Why are gaps opening between my laminate boards?

Click flooring locks board to board, but the joint only resists pulling apart — it does not glue them together. Anything that drags a board sideways over months can open a joint, and once open it stays open.

What you'll need

• A pull bar and a tapping block
• A rubber mallet
• A hygrometer
• Laminate repair glue or joint filler
• A pry bar

Step by step

1. Note when the gaps appear.Gaps that widen in the heating season and close in summer are the boards shrinking with low humidity. That is normal and is not repaired mechanically.
2. Measure the indoor humidity.Most engineered and laminate floors want 40–60 percent relative humidity. Below 35 percent in a heated house in winter is common and will visibly shrink a floor.
3. Look at where the gaps are.Gaps concentrated near a door, a sofa on castors, or a heavy item being dragged tell you the boards have been pulled apart mechanically rather than shrinking.
4. Check the joints have not failed.Press either side of a gap. If one board moves independently and clicks, the locking profile is broken and the board needs replacing, not closing.
5. Check the perimeter gap before closing anything.You are about to push boards towards a wall. If there is no expansion gap there, you will simply create a peak instead of a gap.
6. Work from the nearest wall.Take the beading off, and use a pull bar hooked over the last board with a mallet to draw the run tight. Work along the whole row, not just at the gap.
7. Use a tapping block in the field.Where you can push rather than pull, a tapping block against the board edge and a mallet closes the joint without damaging the locking profile.
8. Never hit a board edge directly.The locking tongue is thin and brittle. A mallet on a bare edge crushes it and the joint will never close properly again.
9. Glue the joint only as a last resort.A drop of PVA in a joint that keeps opening will hold it, but it also stops the floor moving as a floating floor and can transfer the problem elsewhere.
10. Fill hairline gaps cosmetically.A colour-matched flexible laminate joint filler is acceptable for a permanent 1mm gap in a floor that is otherwise sound.
11. Address the humidity.Lower heating flow temperatures, a humidifier in a very dry room, or simply drying washing indoors occasionally all raise winter humidity into the right range.

Tips

• Photograph the gaps in February and again in July. If they change, you have your answer and a mechanical repair is the wrong response.
• Felt pads on every piece of furniture, and lifting rather than dragging, prevents the mechanical version of this problem entirely.
• A floor laid over underfloor heating shrinks more than one over a cold slab. Both the fitting gap and the humidity range matter more there.

Common mistakes

• Closing seasonal gaps in winter — The boards are at their driest and smallest. Close them tight and the floor has no room when it takes up moisture again in summer, which produces peaking — a far worse problem than a hairline gap.
• Hammering a board edge without a tapping block — The click profile is a thin machined tongue. Struck directly it crushes or shears, and that board can never lock properly again, so a cosmetic gap becomes a board replacement.

If it doesn't work

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