Brick is common across St. Louis, from older rowhouses in the city to brick ranch homes in the county. Many of those walls are not solid masonry. They are a brick outer layer, called a veneer, separated from the wood framing or block behind it by an air gap. That gap is meant to catch the small amount of water that gets past the brick and send it back out. Weep holes are the openings that let that water drain. When they are blocked or missing, moisture can settle into the wall and show up indoors as damp drywall, peeling paint, or a musty smell near an exterior wall.

What a weep hole does

Rain does not stop at the surface of brick. Some of it soaks in and runs down the back of the brick until it meets a flashing, a thin metal or plastic strip set at the base of the wall or above a window or door. The flashing directs that water toward the outside. Weep holes sit just above the flashing line, usually in the bottom course of brick, and let the water run out instead of pooling. They also let air move so the cavity can dry.

Signs the drainage may be blocked

  • Mortar or debris packed into the openings at the base of the brick
  • Efflorescence, the white powder left when water moves through masonry and dries on the surface
  • Damp or stained interior drywall along an exterior wall, especially near ground level
  • Paint bubbling or flaking on the inside of an exterior wall
  • Soil or mulch piled high against the brick, covering the lowest courses

How to check from outside

Walk the perimeter on a dry day and look at the bottom course of brick around each exterior wall, including the sides of porches and steps. Look for a row of openings along the mortar line. Holes filled with mortar, paint, caulk, or insulation are blocked. On some St. Louis homes, weep holes were never installed or were covered during an earlier repair, so a missing opening can matter as much as a clogged one.

Watch the wall after a steady rain. If water flows out of the openings, drainage is working. If the bottom course stays dry while the wall is wet, or water seeps through the mortar somewhere else, the cavity may be holding water.

Look at the soil too. Grade should slope away from the house. Soil or mulch that sits above the flashing line can hold moisture against the brick and cut into the drying space the wall needs.

How to check from inside

Inside, look at the wall along the base and at the corners near a window or door. A moisture meter gives a quick reading on drywall or plaster, and your hand can find cool, soft, or damp spots. Stains that grow after rain, rather than after a plumbing or appliance problem, point toward the outside wall. Keep a note of when stains appear and what the weather was like. That record is useful when you talk with a contractor.

Clearing openings safely

If a weep hole is plugged with loose mortar or debris, you can often clear it with a thin, non-metal tool such as a plastic putty knife or a stiff brush. Work gently so you do not chip the brick or disturb the flashing. Do not seal the openings with caulk or foam, since that stops the drainage the wall depends on. Avoid pressure washing close to the mortar line, because high pressure can push water into the joints.

If the flashing is damaged, bent, or missing, or if the mortar is crumbling, that is repair work for a mason or a qualified exterior contractor. Ask for a written description of what they plan to fix and why.

Interior moisture and what to do next

Damp air inside the home can make a wall problem look worse than it is. Keeping indoor humidity steady helps you tell whether a stain is coming from the air or from the wall. Keep gutters clear, direct downspouts away from the foundation, and check the grade before the wet season each year. In St. Louis, spring storms and winter freeze-thaw cycles can open small gaps in mortar, so a yearly walk-around is a practical habit.

When in doubt, take dated photos of the wall, the openings, and any stains, then compare them after the next heavy rain. Clear notes and photos make it much easier to decide whether you have a simple cleaning job or a repair that needs a professional.