How the Freeze-Thaw Cycle Damages Bricks (and How to Prevent It)

John Screen
Mar 20
2 min read

Bricks are strong and long-lasting, which is why they’ve been used for building for centuries. But even bricks can get damaged by weather — especially from something called the freeze-thaw cycle. If you’ve ever noticed bricks cracking, flaking, or falling apart in the winter, the freeze-thaw cycle is probably to blame.

What is the Freeze-Thaw Cycle?

The freeze-thaw cycle happens when water gets into small cracks and holes in bricks. When the temperature drops below freezing, that water turns into ice and expands — pushing against the brick from the inside. When the ice melts, the pressure releases, but the cycle repeats over and over with each freeze.

Since water expands by about 9% when it freezes, that pressure can cause serious damage to bricks over time. If you live in an area with cold winters and lots of freezing and thawing (like Boston!), this cycle can happen dozens of times in a season.

How It Damages Bricks

Spalling – This is when pieces of brick start flaking or chipping off. It happens because the pressure from freezing water breaks apart the surface of the brick.
Cracking – Small cracks form when bricks expand and contract with the freeze-thaw cycle. Over time, these cracks grow bigger, letting in more water and making the problem worse.
Weak Mortar Joints – The mortar (the material between bricks) can also crack and fall apart from the freeze-thaw cycle. This makes the whole structure weaker.
Efflorescence – If you’ve seen white powdery deposits on bricks, that’s efflorescence. It happens when water carrying salts evaporates, leaving the salt behind. It’s a sign that too much moisture is getting into your bricks.

How to Prevent Freeze-Thaw Damage

jms masonry crew working on a historic restoration in boston

Use the Right Bricks – High-density bricks absorb less water and are more resistant to freezing and thawing.
Seal the Bricks – Applying a breathable water repellent helps keep moisture out without trapping it inside.
Maintain the Mortar – Repointing (replacing damaged mortar) helps keep water out of the joints between bricks.
Improve Drainage – Make sure water flows away from your home by installing gutters and grading the ground.
Fix Damage Early – Small cracks and chips are easier to repair before they become bigger issues.

Dealing With Brick Issues in the Greater Boston Area? We Can Help.

If you’re noticing damage to your bricks or want to protect your home from the freeze-thaw cycle, JMS Masonry & Restoration can help. We specialize in repairing and protecting brick structures, so you don’t have to worry about winter damage.