What Are Weep Holes in Brick?

What are weep holes in brick? They are the small open gaps you can see in the mortar along the bottom course of a brick wall, usually every third or fourth brick, and they are not missing mortar, sloppy work, or insect damage. They are drains, put there on purpose, because a brick veneer wall is designed on the assumption that water will get behind the brick and needs a way back out. The two things every owner of a brick house should know about them fit in one sentence: never seal them, and never let soil or mulch bury them. This page covers the mechanics of why a wall needs drains, what sealing them quietly does to the framing behind the brick, the pest solution that does not trap water, and the useful trick of reading your weep-hole row as a free gauge of whether your grade is creeping up your foundation.

Why a brick wall is built to leak

Modern brick on a house is veneer: a single width of brick standing in front of the framed, sheathed wall that actually holds the house up, tied back to it with metal straps and separated from it by an air gap of an inch or so. That gap is the whole trick. Brick and mortar are not waterproof; a hard, wind-driven Texas rain wets a brick wall through, and the water that makes it past the brick runs down the back face inside the cavity. At the bottom of the cavity, flashing catches that water and tilts it back outward, and the weep holes are the exits it leaves through. Building codes have made the arrangement mandatory for decades; the residential code calls for weeps at least 3/16 of an inch across, spaced no more than 33 inches apart, sitting immediately above the flashing, per IRC section R703.8.6. In practice masons leave every third or fourth vertical joint open on the course above the foundation line, which is why the holes march along the wall at knee height in a tidy rhythm. Open joints, moving air, drained cavity, dry wall. That is the system.

Why sealing them backfires

Weep holes bother people. They look like mistakes, they whistle in a norther, and they read as open doors for everything that crawls. So owners caulk them, and handymen mortar them, and every one of those walls begins a slow experiment in what happens when a drain is plugged. The water does not stop coming; the next storm wets the brick exactly as before, and the cavity fills with water that now has no exit. It pools on the flashing, wicks up into the mortar, and finds the wood: the sill plate at the base of the framed wall, the sheathing behind the cavity, the ends of the studs. Wet wood softens and rots, and it does so invisibly, behind a wall that looks perfect from the lawn. The metal ties holding the veneer to the frame rust in the damp cavity. Interior baseboards and drywall at the bottom of the wall stain and swell years before anyone connects the dots to a bead of caulk outside. We see the end state on inspections: a wall that weeps indoors because it was forbidden to weep outdoors. The repair for rotted sills and sheathing runs into the thousands and involves opening the wall; the caulk that caused it cost a few dollars. If your weeps are already sealed, the fix is pleasantly dumb: dig the caulk or mortar out of each hole with a screwdriver or an old drill bit until the cavity is open again, and let the wall get back to work.

Pests, honestly

The fear behind most sealed weep holes is not water, it is what else uses the door. Fair enough: in Central Texas the candidate list includes roaches, wasps, scorpions, mice, and the occasional snake, and pest-exclusion guidance from Texas A&M AgriLife is blunt that gaps far smaller than a weep hole will admit mice. The mistake is treating the weep like any other gap, because it is the one gap on the house that must stay open. The answer is a barrier that drains. Purpose-made weep inserts, small stainless or plastic grids that press into the open joint, keep out anything bigger than an ant while letting water and air move freely; corrugated plastic weep vents do the same on new work. Stainless mesh cut and tucked into the hole works too. What does not work: steel wool, which rusts into a solid plug within a couple of seasons, and mortar or expanding foam, which are just the sealing mistake wearing a pest-control costume. Two dollars a hole and an afternoon settles the whole question, drainage intact.

The foundation tie: your weep row is a grade gauge

Here is the part of the weep-hole story that belongs on a foundation company's site. Masons lay the weep course just above the slab edge or foundation line, level, at a consistent height. That makes the row of weep holes a permanent reference line around your house, and what it measures is grade. Walk the perimeter after reading this and look for where the weep holes disappear: behind a flower bed that has been mulched annually for many years, under soil washed against the wall by a downspout, behind the landscape stone someone stacked against the brick. Everywhere the weep row is buried, two bad things are true at once. The weeps there cannot drain, so that section of wall stays damp. And the soil is sitting above the top of your foundation edge, holding moisture directly against the slab and feeding the wet side of the clay's shrink-swell cycle. On expansive soil, a perimeter that stays wet on one side and dries on the other is how differential movement starts, which is why grade that buries the weep row is on the short list of things our inspectors flag most. The fix is grading, not caulk: pull soil and mulch back below the weep line, slope the beds away, and get roof water carried off with the methods on our drainage correction page. If pulling the grade back leaves washed-out gaps and low spots along the slab edge, how to fill holes around a house foundation covers the right way to dress them. And read the wall above while you are down there: weep holes with quiet, straight courses above them are a healthy wall, while weeps sitting under stair-step cracks that climb the mortar are a wall reporting movement below, which is a measuring job, not a landscaping job. The measuring is free, and about a third of our inspections end with no repair needed.