Skirting looks like the simplest measurement in a room: go round the walls, subtract the doors, buy that many metres. It is nearly that simple, and the parts that make it not simple are worth knowing before ordering. Every length you buy produces at least one cut end and most produce two, the offcuts only get used if a later piece happens to need exactly that length, and the visible result depends on where the joints land rather than on how much you bought. This walks the perimeter as a single line, shows each length and each joint, and separates what you lay from what you cut off.
Room, openings and lengths
The perimeter is easy. The openings and the joints are what change the order.
Skirting stops at the architrave, so the opening width is what comes off.
MDF and softwood skirting commonly comes in 2.4 m and 3.0 m; some in 4.2 m.
Ten percent for a simple room; twenty for one with many short walls.
Result
Perimeter minus openings is the easy half
Twice the length plus twice the width gives the perimeter, and the openings come off it. The subtlety is what counts as an opening. A door opening is deducted at the width of the architrave rather than the width of the door, because the skirting stops against the architrave, not against the frame. A fireplace, a fitted wardrobe and a run of kitchen units are all deductions of the same kind.
A bay window is the opposite: it adds perimeter, and it adds more than it looks like it should, because a bay is usually three short walls or a curve rather than one straight line. Measure the bay face by face. A chimney breast is the one that catches people out in the other direction — it adds two returns of maybe 200 millimetres each, which is trivial in isolation and adds up across a house.
Joints are the real cost of buying in lengths
Skirting is sold in fixed lengths and cut on site, and every cut produces a joint. A joint in a run of skirting is a visible line that has to be filled, sanded and painted, and it is the place where the mitre opens up in a year when the house moves. The material cost of the extra length is small; the finishing cost of the extra joint is not.
That is why the length you buy matters more than the price per metre. In a room with several walls around 2.4 m, buying 2.4 m lengths means nearly every wall is one piece with no joint at all. Buying 3.0 m lengths means every wall has a joint and the offcuts are too short to use elsewhere. The same total metreage, a worse result, and more filler.
The practical rule is to choose a length that relates to your wall lengths rather than the cheapest per metre. If most walls are about two and a half metres, a 2.4 m length with a small infill beats a 3.0 m length with a large offcut, even at the same price.
Internal corners are scribed: one piece is cut square and pushed into the corner, the other is coped to fit over its profile. A mitre on an internal corner opens up as timber moves.
External corners get a true mitre, and they are worth cutting carefully with a proper mitre gauge rather than freehand.
Where the joints should land
A joint in the middle of a long, prominent wall is visible for as long as the room exists. A joint in a corner, behind a door that stands open, or at the end of a run is invisible. With a fixed number of lengths to place, you have real freedom about where the joints fall, and using it is free.
The planning order is: start at the most visible corner, run the longest lengths into the longest walls, and let the short pieces and the joints accumulate in the least visible part of the room. It takes five minutes with the lengths laid on the floor before fixing, and it is the difference between a job that looksDIY and one that looks professional.
| Typical wall length | Best length to buy | Joints per wall | Why |
|---|---|---|---|
| Up to 2.4 m | 2.4 m | 0 | One piece, no joint at all |
| 2.4 to 3.0 m | 3.0 m | 0 | Worth the extra length to avoid a joint |
| 3.0 to 4.2 m | 4.2 m | 0 | If the supplier stocks it |
| 4.2 to 4.8 m | 2.4 m | 1 | Two halves meet in the middle |
| Mixed and awkward | Longest available | 1 | Fewer joints beats less waste |
| Whole house | Longest available | Varies | Offcuts cross between rooms |
A worked example
- PerimeterTwo times 5.4 plus 4.2 is 19.2 m around the room.
- Deduct the openingsTwo door openings at 0.9 m take off 1.8 m, leaving 17.4 m to fit.
- Allow for cuttingTen percent takes that to 19.14 m.
- Convert to lengthsAt 2.4 m a length that is eight lengths — 19.2 m bought, with 7 joints and 1.8 m of offcuts.
- Price itEight lengths at $14 is $112, or $6.44 per metre fitted.
Now change one input: buy 3.0 m lengths instead. Nineteen metres is seven lengths, 21 m bought, six joints and 3.6 m of offcuts — $98 of material, six joints and twice the waste. Whether that is a saving depends entirely on where those six joints land.
Measuring and fitting
Measure each wall individually rather than trusting the perimeter, because rooms are rarely square and a room that is out by fifty millimetres across its length changes which pieces fit where. Write the wall lengths down in order as you go round, and lay the cut pieces out on the floor in that order before fixing anything.
Cut slightly long and scribe back. A piece cut exactly to the measured length will be short, because the walls are not square and the tape was not straight. Cutting two millimetres long and easing it in with a block plane or a sanding block takes a minute and closes the gap.
Fix to the wall, not to the floor, and fix into studs or use grab adhesive plus a few pins. Skirting fixed only to the floor skirting-board moves every time the floor does. If the skirting is being replaced as part of a flooring job, it comes off and goes back — which is why the floor is laid first and the skirting covers the expansion gap.
Do
- Measure each wall individually, in order, going round the room.
- Choose the length that minimises joints, not the cheapest per metre.
- Scribe internal corners and mitre external ones.
- Plan where the joints land before fixing anything.
- Cut a couple of millimetres long and ease it in.
Avoid
- Using the perimeter without measuring each wall.
- Choosing a length on price and accepting extra joints.
- Mitring internal corners, which open up as the house moves.
- Letting a joint land in the middle of a prominent wall.
- Fixing only to the floor, so the skirting moves with it.
Where the numbers stop being true
The room is treated as a rectangle. L-shaped rooms, bays and chimney breasts need the perimeter measured wall by wall — the room area figure handles the L shape and the trapezoid and gives you the dimensions to add up here.
The cutting allowance is a flat percentage. In a room with one long wall and several short ones it is too generous, because the offcuts from the long wall fit the short ones; in a room where every wall is just over half a length it is too tight, because every piece wastes nearly half. Ten percent is a working average, not a rule.
Nothing here covers the profile. A tall ogee or a torus profile has a much larger scribe and wastes more at internal corners than a simple chamfered board, and a deep profile cannot be scribed at all on a very short return. Nor does any of this account for the architrave around the openings, which is the same calculation with different numbers and is covered by the trim length figure.
How the figures are produced
The perimeter is twice length plus twice width. Opening widths are subtracted to give the length to fit. The cutting allowance is applied to that, and the result is divided by the length you are buying and rounded up to whole lengths. Joints are one fewer than the number of lengths, assuming every length but the last needs a joint at one end. Offcuts are what you buy minus what you fit.
Questions people ask
Do I deduct the door width or the architrave width?
The architrave. Skirting stops against the architrave, so deduct the width of the opening including its trim — 0.9 m is a working figure for a standard door.
How much waste should I allow?
Ten percent for a straightforward rectangular room, twenty for one with many short walls or a bay. Less if the offcuts from long walls will fit the short ones.
Why are there so many joints?
Because lengths are fixed and walls are not. Eight lengths produce seven joints. Choosing a length closer to your wall lengths is the only way to reduce it.
Should I use MDF or softwood?
MDF is stable, straight, primed and cheaper, and it is the right choice for painting. Softwood is better if it is being stained or if it will take knocks.
Can I reuse the old skirting?
Often yes, and it is worth doing because the profile matches and the mitres are already cut. Score the paint line first or it will tear away with it.
What height should skirting be?
Proportional to the room: 95 to 120 mm for a standard ceiling height, taller in a room with high ceilings, and a simple square edge in a contemporary one.