Brick Veneer and Masonry Wall Construction: Ties, Weep Holes, Flashing, and Mortar Joints | Projul

Brick Veneer: Not Just a Pretty Face

Brick veneer is one of the most popular exterior cladding systems in North America, and for good reason. It looks great, lasts for decades, and adds real value to a property. But behind that clean brick face is a system of components that all need to work together: the air gap, the weather barrier, the wall ties, the flashing, and the weep holes.

Get any one of those wrong, and you end up with moisture damage that can cost tens of thousands of dollars to repair, most of it hidden behind a wall that looks perfectly fine from the outside.

This guide covers the full brick veneer assembly from foundation to cap, with a focus on the details that separate quality masonry work from the kind that leads to warranty claims and lawsuits.

How Brick Veneer Walls Work

Before we get into the how, it helps to understand the why. Brick veneer is a rain screen system. That means it is designed with the assumption that water will get through the outer layer. The system does not try to stop all water at the brick face; instead, it manages the water that gets past it.

Here is the basic assembly from outside to inside:

1. Brick veneer (the outer wythe)
2. Air gap (1 to 2 inches)
3. Weather-resistant barrier (WRB) on the sheathing
4. Sheathing (OSB, plywood, or exterior gypsum)
5. Structural framing (wood studs or steel studs)
6. Insulation (in the stud cavity, on the exterior, or both)
7. Interior finish (drywall)

Water that penetrates the brick runs down the back face of the veneer, across the air gap, and hits the WRB. It then runs down the WRB to the flashing at the base of the wall and exits through the weep holes. As long as the air gap is clear, the flashing is intact, and the weep holes are open, the system works.

When any of those components fail, moisture gets trapped. Trapped moisture causes rot in wood framing, corrosion in steel framing, mold growth, insulation degradation, and eventually structural failure.

Foundation and Base Support

Brick veneer is heavy. A standard modular brick wall weighs about 40 pounds per square foot. That weight needs to sit on something solid, and in most cases, that means a shelf on the foundation wall or a steel shelf angle bolted to the structure.

Foundation Shelf

For new construction, the foundation wall is typically widened to provide a shelf for the brick. The shelf should be at least as wide as the brick plus the air gap. For a standard 3-5/8 inch brick with a 1-inch air gap, the shelf needs to extend at least 4-5/8 inches beyond the face of the sheathing.

The top of the shelf should be at or slightly below the bottom of the wall sheathing. This puts the first course of brick and the base flashing in the right position to manage water.

Shelf Angles

On multi-story buildings or renovations where the foundation cannot be modified, steel shelf angles provide the bearing surface for the brick. Shelf angles are typically hot-dipped galvanized or stainless steel L-shaped angles bolted to the structure at each floor line.

Shelf angle installation requires careful attention to:

• Deflection. The angle must be stiff enough to support the brick above without excessive deflection. Typical limits are L/600 or 0.3 inches, whichever is less.
• Attachment. Bolts must be sized and spaced per the structural engineer’s design.
• Soft joint. Leave a compressible joint (usually sealant over backer rod) directly below the shelf angle to accommodate structural movement. This joint is not mortar; it is a flexible sealant that allows the building frame to deflect without cracking the masonry.

Weather-Resistant Barrier and Air Gap

The WRB is the last line of defense against water reaching the structural wall. It must be lapped correctly (like shingles, with upper layers overlapping lower layers), sealed at all penetrations, and integrated with the window and door flashing.

Common WRB options include:

• Building wrap (Tyvek, Typar, etc.)
• Self-adhered membranes (peel-and-stick products, used at high-risk areas)
• Fluid-applied membranes (sprayed or rolled on)

The air gap between the WRB and the back of the brick is critical. A minimum of 1 inch is required by most codes. This space serves two purposes: it provides a drainage path for water, and it allows air circulation that helps dry out any moisture in the cavity.

Keeping the air gap clean during construction is one of the biggest challenges on a masonry job. Mortar droppings, debris, and insulation that sags into the cavity can bridge the gap and create moisture paths to the structural wall.

Tips for Maintaining a Clean Cavity

• Use a mortar collection device. A board, a strip of mesh, or a commercial cavity drainage mat placed at the bottom of the cavity catches mortar droppings as the wall goes up. Pull it out and clean it every few courses.
• Do not over-butter joints. Excess mortar squeezes out the back of the brick and falls into the cavity. Consistent, moderate mortar application keeps the cavity cleaner.
• Inspect the cavity regularly. Use a flashlight or camera to check the cavity at weep hole locations before installing flashing. If you can see mortar bridges, clear them.

