Home › Blog › Brick Weep Holes and Wall Drainage
August 5, 2026 · Brick Repair
Weep holes are the small gaps left open in the bottom mortar joints of a brick veneer wall. Brick is not waterproof, so water that soaks through runs down the back of the veneer, lands on flashing, and leaves through those openings. Block them and the water stays in the wall, which is how spalling, efflorescence, and rusted lintels start.
Every few months someone asks us to fill in the little holes along the bottom of their brick. Bugs get in. It looks unfinished. A previous contractor "missed" them. We understand the instinct, and we say no every time, because those holes are the only way water gets back out of the wall. Seal them and you have built a bathtub out of your house.
Brick sheds most rain. It does not shed all of it. Wind-driven rain pushes moisture through the face of the brick and through hairline separations at the mortar joints, and on a West Michigan house that happens dozens of times a year. What the wall does with that water next is the whole story.
Almost every brick home built in Grand Rapids since roughly the 1950s is a veneer, not a solid masonry wall. The brick is a single wythe hung on the outside of a wood-framed structure, tied back with corrugated anchors, with an air gap between the brick and the sheathing. That gap is not sloppy construction. It is the drainage plane, and it is doing a job.
Water that gets through the brick hits the back face, runs down, and collects on flashing set at the base of the wall and above every opening. The flashing turns the water outward. The weeps let it leave. Air moving through the cavity dries what is left. Three parts, and the system only works when all three are present and clear.
The Michigan Residential Code, Section R703.8, spells the requirements out plainly. Weepholes go in the outer wythe at a maximum of 33 inches on center, no smaller than 3/16 inch in diameter, located immediately above the flashing. The code also calls for a nominal 1 inch air space behind the veneer, and flashing beneath the first course above grade and at lintels and shelf angles. Those numbers are not suggestions. They are the minimum for the wall to function as designed.
Water trapped in a cavity does not sit politely. It goes looking for somewhere to go, and it takes salt and freeze-thaw damage with it.
| Symptom on the wall | What the trapped water is doing |
|---|---|
| White chalky bloom on the brick face | Moving through the brick and depositing salts as it evaporates |
| Faces of brick flaking or popping off | Freezing inside a saturated brick and breaking it from within |
| Rust stains and a level crack above a window | Sitting on the steel lintel and corroding it |
| Damp interior wall or musty smell on one elevation | Bridging the cavity and reaching the sheathing behind |
| Mortar joints crumbling at the bottom courses | Cycling wet and frozen at the lowest, wettest point in the wall |
The freeze-thaw part is what makes this a West Michigan problem rather than a general one. The National Weather Service Grand Rapids forecast office tracks roughly 40 to 60 days a winter where temperatures cross the freezing mark. Each crossing is another chance for water sitting in a brick to expand and take a piece of the face with it. Our notes on what causes brick spalling and how to fix it walk through that damage in detail, and drainage is usually the root cause underneath it.
This is the most common one by a wide margin, and it happens during the original build. As the mason lays each course, mortar squeezes out the back of the joint and falls into the air space. If nobody cleans it out as the wall goes up, it piles on the flashing and hardens into a shelf that dams the water above the weeps. The holes are technically there. The water cannot reach them.
Caulk, mortar, spray foam, steel wool packed in tight. Almost always done with good intentions, usually to stop insects or because someone thought the gaps looked like sloppy work. The wall stops draining that day.
Landscaping creeps upward over the decades. Beds get topped off, mulch gets added, a new patio goes in an inch higher than the last. Bury the bottom course and you bury the weeps with it, and now the drainage path exits into wet soil instead of open air. We see this more than anything else on homes that have had thirty years of well-meaning yard work.
On a true solid-masonry wall, common on Grand Rapids homes built before the 1930s, there is no cavity and there were never weeps. Those walls were designed to absorb moisture into the mass and release it slowly, which is why matching historic mortar matters so much on them. Repointing one of those walls with a hard modern portland mix takes away its ability to breathe and traps water in the brick instead. On a post-war veneer wall, though, missing weeps are simply a defect.
You can do most of the first pass yourself. Walk the perimeter of the house and look at the bottom course of brick, right where it meets the foundation. You are looking for open head joints, or small plastic or metal vents, spaced every couple of feet. Then look above the windows and doors, because the lintel line needs weeps too.
