A brick veneer wall is not a barrier. It is a drainage system that happens to look like a wall. Water gets behind the brick face every time it rains hard or snow melts. The IRC Section R703.7 code framework for masonry veneer accounts for that: flashing catches the water, and weep holes let it out. Remove the weep holes from the system and you have trapped water with nowhere to go.
Most homeowners do not know this. Some find out when the damage bill arrives.
What a Brick Veneer Wall Actually Is
The term “brick veneer” describes a construction method, not a cosmetic veneer in the decorative sense. A veneer wall consists of a single wythe of brick, four inches thick, anchored to a separate structural backup wall. That backup wall carries the load. The brick carries almost none of it. Between the brick and the backup wall there is a cavity - typically an inch to an inch and a half wide - that serves as a drainage plane.
The cavity exists because designers recognized a fact that seems counterintuitive: you cannot stop water from getting behind a brick face. Wind-driven rain finds every hairline crack in mortar joints. Water vapor moves through brick by absorption and diffusion. At some point, in any weather event, water is behind your brick. The question is not whether water enters the cavity. The question is whether it can leave.
According to BIA Technical Note 7B, water penetration resistance depends on the continuous functioning of the flashing and drainage system - not on the assumption that the brick face stays dry. The weep holes are load-bearing parts of that system.
This construction approach became standard in the North Shore and northwest suburbs during the post-war building boom. If your home is in Northbrook or Glenview and was built between 1950 and 1980, it was almost certainly framed in wood with brick veneer attached - hard machine-pressed brick over a wood-framed cavity wall. Northbrook’s median home was built in 1968, right in the middle of the era when cavity veneer became the regional standard. Glenview’s housing stock from the same period - ranches, split-levels, colonials along Golf Road and Waukegan Road - follows the same pattern.
This is why solid masonry construction and cavity veneer construction require completely different maintenance thinking. If your home is a Chicago bungalow, a two-flat, or any pre-1950 building where the brick walls are structural and multiple brick wythes thick, you likely do not have a drainage cavity. You have a different system built on mass and absorption. The solid brick versus brick veneer post covers that distinction if you are unsure which system your home uses.
Where Weep Holes Are Located and What They Look Like
Weep holes are small gaps in the mortar head joints - the vertical joints between bricks. They are positioned at specific locations in a veneer wall, not randomly.
The first and most important location is the bottom course of the wall, immediately above the through-wall flashing. This flashing is a membrane, typically rubberized asphalt, sheet metal, or a combination, that runs continuously across the full width of the wall at the base. It is sloped slightly outward so water draining down the back of the cavity runs onto the flashing and toward the weep holes. Without the weep holes at this level, the water pools above the flashing and eventually finds another way out - typically through the backup wall framing, the foundation wall, or the interior finish.
The second location is above each window and door opening, at the lintel. Lintels are typically steel angles that carry the brick load above an opening. A flashing membrane runs above the lintel and water that accumulates there needs weep holes at the outer face of the lintel to drain forward. When you stand outside and look at a window in a brick veneer wall, the first course of brick above the window frame is where these weep holes should appear.
In multi-story buildings, weep holes also appear at each floor level where shelf angles carry the brick above the first story, and at any other horizontal flashing plane.
Weep holes are typically spaced every 24 to 33 inches on center, corresponding to every third or fourth head joint along the course. In standard modular brick, that puts them roughly at two-brick intervals. Some builders use open head joints. Others install small tubes called weep hole inserts, or mesh screen inserts that allow drainage while limiting pest entry.
Why Water Gets Behind Brick Veneer Walls
Understanding the drainage function of weep holes requires accepting that water penetration behind a brick face is normal and expected - not a construction defect. Brick is a porous material. Per BIA Technical Note 3A, brick’s absorption characteristics vary by type and firing temperature, but even low-absorption units transmit moisture through their mortar joints over time. Mortar joints, even well-executed ones, develop micro-cracks as the wall moves through thermal cycles.
The brick industry’s approach, reflected in building codes and technical standards, has been to design the wall to drain rather than to design it to be impermeable. A wall designed purely for impermeability requires perfectly intact mortar joints and perfectly sealed brick surfaces at all times - not achievable over decades of freeze-thaw cycling in a Great Lakes climate where the region logs dozens of freeze-thaw transitions each winter. A wall designed for drainage requires only that the flashing and weep holes remain functional - a maintainable standard over the long run.
This is also why sealing a brick wall requires careful evaluation before you act. Sealers applied to the face reduce water entry from the exterior but can trap moisture that entered from the interior side. In a veneer wall, interior-sourced moisture still has a path through the drainage cavity - but only if the weep holes are open. The post on whether to seal your brick wall covers the sealing question in detail.
What Happens When Weep Holes Are Blocked
The failure sequence is predictable and the damage accumulates faster than most homeowners expect.
