What Causes Brick Spalling?

Brick spalling occurs primarily due to water infiltration and the damaging effects of freeze-thaw cycles. When water seeps into the porous surface of bricks and freezes, it expands, exerting pressure that can cause the brick’s outer face to break off. Other contributing factors include:

• Incompatible Mortar: Using hard, modern cement mortar on older, softer bricks can create stress due to different expansion/contraction rates.

• Water Infiltration: Faulty gutters, cracked mortar, or poor drainage allow excess water to penetrate the brickwork.

• Improper Sealants: Non-breathable sealants trap moisture inside bricks, leading to internal stress and deterioration.

• Rust-Jacking: Steel components like lintels inside the masonry rust and expand, pushing bricks apart.

Areas Prone to Spalling:

Certain locations are more susceptible to spalling due to exposure to moisture and structural stress:

• Chimneys

• Below window sills

• Lower walls near the ground

• Retaining walls

How to Repair Spalling Bricks

Repairing spalled bricks involves several steps:

1. Identify and Fix the Source of Water Infiltration

Before repairing the bricks, eliminate the water source—repair gutters, fix cracks, improve drainage, and reseal joints to prevent future damage. Also look for signs rusted steel components and structural movement.

2. Remove Damaged Bricks

Carefully remove the deteriorated bricks:

• Remove the mortar surrounding the damaged brick.

• Take out the broken or spalled brick.

3. Determine Existing Mortar Type and Strength

Matching the mortar is vital for durability and aesthetic consistency:

• Old buildings (pre-early 1900s): Use lime-based mortar or weak modern mixes like Type O (350 psi).

• Newer buildings (post-early 1900s): Use Type N (750 psi), suitable for most above-grade applications.

• Heavy load areas: Use stronger mortars like Type S or M, but avoid these with softer, older bricks.

For complex projects or historic restorations, consult a professional for mortar testing.

4. Replace Damaged Bricks

• For extensively damaged bricks, cut out the old units and replace them with matching bricks.

• For minor damage, apply a breathable, color-matched mortar patch to fill small cracks or chips.

5. Use Breathable Mortar for Repointing

Apply a lime-based or compatible mortar that allows moisture to escape, preventing future spalling.

Additional Tips for Long-Term Durability

1. Regularly inspect your brickwork for early signs of damage.

2. Maintain proper drainage around your property.

3. Avoid using hard, incompatible mortar on historic or soft bricks.

4. Consult professionals for extensive repairs or historic preservation.