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How to repair walls and ceilings

Difficulty rating: Low

These tasks should be fairly straightforward, whether you have experience doing DIY or none at all.

Before you get started on any of our 'how to' guides, please take a moment to read through our DIY safety tips.

Patching a plastered masonry wall

1. Preparing the damaged area 

Use a bolster chisel and club hammer to remove all loose material round the area to be patched (fig. 1) and undercut the edges. Then, wire brush the brickwork to remove all traces of loose material. 

2. Mixing the new plaster
  • Mix the plaster according to the manufacturer's instructions. Use a gauging trowel to sprinkle the plaster powder into the water, while stirring with a clean stick (fig. 2).
  • When the plaster is thick and creamy without lumps, turn it onto a dampened board.

Patching a plastered masonry wall

1. Preparing the damaged area

Use a bolster chisel and club hammer to remove all loose material round the area to be patched (fig. 1) and undercut the edges. Then, wire brush the brickwork to remove all traces of loose material.


2. Mixing the new plaster
  • Mix the plaster according to the manufacturer's instructions. Use a gauging trowel to sprinkle the plaster powder into the water, while stirring with a clean stick (fig. 2).
  • When the plaster is thick and creamy without lumps, turn it onto a dampened board.


3. Filing the patch with plaster
  • Thoroughly dampen the area to be plastered. 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. With a continuous movement, lift half the plaster onto the trowel (fig. 3).
  • Hold the trowel horizontally but slightly angled towards the wall. Press the plaster into the patch and move the trowel up the wall, gradually flattening it. Don't completely flatten the trowel against the wall. This causes suction and pulls the plaster off the wall (fig. 4).
  • Repeat this process until the patch is slightly overfilled. Don't overwork the plaster as this weakens it and makes it fall off.


4. Smoothing off
  • Once the surface is covered, go back over it to smooth the plaster to an even thickness. Hold the trowel at a slight angle so only one edge touches the plaster at any one time.
  • The plaster will start to set after about 45 minutes. Go over it again lightly with a dampened trowel to smooth the surface.
  • After a further 20 to 30 minutes, splash the surface with cold, clean water then trowel to a fine, smooth surface. Keep the trowel damp and don't 'over-trowel'.


5. Filling deep holes
  • If the patch is deep you might need to put on two layers of plaster. Apply the first layer to half the depth of the patch. When it has partially set, scratch up the surface and leave it to set fully without drying out. Apply a second coat and rule it off. When set, smooth off.
Take a bolster chisel and club hammer and remove all the loose material around the damaged area.
Figure 1
Sprinkle the powder into the water with a gauging trowel and stir with a clean stick.
Figure 2
In one continuous movement, lift half the plaster off your hawk and onto the plastering trowel.
Figure 3
Press the plaster into the damaged area and move the trowel up the wall.
Figure 4

Patching a lath and plaster wall

  • Tap the surface to determine the extent of any loose plaster. Mark the perimeter of the bad area with chalk, then score this line deeply with a heavy-duty craft knife. Remove the loose plaster and wire brush the laths and studs.
  • Dampen the laths and edges of the surrounding plaster, then 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.
  • When this first layer is partially set, scratch up the surface and leave it to set fully without drying out.
  • Then follow steps 3 and 4 in 'Patching a plastered masonry wall'.
 

Repairing brick in-fill stud walling

  • 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 the metal extends over the damaged area to the solid brickwork either side (always wear thick leather gloves when handling exposed metal) (fig. 5).
  • Then follow steps 3 and 4 in 'Patching a plastered masonry wall'.
 
Use galvanised clout nails to fix 150mm-wide galvanised expanded metal to the studs
Figure 5

Repairing plasterboard - small holes

1. Preparing the hole for repair
  • Feel inside the hole to check for concealed pipes or cables. If you find one, push it to one side. Make sure the electricity is turned off at the mains while you check for pipes and cables.
  • If there aren't any, use a plasterboard/utility saw or pad saw to clean up and straighten the damaged edges of the hole.
  • Finally, without making the actual hole any bigger, gently chip away a 25mm strip of surface plaster from around the hole.


2. Fixing a backing patch in place
  • Tie off the string until the adhesive has set and scrape off any excess adhesive. Cut off the string flush to the patch.
  • Holding the 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 fits OK, pull the patch back through the hole and coat its contact surface with panel adhesive. Feed the patch through the hole again and pull it firmly into position.
  • Cut a piece of plasterboard 25mm wider and longer than the hole. This is your patch. Drill a small hole through the centre of the patch and thread a knotted piece of string through it.

 

3. Filling the patched hole
  • Cut another piece of plasterboard very slightly smaller than the hole. Glue it in place with panel adhesive and leave to dry (fig. 7).
  • Finally, apply strips of self-adhesive plaster scrim over the joints and tidy up with finishing plaster filler.
 
Poke the patch through the hole and pull firmly into position.
Figure 6
To fill the patched hole, cut a new piece of plasterboard slightly smaller than the hole and glue it in place.
Figure 7

Repairing plasterboard - large holes

1. Locating the adjacent studs
  • First use 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.

 

2. Removing the damaged board
  • Mark a rectangular section around the whole area that's damaged and use a plasterboard/utility saw or pad saw to remove the section.
  • Clean up the edges with sandpaper.
  • Remove a 25mm strip of finishing plaster around the edge of the hole.

 

3. Fixing battens to the studs
  • Use 50mm plasterboard nails to fix sections of 25mm x 50mm sawn, treated batten to the studs. Keep the battens flush with the front edges of the studs.
  • Use panel adhesive to glue further lengths of batten horizontally behind the plasterboard. Hold the battens in place with G-clamps.

 

4. Fixing the new patch in place
  • Once the battens are set, cut and fix a piece of plasterboard to fit the hole, leaving a 3mm gap round the edges. 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.
  • Remove a 25mm strip of finishing plaster around the edge of the hole.
 

Repairing damaged corners

 1. Small areas
  • Cut away any damaged and loose plaster.
  • Use masonry nails to fix a length of 25mm 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.
  • Dampen the damaged area and apply plaster to fill the patch. See steps 3 and 4 of 'Patching a plastered masonry wall'.
  • When the plaster has set, carefully remove the batten and refix it over the recently plastered face. Then plaster the second face.
  • Remove the batten when the plaster has set. Gently smooth off the corner with abrasive paper and apply a coat of finishing plaster.

 

2. Large areas
  • 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).
  • Cut plasterboard to length and press it into the dots until it's vertical and lines up with the adjacent old plaster surfaces. Check using a spirit level (fig. 8).
  • When the 'dots' are set, plaster and finish as in steps 3 and 4 of 'Patching a plastered masonry wall'.
 
 press plasterboard into the dots until it's vertical and lines up with the adjacent old plaster surfaces
Figure 8
Helpful hint...

Always add the plaster to the water and not the water to the plaster. This ensures the plaster isn't lumpy.

 
Watch how to repair holes in walls

If you have a hole or crack in your wall here is a simple how to guide to take you through step by step on how to repair and give a professional finish.

Tools for the job


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