Aside from being ugly marks on walls, cracked plaster finishes may be signs of structural weakness. They must be dealt with at once. Basic knowledge on how to repair cracks on plaster work should be enough to fix the problem.
Identify the Crack
Before dealing with the wall plaster finish, make sure the problem is indeed the plaster work. Cracks may merely be paint-deep, just a tear on the paint. In this case, the job does not call for fixing wall plaster cracks. The wall needs repainting. In some cases, the task may be more than just applying knowledge on how to repair cracks on plaster work. The crack might mean a major repair.
Chisel Off the Cracked Area
If it is not a paint crack, find out if it is plaster-deep or deeper than that. Do this by chiseling off the areas of the crack. Break off concrete 3 to 4 inches around the crack until the layer of the plaster and the hollow block show. This is the first step on how to repair cracks on plaster work. If it is just plaster-deep, the crack won’t show on the hollow block. The work will merely be a re-plastering patch up work. If the crack goes deeper into the hollow block, it may need a major wall repair or replacement, not just fixing wall plaster cracks.
For Plaster-Deep Cracks
For cracks that are merely plaster-deep, chisel off the area around it. Do this until the hollow block underneath appears. Then wipe the area clean, making sure there are no bumps, humps, or protruding portions. Clean all debris. Then splash liberally with clean water. This is important in how to repair cracks on plaster work. The surface to be repaired should be roughen up and leveled up. It must also be well watered. These procedures make sure that the new plaster cement would stick to the surface well.
Apply New Cement Plaster
Cement plaster is composed of sifted sand, cement, and in some cases, a powdered water proof sealant, which is optional. Mix these aggregates well, first by stirring them well while dry, then by adding enough water while mixing to turn it into a thick paste. The ideal ratio is 1:1:1. One part cement with one part sand with one part water.
When fixing wall plaster cracks with new plaster, throw the wet plaster to the surface to be repaired using a flat masonry trowel, aided by a wooden flattener. This action helps the plaster to stick more to the surface. Then, smoothen the surface by dusting cement powder on the wet plaster. Allow for 2 to 3 minutes before smoothening with an iron flattener.