Wall Ties

Wall ties are the mechanical connection between the brick veneer and the structural wall. They hold the brick in place while allowing for slight differential movement between the veneer and the frame.

Types of Wall Ties

Corrugated ties are the old standard. They are flat, corrugated metal strips nailed to the framing. They still meet code in many areas, but they are not the best choice. They have limited pullout resistance and can allow too much movement.

Adjustable ties are a two-piece system with a plate attached to the framing and a separate wire or tab that connects to the plate and embeds in the mortar joint. The adjustable connection allows you to accommodate slight variations in coursing without bending the tie.

Wire ties are single-piece bent wire ties that nail or screw to the framing and embed in the mortar. They provide good resistance in all directions and are simple to install.

For any tie type, make sure you are using corrosion-resistant materials. Hot-dipped galvanized or stainless steel is the minimum. In coastal areas or high-corrosion environments, stainless steel is the only acceptable option.

Tie Spacing and Placement

The standard requirement is one tie per 2.67 square feet of wall area. Most contractors achieve this with ties at 16 inches on center horizontally and 16 to 24 inches vertically. That works out to a grid pattern that is easy to track as the wall goes up.

Additional ties are required:

• Within 12 inches of all openings (windows, doors, corners)
• At changes in wall plane
• Around penetrations

Do not skip ties to save time. Insufficient tie connections can lead to brick veneer pulling away from the building during high winds. This is not a theoretical concern; it happens, and the results are both dangerous and expensive.

Flashing

Flashing in a brick veneer wall directs water out of the cavity at every point where it could otherwise get trapped. Missing or poorly installed flashing is one of the most common causes of moisture damage in masonry walls.

Where Flashing is Required

• Base of the wall (above the foundation shelf or shelf angle)
• Above all window and door heads
• Above shelf angles at each floor line
• At roof-to-wall intersections
• Above any horizontal penetration (pipes, conduit, etc.)
• At the top of parapet walls

Flashing Materials

Copper is the gold standard for masonry flashing. It is durable, does not degrade, and can be soldered at laps for a watertight connection. However, it is expensive.

Stainless steel, lead-coated copper, and rubberized asphalt membranes are all common alternatives. Self-adhered peel-and-stick flashing is widely used for residential work. Whatever material you choose, make sure it extends from behind the WRB, across the bottom of the cavity, and out through the face of the wall with a drip edge that directs water away from the brick below.

End Dams

Flashing must turn up at the ends to prevent water from running off the side of the flashing and into the adjacent wall area. These upturned edges are called end dams, and they are frequently forgotten or poorly executed. An end dam should extend at least 1 inch above the top of the flashing and be sealed to the WRB.

Weep Holes

Weep holes are the exit points for water in the cavity. Without them, water has nowhere to go except to sit at the base of the wall and cause problems.

Types of Weep Holes

Open head joints are the simplest. The mason leaves the vertical mortar joint empty at designated locations in the first course above the flashing. Simple, effective, and easy to inspect.

Cotton wicks are small ropes of cotton or synthetic fiber inserted into head joints. They use capillary action to wick moisture out of the cavity. The downside is that they can clog with dirt over time and are hard to inspect.

Plastic or metal weep hole inserts are tubes or vents placed in the head joint. They allow water and air to move through while keeping insects out. These are a good choice when bug infiltration is a concern.

Cell vents are small, louvered vents that replace the mortar in a head joint. They provide both drainage and ventilation. They are more visible than other options but function well.

Weep Hole Spacing

Space weep holes at a maximum of 33 inches on center (every third head joint for standard modular brick) along every flashing location. That includes the base of the wall, above windows and doors, above shelf angles, and at all other flashing lines.

The Mortar Dropping Problem

Here is the reality of the field: mortar droppings collect at the base of the cavity and block the weep holes. The mason does clean work, but some mortar always falls. A single blocked weep hole might not cause a problem, but a row of blocked weep holes turns a properly designed drainage system into a bathtub.