Water drains down the back of the cavity and pools above the flashing because it has nowhere else to go. In moderate weather, it may eventually evaporate. In fall and winter in northern Illinois, it does not. Saturated cavity walls carry that moisture into the freeze-thaw cycle. Water expands approximately 9 percent by volume when it freezes. Brick and mortar absorb moisture and then cycle through freezing and thawing repeatedly each winter in this region - the GLISA freeze-thaw data confirms the Great Lakes basin as one of the highest-frequency freeze-thaw zones in the country. That mechanical pressure is what drives spalling and the mortar joint deterioration that requires tuckpointing.
The most visible early sign is typically efflorescence - white mineral staining that appears when water moving through masonry carries soluble salts to the surface. When efflorescence appears in a horizontal band near the base of a veneer wall or just above a window opening, that pattern says water is pooling at those levels. Wilmette homeowners along the lake corridor see this regularly on their north-facing walls, where the combination of limited sun exposure and lake-proximity humidity keeps the base courses saturated longer into spring. Wilmette’s high water table compounds the problem: moisture migrates upward through foundation masonry as well as inward through the cavity. The efflorescence is often read as a surface stain. It is a drainage failure signal. The efflorescence post covers how to read these patterns.
As water pools above blocked weep holes, it eventually finds a path of least resistance. That path is often through the backup wall. In wood-framed veneer construction, water reaching the structural sheathing and framing causes rot, mold, and structural degradation that is far more expensive to address than any masonry repair. In homes where the backup wall is concrete block or masonry, the water migrates inward toward the interior finish. Basement and crawl space walls below a veneer system with blocked weep holes often show chronic dampness that homeowners incorrectly diagnose as groundwater intrusion.
Spalling brick near the base of a veneer wall is another consistent finding. Because the flashing-level weep holes are blocked, the saturated zone at the base of the cavity subjects the lowest few courses of brick to repeated freeze-thaw cycling under continuously high moisture. Those bottom courses deteriorate before the rest of the wall. Brick replacement in this zone runs $50 to $150 per brick in the Chicagoland market, plus the labor to address the underlying drainage failure. It is substantially more expensive than clearing weep holes would have been.
Palatine presents a specific variation on this pattern. Manufactured stone veneer installations from the 1990s and early 2000s - Palatine has a significant inventory of homes from this era - use a scratch coat and metal lath system rather than a true drainage cavity with flashing. When moisture gets behind the veneer at the lath layer, the lath corrodes and the scratch coat degrades. The stones loosen and fall. This is the same underlying failure: a cladding system that assumes water will enter, with no reliable path for it to exit. Manufactured stone adhesion failure is among the most common calls we receive from Palatine.
How Weep Holes Get Blocked
Several things block weep holes in practice, and most happen during maintenance work rather than during original construction.
Painters are a frequent source. Exterior painting crews working quickly across a brick surface sometimes fill weep hole openings with caulk or paint while sealing gaps before painting. The opening looks like a crack or an oversight. It is neither.
Mortar droppings from original construction sometimes block weep holes before the wall is even occupied. When the veneer is laid, mortar squeezed out between bricks can fall into the cavity and pile up on the flashing, blocking the weep hole openings from behind. Properly executed construction includes clearing these droppings. Not every crew does this.
Caulk applied during a general exterior maintenance project is another common source. A homeowner or general contractor caulking windows, trim, and “any gaps they see” sometimes fills the weep holes. The same problem occurs when repointing crews fill every open joint they see, not recognizing that open head joints at regular intervals in a specific course are intentional.
Insect nests and debris also block weep holes over time. Mud-dauber wasps readily fill weep hole openings with mud nests. This is worth checking every spring. The fix is simple - a wire or wooden skewer clears most nests without any damage to the wall.
Solid Masonry Homes: A Different Story
The weep hole discussion applies specifically to cavity veneer construction. If you own a pre-1950 home in Winnetka or Wilmette built as solid masonry, the weep hole standard does not apply to your exterior walls the same way.
Winnetka’s housing stock is predominantly 1920s through 1940s construction - Georgian Colonials and Tudor Revivals built with soft Chicago common brick laid in multiple solid wythes. There is no drainage cavity in these walls, no flashing plane in the veneer sense, and no weep hole system. The median Winnetka home was built in 1942. Wilmette’s bungalows and Cape Cods from the same era follow the same pattern: solid masonry built for mass absorption, not active drainage. Wilmette’s median home was built in 1948, right at the transition point between solid construction and cavity veneer.
Solid masonry walls rely on thick mass to absorb and re-release moisture. A solid wall is typically 8 to 12 or more inches of brick and mortar. These walls were designed for a different moisture management strategy.
