Different types of defects occur in plastering work such as blistering, cracks, efflorescence, flaking, peeling, popping, softness and uneven surfaces. These defects in plastering need to be repaired as soon as they are observed.
Types of Defects in Plastering
1. Blistering of Plastered Surface
Blistering of the plastered surface occurs when small patches swell out beyond the plane of the plastered surface. Blistering is seen in case of plastered surface inside the building.
2. Cracks in Plastering
Cracks are formed on the plastered surface. These cracks can be hairline cracks which are difficult to notice, or it can be wider cracks which are easily seen. The development of fine cracks is known as crazing.
Cracks on a plastered surface can be due to thermal movements, discontinuity of surface, structural defects in the building, faulty workmanship, excessive shrinkage etc.
3. Efflorescence on Plastered Surface
Efflorescence is formed on plasters when soluble salts are present in plaster making materials as well as building materials such as bricks, sand, cement etc. Even water used in the construction work may contain soluble salts.
When a newly constructed wall dries out, the soluble salts are brought to the surface and they appear in the form of a whitish crystalline substance. Such a growth is referred to as efflorescence and it seriously affects the adhesion of paint with the wall surface.
Efflorescence gives a very bad appearance and can be removed to some extent by dry-bushing and washing the surface repeatedly.
The formation of a very small loose mass on the plastered surface is known as flaking and it is mainly due to bond failure between successive coats of plaster.
The plaster from some portion of the surface comes off and a patch is formed. Such formation is termed as peeling and it is mainly due to bond failure between successive coats of plaster.
Sometimes the plaster mix contains particles which expand on being set. A conical hole in plastered surface is formed in front of the particle. This conical hole is called as blow or pop.
7. Uneven Plaster Surface
Uneven surface defect becomes prominent only due to poor workmanship of the plastering work.
8. Softness of the Plaster
The excessive dampness at certain points on the plastered surface makes that portion soft. The main reasons for such softness are undue thinness of the finishing coats, presence of deliquescent salts, excessive suction of the undercoats etc.
9. Rust Stains on Plastered Surface
Rust stains are sometimes seen on the plastered surface especially when plaster is applied on metal lath.