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What Makes My Brick Walls Absorb Water During Storms?

Last updated October 20, 2026

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The short answer

The Porous Nature of Brick and Mortar

Brick itself is a porous material, meaning it naturally contains tiny spaces that can soak up moisture. The mortar between bricks is also absorbent. Over many years, these materials can become even more porous due to weathering and erosion from repeated storms. This is a primary reason water enters during heavy rain, even if the wall looks solid from a distance.

The rate of absorption depends on the age and quality of the bricks and mortar. Older, softer bricks or mortar with a high sand content tend to absorb water more readily. During a downpour, this absorption happens continuously as long as the surface remains wet. It is a gradual process that can lead to significant moisture inside the wall cavity over time.

Common Entry Points for Storm Water

Small cracks in the mortar joints, known as mortar deterioration, are a major entry point for water. These cracks can develop from foundation settlement, freeze-thaw cycles, or simple aging. Once water enters a crack, it can travel through the brick and into the interior wall structure, potentially causing hidden damage behind the brick facade.

Failed sealants around windows, doors, and where the roof meets the wall also allow water intrusion. Flashing, the metal strips designed to divert water, can rust or become dislodged. In severe storms with wind-driven rain, water is forced against the wall with enough pressure to exploit these weaknesses, bypassing the brick's natural shedding ability.

  • Hairline cracks in mortar joints.
  • Deteriorated or missing caulk around windows and doors.
  • Damaged or missing flashing at roof-wall intersections.
  • Spalled bricks where the surface has chipped away.
  • Weep holes that are clogged with debris or insect nests.
  • Cracks in the brick itself from structural stress.

How Drainage and Grading Affect Your Walls

If the ground around your home slopes toward the foundation, stormwater pools against the brick. This hydrostatic pressure forces moisture through the porous materials. Proper grading should direct water away from the house. Ensuring your yard drains correctly is a key defense against intense rainfall from flash floods.

Clogged gutters and downspouts that dump water directly next to the foundation are a common problem. The water saturates the soil and remains in contact with the brick wall for extended periods. This constant moisture supply allows more water to be absorbed than during a brief rain shower. Installing downspout extensions can make a significant difference.

The Process of Water Damage Behind Brick

Once water gets past the brick veneer, it enters the wall cavity. This space typically contains insulation, wood framing, and the interior drywall. The absorbed moisture can soak these materials, leading to rot, mold growth, and structural weakening. The damage often remains hidden until stains appear inside or a musty odor develops.

This trapped moisture also creates an environment for mold spores to grow. Mold can affect indoor air quality and may require professional remediation. Because the brick face dries faster than the cavity, it creates a false sense of security while problems worsen unseen. This is why inspection after suspected water intrusion is important.

Steps to Take After Noticing Water Absorption

If you see damp bricks, interior stains, or efflorescence (a white, powdery deposit on the brick), act quickly. Contact local water damage pros for a thorough inspection. They use moisture meters and thermal imaging to find the extent of water behind the walls. This assessment is the first step toward a targeted repair plan.

Do not ignore the issue, as ongoing moisture leads to more expensive repairs. Document any visible damage with photos for your insurance records. Policies vary, and your insurer decides what is covered. A professional inspection report can be crucial for an insurance claim, detailing the cause and necessary repairs to prevent recurrence.

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Frequently asked questions

Can sealing my brick walls stop water absorption?

Applying a breathable, penetrating sealant can help reduce water absorption. However, it is not a cure for existing cracks or drainage problems. Sealant should only be applied to completely dry, clean brick by a qualified professional. It is part of a solution that must also address mortar repairs and proper drainage.

How do I know if water behind brick has caused mold?

Signs include a persistent musty odor, visible mold growth on interior walls or baseboards, and worsening allergy symptoms. Mold often grows in the wall cavity out of sight. If you suspect mold, limit exposure and consult a mold assessment professional. Do not disturb the area, as this can spread spores.

Will my homeowners insurance cover repairs for this damage?

Coverage depends on the specific cause stated in your policy. Sudden, accidental water intrusion from a storm may be covered, while long-term seepage often is not. You must file a claim with your insurer. Policies vary, and your insurer decides what is covered. An inspection report from the pros supports your claim.

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