Brick Veneer Weep Holes — IRC 2018 Requirements

Quick Answer

Yes. IRC 2018 R703.7.4 requires weep holes in brick veneer walls at every through-wall flashing course — at the base of the veneer and above all wall openings — at a maximum spacing of 33 inches on center. Weep holes allow water that collects on the through-wall flashing to drain out of the drainage cavity to the exterior, preventing hydrostatic buildup that would otherwise force water into the backing wall.

What R703.7.4 Actually Requires

Section R703.7.4 of the IRC 2018 states that weep holes shall be provided in the outside wythe of masonry walls at a maximum spacing of 33 inches on center. Weep holes must be located immediately above each flashing course — at the base of the veneer, above each window and door opening, at each floor line in multi-story construction, and wherever else through-wall flashing is required.

Weep holes are formed in one of three ways: (1) leaving open head joints in the brick course immediately above the flashing — an omitted mortar joint creates a slot approximately 3/8 inch wide and 2.5 inches tall; (2) inserting a cotton rope or plastic tube through the mortar joint during laying, which is then removed or left in place to maintain an open channel; or (3) installing manufactured weep hole vents — plastic inserts that maintain an open drainage channel while providing a screen to limit insect entry.

The 33-inch maximum spacing means at least one weep hole in every brick module length (bricks are approximately 8 inches long on face, so 33 inches equals approximately four bricks). In practice, many specifications call for weep holes every three bricks (approximately 24 inches) to provide better drainage capacity.

The weed holes must be kept clear of mortar during construction. This is the most frequently compromised aspect of weep hole installation — mortar droppings from above fall into the air cavity and plug the weep holes. Inspectors may probe weep holes to confirm they are open and communicating with the air space above. The air space itself must also be clear — mortar accumulation in the air cavity prevents drainage even if weep holes are open.

Above-grade weep holes must open to the exterior above the finish grade — a weep hole buried in soil or landscaping mulch will not drain. The bottom course of brick must be set high enough above grade to allow drainage from the weep holes above finish grade.

Why This Rule Exists

Without weep holes, water that penetrates the brick veneer or condenses within the air cavity has no exit path. It accumulates on the through-wall flashing until the flashing overflows, at which point water enters the backing wall assembly. Over time, accumulated water also creates hydrostatic pressure against the flashing that can dislodge it or cause it to leak at laps and seams. Weep holes relieve this pressure by providing a continuous drainage outlet, working in coordination with the air space and flashing to create a functional cavity drainage system.

What the Inspector Checks at Rough and Final

At the brick veneer inspection, the inspector checks:

• Weep hole presence — at each flashing course, with spacing not greater than 33 inches on center.
• Weep holes open — probe each weep hole to confirm it communicates with the air space above and is not plugged with mortar.
• Weep hole elevation — the weep hole must be above finished grade to allow drainage to the exterior surface.
• Air space clear — inspection from accessible weep holes may reveal mortar droppings blocking the drainage path.
• Weep hole vent screens (if used) — confirm they are the correct product and are fully seated.

What Contractors Need to Know

Protect weep holes during bricklaying to prevent mortar from entering them. The most reliable method is to install manufactured weep hole vents as work progresses — the vent body occupies the joint and cannot be mortared over. If forming weep holes by omitting the head joint mortar, use a masking technique (tape over the joint opening) to prevent mortar from adjacent joints from flowing in.

Mortar drop protection is essential for maintaining clear weep holes and a clear drainage cavity. Install a mortar drop collection device — corrugated drainage mat, mesh fabric, or boards — in the air cavity during construction to catch mortar droppings. Remove or inspect the cavity at each flashing level before closing the air space above with additional courses.

During construction, the most reliable way to protect weep holes is to insert plastic weep hole vents as brick laying progresses. The vent occupies the head joint and cannot be mortared over by accident during joint tooling. If open head joint weep holes are used instead, the mason must be specifically instructed to leave those joints open and must not return to fill them. Marking intended weep hole locations with chalk or tape on the flashing before laying begins helps ensure they are not mortared over out of habit during continuous laying operations.

In occupied buildings, blocked weep holes become a maintenance item. Inspect weep holes annually and after any landscaping work that might bury the base course. A probe wire inserted into each weep hole confirms drainage. Resistance before reaching the air space indicates a mortar or debris plug. A masonry contractor can clear plugged weep holes with a drill bit or cleaning tool without disturbing the brick above. Do not use high-pressure air to blow out weep holes from inside the air space, as this can dislodge mortar joints and spray debris into the building interior.

