Why Does Water Run Down Inside My Exterior Walls?

Water finds its way into exterior walls through several weak spots. Gaps around windows and doors, cracked caulking, or damaged siding allow rain to seep in. Flashing that is missing or improperly installed at roof-to-wall junctions is another frequent culprit.

Once water penetrates the outer layer, gravity pulls it downward inside the wall cavity. It can soak insulation, rot framing, and stain interior drywall. You might notice damp spots, peeling paint, or a musty smell before you see the actual water.

• Cracked or missing caulking around windows and doors
• Damaged or loose siding boards
• Faulty or missing flashing at roof intersections
• Clogged or missing weep holes in brick or stucco
• Failed sealant around vents, pipes, or electrical boxes
• Improperly lapped house wrap or building paper

Look for discoloration on interior walls, especially near the ceiling or baseboards. Bubbling or peeling paint, warped drywall, and a damp or musty odor are common indicators. You might also see rust on nails or screws, or notice that the wall feels soft to the touch.

If you suspect water is running down inside your exterior walls, act quickly. Turn off the water supply if a plumbing leak is possible, and remove any wet belongings from the area. Drying the space and identifying the source early can help limit the damage.

Regular maintenance can reduce the risk of water entering your exterior walls. Inspect caulking and seals around windows and doors each year, and repair any cracks promptly. Keep gutters and downspouts clear so rain is directed away from the foundation.

Ensure exterior paint is in good condition, as cracked paint can allow water to seep behind siding. The risk from rain varies by region, but a sudden storm can still catch you off guard. Consider a periodic inspection, especially after heavy weather.