Weep Holes: The Most Misunderstood Part of Your Brick Wall

Somewhere along the bottom course of a lot of Chicagoland brick houses, there's a line of small gaps in the mortar — evenly spaced, deliberate, and to most homeowners' eyes, unfinished.

They aren't unfinished. They're the drain. And filling them is one of the most reliably damaging things anyone does to a modern brick wall. Paul Lally's Masonry has been repairing Chicagoland veneer walls since 1988, and reopening weep holes somebody caulked shut is a job we do more often than we'd like.

What weep holes actually are

A weep hole is an open path through the bottom course of a brick-veneer wall — an unfilled head joint, a plastic vent insert, or a rope wick — that lets water drain out of the space behind the brick.

You'll typically find them:

• Along the bottom course, just above the foundation
• Above windows and doors, over the lintel flashing
• Above shelf angles on taller buildings
• Anywhere flashing directs water back out of the wall

Spacing is usually every couple of feet, and they should be open — you should be able to see into a small void.

Why a wall would be designed to let water in

This is the part that surprises people, and it's the whole point.

A brick-veneer wall is not waterproof, and was never meant to be. It's a single wythe of brick — roughly four inches — hung on a framed or block structure, carrying no building load. Behind it is a deliberate air cavity, then a water-resistant barrier, then sheathing and framing.

Wind-driven rain will get through a single wythe of brick. Through the joints, through the brick itself, through hairline cracks. That's assumed.

So the wall is built as a rain screen: water that gets through the brick runs down the back of it, lands on flashing, and is directed back out through the weep holes.

The brick is the shield. The cavity and the weeps are the drain. Both have to work.

What happens when they're sealed

Block that drain and the water has nowhere to go. In order:

1. Water enters the cavity as designed.
2. It reaches the flashing and tries to exit — and can't.
3. It pools at the base of the cavity, sitting against the back of the brick and against the sheathing.
4. Winter arrives. Trapped water freezes and expands roughly nine percent, spalling the brick faces from behind — which is why blocked-weep damage concentrates in the bottom courses.
5. The shelf angle and wall ties sit in standing water and corrode. Corroding ties let the veneer bow; a corroding shelf angle rust-jacks the brick above it.
6. Water reaches sheathing and framing.

It is genuinely hard to damage a veneer wall faster than by sealing its weep holes, and it's usually done with good intentions — by someone tidying up the mortar line, sealing for "energy efficiency," or trying to keep insects out.

Who seals them, and why

We see it from:

• Painters running a bead along the base course for a clean line
• Caulking contractors treating every gap as a joint to be sealed
• Well-meaning homeowners filling what look like holes in the mortar
• Masons who should know better, skimming the base course during a repointing job
• Landscapers, indirectly — soil, mulch, and beds built up over the base course
• Energy-efficiency work, sealing "air leaks" that are actually drains

If a contractor proposes caulking along the bottom course of a brick veneer wall, stop and ask what they think those openings are for.

Weep holes vs. failed mortar — telling them apart

Homeowners regularly mistake one for the other, and they want opposite responses.

	Weep holes	Failed mortar joints
Location	Bottom course, above openings	Anywhere on the wall
Spacing	Regular, deliberate, even	Irregular, patchy
Appearance	Clean void, or a vent/wick insert	Crumbling, sandy, receding
Surrounding mortar	Sound	Soft, diggable with a key
Correct response	Leave open	Repoint

The key test settles it: run a house key along the mortar beside the opening. If the surrounding mortar is hard and the opening is clean and evenly spaced, it's a weep hole. If mortar crumbles out as sand, you have a repointing problem — and the repointing must be done without filling the weeps.

Signs your weeps are blocked

• Visible caulk, mortar, or paint filling the openings along the base course
• No weep holes at all on a wall you've identified as veneer
• Soil, mulch, or landscaping built up over the bottom course
• Efflorescence concentrated low on the wall
• Spalling brick in the bottom three courses specifically
• Persistent damp or musty interior walls on an exterior-facing room
• Rust staining at the base course or at a shelf angle
• A veneer panel bowing outward — corroded ties, often downstream of trapped water
• Standing water or dark saturation at the base after rain

