Laminate that lifts at the seams or swells at the edges is almost always sitting on water. Swelling along one wall points to an appliance, a bath seal or damp from outside; lifting mid-room points to a pipe under the floor. Lift one board at the worst spot, then have the source traced before the rest comes up.
It usually starts with a ridge you can feel with a bare foot. Then a couple of joints peak up, an edge goes dark, and a musty smell settles in the room that airing does not shift. Laminate does not get wet quietly. The fibreboard core drinks water and swells, and because the boards are locked together with nowhere to go, they buckle upwards instead.
The awkward part is that by the time the surface moves, the water may have been there for weeks. This guide explains what the pattern of damage tells you, where the water usually comes from, which boards to lift and which to leave, and how our water leak detection service finds the source before the whole floor comes up.
Edge swelling or middle-of-room lifting?
Where the damage sits is the first clue, and often the best one. Water spreads sideways under a floating floor, so the damage tends to radiate out from the source. Stand at the doorway and look for the worst point.
| What you notice | Most likely cause | What to do |
|---|---|---|
| Swelling along the wall behind the washing machine or dishwasher | Appliance hose, seal or valve weeping during cycles | Pull the machine out and run a cycle with a towel underneath |
| Dark edges along the wall shared with the bathroom | Failed bath or shower seal, or a waste joint | Check the silicone and the trap, then look for a tide line |
| Boards peaking under or beside a radiator | Radiator valve or tail dripping onto the floor | Wrap dry kitchen roll round the valve and check it in an hour |
| Lifting in the middle of the room, nowhere near plumbing | Heating or supply pipe leaking under the floor | Check the boiler pressure and water meter, then book a survey |
| Damp edges along an outside wall, worse after rain | Penetrating damp or a bridged damp-proof course | Check ground levels and gutters outside before lifting anything |
Edge damage on one wall is usually something you can see once you know where to look. Middle-of-room lifting is the one that needs equipment, because the pipe feeding it is under the boards, under the underlay, and often under a screed or a timber floor as well.
Why laminate hides a leak for months
A laminate floor is laid floating: boards clipped together, sitting on a foam or fibre underlay, not fixed to anything. That construction is exactly why it hides water so well. A small leak wets the underlay first, and the underlay holds it like a sponge. The water spreads sideways across the subfloor, sometimes a couple of metres from where it started, without any of it reaching the surface.
Meanwhile the wear layer on top is waterproof. Nothing evaporates through it, so the moisture stays trapped and the core soaks it up slowly from below. You only see the result when the swelling is enough to lift the joints. On a heating pipe the water can evaporate underneath almost as fast as it escapes, which keeps things quieter for longer still.
In a holiday let, the delay is longer still. A cottage in Newquay that is booked every week in summer might stand empty for a month at a time in winter, and a changeover clean is not the moment anyone notices a slightly soft board by the sofa. Often the first anyone knows is a guest review mentioning a damp smell.
The usual sources, in order of likelihood
- A plumbed appliance. Dishwashers and washing machines leak a little at a time, during a fill or a drain, then stop. The hose connection, the door seal and the drain hose into the standpipe are the three spots to check. Damage radiates out from the machine.
- A bath or shower seal. A failed silicone bead lets a small amount of water past every time someone showers. It runs down behind the panel, under the bathroom floor, and out under the laminate in the hall or bedroom next door. This is the one that catches people out most, because the wet floor is not in the bathroom.
- A radiator valve or tail. A slow drip from a valve nut lands on the floor beside the radiator and creeps under the boards. It leaves a crusty green or white deposit on the nut.
- A heating pipe under the floor. Pipes run under a laminate floor in the screed or between the joists. A pinhole in one wets the floor from below, usually feels warm, and shows up as the boiler needing a top-up more often. If the patch is warm, read our guide to a warm patch on the floor.
- A cold supply pipe. Less common, but a leaking mains pipe under the floor keeps the subfloor permanently wet and moves the water meter with everything off.
