Troubleshooting Brick Veneer

Integrating the Flashing

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The offices under this curved glass roof had been getting wet fo… Read More The offices under this curved glass roof had been getting wet for years. The drops of water usually came down days after the rain — not surprising, given the height of the brick wall above, a likely water reservoir. I started with some controlled testing and discovered that water was showing up inside about 10 feet away from an area where I could see a lap in the metal through-wall flashing outside.

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Next I called for removal of the drywall ceiling to further narr… Read More Next I called for removal of the drywall ceiling to further narrow the possible entry location. From what I could see inside, I suspected that the laps in the flashing had failed, if they ever worked in the first place. We had no choice but to rent a  bucket truck and — very carefully, considering the glass below — start deconstruction.

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We first uncovered the suspect lap joint, which — sure enough … Read More We first uncovered the suspect lap joint, which — sure enough — was not sealed.

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I also pulled off the brick at the end of the solarium, pretty s… Read More I also pulled off the brick at the end of the solarium, pretty sure that I would find no end dam in the flashing there. Without dams, water would eventually make its way down into the walls at each end.

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When the roofing contractor did the repair, he soldered the new … Read More When the roofing contractor did the repair, he soldered the new copper flashings wherever he could, and sealed them with Carlisle’s Water Cut-Off Mastic, a clay-based caulk that effectively stops water as long as it’s in compression and out of direct sunlight.

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For good measure, we also added a layer of uncured rubber membra… Read More For good measure, we also added a layer of uncured rubber membrane over the flashing laps. . . .

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. . . and at the ends of the flashing. It’s been years now and… Read More . . . and at the ends of the flashing. It’s been years now and they’ve not had any leaks since.

Through-wall flashing should extend to the outer face of the brick. Anything short of that is that much less effective at getting the water out. And the back upper leg must be placed under the layers of building paper that protect the sheathing.

Building paper. In my opinion, brick — like stucco — should be installed over two moisture barriers. I like to see a layer of 30-pound felt covered with a plastic housewrap like Typar or Tyvek. That way, the Tyvek protects the felt from the sun during construction. The housewrap acts as a first line of defense against any moisture that might be held by excess mortar in the cavity; the thick felt ensures that the moisture is held at bay until it can evaporate.

There are several new construction materials that claim to be a combination structural sheathing and moisture barrier. Even if these products meet the requirements from a structural standpoint and pass the moisture-resistance tests, their ability to properly shed moisture at critical points depends on adhesives. Unfortunately, peeling flashing tape is all too common, in my experience. The tapes lose their tack and begin to roll down along the top of a window; ironically, the same material that was being relied on to keep water out now traps it. There are of course various primers that can be applied to improve adhesion, but their chances of being used are slim to none.

If you insist on relying on tape over housewrap, at least make sure that both products come from the same manufacturer and that you explicitly follow the installation instructions. (Don’t use your client as a guinea pig!)

Keep the Cavity Clean

If wall cavities were created in a perfect world, they would be just that — cavities. The mortar, and any water it holds, would stay completely away from the felt or housewrap that guards the wall sheathing. But since masons are usually pressed to do their jobs as quickly as possible, excess mortar on the back of the brick will naturally collect along the bottom of this cavity. As a precaution, always make sure that the back leg of the through-wall flashing at the base of the wall reaches above the likely level of the mortar droppings — 8 inches is good for a single-story house, more for additional stories.

There are some new plastic mesh products designed to catch mortar droppings above the bottom of the cavity so as to keep the weep holes clear. One possible problem with this approach is that the mortar may collect above the back leg of the base flashing, so if you use a mortar mesh you have to make sure the flashing extends above the point where the mortar might collect.