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How many metres of skirting do I need?

Take the room's internal perimeter, subtract the door openings, and add 10% for mitres and off-cuts — then round up to whole lengths in whatever size the shop sells.

Step 1: The perimeter

Skirting follows the room's walls, so the figure you need is the room's internal perimeter in running metres — not the area. For a rectangular room, the perimeter is 2 × (length + width).

Example: The room is 4.00 m × 5.00 m. Perimeter = 2 × (4.00 + 5.00) = 18.00 m.

If the room has a jog, alcoves or a bay, add the extra stretches of wall. Watch out for the trap: a notch in the wall lengthens the perimeter, even though it shrinks the area. An alcove 60 cm wide and 30 cm deep doesn't remove any skirting — it adds 2 × 0.30 = 0.60 m extra. That's the opposite of what most people intuitively assume.

If you have a measured floor plan, the wall lengths per room are already there, and the perimeter is simply the sum of them. HouseSense works out wall lengths and perimeter from the scanned or drawn plan, so alcoves and jogs are automatically included with the right sign.

Step 2: Subtract the door openings

There's no skirting across a door opening. Subtract the width of each opening — typically 0.80-0.90 m for an ordinary internal door, 0.70 m for a narrow one, and 1.20-2.00 m for a sliding door or an open passage.

Example: Two doors at 0.90 m each: 18.00 − 1.80 = 16.20 m.

What you don't need to subtract: windows (the skirting runs beneath them), radiators (the skirting runs behind them, unless the radiator sits right down on the floor), and built-in cupboards, if you want the skirting to continue behind them. If the skirting isn't going behind a fitted kitchen unit, you can subtract the unit's width — but it's often wiser to leave it in the sum, because kitchens get moved.

Step 3: Add wastage for mitres

Skirting boards are joined at corners with a 45° mitre cut, and every cut costs a piece of the board. On top of that, a 2.40 m length rarely fits a 3.10 m wall exactly — the remainder of the next board becomes an off-cut.

• An ordinary room with 4 corners: 8-10% wastage.
• A room with alcoves, a bay or many corners: 12-15%.
• Profiled skirting, where the pattern has to line up at the joints: 15%.
• Very long walls, where the board has to be butt-joined: add 2-3 percentage points on top — every butt joint should be cut at 45° "over each other", not square, and that costs extra.

Example: 16.20 m × 1.10 = 17.82 m.

Step 4: Round up to whole lengths

Skirting is sold in fixed lengths — often 2.40 m, 2.70 m or 4.20 m, and up to 5.40 m in some places. You can't buy 17.82 m.

With 2.40 m lengths: 17.82 ÷ 2.40 = 7.43 → 8 lengths = 19.20 m.

With 4.20 m lengths: 17.82 ÷ 4.20 = 4.24 → 5 lengths = 21.00 m.

Notice that longer lengths give you more surplus in this room, but fewer butt joints on the walls. If the room has 5.00 m walls, a 4.20 m length is still too short to span a wall in one piece, while a 5.40 m one would manage it. It's worth checking your wall lengths against the available board lengths before you choose: one visible joint in the middle of a living-room wall is often the detail people regret afterwards.

The skirting height has to suit the expansion gap

A floating floor typically needs 8-12 mm of clearance to every fixed part of the building all the way round, so it can move with the seasons. That's the gap the skirting has to cover — and the skirting must not be screwed down into the floor, only into the wall. Screw the skirting into the floor, and you lock the floor in place, and then it buckles.

Bear in mind that a very slim skirting profile (10-12 mm thick) can struggle to cover a 12 mm gap if the wall is also bowed. Old walls in brick houses are rarely straight. A 15-20 mm thick profile, or one with a flexible sealing edge, gives you more to work with.

Four things that change the sum

• Reusing the old skirting. It sounds cheap, but old boards often break during removal, and they carry marks from the old floor along the bottom. Assume you can reuse 60-80% of it — the rest has to be bought, and the new pieces need to match the profile.
• New flooring on top of the old. The floor level typically rises 8-20 mm, and that almost always means new skirting: the old boards sit too low to cover the new gap.
• Skirting in the bathroom. Here a tiled skirting or a bead of sealant is typically used instead — in that case, work in running metres of tiled skirting and ask how many metres come out of one box of tiles.
• Curved stairs and sloped ceilings. Every irregular corner needs a mitre that isn't 45°, and it often takes several attempts to get right. Add 1-2 extra lengths for that reason alone.

Quick checklist before you order

1. Measure each wall internally at floor level, and add them up to get the perimeter.
2. Subtract the width of the door openings.
3. Add 10% (12-15% for many corners or profiled skirting).
4. Check which lengths the shop stocks, and compare them against your longest walls.
5. Round up to whole lengths, and throw in 1-2 extra — an extra length doesn't take up much room, and an extra trip to the builders' merchant costs half a day.