Exterior Brick &
Stair-Step Cracks

The signature crack of foundation movement. Because mortar is weaker than brick, stress travels the path of least resistance . stepping diagonally through the joints. In Austin, these typically originate near a corner where the foundation has settled more than the center. A stair-step crack wider than 1/4" or one that spans more than 4 courses of brick almost always means active differential settlement that won't self-correct.

Location

Exterior brick veneer, typically near corners or below windows

Typical Width

1/8" to 3/8"

Pattern

Zig-zag following horizontal and vertical mortar joints

Likely Cause

Differential foundation settlement

Horizontal cracks in brick are rarely cosmetic. When they appear near the top of a wall, they often indicate the brick veneer is separating from the framing . corroded or missing brick ties allow the veneer to bow outward under its own weight. At the foundation ledge, they can indicate the slab edge is dropping away from the brick. Either scenario demands professional assessment because veneer separation is both a structural and safety risk.

Location

Mid-wall, often 2–4 courses below the roofline or at the brick ledge

Typical Width

1/16" to 1/4"

Pattern

Straight horizontal line following one mortar bed joint

Likely Cause

Lateral soil pressure, lintel failure, or brick tie corrosion

When a crack passes through the brick rather than following the mortar, the force involved is significant . mortar is designed to be the weak link. Vertical brick splits near corners can indicate compressive stress from lateral expansion of a long wall without adequate expansion joints. Near windows or doors, they may indicate lintel bearing failure. Unlike mortar cracks, these cannot be simply repointed and often indicate a systemic issue.

Location

Cracking through the brick itself, not the mortar

Typical Width

Varies . often 1/16" to 1/8"

Pattern

Straight vertical line splitting individual bricks

Likely Cause

Compressive overload or extreme thermal expansion

Steel lintels above windows and doors carry the weight of the brick above them. When a lintel corrodes (common in Austin's humidity), deflects, or when the foundation beneath settles, diagonal cracks form at the corners of the opening. If both corners crack, the lintel is likely failing. If only one corner cracks, differential settlement is the more probable cause. In either case the crack will widen until the root cause is addressed.

Location

Diagonal cracks originating at the upper corners of openings

Typical Width

1/8" to 1/4"

Pattern

Diagonal 30–45° from lintel ends

Likely Cause

Lintel deflection or foundation settlement beneath the opening

Expansion joints are engineered relief points . they're supposed to move. But movement beyond design tolerances signals a problem. If a gap has crushed closed and buckled the adjacent brick, the wall has expanded beyond what the joint can absorb, often due to missing joints elsewhere. If a gap has opened wider than the original design (typically 3/8"–1/2"), the structure on one side has moved away, which can indicate settlement or heave.

Location

Vertical gaps (caulked joints) where brick meets a corner, window frame, or different material

Typical Width

Gap appears crushed closed or opened beyond 1/2"

Pattern

Caulk squeezed out or gap opened with visible backing

Likely Cause

Thermal expansion (closing) or foundation settlement (opening)

Eroded mortar without cracking is usually a maintenance issue, not a foundation symptom. Soft mortar at the base of a wall typically means splash-back from rain or sprinkler systems is dissolving the mortar over time. Repointing (grinding out old mortar and applying new) is the fix. However, extensive mortar erosion weakens the wall and can allow moisture into the wall cavity, leading to brick tie corrosion . so address it before it cascades into a structural issue.

Location

Mortar receding between bricks, especially at lower courses

Typical Width

Mortar recessed 1/4" to 1/2" behind brick face

Pattern

Widespread along the base or on weather-exposed faces

Likely Cause

Water infiltration, efflorescence cycling, or age