Flashing brick veneer walls
Write this down: A proper masonry installation will block most rainwater – and proper flashing details expel what gets through. Even with effective and careful installation practices for flashing brick veneer walls, some brick veneer jobs will have water penetration.
This much we know – as sustainable as masonry walls are, the one weak link is water penetration. This can involve rain, humidity, snow or frost, to name a few. In fact, freeze-thaw cycles can add an enormous amount of stress on brick veneer structures.
All brick veneer walls are drainage walls, which is why they must be designed on the premise that water is going to enter the wall system. To ensure the wall’s successful performance, the wall design must incorporate a means for water egress.
Without proper flashing, moisture and the structural stress it causes can migrate to the building’s interior. Flashing, which is designed to collect and divert any moisture penetrating the wall or sill, is the material (usually of metal or plastic) that makes the transition between the brick veneer and dissimilar types of cladding present on the building exterior, such as siding, trim, other types of masonry, roof coverings, etc.
If you see water stains on framing in attics adjacent to chimneys, poor flashing is almost always the culprit.
When flashing brick veneer walls, these flashing issues can occur:
- Lack of or discontinuity in brick sill flashing
- Lack of flashings at lintels
- Lack of end dams at flashings
- Lack of knee wall flashings at roof and side wall junctions and improper chimney flashings
- Missing or non-continuous sill flashing at the brick ledge can lead to many issues, such as moisture intrusion and those ubiquitous cracks at the outside corners of slab-on-ground foundations (known as truncated cone fractures)
In addition, the lack of end dams in all horizontal flashings can lead to lateral movement of water into the walls.
Following are some tips for flashing brick veneer walls that will fortify your flashing installation:
Foundation or base flashing must be placed above the level of the final grade (which will not always be the brick ledge). Any buried base or foundation flashing will not allow for proper drainage.
Wherever there is a break in the flashing, such as at the end of a roll or an inside or outside corner, a 6-inch overlap is required and must be sealed. All brick flashing applications must be tucked under house wrap and form a 1/4-inch down leg after exiting the brick. This forms a proper drip edge.
Weep Hole Protection
For flashing to drain water properly, you must have weep holes in place (16-inches (max) for wick-type and 24 inches maximum for open weep holes).Whether plastic mesh or gravel is used to protect them from being blocked by mortar droppings, your flashings must be supported by a mortar bed that conforms to its shape.
Overlapping flashing at corners must be properly sealed to provide continuous protection against water. The layout and cutting details show how to cut and fold the flashing. Outside corners are made of two pieces that have mirrored cuts. On inside corners, first butt the two ends of flashing into the corner. Next, install the folded and sealed corner pan.
All windows, doors, and any protrusions from the building must be properly integrated into the weather-resistive barrier prior to installing. A flashing pan is a piece of flashing that’s non-continuous. It is used to protect any openings in the brick wall. The use of end dams on pans directs water away from these openings. End dams are created by folding and sealing the flashing.
The flashing that protects the window (sill and jamb flashing) must sit inside the sill pan. Also, sill pan flashing must extend to the first head joint beyond the window jamb
flashing. And at that point, the flashing must be turned upward at least 1 inch to form an end dam. In addition, weep holes and drip edges must be used.
The head pan must sit directly on the lintel. As with the sill, the head pan must extend to the first head joint beyond the window jamb flashing. At that point the flashing must be turned upward at least 1 inch to form an end dam. Again, weep holes and drip edges must be used.
For more information on flashing brick veneer walls, check out the Brick Industry Association PDF: Brick Veneer Construction: Basics of Resisting Water Penetration in Residential Construction