What are the weep holes in my brick wall for — and is it OK to seal them?

Walk along the base of most modern brick houses and you'll see small, regular openings in the mortar joints — open gaps, plastic inserts, or short lengths of rope — spaced every few bricks along the bottom course, and often above windows and doors. These are weep holes, and they exist because brick walls are designed to get wet inside.

Brick veneer is a drainage system, not a raincoat

Most brick on American houses built in the last several decades is brick veneer: a single wythe of brick standing an inch or so (about 25 mm) in front of the wood-framed structural wall, tied back with metal ties. Brick and mortar are absorbent — wind-driven rain soaks in and some of it reaches the back face of the brick. The assembly handles this with three parts working together:

• The air cavity behind the brick, which lets water run down the back face instead of touching the framed wall.
• The water-resistive barrier and flashing on the framed wall, which catch that water and direct it down and out.
• The weep holes, which are the exits — the drain openings that let collected water leave and let some air circulate to help the cavity dry.

This "drained cavity" approach is standard residential moisture-control practice; the DOE's Building America guidance on moisture control describes exactly this layered strategy of shedding, draining, and drying for keeping water out of the framed wall behind the cladding.

So is it OK to seal them?

No. Caulking weep holes shut — usually done to keep insects or mice out, or because they look like mistakes — closes the drain on a system that's still collecting water. Rain keeps penetrating the brick; it just no longer has an exit. The likely results over time are dampness at the base of interior walls, deteriorating sheathing, staining, and efflorescence (the white mineral crust) on the brick itself. The EPA's moisture control guidance frames the general rule well: any water that gets into an assembly needs a deliberate way out, and blocking that path converts an occasional wetting into trapped moisture.

If pests are the concern, the accepted answer is a weep hole insert or screen — stainless mesh or plastic vent inserts made for the brick joint — which keeps insects out while leaving the opening able to drain and breathe.

Weep holes that don't work

Weep holes can fail without being caulked:

• Mortar droppings from original construction can pile up in the cavity and bridge across the flashing, damming water above the weeps.
• Grade or landscaping creep — soil, mulch, or a new patio slab built up over the bottom course buries the weeps entirely.
• Paint or heavy repointing can close small openings unnoticed.

A quick homeowner check: find the weeps (bottom course, and above openings), confirm they're open, and after a hard rain look for water actually weeping out — that's the system working, not a defect. Persistent dampness on interior walls that back onto brick, despite open weeps, suggests a flashing or cavity problem, and that diagnosis is worth putting to a mason or building professional rather than guessing. If you want to gauge whether such a wall is holding moisture before making that call, comparative moisture-meter readings inside, low on the wall, are a reasonable first step.

"Weeping walls" vs. weep holes

One terminology note: people sometimes describe an interior wall with water beading or running on its surface as a "weeping wall." That's usually condensation or a leak showing on the room side — a different problem from the deliberate exterior weep holes described here, and one that starts with finding the moisture source rather than the drainage path.