in winter when the heating has just come on.

Stack them flat, not on their edges, and leave the packaging intact but the ends open so air can circulate. Keep the room between roughly 18°C and 24°C, keep the heating steady, and do not store packs in a cold garage or a damp conservatory beforehand. MDF-core boards are especially sensitive to moisture, so avoid fitting in a newly plastered or freshly screeded room until everything has fully dried out.

Allow Expansion Gaps and Keep the Layout Honest

A floating floor must be able to move, so leave a 10–12mm gap all the way around the perimeter. Use spacers as you go rather than eyeballing it — it is very easy to drift tight against a wall in a long run.

Doors and thresholds need the same consideration. Under-cut the door architraves and linings so the boards slide underneath with room to spare, and use a matching threshold bar at every doorway between rooms. For runs longer than about 10m, or in a room wider than 10m, check the manufacturer's guidance on intermediate expansion breaks.

Plan the layout first: measure the width of the room and divide it so the first and last rows are roughly equal, rather than starting with a full board and ending with a 40mm sliver. Stagger the end joints by at least 300mm between rows, and mix boards from two or three packs as you go so any shade variation blends naturally.

Finishing Touches That Keep It Quiet and Stable

Once the last board is clicked in, remove the spacers and fit your skirting or beading. Scotia bead is quick and forgiving, but it does eat into your expansion gap, so fix it to the skirting board rather than the floor itself wherever possible.

Walk the whole floor afterwards and listen. A single hollow-sounding spot usually means a local dip you missed — you can sometimes lift the last few rows and correct it rather than starting over. Give the floor a couple of days to settle, keep the room at a steady temperature, and wipe up spills promptly. Do that, and an uneven Victorian or 1970s room can still take a laminate floor that feels solid, sounds quiet underfoot, and stays that way.