How not to flash a window.

Exterior walls with a properly installed cladding/siding are designed to keep water out of the wall system. Then we want to poke holes in it with windows, doors and other penetrations. These penetrations are always a potential for moisture entry into the system.

It is important that we take proper steps to integrate these penetrations into the cladding and drainage plane. Proper sequentially installation of flashing materials shed water from around the window perimeter, and any rainwater that may make it past the flashing needs to be captured by the drainage plane where it can flow out without penetrating the wall and causing moisture issues.