Q: I know that you should put an end dam at the end of flashing that terminates against a door frame. My question relates to a fairly common situation where there is a masonry return adjacent to the door frame (inside corner). In this case, if you put an end dam at the end of the flashing, the water would just flow against the door frame. It would seem that the end dam would need to wrap around to prevent this from occurring. Can you recommend a solution?
A: This is a situation that occurs quite frequently in buildings but is often handled incorrectly. A special end dam, which many people refer to as a three-sided end dam, should be used in this case. The end dam is illustrated in Figures 4 and 5.
When I use a three-sided end dam, I design it so that the end dam extends about ½ inch beyond the face of the door frame. Since this portion will be exposed, it should be fabricated out of corrosion-resistant metal such as stainless steel or prefinished aluminum.
To avoid having a straight vertical edge that would complicate sealant installation, I slope the edge of the end dam back at a 45-degree angle. This way, the sealant between the door and the masonry would initially be applied to the lower half-inch of this triangular end dam. Then, above that point would be extended between the door frame and the masonry. Aesthetically, there is only a half-inch corner of the flashing that is visible. Functionally, this allows the end dam to work very effectively.