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How to Repair Plaster Walls?

Repairing of plaster walls is needed from time to time as the building ages. The most common problem with plaster walls is crumbling, water damage, cracking or pulling away from the lath behind it. Repairing process of plaster walls is presented in the following sections.

Table of Contents

• Repairing of Plaster walls 
  • 1. Identify Plaster Wall Problem
  • 2. Setting up Scaffolding
  • 3. Protective Measure
  • 4. Cutting of Old Plaster
  • 5. Preparation of Surface
  • 6. Application of Plaster
  • 7. Curing of Plaster
  • 8. Finishing of Plaster

Repairing of Plaster walls 

Procedures involved in repair of plaster are:

1. Identify Plaster Wall Problem

The type of damage shall be specified prior to the commence of repairing operation. In this manner, the most suitable technique and equipment can be employed to repair the damage and best outcome could be achieved.

Table 1 provide types of plaster wall problems and their causes, and Fig.1 to Fig.3 shows number of plaster wall problems that need to be repaired.

Table 1 Common types of plaster wall problem and their causes

Common types of plaster wall problem	Cause of the plaster wall problem
Cracks	Hairline cracks due to moisture evaporation, delaminating crack because plaster pulling away from the lath behind it, and Settlement Cracks because of building settlement.
Damage	activity inside the home like a collision due to moving a piece of furniture
Blistering	improper slaking of lime particles in the plaster
Flaking	poor bond
Discoloration	Water seepage

Fig. 1: Delaminating cracks in plaster wall

Fig. 2: Hairline cracks in plaster wall

Fig. 3: settlement cracks

2. Setting up Scaffolding

Scaffolding is required for the proper execution of the repair work should be erected. Ladder can also be used in case of scaffolding if the work can be done safely.

Fig. 4: Setting up scaffolding or ladder

3. Protective Measure

Doors, windows, floors, articles of furniture etc. and such other parts of the building should be protected from being splashed by mortar.

4. Cutting of Old Plaster

The mortar of the patch, where the existing plaster has cracked, crumbled or sounds hollow when gently tapped on the surface, is first removed.

The patch is be cut out to a square or rectangular shape at position where repairing is needed. The edges of cut plaster is made under cut to provide a neat joint.

5. Preparation of Surface

The masonry joints which become exposed after removal of old plaster is raked out to a minimum depth of 10 mm in the case of brick work and 20 mm in the case of stone work.

The raking is carried out uniformly with a raking tool, and loose mortar is dusted off. The surface is then thoroughly washed with water, and kept wet till plastering is commenced.

In case of concrete surfaces, the old plaster is thoroughly scrubbed with wire brushes after the plaster had been cut out, and pock marked the surface is roughened by wire brushing, and all the resulting dust and loose particles cleaned off. The surface is washed and cleaned and kept wet till plastering is commenced.

Fig. 5: Surface preparation

6. Application of Plaster

Mortar of specific mix such as 1:4 or 1:6 with the good quality plaster sand is used. After the plaster has been applied to the surface, finishing of plaster is done to match with the old surrounding plaster.

Fig. 6: Application of plaster

7. Curing of Plaster

Curing of plaster is necessary to prevent cracking. It should be done for at least 3 days at regular interval.

8. Finishing of Plaster

After the plaster is thoroughly cured and dried the surface is then painted with the color of the surrounding area.