How to Wallpaper Internal and External Corners
Measuring a corner at three heights, how far to turn, marking a fresh line on the next wall, and the one place where a small overlap is the right answer
Never carry a full width of wallpaper around a corner. Cut the length so it turns onto the next wall by about 1cm on an internal corner, or 2cm on an external one, then start the next wall against a fresh plumb line using the offcut. Measure the gap to the corner at three heights and work from the widest.
Corners are where wallpapering goes wrong, and always for the same reason: no corner is square, plumb or the same width top to bottom.
The one place a small overlap is correct
Our papers are butt-joined everywhere on a flat wall. The edges meet, and they never sit on top of one another. An internal corner is the single exception. The 1cm you turn onto the next wall is covered by the piece that starts that wall, because there is no way to butt two lengths in a corner that is not truly vertical without a gap opening somewhere along it.
Keep the turn small and the overlap is invisible. Try to avoid it altogether and you get a white line down the corner.
Internal corners
- Measure the gap. With your last full length hung, measure from its edge to the corner at the top, the middle and the bottom.
- Take the widest measurement and add 1cm.
- Cut a length down its width to that measurement, keeping the offcut, because it becomes the first piece on the next wall.
- Hang it, butting it to the previous length and letting the extra 1cm turn onto the next wall.
- Work it into the corner with the smoother so there is no air trapped in the angle.
- Mark a fresh plumb line on the new wall, at the width of your offcut measured from the corner.
- Hang the offcut to that line, covering the 1cm turn, matching the pattern as closely as the corner allows.
The pattern will not match perfectly in a corner. Nothing you can do makes an out-of-true corner match, and it reads as a corner rather than a mistake.
External corners
Chimney breasts, boxed-in pipes, the returns of a bay.
- Measure to the corner at three heights, take the widest, and add 2cm rather than 1cm.
- Cut the length to that width and hang it, wrapping the 2cm around the corner.
- Smooth the wrap down firmly and work out any air behind it, because an external corner is the first place a lifted edge gets knocked.
- Mark a plumb line on the new face and hang the next length to it, butting against the wrapped edge where possible or overlapping it very slightly if the corner is badly out.
If the corner is chipped or rounded, fill and sand it before you start. Wallpaper will not bridge a broken arris, and the damage shows through immediately.
Heavy-grade paper in corners
A 300gsm paper is stiff and does not want to fold into an angle. Keep the turn to the minimum, smooth it firmly into the corner, and expect to hold it in place for a moment. Do not force a full width around a corner in heavy-grade, because it will lift.
Peel and stick in corners
Same principle, with one difference: work the length into the corner in short sections, peeling and smoothing as you go, so the paper is pressed into the angle rather than bridging it. A bridged corner in peel and stick will pull away within days.
Why not just wrap the whole width?
Because the corner is not vertical. A full width wrapped around it arrives on the next wall out of plumb, and every length after it inherits the error, which is exactly the drift that makes a pattern run uphill across a room.
How much wallpaper should I turn around an internal corner?
About 1cm. Enough to seal the angle, little enough that the piece starting the next wall covers it invisibly.
How much around an external corner?
About 2cm, smoothed down firmly so the edge cannot catch.
Why measure at three heights?
Because the distance from your last length to the corner is almost never the same at the top and the bottom. Cutting to the narrowest measurement leaves a gap.
Will the pattern match around a corner?
Approximately, not exactly. Get it as close as the corner allows and move on. It is normal on every wallpaper.
Do I need a new plumb line on every wall?
Yes, every time you turn a corner.
What if my corner is very badly out of true?
Turn a smaller amount, hang the next length to a fresh line, and accept a slightly wider overlap in the angle.
