Patching up your plaster

General, Interiors

Plaster is the perfect way to give almost any material a smooth, uniform finish. If your home was built before the end of World War II you may find that your home has non-load-bearing/ dividing interior walls and ceilings make from lath and plaster. The laths are narrow strips of wood nailed to battens providing a key for the plaster to attach to. Load-bearing walls had plaster applied directly to the brick or stone in a series of coats.

crack-353218_1280After World War II plasterboard became popular in England. It is sometimes skimmed with a couple of coats of plaster to give a smooth and uniform finish. Sometimes it’s simply fixed in place and the joints taped and filler. This process is known as dry-lining.

Unfortunately, whilst plaster has a great aesthetic finish, it is not that hard wearing. Plaster crack, removing picture hooks can take chunks of plaster with them, and corners are susceptible to damage.

Getting Prepped

Whichever plaster repair you are undertaking always start with the following steps:

  1. Always put down a dust sheet. You’re guaranteed to make a bit of mess and it’s better to be prepared.
  2. For vertical and overhead filling jobs (i.e. most of them), mix the filler powder with water until it becomes a stiff paste. How stiff? We reckon it’s ready to use when you can do this with a filler-knife full and the filler doesn’t fall to the floor.

Repairing cracks

  1. Dig out cracks in plaster with a Stanley-type knife. Cut in until you can no longer see the original crack. For this step you’re aiming to make a V-shaped groove where the crack once was. This will be ideal for taking the filler with no visible marks.
  2. Get rid of any loose dust and debris from your new V-shaped groove. A vacuum cleaner will make short work of this task.
  3. For more persistent loose dirt you can dampen the groove using a spray bottle. This will help the filler to stay put.
  4. Spread the filler into the groove making sure that it has gone right to the bottom. Leave the filler a little proud over the groove but remove the excess either side before the filler dries.
  5. When the filler is thoroughly dry lightly sand it down to create smooth, uniform surface ready for painting.

Corner damage

Corners are a vulnerable to larger patches of damage. This can be a bit more tricky as gravity will prevent the filler from staying in the shape you require. Repaired corners are also vulnerable to scuffs as people walk past.

  1. Apply the filler to the corner and get the shape roughly correct.
  2. Use some wide masking to cover both sides of the corner and leave the filler to dry. The tape protects the filler and keeps it in shape.
  3. A light sanding later on will deliver the perfect corner repair.

Chunks of missing plaster

Chunks fall out of plaster walls for a number of reasons: household clumsiness is one contributory factor, but fitting or adjusting a door frame (as here) can create a real mess.

  1. First remove any loose chunks of plaster use a hammer and chisel if necessary then vacuum out the area to get rid of the dust and debris.
  2. Brush in a PVA mix to give the plaster the best possible chance of bonding with the existing wall.
  3. Mix up plaster according to the manufacturer’s instructions.
  4. Apply a thin coat of plaster (2-3mm) onto the area to be repaired. Don’t try to fill the whole thing at once or the plaster will just dribble out of the repair.
  5. When the plaster starts to dry, lightly scratch the surface with the end of the trowel in a criss-cross pattern. This allows the next layers something to grip onto.
  6. Once the first coat is dry, mix up plaster as before and use a plastering coat to apply. Once the shape is correct, leave the job alone for ten minutes then wet the float and smooth the surface over

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