How do I fill gaps between skirting boards and the floor?

The gap exists because floors and walls move independently, and because floorboards shrink. Any filler that cannot flex will crack along the same line within weeks, which is why the material choice matters more than the technique.

What you'll need

• Decorator's caulk and gun
• Quadrant beading (optional)
• Damp cloth (optional)
• Caulk smoothing tool (optional)

Step by step

1. Measure the gap and choose accordingly.Under 5mm: caulk. 5-20mm: quadrant or scotia beading. Larger or uneven: a timber strip scribed to the floor.
2. Clean the gap out thoroughly.Vacuum out dust and debris. Caulk will not adhere to a dusty edge and will pull away later.
3. Cut the caulk nozzle small and at an angle.Start smaller than you think — you can enlarge it, but you cannot reduce it, and an oversized bead is wasteful and hard to tidy.
4. Apply one continuous bead with steady pressure.Move at a constant speed. Stopping and starting leaves lumps that show through paint.
5. Smooth immediately with a wet finger or a smoothing tool.Within a minute or two, before it skins. This is the step that determines how it looks.
6. Wipe excess with a damp cloth as you go.Caulk removes easily while wet and is very hard to remove once cured, especially from textured surfaces.
7. For larger gaps, fit beading instead.Pin quadrant beading to the skirting rather than the floor, so the floor can still move independently. This is the detail that prevents cracking.
8. Let it cure fully before painting.Usually a few hours to overnight. Painting uncured caulk causes the paint to crack as it finishes shrinking.

Tips

• Caulk shrinks slightly as it cures. On a deep gap a second thin bead the next day gives a much better finish than one heavy pass.
• Do not use rigid filler in this joint. It will crack along the line within weeks — it is a moving joint by nature.
• If the gap is because the skirting has come away from the wall, fix the fixings first. Filling around a loose board just delays the problem.

Common mistakes

• Using rigid filler — The joint moves seasonally. Anything rigid cracks along the same line, usually within weeks.
• Pinning beading to the floor — It stops the floor moving independently, which causes squeaks and eventually splits the beading.
• Applying too large a bead — It is difficult to smooth, wastes material, and shows as a thick ridge under paint.

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