During construction, the most reliable way to protect weep holes is to insert plastic weep hole vents as brick laying progresses. The vent occupies the head joint and cannot be mortared over by accident during joint tooling. If open head joint weep holes are used instead, the mason must be specifically instructed to leave those joints open and must not return to fill them. Marking intended weep hole locations with chalk or tape on the flashing before laying begins helps ensure they are not mortared over out of habit during continuous laying operations.

In occupied buildings, blocked weep holes become a maintenance item. Inspect weep holes annually and after any landscaping work that might bury the base course. A probe wire inserted into each weep hole confirms drainage. Resistance before reaching the air space indicates a mortar or debris plug. A masonry contractor can clear plugged weep holes with a drill bit or cleaning tool without disturbing the brick above. Do not use high-pressure air to blow out weep holes from inside the air space, as this can dislodge mortar joints and spray debris into the building interior.

During construction, the most reliable way to protect weep holes is to insert plastic weep hole vents as brick laying progresses. The vent occupies the head joint and cannot be mortared over by accident during joint tooling. If open head joint weep holes are used instead, the mason must be specifically instructed to leave those joints open and must not return to fill them. Marking intended weep hole locations with chalk or tape on the flashing before laying begins helps ensure they are not mortared over out of habit during continuous laying operations.

In occupied buildings, blocked weep holes become a maintenance item. Inspect weep holes annually and after any landscaping work that might bury the base course. A probe wire inserted into each weep hole confirms drainage. Resistance before reaching the air space indicates a mortar or debris plug. A masonry contractor can clear plugged weep holes with a drill bit or cleaning tool without disturbing the brick above. Do not use high-pressure air to blow out weep holes from inside the air space, as this can dislodge mortar joints and spray debris into the building interior.

What Homeowners Get Wrong

Homeowners who notice weep holes in their brick walls sometimes assume they are a defect and fill them in — with caulk, sand, or spray foam — to keep insects and moisture out. This is exactly backward: weep holes are a required drainage feature, and filling them eliminates the drainage system that protects the wall from water damage. Never block or fill weep holes.

Another common misconception is that modern brick laying techniques with tight mortar joints eliminate the need for weep holes. The code requirement exists because no mortar joint is perfectly waterproof — even the tightest mortar installation allows some water penetration, especially under wind-driven rain conditions. The drainage system behind the brick is always necessary.

In new construction, the mortar drop protection system installed during construction is not a permanent component and is removed or cleaned out after each story of brick is completed. However, the drainage cavity condition should be confirmed by probing through the weep holes before proceeding to the next flashing level. If mortar has accumulated in the cavity despite the protection measures, the contractor must clean it out before it hardens and blocks the drainage path at that level. A small mirror and flashlight inserted through the weep holes can reveal the cavity condition without demolishing the brick face.

State and Local Amendments

Brick veneer weep hole requirements in IRC 2018 R703.7.4 are adopted without significant modification across TX, GA, VA, NC, SC, TN, AL, MS, KY, and MO, where brick veneer is among the most popular exterior cladding systems. In high-rainfall coastal areas, inspectors look closely at weep hole clearance and air space integrity. Some local building practice guides recommend 24-inch weep hole spacing (rather than the 33-inch maximum) for improved drainage capacity in high-rainfall climates.

IRC 2021 retained the 33-inch maximum weep hole spacing in R703.7.4 without change. The 2021 edition added more detail about the air space protection requirements that work in conjunction with weep holes, improving the overall cavity drainage system description. For jurisdictions on IRC 2018, the 33-inch maximum and the need for clear weep holes and clear air space remain the operative requirements.

When to Hire a Licensed Contractor

Brick veneer installation is licensed masonry work. A licensed masonry contractor familiar with through-wall flashing, air space maintenance, and weep hole installation should lay all brick veneer. The drainage system details — including mortar drop protection and weep hole formation — are part of the masonry scope. For inspection of existing brick veneer to assess weep hole and drainage cavity condition (a common concern in older homes), a licensed masonry contractor or building envelope consultant should perform the evaluation.

Common Violations Found at Inspection

• Weep holes absent at the base flashing course — no drainage from the primary drainage location at the bottom of the veneer.
• Weep holes present but plugged with mortar — no drainage despite the holes being nominally there.
• Weep hole spacing greater than 33 inches — insufficient drainage capacity if water accumulates faster than it can exit.
• Weep holes below finished grade — buried weep holes cannot drain to the exterior; landscape installation has covered them after the fact.
• Air space filled with mortar — even with open weep holes, blocked air space prevents water from reaching the weep holes.
• No weep holes above window or door openings where through-wall flashing is required — water accumulates on the lintel flashing with no way to exit.
• Weep hole vents not fully seated — partially inserted vents are dislodged by water pressure and allow large insects or rodents to enter the cavity.