Advanced options
Internal corners are scribed (one board cut to the profile of the other), external corners mitred at 45 degrees; the 10% allowance covers both plus the odd miscut. Fix with grab adhesive to sound plaster, screws or cut nails to masonry, and caulk the top edge before painting.
What The Skirting Board Calculator Works Out
- Skirting run needed: the room perimeter (2 x length plus 2 x width) minus 0.9 m per doorway, plus a 10% allowance for scribed internal corners, mitred external corners and the odd miscut. A 4 m x 3 m room with one door needs about 14.4 m.
- Boards to buy: the run divided by the board length you can get home, rounded up. Longer 3.6 m or 4.2 m boards mean fewer joins on long walls, and a full uncut wall always looks better than a joined one.
- Fixings: one fixing point every 600mm along the run, plus grab adhesive at roughly one tube per three or four boards and decorator's caulk for the top edge. Screws and plugs or cut nails where plaster is rough; never nails alone into crumbly masonry.
- Cutting allowance (advanced): edit the 10% default. A simple square room with few corners can manage 5%; rooms with chimney breasts, bay windows and alcoves generate many short pieces and deserve 15%.
- Doorway width and extra run (advanced): standard internal doors take 0.9 m out of the run including the architrave; double doors or wide openings more. Add the extra metres a chimney breast (typically 1.5 to 2 m of skirting around three faces) or bay window adds to the plain rectangle.
- Board cost (advanced): whole boards multiplied by the price per board. Pre-primed MDF in 2.4 m lengths runs from about GBP 8 to GBP 15 per board; pine and taller period profiles (145mm up) cost more.
- Paint needed (advanced): the face area (net run x skirting height) per coat, at about 12 m2 per litre for satinwood or eggshell. Painting boards before fitting, with one caulked and touched-in coat after, beats cutting-in on your knees.
- Offcut left over (advanced): the timber bought but not needed, which tells you whether a different board length would waste less.
- Cutting guide (advanced): a wall-by-wall table of full boards and the last cut piece for the chosen board length. Internal corners are scribed rather than mitred, because internal mitres open up as timber and buildings move; joins along a wall use 45-degree splice cuts.