How do I fit skirting board neatly?

Skirting looks like straightforward carpentry and is judged entirely on its corners. The technique that makes them work — scribing — is not obvious and is the reason professional skirting looks different from DIY skirting.

Safety

Step by step

1. Let the boards acclimatise.Flat in the room for several days. Timber and MDF move with humidity, and fitting straight from a cold van is why joints open a fortnight later.
2. Plan the run to hide the joins.Start with the wall opposite the door and work outwards, so any joint falls where it is least seen. Use full lengths on the visible walls.
3. Scribe internal corners, do not mitre them.Butt the first board into the corner. Cut the second at 45 degrees to reveal the profile, then cut along that profile line with a coping saw so it sits over the face of the first. It stays closed as the timber moves — a mitre does not.
4. Mitre external corners.Two 45-degree cuts. Check the actual angle first with a bevel gauge, because corners are rarely exactly 90 degrees, and cut a fraction long so it closes tight.
5. Use a scarf joint on long walls.Two 45-degree cuts overlapping rather than square butt ends. It hides shrinkage and is far less visible when the joint moves.
6. Deal with the uneven wall.Hold the board up and look for the gaps. Small ones are pulled in by the fixings; larger ones need scribing the back edge or packing behind and filling.
7. Fix into something solid.Grab adhesive plus screws into masonry with plugs, or into the studs on a stud wall. Adhesive alone on a slightly bowed wall lets go, and plaster alone holds nothing.
8. Countersink and pilot every fixing.MDF and softwood both split at the ends without a pilot hole. Countersink so the head sits below the surface and can be filled.
9. Fix low as well as high.Fixings near the bottom edge as well as the top pull the board flat against the wall. Fixing only along the top leaves the bottom edge open.
10. Fill and caulk the right things.Wood filler in nail holes and joints, sanded flush. Flexible decorator's caulk along the top edge where it meets the wall — that gap moves and rigid filler cracks.
11. Leave a small gap at the floor if flooring is coming.Laminate and wood need an expansion gap under or beside the skirting. Fitting the skirting hard to a floor that then expands causes lifting.
12. Prime the cut ends before painting.MDF cut edges soak up paint and swell. A coat of primer or diluted PVA on every cut end first gives a finish that matches the factory face.

Tips

• A coping saw and ten minutes of practice on an offcut is what separates neat skirting from bad skirting. Mitred internal corners always open.
• Check corners with a bevel gauge rather than assuming 90 degrees. Almost none are.
• Caulk the top edge, fill the joints. Using filler where caulk belongs produces a crack within a season.

Common mistakes

• Mitring internal corners — As the timber shrinks the mitre opens into a visible gap that filler will not hold. A scribed joint keeps its face and stays closed.
• Fixing with adhesive alone — On anything but a perfectly flat wall it eventually lets go, particularly at the bottom edge. Use adhesive with mechanical fixings into masonry or studs.

If it doesn't work

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