Solutions include:

• Cavity drainage mats or mesh installed above the flashing to catch droppings and keep weep holes clear
• Mortar collection boards that are pulled and cleaned during construction
• Regular inspection of weep holes after the wall is complete, before the scaffold comes down

Mortar Joints

The mortar in a brick wall does more than hold the bricks together. The joint profile, the mortar type, and the quality of the tooling all affect the wall’s weather resistance, appearance, and longevity.

Mortar Types

Mortar is classified by type, with each type offering different properties:

• Type N (general purpose): Good balance of workability and strength. Best for above-grade veneer.
• Type S (structural): Higher bond strength. Used for below-grade work, high-wind zones, and retaining walls.
• Type M (maximum strength): Highest compressive strength but lower bond strength. Rarely used for veneer.
• Type O (low strength): Used for interior and non-load-bearing applications.

For most brick veneer work, Type N is the right choice. It has enough strength to hold the veneer together, enough flexibility to handle minor movement, and good workability that makes the masons happy.

Joint Profiles

The way you tool (finish) the mortar joint affects its ability to shed water. Some profiles are better than others:

• Concave joint (best): The curved profile compresses the mortar and directs water away from the joint. This is the standard for exterior walls.
• V-joint (good): Similar water-shedding performance to concave. Provides a slightly different look.
• Weathered joint (acceptable): Angled to shed water outward. Less common but functional.
• Raked joint (poor for exterior): The recessed profile creates a ledge that collects water. Looks nice but should only be used on interior or protected walls.
• Flush joint (poor): Does not compress the mortar, leaving it more porous. Not recommended for exposed exterior walls.

If the design calls for a raked joint on an exterior wall, have a conversation with the architect or owner about the moisture implications. A raked joint in a rain-exposed wall will let in significantly more water than a concave joint.

Joint Size

Standard mortar joints are 3/8 inch thick. Consistent joint thickness is a sign of quality masonry work. Joints that vary in thickness look sloppy and can affect the structural performance of the wall. Use spacers or a story pole to keep your coursing consistent.

Common Mistakes in Brick Veneer Construction

Missing or Incorrect Flashing

This is the number one cause of moisture problems in brick veneer walls. Flashing that does not extend far enough, flashing without end dams, or flashing that is left out entirely will cause water damage. Every time.

Bridged Air Gap

Mortar droppings, insulation pushed into the cavity, or debris left in the cavity bridges the air gap and provides a path for water to reach the structural wall. Keep the cavity clean.

Blocked Weep Holes

Related to the bridged air gap issue. If weep holes are blocked, water has no exit. Install cavity drainage products and inspect weep holes before the scaffold comes down.

Insufficient Wall Ties

Skipping ties or using the wrong type leaves the veneer inadequately attached to the structure. This is a life-safety issue in high-wind areas.

Wrong Mortar Type

Using Type S or Type M mortar when Type N is called for creates a mortar that is stronger than the brick itself. When movement occurs, the brick cracks instead of the mortar, which is much harder and more expensive to repair.

No Movement Joints

Brick expands over time due to moisture absorption, and the building frame shrinks, settles, and deflects under load. Without properly placed movement joints (soft joints filled with sealant, not mortar), the masonry cracks. Movement joints should be located at corners, at changes in wall height, at shelf angles, and at regular intervals (typically every 20 to 25 feet for clay brick).

Managing Masonry Projects Effectively

Masonry work involves coordinating material deliveries, scaffold moves, weather delays, and crew schedules across multiple job sites. A single missed delivery can shut down a crew for the day, and a missed scaffold move can delay progress for a week.

Construction management software like Projul gives masonry contractors visibility into all of their active projects from one place. You can track material orders, schedule crew assignments, manage subcontractors, and keep your billing on track without juggling spreadsheets and phone calls.

If you are running masonry crews and looking for a better way to manage the chaos, schedule a demo and see how Projul works in the field. Check pricing for options that fit your business size.

Wrapping Up

Brick veneer is a proven, durable cladding system that performs well for decades when installed correctly. The details matter: the air gap, the flashing, the weep holes, the wall ties, and the mortar joints all work together as a system. Skip any one of them, and the whole system is compromised.

Take the time to do it right. Train your crews on the why, not just the how. When your masons understand that the weep holes and flashing are there to protect the building from water damage, they are more likely to keep those components clean and properly installed.

Good masonry work is a point of pride in this trade. Build walls that will still be standing and performing long after everyone has moved on to the next job.