Plaster walls can be repaired fairly easily, as long as the walls are mostly in good shape. The walls have a layer of wood, rock, or metal lath behind the plaster, which holds in it place. If the lath is in bad shape or the plaster is soft, it is better to consult a professional than to attempt repairing plaster yourself.
Using latex bonding liquid for repairing plaster has a number of advantages. The bonding liquid ensures that you will have a crack-free patch and a good bond. In addition, bonding liquid eliminates any need to get the plaster and lath wet, which might cause premature drying and shrinkage.
To fill cracks in plaster, you should first scrape away any loose plaster or other debris around the crack. Then, reinforce the crack with fiberglass wallboard tape. Apply wallboard compound or spackle to the area until a thin layer conceals the tape. If the tape is not covered completely, add another thin layer of spackle or wallboard compound. If the layer is too thick, it will crack easily. Next, sand the area lightly, apply primer, and retexture the wall if needed.
If small holes or dents are present in your plaster walls, the procedure begins in the same way. Remove any peeling paint or loose plaster by scraping or sanding the area. Next, apply spackle to the hole, ensuring that the spackle is level with the rest of the wall. When the spackle is dry, sand the area lightly with 150-grit sandpaper, and wipe the dust away from the wall. The wall can then be primed and painted to match the surrounding area.
Repairing plaster when there are large holes is a little more challenging. Make sure that the lath backing is not damaged. Avoid repairing plaster walls yourself when the lath is not solid; it is better to call in a professional.
The first steps of repairing plaster walls with large holes is similar to small cracks. Sand or scrape all loose paint and texture away from the area with the hole. Using a wallboard knife, test the plaster around the hole and scrape away all soft or loose plaster around the hole. Apply a latex bonding liquid over the base lath and all around the edges of the whole to keep the plaster from separating or cracking.
Mix the patching plaster according to the directions and apply it to the hole, using a wallboard knife. Apply in thin layers so that the layers don't crack. If the hole in the plaster is especially deep, apply a thinner first coat, then scratch a crosshatch pattern in the wet plaster. After this is dry, add another coat of plaster. Let the second coat dry, then sand the area, prime and paint it, and add any texture that is needed.
Written by Bronwyn Harris
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