Why Do Gaps Appear in Skirting Boards?
Gaps between skirting boards and walls, floors, or at corner joints are extremely common in UK homes. They appear for several reasons: natural movement in timber or MDF as temperature and humidity change, settlement in the building structure, poor original installation, or simply age. The good news is that most gaps are straightforward to fill and repair yourself with the right materials and technique.
Types of Gaps and How to Fix Them
1. Gap Between Skirting Board and Wall
This is the most common gap — a visible line where the back edge of the skirting board has pulled away from the wall plaster. It's usually caused by slight movement in the board or the wall surface.
How to fix it:
- Clean the gap of any dust, loose plaster, or old filler using a stiff brush or vacuum.
- Apply decorator's caulk (also called flexible filler or acrylic sealant) along the gap using a caulk gun. Caulk is the correct product here — not rigid filler — because it remains flexible and won't crack as the board moves.
- Smooth the caulk with a damp finger or a caulk tool, pressing it firmly into the gap.
- Wipe away any excess with a damp cloth before it skins over.
- Allow to dry fully (usually 1–2 hours), then paint over to match.
2. Gap Between Skirting Board and Floor
A gap at the bottom of the skirting board is common on uneven or undulating floors, or where the floor covering has been removed and replaced with a thinner material.
How to fix it:
- For small gaps (up to 3–4mm), use flexible decorator's caulk as above.
- For larger gaps, use an expanding foam filler to fill the bulk of the gap, allow to cure, trim flush with a knife, then finish with caulk and paint.
- Alternatively, fit a floor bead or quad moulding — a small triangular or rounded MDF strip that sits in the angle between the skirting and the floor, covering the gap neatly. This is the most professional solution for larger or uneven gaps.
3. Open Mitre Joints at External Corners
Mitre joints at external corners can open up over time as the boards move. A gap at a mitre joint is unsightly and can be tricky to fill invisibly.
How to fix it:
- For small gaps, apply a thin bead of flexible wood filler or caulk into the joint, smooth flush, sand lightly when dry, and repaint.
- For larger gaps, carefully remove one of the mitred pieces, apply wood adhesive to the joint, refix, and clamp or tape while the adhesive sets. Fill any remaining gap with caulk before painting.
- To prevent recurrence, apply a small amount of wood glue to the mitre joint when originally fitting — this significantly reduces movement over time.
4. Open Cope Joints at Internal Corners
A well-cut cope joint should stay tight, but if the original cut was slightly off or the boards have moved, a small gap can appear at internal corners.
How to fix it:
- Apply decorator's caulk into the gap and smooth flush. Because internal corners are less visible than external ones, caulk alone is usually sufficient.
- For a more permanent fix, carefully remove the coped piece, recut the profile slightly tighter, and refix.
5. Nail Holes and Surface Damage
Nail holes, dents, and minor surface damage are easily repaired before painting.
How to fix it:
- Apply a small amount of fine surface filler or wood filler to the hole or dent using a filling knife.
- Allow to dry fully, then sand smooth with 180 grit sandpaper.
- Prime the filled area (especially important on MDF) and repaint to match.
Choosing the Right Filler
| Gap Type | Best Product |
|---|---|
| Skirting to wall | Decorator's caulk (flexible) |
| Skirting to floor (small) | Decorator's caulk |
| Skirting to floor (large) | Expanding foam + caulk, or quad moulding |
| Mitre / cope joints | Flexible wood filler or caulk |
| Nail holes / dents | Fine surface filler |
Key Tips for a Professional Finish
- Always use caulk, not rigid filler, for gaps between skirting and walls — rigid filler will crack as the board moves.
- Prime before painting on MDF — any bare or sanded MDF must be primed before the topcoat or the paint will sink and look patchy.
- Match your paint sheen — use the same finish (satin, gloss, eggshell) as the existing skirting to avoid visible patches.
- Work in a dry room — caulk and filler need to dry fully before painting; damp conditions slow curing and can cause adhesion issues.
When to Replace Rather Than Repair
If your skirting boards are badly damaged, heavily swollen from moisture, or the gaps are so large that filling is impractical, replacement is often the better long-term solution. Modern moisture-resistant MDF skirting boards are far more stable than older softwood boards and will give a better result with less ongoing maintenance.
Shop MDF Skirting Boards at Univers
We supply moisture-resistant MDF skirting boards in a full range of profiles and heights, factory-primed and ready to fit. Order online with nationwide UK delivery, or visit our Gosport showroom for advice on your project.