How a mason reopens and restores drainage

1. Confirm the wall is veneer. Solid masonry has no cavity and no weeps — see brick veneer vs. solid masonry.
2. Locate the intended weep positions — spacing, and the flashing line they serve.
3. Carefully cut out the caulk, mortar, or paint blocking the head joints, without damaging the surrounding masonry.
4. Check the cavity for obstruction. Mortar droppings inside the cavity are common and dam the drainage path at the base. Clearing them sometimes means opening a course of brick to reach the obstruction.
5. Verify the flashing is intact and directing water out rather than back in — weeps without functioning flashing accomplish very little.
6. Install vents or wicks where appropriate, particularly if insects were the original reason someone sealed them.
7. Clear the exterior — soil, mulch, and grade pulled back below the base course.
8. Repoint the surrounding masonry if needed, deliberately leaving the weeps open.
9. Address anything downstream — spalled brick, a corroding shelf angle, ties.

The related detail nobody checks: head flashing

Weeps at the base get all the attention. The ones above window and door openings matter just as much.

Above each opening there should be flashing over the lintel with weeps in the course above it, so water in the cavity is directed out at that level rather than running further down. When that detail is missing, blocked, or was never installed, water sits on the lintel — which is one route to the rust jacking that cracks brick above openings. See failing lintels and cracked brick above windows.

If you have cracked brick above a window on a veneer wall, look for weeps above that opening. Their absence tells you something.

Chicagoland context: who has weeps and who doesn't

This maps almost perfectly onto construction era, and it's a useful shortcut.

Pre-1930s Chicago — bungalows, greystones, two-flats, three-flats, storefronts. Solid multi-wythe masonry. No cavity, no weep holes. These walls manage water by mass, absorption, and sound mortar joints, and they dry by breathing. Looking for weeps on a greystone is looking for something that was never there.

Roughly 1930s–1960s — mixed construction, the transition period. Check the wall rather than the build year.

1970s onward — the postwar and later suburbs: Oak Lawn, Orland Park, Tinley Park, Homer Glen, Palos Heights, Mokena, New Lenox, Frankfort, Naperville, Downers Grove. Predominantly brick veneer with a drainage cavity, flashing, and weep holes.

So: if you own a suburban Chicagoland home built since about 1970, you almost certainly have weep holes, and they matter. If you own a century-old city building, you almost certainly don't — and your equivalent concern is keeping the mortar joints sound, because on that wall the joints are the barrier.

Either way, our climate raises the stakes. Repeated hard freeze-thaw cycling means any trapped water gets tested dozens of times a winter, and de-icing salt and snowpack at grade are already working on the exact courses where blocked weeps do their damage.

Maintenance

• Never caulk, mortar, or paint over weep holes. The single rule.
• Keep soil, mulch, and landscaping below the base course — leave the weeps visible and clear.
• Check them each spring after the freeze-thaw season.
• Tell any contractor working on your exterior — painter, caulker, mason, landscaper — that the base course openings stay open.
• Watch for spalling in the bottom courses, the early tell that water isn't leaving.
• When repointing a veneer wall, confirm the scope preserves the weeps.

See the masonry maintenance checklist for Chicago and protecting masonry through winter.

Related services

Drainage-related veneer work draws on brick repair, brick replacement, tuckpointing and repointing, lintel repair and replacement, caulking and joint sealant — done correctly, which means around the weeps and not through them — foundation masonry repair, masonry waterproofing, and residential masonry restoration.

The bottom line

Weep holes are the drain on a wall designed to let water in. They are not sloppy mortar work, not holes to be tidied up, and not air leaks to be sealed.

If your home was built since roughly 1970, look along the bottom course this weekend. If those openings have been caulked, mortared, painted, or buried under mulch, that's worth fixing — and it's a considerably smaller job than the spalled brick and corroded ties that follow from leaving them shut.

And if you're about to have anyone paint, caulk, repoint, or landscape around your house: tell them the holes stay open.

Paul Lally's Masonry Inc. is a family-owned, insured masonry contractor serving Chicago and the Chicagoland suburbs since 1988 — tuckpointing, brick repair and replacement, chimney repair and rebuilds, lintel replacement, masonry restoration, and waterproofing for residential and commercial properties. Built on Craftsmanship. Backed by Experience.

We'll tell you what kind of wall you have, whether your drainage path is doing its job, and what it takes to reopen it. Our family name is on every job.

Free on-site estimates — call (708) 448-8866 or request an estimate online.