Then wait for a heavy rain and look again an hour later. Working weeps go dark and often leave a faint clean stain running down the brick below them. A wall that stays uniformly dry at the bottom after a soaking rain, while showing efflorescence higher up, is telling you the water is not getting out. A length of stiff wire slid gently into a weep will tell you if the opening is packed.
What we add on site is the part you cannot see. We check whether flashing is present at all, which on some 1960s and 1970s work it simply is not. We probe the cavity depth. We check the lintel above each opening for the level crack and rust bleed that says water has been sitting on steel, and we look at grade heights against the flashing line all the way around.
The fix depends entirely on what is wrong, and the range is wide.
If the weeps are sealed, we cut the seal out and install stainless or polymer weep vents that screen against insects while leaving the path open. That is a short job. If the cavity is choked with mortar droppings, we remove selected bricks at the base to reach the obstruction, clear the shelf, and rebuild the openings. That is real masonry work, and it is worth doing right, because a cleared cavity is the difference between a wall that dries and a wall that keeps rotting the sheathing behind it.
If there are no weeps and there is a cavity, we cut new ones on 24 inch centers above the flashing line, which comes in under the code maximum and gives the wall margin. If there is no flashing, the conversation gets bigger, because retrofitting flashing means taking down and rebuilding the bottom courses. And if grade has buried the wall, the fix starts with a shovel and regrading away from the house before any brick gets touched, the same principle behind good foundation repair and waterproofing work.
Nearly every one of these jobs includes some tuckpointing at the lower courses, because the joints that have been sitting wet the longest are the ones that have given up first. Where individual bricks have already spalled through, brick repair and replacement goes in the same scope. Our masonry cost guide lays out how we price this kind of work.
Homeowners often want to seal the brick to stop the water. Do not start there. A sealer applied to a wall that cannot drain locks moisture inside the brick and makes spalling worse, not better. We cover the reasoning in our piece on whether to seal or paint brick.
Get the water out first. Clear the weeps, correct the grade, confirm the flashing. Then repoint the failed joints with a mortar matched to the brick. Then, and only then, consider anything applied to the face. Work in that order and the wall stabilizes. Work backward and you pay twice.
Weep holes are the small openings left in the bottom mortar joints of a brick veneer wall, usually every other head joint along the base and above windows and doors. They are the exit door for water that has soaked through the brick. Water runs down the back of the veneer, lands on flashing, and leaves through the weeps.
Yes. Section R703.8 of the Michigan Residential Code requires weepholes in the outer wythe of masonry veneer at a maximum spacing of 33 inches on center, not less than 3/16 inch in diameter, located immediately above the flashing. The same section calls for a nominal 1 inch air space behind the veneer and flashing at the base of the wall and at lintels.
No. Sealing weeps with caulk, mortar, or expanding foam traps water inside the wall, and trapped water is what causes spalling, efflorescence, and rusted lintels. If insects are the concern, the answer is a stainless or plastic weep vent insert that screens the opening while leaving the drainage path clear.
Look at the bottom course of brick after a hard rain. Working weeps stay damp and often show a faint stain below them. Blocked ones stay dry while the wall above shows white efflorescence, flaking brick faces, or a damp basement wall on the same elevation. A thin wire slid gently into the opening tells you whether the path is clear.
Two common reasons on Grand Rapids homes. Older solid-masonry walls built before cavity construction became standard never had them, because they were designed to store and release moisture through the mass of the wall. Or the wall is a veneer built by someone who skipped them, which is a defect rather than a design.
Often, yes. On a veneer wall with a real air space and flashing, a mason can cut new weeps into the head joints above the flashing line and clear the cavity where it is choked with mortar droppings. On a solid-masonry wall with no cavity, cutting holes accomplishes nothing, so the work shifts to repointing, flashing, and drainage at grade.
If you are seeing white bloom, flaking faces, or a damp basement on one side of the house, the drainage is worth checking before anything else. We will walk the wall, read the weeps and the flashing line, and give you a written scope. Request a free estimate or call (616) 345-5247.
About Masonry Grand Rapids. We are a West Michigan masonry contractor working on brick, block, and stone across Grand Rapids, Wyoming, Kentwood, Rockford, Holland, Muskegon, Kalamazoo, and Lansing. Tuckpointing, chimney work, brick repair, retaining walls, and historic restoration. 500 Fulton St E #234, Grand Rapids, MI 49503. (616) 345-5247.