Cracks in the plaster of a wall or ceiling are invariably due to shrinkage as the plaster dries. However, if having repaired a crack in plasterwork it keeps reappearing or gets worse you could have a problem with building settlement or worse subsidence. If you’re concerned about a crack that reappears or seems to get larger; buy a crack monitoring gauge and find out exactly what’s happening with it.
If the crack does continue to get bigger it might be worth taking a look at the brickwork or substrate to the plaster. If that is also showing signs of cracking or deformation you should consult with a builder or structural engineer.
Small Cracks in Wall or Ceiling
Small cracks can easily be filled using any of the proprietary plaster fillers. Using a scraper or palette knife scrape away the loose material, making the crack slightly deeper as this will help to provide a ‘key’ for the filler to adhere to.
Brush away the loose debris and wet the area to be treated with water. If necessary mix the filler and place it on a bat, using the scraper or palette knife press the filler into the crack so that it stands slightly proud of the crack.
After about 24 hours the filler will have dried and you can use a glass-paper to rub the area down so that it’s flat with the original plaster work. If the surface of the plaster wall was recently painted you may be able to get away with just touching up the repaired area with the same colored paint. Otherwise you might need to repaint the whole wall to get a pleasing finish to the job.
Repairing Plaster Cracks between Wall and Ceiling
A common problem in new buildings, due to ‘drying’, is the appearance of a crack where a plaster wall meets the ceiling. A small crack here can be repaired the same as for a small crack on the wall or ceiling itself. However, it’s perfectly OK to press the filler into the crack with a finger, especially at a corner where two walls and the ceiling meet.
In the long run this can actually result in a smoother job than if you try and maneuver tools into what can be a quite confined space and at awkward angles. If the crack between a wall and a ceiling is particularly bad you could alternatively fit molding around the room; these days molding is available in a variety of materials and designs to suit all budgets.
Cracks and Chips on Plaster Corners
Plaster corners can be susceptible to cracking and chipping due to furniture being pushed against them or children’s toys knocking them. To repair one first remove any lose material and ensure the surface is clean, wet the area to be repaired with water and apply a plaster filler until it stands proud of the damaged surface.
Before the filler fully sets mold it to make a good sharp corner with a flat piece of dampened wood, working it from both sides alternately. Finally when fully dry, usually after 24 hours, rub smooth with a glass paper and paint as required.
Fixing Wider Cracks in Plaster
After cleaning out the crack smear in a layer of joint compound to a depth of a 3mm. embed a length, or if necessary lengths, of the tape into the compound and then cover the tape with more of the compound until it’s slightly proud of the surface to be repaired.
Remove any excess and leave to dry. If on drying the repaired surface is below the level of the wall surface, add a second coat of compound and again leave to dry. You can smooth off the repair with a glass paper or, if the surface has been damped, use a rubber grout float.
An alternative to this is to use a painters caulk, being a latex compound it’s easy to work, smooth and clean. Also, being latex it will expand and contract naturally, reducing the risk of further cracking; even better you might even be able to get one that’s a perfect match for the color of a painted wall.