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Guide · 7 min read · Updated 2026

How to Repair Cracks in a Concrete Block Foundation

Block foundations are common on mid-century homes throughout MetroWest and the South Shore. Crack pattern tells you a lot about severity.

Types of cracks

  • Vertical hairline cracks: usually shrinkage, typically cosmetic
  • Stair-step cracks: settlement; monitor and repoint
  • Horizontal cracks: soil pressure; potentially structural

Repair methods

Mortar joints are repointed, cracked blocks replaced, and horizontal bowing is addressed with bracing, wall anchors, or rebuilding under engineering guidance.

Exterior protection

Parging and grading keep water away from the block.

Frequently asked questions

Are horizontal foundation cracks serious?

They can be. Have them evaluated promptly, especially if the wall bows.

Can I fill cracks with caulk?

Caulk is a temporary cosmetic fix and doesn't address movement.

How much does block foundation repair cost?

Minor repairs from $600; structural reinforcement can reach $10,000+.

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