The image above shows a portion of brick veneer wall that is alongside a roof slope. Although we might not initially consider this a significant area of concern, getting the waterproofing detailing correct in these areas is very challenging and requires careful consideration, planning, and execution.
Consider the following perspective of one of these areas as viewed from the interior attic space. What can we see? And what does it tell us?
Note the house wrap or water-resistive barrier (WRB) that is extending into the attic.
The WRB serves as a layer to protect the wall sheathing and direct water down and out of the wall assembly that has migrated through and penetrated the porous brick facade. Given a significant enough rain event, water will soak through the veneer and enter the air gap behind the veneer. If the WRB were not present, the wood panel sheathing would absorb the moisture and degradation of these materials would likely follow. With the WRB present, the water runs down the outside surface of the WRB and then needs to be properly handled and directed back out of the wall assembly.
Going back to the above image, where does the water traveling down the face of the WRB go in this instance? It travels all the way down to the perpendicular roof deck and framing creating the staining seen in the following image and then is dripping down onto the ceiling below causing water staining there.
In order to prevent these kinds of issues, a properly detailed wall assembly would include a through the wall flashing and weep holes near the base of this wall where it meets the roof. This channels the water in the gap behind the veneer down the WRB and then out of the wall and onto the roof. Below is a cross-sectional view showing what the different components and their proper lapping arrangements could look like.
Going further, an even greater challenge, in this case, is that the roof slope runs parallel alongside the wall. Consequently implementing this cross section along a slope is an additional difficulty. The following diagrams are intended to show how this cross-section could be laid out in a step pattern with vertical flashing stops on each side of each horizontal section of through the wall flashing. Note the rear flanges on the horizontal through the wall flashing and on the vertical stops which the WRB is to overlap. The front horizontal flanges on the through the wall flashing extend out beyond the brick veneer face and serve as an attachment point for the counter flashing. This makes future maintenance possible since the roof covering, step flashing, and counterflashing might be replaced, but the through the wall flashing needs to remain in place. Once these details are in place and the WRB has been properly lapped, the upper brick courses can be installed with weep holes in the lower course resting on the horizontal portions of the through the wall flashing.
This is just one situation demonstrating how important it is to consider the building system as a whole and the movement of water in, through, across, down, and out of various assemblies.