What Causes Moisture Behind Exterior Brick Veneer?

Rain and groundwater can seep directly through the brick assembly. Cracked bricks, deteriorating mortar joints, or damaged sealant provide easy entry points. Water also enters through openings for pipes, vents, or light fixtures if they are not properly sealed. Once inside the wall cavity, this moisture has no way to evaporate, soaking the wood or insulation behind the veneer.

Driving rain is a significant factor, especially on walls facing prevailing winds. Faulty construction details, like improperly installed flashing above windows or doors, can funnel water behind the bricks. Inspect your home's exterior after heavy storms for signs of new moisture stains inside, which can indicate a breach in the brick's weather-resistant barrier.

Flashing is a critical component installed where the brick meets other materials, like roofs, windows, or decks. Its sole job is to catch and redirect any water that gets behind the bricks back to the exterior. When this system fails, it creates a direct path for large volumes of water to enter the wall assembly, often during every rain event.

Weep holes are equally important for allowing any incidental moisture that does get behind the brick to escape. If they are blocked, the water has nowhere to go. This trapped moisture can then wick upwards into framing materials or sideways, spreading damage far from the original leak source. Keeping these drainage paths clear is essential for a dry wall.

• Flashing is a thin metal or plastic layer that directs water away from vulnerable joints.
• If flashing is missing, corroded, or installed incorrectly, water flows behind the brick instead of away from it.
• Weep holes are small openings at the bottom of the brick wall that allow trapped water to drain.
• These holes can become clogged with mortar droppings, paint, or debris from insects.
• Blocked weep holes prevent drainage, causing water to pool inside the wall cavity.
• Regularly checking and clearing weep holes is a key maintenance task for brick veneer.

Discovering the source often requires a systematic investigation. Look for interior clues like peeling paint, bubbling wallpaper, or a musty odor on exterior walls. Outside, check for cracked mortar, moss growth, or efflorescence, a white, powdery salt deposit on the bricks. These signs indicate persistent moisture movement. A non-invasive moisture meter can help local water damage pros map the extent of dampness inside the wall. This investigation is a crucial first step before any repairs begin.

Addressing the issue starts with stopping the water source, whether it's repairing a roof leak, re-caulking a window, or repointing mortar joints. After the leak is fixed, the wall cavity often needs to dry out. This may involve removing interior drywall to access the space. Structural drying equipment like dehumidifiers and air movers is then used to remove the trapped moisture and prevent mold. The goal is to restore a dry, stable condition behind the veneer.