Prevent Water Intrusion in Brick Veneer

Article Image: 

Every housing giant seeks to reduce the number of callbacks, especially those related to water intrusion. These callbacks can be especially costly and difficult to repair, wasting significant dollars from your bottom line — exactly what you want to avoid in this economy. Brick veneer is one area that water can damage, and there are ways to prevent problems.

Brick Veneer

In today's market, brick veneer is the most common type of brick construction [1] in the residential home building industry. Unlike older masonry walls, brick veneer is much thinner — typically only 4 inches thick (older masonry walls are typically more than 12 inches thick). Brick veneer is less successful at naturally keeping water out of the interior. Therefore, it's more important than ever to ensure the durability of a brick wall through careful design and workmanship.

Water Management

An essential step in the home building process, water management plays a critical role in making a home durable and comfortable. Water management also helps in controlling risk and maintaining insurance coverage — all positive benefits. However, water management is a tricky principle to implement properly because there are so many potential ways water can enter a home. Always a culprit is water intrusion, and water management going awry is the focus of many warranty complaints.

Despite brick's many benefits, which aren't under contest here, it still remains at heart a porous material. Arlan Burdick, E.I.T., a building performance specialist with IBACOS [2] Homebuilding QC, explains that a porous material such as brick absorbs rainwater quickly. "After a storm, some of the moisture in the brick will move toward the exterior, and some will move toward the interior. A robust water management system acts as a defense against moisture heading toward the interior of the home."

Water can wick through pores in the brick via capillary action. In addition, water can enter through cracks and through mortar joints, as well as through the edges around openings and transitions to other exterior claddings. In fact, if a brick exterior is showing any damage, it's likely to be water-related. Don't let this scare you, though. The solution, as with any exterior finish, is to limit the amount of water intrusion and control any water that does enter the wall assembly.

Errors That Lead to Water Intrusion in Brick Veneer

The most common errors on-site that cause water intrusion can be prevented by using the right design and construction practices. Otherwise, unmanaged water intrusion can lead to mold growth, structural deterioration and cosmetic damage. Think about efflorescence, a common result of water intrusion that leaves a whitish deposit from salts behind on the surface of brick. Although efflorescence does not damage brick, it is unattractive and frequently the first issue homeowners notice.

As always, the best way to ensure errors aren't made on site is through education. On that note, let's look at three of the most common installation errors that cause water intrusion and their best practice solutions.

Common Error No. 1: Lack of Weep Holes

WRONG                                    RIGHT       Install weep holes to allow water to drain out of the air space.                   WRONG                            RIGHT   Install through-wall flashing to collect water within the air space and to drain it to the exterior through the weep holes. Click on the images to view a larger size.

Weep holes allow water that has been collected by through-wall flashing to exit the wall system. Without weep holes, water will remain in the air space behind the brick. In some cases, weep holes are installed but subsequently blocked by mortar droppings.

To prevent this issue, install weep holes directly above the flashing to allow water to drain out of the air space. Weep holes created in the mortar joints can be open-head joints (an open vertical joint between two bricks) or core vents. We recommend core vents because they prevent insects from entering and allow for a clear air space. Make sure weep holes are installed high enough that they won't be covered by the finished grade.

Although it's impossible to eliminate all mortar droppings between the brick and the backup wall, there are several practices that can minimize the potential for clogged weep holes. Burdick suggests, "strategically leaving out one brick at every other weep hole in the first course. Doing so allows masons to 'wash' the accumulated mortar out of the air space, helping to prevent the further blocking of the weep holes." Afterward, the bricks that were left out are installed, completing the wall.

Common Error No. 2: Lack of Through-Wall Flashing

In addition to weep holes, through-wall flashing is also needed to direct bulk water out of the wall assembly. This type of flashing is typically either a metal L-flashing or a plastic-coated flashing membrane that's flexible enough to be folded. Without through-wall flashing, water will collect in the air space, remaining inside the wall system and potentially draining into the home. This problem usually occurs at the base of walls and at the head of any openings.

To prevent this issue, install through-wall flashing to collect water within the air space and to drain it to the exterior through the weep holes. Through-wall flashing is required by code at the base of walls as well as at window and door lintels. It is also required at roof-to-wall intersections. The mason should tuck the through-wall flashing behind the housewrap or building paper. From there, it should be extended across the air space to the exterior of the brick. If the backup wall is concrete block, the through-wall flashing should be inserted into a mortar joint in the block wall to keep water from getting behind the flashing.

Common Error No. 3: Lack of An Air Space

WRONG                          RIGHT Make sure there is a large air space behind the brick. It's recommended that the space be 1 inch wide. Click the image to view a larger size.

A common problem with brick veneer walls is that the air space between the brick and the drainage plane ends up too small or blocked by mortar. When the mason drops mortar behind the veneer, it can bridge the small air space, preventing moisture from moving down the drainage plane.

To prevent this issue, make sure there's a large air space behind the brick to allow moisture to drain to provide sufficient airflow for the backside of the brick to dry and to protect the drainage plane from contact with the brick mortar. The minimum width for the air space is 3/8 inches, but an air space of 1 inch is recommended. A larger space is more likely to provide sufficient airflow and help prevent mortar from bridging the air space.

What's the Lesson Learned?

While construction methods may vary by region and market, the goal of water management is the same for every home: to protect it from water intrusion by guiding water down and away. So, be smart and make sure your teams focus on the number one dollar-wasting culprit, and keep those much-needed dollars flowing to your bottom line.