What Causes Brick Walls to Crack and Separate?
Last updated October 25, 2026
The short answer
Moisture and Water Damage
Water is a major cause of brick wall cracks. Rain can soak into porous brick and mortar, especially if the wall lacks proper flashing or sealant. Over time, moisture weakens the materials and leads to small cracks that widen with each freeze-thaw cycle.
Leaking gutters, downspouts, or sprinklers near the wall add to the problem. If water pools at the base, it can saturate the foundation soil. In humid climates, like where you live, persistent dampness can accelerate decay. Check for efflorescence, a white powdery residue, as a sign of moisture intrusion.
- Inspect gutters and downspouts for leaks or blockages
- Ensure the ground slopes away from the wall
- Seal cracks in mortar with a flexible caulk
- Keep sprinklers from hitting the brick
- Look for white salt stains on the surface
Foundation Movement and Settling
Brick walls sit on a foundation, and any movement in that foundation transfers to the brick. Soil can shift due to changes in moisture content, such as drought or heavy rain. Expansive clay soils, common in many regions, swell when wet and shrink when dry, causing the foundation to move.
Tree roots can also draw moisture from the soil, creating voids under the foundation. As the foundation settles unevenly, cracks appear in the brick, often as stair-step patterns along mortar joints. If you notice doors or windows sticking, that can indicate foundation movement.
- Watch for stair-step cracks along mortar lines
- Notice if doors or windows become hard to open
- Check for gaps between brick and window frames
- Look for a leaning or bulging wall section
Temperature and Thermal Expansion
Brick expands in heat and contracts in cold. Over time, this constant movement creates stress at weak points, especially where the wall meets other materials like concrete or wood. Without proper expansion joints, cracks can form.
In areas with hot summers and spring thunderstorms, the temperature swings can be sharp. The brick heats up quickly in the sun, then cools after a storm. This repeated cycle can cause hairline cracks to appear, particularly in long walls or around openings.
- Look for cracks near corners and window edges
- Check where the brick meets the roofline
- Note any vertical cracks that run straight down
- Observe if cracks appear after a hot day
- Consider if the wall lacks expansion joints
Poor Construction and Material Issues
Sometimes cracks come from how the wall was built. Mortar that is too strong or too weak for the brick can cause problems. If the mortar is harder than the brick, it can cause the brick to crack. If it is too soft, it erodes quickly.
Lack of proper flashing at the top of the wall, or missing weep holes, can trap water inside. Also, if the wall was built without a proper foundation or with low-quality materials, it is more prone to cracking. An inspection can help identify these issues early.
- Inspect the mortar for crumbling or erosion
- Check if weep holes are clear at the base
- See if the wall has a cap or flashing on top
- Look for efflorescence, which signals trapped water
When to Call for Help
Small hairline cracks may be cosmetic, but larger cracks or separation suggest a deeper problem. If you see cracks wider than a quarter of an inch, or if the wall is bowing, get professional help. Water damage can also hide behind the brick, so a moisture inspection can reveal issues.
A water damage inspection can check for hidden moisture and structural issues. If water is involved, structural drying may be needed to dry out the wall and prevent further damage. In Rockwall, if you notice persistent dampness or cracking, act quickly to avoid more extensive repair.
- Cracks wider than a quarter inch need attention
- Bowing or leaning walls are serious
- Signs of water inside the home near the wall
- Mold or mildew smell near the brick wall
Talk to someone now
Phones are answered 24/7 for Rockwall and nearby communities.
Call Now (469) 698-4610Frequently asked questions
Are brick cracks always a sign of foundation problems?
Not always. Small hairline cracks can come from temperature changes or minor settling. But if cracks are wide, stair-step, or accompanied by sticking doors, foundation movement may be involved. A professional inspection can tell you the cause and whether it's serious.
Can I fix brick cracks myself?
You can fill small cracks with a flexible masonry caulk or mortar repair product. For larger cracks or structural issues, it's safer to have a professional assess the situation. Water damage behind the brick may require drying and repair that's usually left to the pros.
How do I know if water is causing the cracks?
Look for signs like efflorescence, damp spots on interior walls, or mold. If you suspect water, a moisture mapping service can detect hidden dampness. That helps you decide if you need leak detection or structural drying before repairing the brick.