The maintenance needs are different too. Solid masonry walls depend on intact mortar joints to limit water entry, because there is no drainage backup if water gets in deeply. This is why tuckpointing is particularly important on pre-1920 solid masonry in Winnetka and Wilmette, and why the mortar specification for those walls - requiring lime-compatible formulations softer than the brick - is non-negotiable. Forcing water out through a weep hole that does not exist does nothing. Keeping water from getting deeply into the wall by maintaining tight joints is the actual strategy.
If your solid masonry home shows spalling near the base of an exterior wall, the cause is usually persistent moisture saturation and freeze-thaw damage, not a drainage failure in the veneer-cavity sense. The fix is mortar joint repair, addressing any grade or drainage issues that concentrate water against the wall base, and possibly brick replacement where spalling is advanced. The post on what causes brick spalling covers how freeze-thaw damage progresses.
The Cavity Veneer Era: Northbrook, Glenview, and the 1950s-1980s Build Wave
If your home is in Northbrook or Glenview and was built during the post-war suburban expansion, you almost certainly have cavity veneer construction. Both communities saw substantial residential development from the mid-1950s through the mid-1980s - the exact window when cavity veneer became standard practice and when the builder-grade mortar used in those joints is now reaching or past its expected service life.
In Northbrook, the 1960s-1980s building wave produced split-levels and colonials with machine-pressed brick over wood-frame cavities. Northbrook’s median home was built in 1968. Those homes are now 40 to 60 years old. The builder-grade mortar joints are eroding, and the weep holes in those base courses have been through decades of maintenance cycles by painters, caulkers, and well-meaning repointers who did not recognize the openings as drainage infrastructure. Finding a Northbrook home from this era with fully open, functional weep holes is less common than finding one where at least some have been partially or fully filled.
Glenview’s situation is nearly identical. The village’s housing stock from this period runs ranches and colonials on generous lots, and the same patterns of builder-grade mortar erosion and weep hole blockage show up on assessment after assessment. Chimney flashing failure is Glenview’s most documented masonry problem - documented directly in the city-specific problem patterns - and it is directly related to the same water management principle that makes weep holes load-bearing rather than decorative.
The sequence on a 1965 Northbrook or Glenview home typically runs like this: weep holes partially blocked by caulk from a 1990s paint job, base course mortar now 60 years old and receding, efflorescence in a band along the bottom two courses, and dampness at the base of the interior wall that gets blamed on the basement. Address the weep holes and the mortar joints and the interior dampness usually resolves without any interior work. Leave them blocked and the problem progresses into the framing.
Understanding what that progression leads to is the subject of what winter does to Chicago masonry - the cumulative damage picture from repeated freeze-thaw cycling on compromised walls.
How to Check Your Weep Holes
Start at the base of the wall on every exterior elevation. Look for the first horizontal course of brick above grade level. If the house has brick veneer on a wood-frame structure, the bottom of the veneer typically sits just above the foundation wall or the sill plate level. Weep holes, if they exist, should be in the head joints of that course or the course immediately above the flashing line.
Look for open head joints - small gaps in the mortar between bricks, typically about 3/8 inch wide and the height of a brick joint - spaced roughly every 24 to 33 inches. These are normal and correct. If the entire course has filled head joints with no openings, and the wall is veneer construction, the weep holes have been filled.
Do the same inspection above window and door openings. Look at the first brick course above each lintel. Weep holes should be visible at intervals there too.
If you find filled weep holes and the wall otherwise shows no damage, clearing them is a straightforward maintenance task. Open the blocked head joints carefully with a small pick or wooden skewer. Do not use a chisel or drill unless the mortar fill is deep. For head joints filled flush with mortar, a mason can reopen them with a small angle grinder in minimal time. This is far simpler and less costly than addressing the damage that accumulates when drainage fails.
If you find evidence of water damage - spalling at the base, efflorescence bands, interior damp spots - the repair sequence starts with restoring the drainage system, not just patching visible spalling on the face. Repairing the face without restoring drainage repeats the same damage cycle. A masonry assessment puts the full picture in front of you before any repair work begins. See how to read a masonry repair estimate for what to expect from that process.
Getting the Drainage System Working
If you have a brick veneer home anywhere on the North Shore or in the northwest suburbs and you have not thought about your weep holes, this fall is a good time to check them. Water management in a veneer wall depends on the entire system working together. The flashing, the cavity, and the weep holes are a chain. One broken link and water accumulates where it should not.
Delta - Masonry and Tuckpointing assesses and repairs brick drainage failures across Chicagoland’s North Shore and northwest suburbs, and has been doing this work since 1987. If your wall shows efflorescence, spalling near the base, or interior moisture near exterior walls, call (847) 713-1648 or contact us online. We work in Winnetka, Wilmette, Northbrook, Glenview, and Palatine. If you have questions about the right repair approach for your wall type, the tuckpointing service page and the brick repair service page cover what each type of work involves and when it is the right answer.
A brick veneer wall is designed to let water in. The only question is whether it can get out.