New clients had a problem with their existing home: A projecting bay would leak at the ceiling during a heavy rain shower. It had happened often enough that they had removed the drywall and insulation, ready—we imagined—to place buckets below to catch any incoming water.
Located on the first floor, the 4-foot-by-10-foot bumped-out bay had a soldered metal roof that appeared to be in good condition. We water-tested the roof and found no leaks. We didn’t want to test the whole structure at once; we wanted to start at the bottom and work our way up so we could locate the issue. So next we moved our gentle water spray up onto the flashing, aiming the water downward to avoid wetting areas above the flashing. The flashing itself didn’t leak, so we moved a bit higher, to the sealant joint at the top of the flashing. This too didn’t seem to leak.
We then started spraying the stone wall just above the flashing. While roofing and flashings often leak within a few minutes, our experience with masonry is it can take 10 minutes or longer for water to leak all the way through and appear inside. Sure enough, after about 10 minutes, a steady drip started off the bottom edge of some building felt that terminated at steel angle shelf.
At this point, we were pretty sure the masonry was missing a through-flashing that would direct water out of the wall above the roof, a common and easily avoided problem we find fairly often in our area. To confirm, we removed some stone above the roof to see how it had been built.
We discovered the roof flashing was cut into the face of the stone and went in only about 1/2 inch. Any water draining down within or behind the stone veneer would simply run down past the roof into the ceiling inside the house (see “Leak at Stone Veneer,” below).
A multilayered solution. We removed the stone down to a block starter course. The existing double WRB layer, which consisted of 30-lb. asphalt felt over a layer of Tyvek, was also removed. (Ultimately, we discovered enough problems with the stone veneer that we ended up removing all of the stone on the addition portion of the home.)
For the first layer of our multilayered solution, we installed a flexible, self-adhesive membrane through-wall flashing over the existing block starter course and up the wall sheathing. The membrane flashing helped dry in the roof-to-wall juncture and would serve as a backup flashing under the metal flashing; metal flashings have a tendency to leak at seams over time.
At roof-to-wall junctures, we typically install a two-piece through-wall flashing, which allows the roof to be repaired more easily later on. The first, “through-wall” piece is fabricated with a 1-inch-tall vertical leg with a hook strip on the outside edge. The second piece, which can be removed and reinstalled as needed, is run vertically between the flashing’s horizontal leg and the roofing and is clipped into the hook strip (see “Through-Wall Flashing,” below).
We installed the water-management layers on the wall so they landed on the through-flashing; any water entering the stone now is directed out onto the roof by the through-flashing. In this case, we used a self-adhered WRB—because of the multiple existing nail holes in the sheathing—added a layer of building paper and a masonry drain-mesh material, and reinstalled the stone veneer.
Photos by Doug Horgan; illustrations by Tim Healey