Whether you’re fixing up a tattered wall or a crumbling ceiling, we’ll show you how you can get it looking as good as new. We’ll refer throughout this guide to walls, but the same principles apply to ceilings.

Skill rating – Intermediate

Should take – 1 hour (approx)

Remember! When undertaking DIY tasks you must always take your own ability into account and you must also read and follow any packaging and manufacturers’ instructions. This is intended to be a basic guide only and is not a substitute for any professional advice.

Patching a plastered masonry wall

Getting the damaged area ready

Take a bolster chisel and club hammer to remove all the loose material around the area you want to patch (fig.1) and undercut the edges. Then, wire brush the brickwork to remove all traces of loose material.

Mixing your plaster

Following the manufacturer’s instructions, mix the plaster and use a gauging trowel to sprinkle the plaster powder into the water, while stirring it with a clean stick (fig.2).

Once the plaster is a thick, creamy consistency with no lumps, turn it onto a dampened board.

Fig. 1 - Take a bolster chisel and club hammer and remove all the loose material around the area you're patching; Fig. 2 - Sprinkle the plaster into the water with a gauging trowel and stir with a clean stick. Always follow the manufacturer's instructions

 Top tip…

Keep plaster from going lumpy by adding to the water, not the water to the plaster.

Filling the patch

Firstly, make the area for plastering nice and damp. Then use the plastering trowel to slide a good amount of plaster onto the plasterer’s hawk.

Standing close to the patch, tilt the hawk towards you and, in one movement, lift half the plaster onto the trowel (fig.3).

Next, holding the trowel horizontally, but slightly angled to the wall, press the plaster into the patch and move the trowel up the wall, gradually flattening it. Try not to totally flatten it, as it’ll cause suction and pull plaster off the wall (fig.4).

Do this again and again until the patch is overfilled. It’s best not to overwork the plaster though as it’ll weaken and fall off.

Fig. 3 - In one movement, lift half the plaster onto your plastering trowel; Fig. 4 - Press the plaster into the patch and move the trowel up the wall.

Smoothing it off

Once you’ve covered the surface, go back over it again to get an even thickness. Try and hold the trowel at a slight angle so only one edge touches the plaster at any one time.

After about 45 minutes your plaster will start to set. Just go over it again lightly with a dampened trowel to smooth the surface. Then, after about another 20 to 30 minutes, add a splash of cold, clean water to the surface.

How to fill deep holes

Sometimes your patches might be deep. If that’s the case, you’ll need to apply two layers of plaster. Apply the first layer to half the depth of the patch then, when it’s partially set, scratch up to the surface and leave it to set fully without drying out. Then apply a second coat and rule it off. When it’s set, simply smooth off.

Patching a lath and plaster wall

First of all, lightly tap the surface to see how much loose plaster there is. Mark around this ‘bad area’ with chalk and score the line deeply with a craft knife. Remove the loose plaster and wire brush the laths and studs.

Then, dampen the laths and edges of the plaster around it, and apply a coat of plaster to half the thickness of the old plaster.

Use enough pressure to force plaster between the laths while still leaving a covering of plaster on them. Then, when the first layer is partially set, scratch up the surface and leave it to set without fully drying out. Simply follow steps 3 and 4 on how to patch a plastered
masonry wall.

Repairing stud walling

You should just treat these in the same way as other walls, except where a wooden stud is exposed.

Use galvanised clout nails to fix 150mm wide galvanised expanded metal to the wooden studs so that the metal extends over the damaged area to the solid brickwork either side. Remember to wear thick leather gloves when handling exposed metal (fig.5).

Then, simply follow steps 3 and 4 to patching a plastered masonry wall.

Fixing plasterboard – large holes

Getting the hole ready

You’ll need to feel inside the hole to check for any hidden pipes or cables. Just push any aside, making sure the electricity is turned off at the mains.

If it’s all clear of pipes and cables, use a plasterboard/utility saw or pad saw to clean up and straighten the damaged edges of the hole.

Finally, without making the hole any bigger, chip away a 25mm strip of surface plaster from around the hole.

Fixing your backing patch

First of all, cut a piece of plasterboard 25mm wider and longer than the hole. This is your patch. Then drill a small hole through the middle of it and thread a knotted piece of string through it.

Take hold of your string, feed the patch through the hole in the plasterboard and pull it into position behind the hole to check it fits (fig.6). If it does, then pull the patch back through the hole and coat its contact surface with panel adhesive. Feed the patch through the hole again and tug it firmly in place.

Then, tie off the string until the adhesive has set and scrape off any excess adhesive. Finally, cut the string flush to the patch.

Fig. 5 - Use galvanised clout nails to fix 150mm wide galvanised expanded metal to the studs; Fig. 6 - Feed the patch through the hole and pull firmly into position.

Filling the hole

Take a steel rule or thin batten to find adjacent studs to the hole and mark them on the plasterboard.

Make sure you feel inside the hole to check for concealed pipes or cables before doing anything and move them to one side.

Repairing plasterboard – small holes

Finding the adjacent studs

Take a steel rule or thin batten to find adjacent studs to the hole and mark them on the plasterboard.

Make sure you feel inside the hole to check for concealed pipes or cables before doing anything and move them to one side.

Taking out the damaged board

Firstly, mark a rectangular section around the whole area that’s damaged and use a plasterboard/utility saw or pad saw to remove the section. Then clean up the edges with sandpaper.

Remove a 25mm strip of finishing plaster around the edge of the hole.

Attaching battens to the studs

You should use 50mm plasterboard nails to fix sections of 25mm x 50mm sawn, treated batten to the studs. Try and keep the battens flush with the front edges of the studs.

Use panel adhesive to glue further lengths of batten horizontally behind the plasterboard. Then hold the battens in place with G-clamps.

Putting your new patch in

Once the battens are set, cut and fix a piece of plasterboard to fit the hole, leaving a 3mm gap around the edges. Then fix the plasterboard in place using 32mm plasterboard screws.

Finally, apply strips of self-adhesive plaster scrim over the joints and tidy up with finishing plaster filler.

Fixing damaged corners

Small areas

First of all cut away any damaged or loose plaster. Then use masonry nails to fix a length of 25 x 75mm prepared batten to one face of the corner, positioning the edge of the batten so it’s flush with the surface of the plaster on the adjacent face.

Then dampen the damaged area and apply some plaster to fill the patch. Have a look at steps 3 and 4 for patching a plastered masonry wall.

When the plaster’s set, gently remove the batten and refix it over the recent plastered face. Then plaster the second face.

Take away the batten once the plaster’s set. Smooth off the corner with abrasive paper and apply a coat of finishing plaster.

Large areas

Firstly, cut away the plaster all the way from the skirting to the ceiling. Use hardwall or basecoat plaster to apply ‘dots’ to both surfaces at the corner of the walls (fig.8).

Then cut plasterboard to length and press it into the dots until it’s vertical and lines up with the adjacent old plaster surfaces. Check this out using a spirit level (fig.8).

When the ‘dots’ are set, plaster and finish as described in steps 3 and 4 ‘patching a plastered masonry wall’.

Fig. 7 - Cut a new piece of plasterboard a bit smaller than the hole and glue into place; Fig. 8 - Press plasterboard into dots and check it lines up with a spirit level.

Print this page