We’re taught to air seal the interior side of a window with foam or tape. We’re also taught to provide some sort of back dam or positive slope to the sill.
What is the point of sloping the sill to the exterior if the window is foamed/taped/caulked to the framing? We are also taught to not caulk/tape the exterior nailing flange to the housewrap for the same purpose, i.e., give water a path to escape.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part