It’s easy to find advice on flashing windows. But what about exterior doors? For some reason, most construction experts haven’t provided builders with much advice about flashing doors.
Don’t be fooled, though: The lack of online advice on door flashing doesn’t mean that door flashing is unimportant. If you screw up these details, you can rot out your subfloor and floor joists.
If it’s a PVC sill pan, you need to glue the sections together (after fitting them to the opening). Most sill pan manufacturers recommend the installation of three parallel beads of caulk (usually, elastomeric or polyurethane caulk) at the rough threshold before the sill pan is secured in place.
If you prefer to make a site-built sill pan, you can do that. Remember, though, that a site-built sill pan needs either (a) an interior dam, or (b) a positive slope toward the exterior.
4. In most cases, an exterior door shouldn’t be installed until after the water-resistive barrier (WRB) has been installed on the wall. If your walls have conventional housewrap, you’ll need to create a flap in the WRB at the head of the door opening by cutting two diagonal slits (each about 6 inches long) in the WRB, beginning at each upper corner of the rough opening. Fold up this flap temporarily, holding it in place with cheap tape.
5. On the rough jambs, you have two choices. Many builders fold the housewrap into the rough jambs, so that the housewrap is used as the rough jamb flashing. A better approach is to install real jamb flashing. (Although door manufacturers sometimes neglect to mention the need for rough jambs to be flashed, installing jamb flashing is a good idea.) If you are going to install flashing on the rough jambs, first…