1. A bib or apron will allow the housewrap or building paper
to be slipped under the window flashing later. The one shown was made from a
non-adhesive fiber-reinforced flexible flashing. Extend it 6 to 12 inches past
the sides of the window and staple it at the top. Do Not staple below the
3. Embed pre-made inside and outside Corner Flashings in the
sealant and staple the vertical legs. Don't staple the horizontal legs.
4. Cut along the fold of the Corner flashing where it extends
past the opening, wrap the legs onto the sheathing, and staple the legs in
place. Finish the Corner Flashings with pieces of folded flashing tape, as
5. Install the flashing pan. The pan in the photos was made
on site from 40-mil thick flashing. Two sets of hands make it easier to install
the pan without wrinkles that could trap water.
7. Install a piece of Grade D building paper over the
peel-and-stick membrane to prevent UV damage. If the house will be sided with
stucco, the membrane serves as a slip sheet between the stucco and the flashing
8. Install a layer of reinforced flashing (the same stuff
used for the apron) from one side of the opening to the other.
9. Install vertical flashing up the sides of the opening,
overlapping it past the bottom piece installed in step 8. Staple the side
pieces to the face of the trimmer studs and the sides of the recess. Run the
vertical flashing pieces past the bottom of the inset. Crease it into the
corner and cut it with a utility knife or scissors, being careful not to cut
into the preceding layers. Note that a non-adhesive product is being used in the
photo. You can use a peel-and-stick flashing for this, but it can be difficult
to work with and to avoid wrinkles.
10. Before installing the window, apply a heavy bead of
sealant to the nailing flange, then place the window into the opening, checking
the reveal from the inside. Fasten through the flange according to the window
manufacturer’s instructions. Then tool sealant over the nails and over every
11. At the top of the window, staple Corner Flash inside and
outside corners in place over the vertical flashing installed in step 9. Cut
along the fold, wrap the legs onto the sheathing, and stapling the legs in