Damaged plasterboard corner bead: how to repair it

How to judge the damage before you start

Run a finger along the corner. If the edge feels like a smooth, slightly rounded line under a crack in the paint, the bead is probably intact and you are dealing with filler damage only. If the corner feels sharp, wavy, or you can see grey metal through a chip, the bead itself is bent or torn and needs attention, not just a skim of filler.

Press gently on the plasterboard either side of the corner. If it flexes or feels soft, water may have got in at some point, or the board itself has crumbled behind the bead. That changes the job from a bead repair to a board replacement, which is worth knowing before you buy materials.

A corner that has been knocked once, cleanly, with the bead bent inward or the paper tape split, is a good candidate for a weekend repair. A corner that has been hit repeatedly over a long section, or where the plasterboard is soft to the touch, is better assessed in person.

What you will need for the job

Most of what you need for a corner bead repair is available from any builders' merchant in Tallinn, and none of it is specialist. The main decision is whether to buy a fresh length of corner bead to match the existing profile, or reform the section you have if the damage is only a mild bend.

Buy slightly more bead than the damaged length, since you will cut back further than the visible damage to get a straight joint at each end.

• Metal or plastic corner bead, matching the profile of the existing one
• A sharp utility knife and a small filling knife or scraper
• Joint filler (powder or ready-mixed) and a wider finishing knife, around 150 mm
• Fine abrasive mesh or sandpaper, around 120–180 grit
• A straightedge or spirit level to check the corner is true
• Tin snips if you are cutting a new metal bead to length
• Dust sheet, mask and safety glasses for the sanding stage

Cutting back the damaged filler and bead

Score along both sides of the corner with a utility knife, about 50–80 mm beyond the visible damage in each direction, and lift off the old filler with the scraper. Work carefully rather than quickly, since gouging into sound plasterboard nearby only makes more work later.

Once the filler is off, you will see how the bead is fixed, usually with a thin layer of joint compound bedding it to the board rather than screws. Cut the damaged section of bead free with tin snips, making clean cuts at each end so the replacement piece butts up neatly rather than overlapping badly.

Check the exposed board edges underneath. If the paper facing is torn or the board core is crumbled at the corner, that area needs a bit of extra filler or a small offcut of plasterboard to build it back level before the new bead goes on, otherwise the corner will sit proud or hollow.

Replacing or reforming the corner bead

For a mild bend with no split metal, you can sometimes reform the bead in place by pressing it straight with a block of wood and a straightedge, checking the line as you go. This works only if the bead has not kinked sharply or torn away from the board.

For anything more than a mild bend, cut out the damaged length and fit a new piece. Apply a bed of joint filler along both wall faces at the corner, press the new bead into it, and check with a spirit level or straightedge that it sits proud evenly and runs true with the sound bead above and below.

Hold the new bead in place with a couple of strips of masking tape while the bedding compound goes off, and leave it the time stated on the filler tub before touching it again, usually a few hours.

Filling and sanding the corner flush

Once the bead is fixed, apply the first coat of filler with the finishing knife, feathering it out well beyond the repair on both sides so there is no visible ridge where old and new filler meet. Let it dry fully, which takes longer at a corner than on a flat wall.

Apply a second, thinner coat to fill any low spots or knife marks, again feathering the edges wide. Two thin coats give a straighter result than one thick one, which tends to crack or sag at a corner.

Sand lightly with fine abrasive mesh once fully dry, running your hand along the corner in both directions to check it is straight and flush before you prime or paint. Our plasterboard team handles this kind of corner repair as a standalone job from 28 €, and if you would rather not do the painting afterwards, that is a separate call-out from 12 €.

When to leave the repair to someone else

A single knocked corner with an intact board behind it is a reasonable DIY job for anyone comfortable with a filling knife and a bit of patience. Where it gets harder is a corner that has been hit more than once, runs the full height of a doorway, or where the board behind feels soft or damp.

If several corners in the same room show the same damage, or the wall has been patched before and is starting to look uneven, it is often quicker and tidier to have it done properly than to keep touching up the same spot. Call-out within Tallinn is 25 €, deducted from the bill if the work goes ahead, and larger jobs get a fixed quote after a photo or a description of the damage.