Repair a hole in a plasterboard wall
Whether it was some wayward furniture, an angry shoe or an attempt to remove a
molly bolt that caused a dent or a hole in the wall, a hole is a hole and it has to be filled.
To fix a dent in drywall or plasterboard
Whether it’s a large or small dent, you can fill it with a painter’s water-based filler. It comes in a small pot and can be applied with a putty knife or a plasterer’s trowel. A deep dent must be filled layer upon layer, allowing the filler to dry in between coats. Apply each layer and smooth off the surface each time with a smooth, wet cloth, making sure the filler doesn’t stand out from the wall surface. When the hole is nearly filled, sand off any rough, dry edges before applying the last smooth coat. Sand the final coat when it is dry with a fine sandpaper (grit 450 or more) so that no edges can be seen...make sure you use a sanding block so that your sanding is smooth and even. Undercoat the patch with a sealer and then paint it the same colour as the wall.
To fix a hole in drywall or plasterboard
Plasterboard has a paper lining on both sides, so holes are never neat. Using a cutting knife, neaten and clean up the edges of the hole.
Measure the width and height of the hole and cut a strip of thick, firm cardboard (or plasterboard if you have some) 10 mm narrower than the height and 50 mm longer than the width of the hole, to act as a atch behind the hole.
Screw a screw through the patch material at its centre, leaving the head protruding enough that you can grip it well with your fingers (but also making sure that it is protruding less than the thickness of the wall material. See first illustration below.)
Holding the screw, gently slide one end of the patch into the hole, move it across until the other end can slip in too. If it’s too long simply trim an end.
When you know the patch fits, apply some quick-grip glue to each end of the patch. Slip the patch in again, centre it and gently pull the strip towards you so that the glue attaches the patch to the inside of the hole.
Allow the glue to dry. Buy a small pot of pre-mixed wall plaster.
Holding the screw to ease pressure on the glue, build up the edges of the hole with plaster, making sure none is left on the face of the wall.
This will firm up the attachment of the patch strip.
Leave it to set for about an hour, then build up the hole, covering the screw,
until the hole is just short of being full.
Final layer or layers
Allow the plaster to set. Sand any protruding or rough edges. Remove any dust.
Apply another coat of plaster (using a scraper that is wider than the hole) with a smooth, confident stroke. Don’t worry if it is a little thick, as it is easy to sand off when dry... but make sure you use a sanding block so that your sanding is smooth and even. A sandpaper grit of 450 to 600 will give a smooth finish.
The plastering in the photo above is not complete. You might find you need to do a few thin coats to get a fine finish. Make sure you allow the plaster to dry in between sanding and recoating. Use a plasterer's float for holes larger than your scraper to get a smooth finish over a wider area. Sand so the new plaster is flush with the wall around the edges.
Paint the plaster with sealer undercoat and then paint the patch to match the wall.