Repair & Maintenance of Plastered Surfaces

Module 5: Repair & Maintenance of Plastered Surfaces

Plaster repair and maintenance are essential skills for preserving the structural integrity and aesthetic appeal of walls and ceilings over time. This module covers diagnosing common plaster problems, executing durable repairs, and implementing preventive maintenance strategies to extend the lifespan of plastered surfaces.

1. Identifying Common Plaster Defects

Understanding the root cause of damage ensures effective repairs:

• Cracks:

• Hairline cracks: Often caused by minor settling or drying shrinkage.

• Structural cracks: Wider gaps (≥3mm) due to foundation movement or load stress.

• Delamination/Bubbling: Plaster separates from the substrate due to poor adhesion, moisture, or incorrect mixing.

• Efflorescence: White salt deposits from water seepage, indicating dampness.

• Staining: Watermarks, mold, or rust from leaks or metal lath corrosion.

• Pop-outs: Small craters where contaminants (e.g., unburnt lime) in the plaster expand and burst.

2. Step-by-Step Repair Techniques

A. Patching Small Cracks & Holes:

1. Clean the Area: Remove loose plaster, dust, and debris with a scraper or wire brush.

2. Undercut Edges: Widen cracks slightly (in a "V" shape) to improve filler adhesion.

3. Apply Bonding Agent: Brush on PVA or acrylic primer for better bonding.

4. Fill & Smooth: Use a pre-mixed patching plaster or setting compound for small repairs. For deeper holes, apply in layers, embedding fiberglass tape for reinforcement.

5. Sand & Blend: Once dry, sand lightly and feather edges to match the surrounding surface.

B. Reattaching Delaminated Plaster:

1. Drill & Inject: For hollow spots, drill small holes and inject bonding adhesive (e.g., epoxy or plaster weld) behind the loose section.

2. Press & Secure: Clamp or screw plaster washers to hold the area flat until the adhesive sets.

3. Patch & Finish: Fill gaps with base coat plaster, then skim to match the texture.

C. Large-Scale Replastering:

• For severely damaged walls (e.g., bulging or crumbling sections), remove unsound plaster entirely, reapply metal lath if needed, and rebuild layers (scratch coat → finish coat).

3. Moisture & Mold Remediation

• Locate & Fix Leaks: Repair roof, plumbing, or drainage issues before replastering.

• Anti-Mold Treatments: Apply fungicidal washes or lime plaster (naturally mold-resistant) in damp areas like bathrooms.

• Breathable Finishes: Use vapor-permeable materials (e.g., clay or lime plaster) to prevent trapped moisture.

4. Preventive Maintenance

• Regular Inspections: Check for early signs of cracks or dampness, especially after extreme weather.

• Climate Control: Avoid rapid drying (use humidifiers in arid climates) or excess humidity (ventilate bathrooms/kitchens).

• Protective Coatings: Seal porous plasters with breathable silane/siloxane water repellents for exteriors.

5. Tools for Repair Work

• Angle grinder (for removing damaged sections).

• Pointing trowel (for precision patching).

• Masonry chisel & hammer (for undercutting cracks).

• Dehumidifier (for drying damp walls pre-repair).

Why This Matters: Proper repair techniques prevent costly structural damage and maintain the visual quality of plasterwork. This module emphasizes problem-solving and material science, equipping learners to tackle everything from DIY touch-ups to professional restorations.