- Damp from outside. A raised patio or a leaking gutter can wet the base of an outside wall so that the laminate edge stays damp. It follows the weather and is never warm.
Two quick checks split the list in half. Read the water meter last thing at night and again first thing, with nothing used in between; movement means a supply pipe. Note the boiler pressure cold each morning for a few days; a steady fall means the heating circuit. If neither moves, the water is coming from an appliance, a seal, a waste pipe or the outside.
What to lift and what to leave alone
The temptation is to pull up boards until you find the wet bit. Resist it. Every board you lift disturbs the underlay that shows where the moisture sits and makes the floor harder to put back. Lift in this order.
- Skirting or beading at the worst edge. Prise off a short length where the damage is worst. You can see the subfloor and the underlay without touching a single board, and the underlay tells you straight away whether it is wet.
- One board at the peak. If the room has an expansion gap at the edge, the last board can usually be lifted out and clipped back in. Look at the underside and the underlay beneath it. Wet, warm underlay means a heating pipe. Wet, cold underlay with a smell of drains means a waste pipe or seal.
- Nothing in the middle. Do not cut into or lever up boards in the centre of the room. They will not go back, and the pattern of moisture underneath is exactly what a survey needs to trace the source.
If the whole room lifts anyway, keep the photos. The same advice applies if you have a wet carpet that keeps coming back in the next room, which is often the same leak showing itself twice.
How we find the source without stripping the room
A survey starts by mapping the moisture. A meter reading taken every half metre across the floor and along the skirtings shows the wettest point and the direction the water has travelled, through the boards, without lifting them. That map alone often points straight at an appliance or a bathroom wall.
If it points to the middle of the room, we bring in the rest of the kit. A thermal imaging camera picks out the warm plume of a heating pipe leak or the cooler patch of a cold one. Acoustic listening equipment hears pressurised water escaping through the floor. Where we need to confirm the exact point, tracer gas is introduced into the isolated pipe and picked up on the surface directly above the leak. The result is a mark on the floor, so the repair lifts a few boards in the right place rather than the lot. We offer leak detection for homes across Cornwall, and a laminate floor is one of the most common things we are asked to look at.
Will the insurance pay for the floor?
Most UK buildings policies include trace and access cover, which pays towards finding a hidden leak and making good whatever had to be disturbed to reach it, usually up to a limit. The damage the water caused, including the ruined laminate, is normally a separate escape of water claim. Neither pays to fix the leaking pipe itself. Our guide to what trace and access cover includes explains how the two fit together. Photograph the floor before anything is lifted and keep the boards you remove; the loss adjuster will want to see them.
Frequently asked questions
How can I tell if it is a spill or water under the laminate?
A spill dries out and the boards settle back within a week or two. Trapped water keeps going: the swelling spreads past where it was, the joints stay lifted, the floor feels spongy and the musty smell does not clear with airing. If the damaged area is growing, there is a source feeding it.
Can laminate dry out and go back down?
Rarely. Once the fibreboard core has swollen it does not shrink back, so peaked joints and thickened edges stay that way even after the floor underneath is dry. A very light wetting caught early can sometimes settle, but boards that have visibly lifted usually need replacing once the leak is fixed.
Why is the laminate wet when the bathroom floor is dry?
Because the water runs downhill under the bathroom floor and comes out next door. A failed bath or shower seal sends water behind the panel and under the floorboards, and it surfaces wherever the floor covering is thinnest or the joint is lowest, often in the hall or bedroom.
Do I need to lift the whole floor to find the leak?
No. Moisture mapping through the boards, thermal imaging and acoustic listening locate the source from the surface, and one board or a length of skirting is usually enough to confirm it. The repair then lifts a small area in the right place, which keeps most of the floor intact.
Find the water under the boards
If your laminate is lifting and you cannot see where the water is coming from, we will trace it through the floor and mark the spot, with a trace and access report your insurer can work from.
