Defects and Remedial Measures in Plastering

1. Defects

Usual defects which are noticed in plastering are discussed below.

1. Cracks may appear on the plastered surface which may be easily seen (called hair cracks).
2. Sometimes the soluble salts are brought to the surface. Such materials appear in the form of a whitish crystalline substance which is called efflorescence. Efflorescence affects the adhesion of paint with wall surface.
3. Small patches sometimes swell out beyond the plane of the plastered surface. These are called as blistering.
4. Because of inadequate bond available on brick work or concrete, the adhesion of plaster may not be complete.
5. Presence of soluble salts on the surface adhesion might have been lost by their crystallization and expansion.
6. Failure of bond of successive layers may cause formation of loose mass which is called flaking.
7. Failure of plaster may also occur if the suction of the background is not uniform. Further-background which are absorbing a lot of water from the plaster may affect the strength of the plaster.
8. Failure of bond between successive coats may cause peeling of some portion of plaster.
9. Plaster sometimes contains particles which expand on being set. Because of this a conical hole is formed in the plastered surface. The conical hole is termed as the blow or pop.
10. Because of poor workmanship, uneven surfaces may be formed.
11. Presence of excessive dampness at certain parts of the plastered surface makes that portion soft. Further thin coats may also cause soft points.
12. Plastering done on metal lath may show sometimes rust-stains.

2. Remedies

1. Primarily the workmanship towards brickwork and plastering should be the best.
2. The bond of the brickwork should be properly maintained so as to give the plaster a proper bond.
3. The surfaces which are affected by efflorescence should be removed by rubbing with brushes. Then a solution of one part of hydrochloric acid or sulphuric acid with five parts of clean water is prepared. The solution is applied on the affected surface. Then the surface is washed with water. The efflorescence should be prevented by selecting a suitable material for mortar.
4. Good quality bricks only should be used.
5. For brickwork and plastering work, water free from salts should be used.
6. In order to avoid the absorb of water in plaster by the background, the background should be well watered.
7. Excessive trowelling leads to cracking which should be avoided.
8. Prevention of water on to the wall should be avoided.
9. Damp proof courses should be provided whenever needed.
10. The plastered surface should not be exposed to excessive water by natural agencies or otherwise.