Pull the strap out to the window corner, or a mullion
and use a screw to anchor it to the head board. 
Do this on both sides.
Depending on the projection, make a hip rafter out 
of 2x4's (when space is limited 5/4 stock or 1-1/4"
thick wood is desirable) as shown. Install an end
rafter on each side. 
Fasten additional hip rafters, (about every 16”) 
as necessary. Place a batt of insulation on the 
head board, and sheath the roof with 3/8" 
exterior plywood as shown. 
If desired, a preformed drip edge can be nailed to 
the sheathing before roof shingles are applied. 
It is imperative that step flashing be used under 
the siding, and strip flashing be used over the 
shingles to keep water from the headboard area. 
Use a roof sealant as necessary to seat the flashing. 
Fasten hip shingles over the hip ridges, and trim the
shingles to finish the roof.
The sides of the unit, and the joint of the siding to
the seat board should be sealed with moulding and
caulk as necessary. As stated before, “J” channels
can be applied and lapped to the rough opening prior
to the installation, and caulk and necessary capping
applied after the Bay, Bow, or Garden Window unit is
mounted, braced, and the roof installed.
If the new window is installed over an existing head
and seat board, re-apply, or replace the channels,
drip caps, and capping as necessary. Caulk at all
joints.
Finishing the Interior
Once the new window has been supported and sealed
on the exterior, the interior moulding can be applied. 
Install insulation into the space between the side
boards, the head board, and the rough opening.
Using casing, install the trim on all four sides as
shown. Using wood putty, fill and sand the mounting
screw holes in the side, head, and seat boards.
Finish the headboard, seat board, and side jambs
with paint or stain. For Garden Windows, you might
want to finish the seat board with a plastic laminate
to prevent water stains from the plants.
Sheathing
2" x 4" Hip
Rafter
Insulation
Step
Flashing
Window Fitters Guide to Window Installation 
65                ©2022 AWDI, LLC Do not reproduce without permission
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