4.1 Causes of Cracks in Walls
Cracks in masonry are a common problem caused by structural, environmental, or material issues. Identifying the cause is crucial for selecting the right repair technique.
4.1.1 Bulging of Wall / Shrinkage
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Bulging: Caused by moisture weakening mortar or loss of bonding.
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Result: Walls bend outwards or become unstable.
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Example: Rain-soaked old brick walls without damp-proofing.
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Shrinkage: Happens when plaster or mortar loses moisture.
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Cracks appear along joints or corners.
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More common in clay bricks and lime mortar.
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4.1.2 Bonding / Shear Cracks
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Caused by poor interlocking of bricks or inadequate bond between mortar and brick.
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Shear cracks develop due to lateral loads or foundation movement.
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Example: Diagonal cracks during earthquakes or settlement.
4.1.3 Tensile Cracks
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Bricks and mortar are weak in tension.
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Tensile stress from temperature changes or structural movement can cause vertical or horizontal cracks.
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Common in boundary walls and tall free-standing walls.
4.1.4 Vegetation
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Roots of plants or trees growing near walls can exert pressure.
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Vegetation inside cracks retains moisture and accelerates deterioration.
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Example: Ivy or fig tree roots widening cracks in compound walls.
4.2 Probable Crack Locations
Cracks tend to form at stress concentration zones or where different materials join.
4.2.1 Junction of Main and Cross Walls
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Differential movement between walls.
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Poor connection or bond causes vertical or inclined cracks at the intersection.
4.2.2 Junction of Slab and Wall
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Occurs due to different thermal expansion or slab deflection.
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Common in multi-storey buildings where RCC slab meets brick walls.
4.2.3 Cracks in Masonry Joints
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Can appear due to poor workmanship or drying shrinkage.
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Horizontal cracks follow mortar joints and can lead to water leakage.
4.3 Repair Methods Based on Crack Type
4.3.1 Minor to Medium Cracks (0.5mm–5mm): Grouting
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Cement or polymer grout is injected into cracks to seal and bond.
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Ideal for non-structural cracks.
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Tools: Hand pump, grouting gun.
4.3.2 Major Cracks (>5mm): Mesh Fixing
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Galvanized wire mesh is fixed over cracks and plastered.
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Provides flexible bonding and prevents crack widening.
4.3.3 RCC Band
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Horizontal RCC band (reinforced concrete) at lintel or sill level.
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Enhances structural integrity and distributes loads.
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Mandatory in seismic zones.
4.3.4 Ferrocement Plates at Corners
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Thin, reinforced plates are placed on corners or junctions.
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Used where large diagonal cracks or separation exists.
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Offers high crack resistance and easy installation.
4.3.5 Dowel Bars
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Steel rods inserted across cracks and fixed with epoxy.
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Transfers load across crack and prevents separation.
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Used in structural cracks or retrofitting.
4.3.6 Propping of Load-Bearing Walls
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Temporary support using props or jacks.
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Ensures safety during repair or replacement.
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Required when cracks compromise the load-carrying capacity.
4.4 Remedial Measures for Dampness & Efflorescence
Dampness:
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Entry of water through walls causes plaster damage, fungal growth, and weakening.
Remedies:
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Surface waterproofing using polymer coatings.
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Injection grouting with waterproof chemicals.
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Damp-proof course (DPC): Horizontal barrier at plinth level.
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Improved drainage to reduce water contact.
Efflorescence:
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White powdery deposit on wall surface due to salt crystallization from water.
Remedies:
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Dry brushing and washing with dilute acid (e.g., vinegar or mild HCl).
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Seal cracks to prevent water ingress.
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Use of low-alkali cement and clean water in repairs.
✅ Summary Table for Crack Repair Techniques:
| Crack Type | Width | Method | Materials Used |
|---|---|---|---|
| Minor | 0.5–1 mm | Grouting | Cement/polymer grout |
| Medium | 1–5 mm | Grouting + Sealing | Polymer mortar |
| Major | >5 mm | Mesh, RCC band, Ferrocement | Steel mesh, epoxy, RCC |
| Structural | Any | Dowel bars, propping | Steel rods, props |
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