Step 3:
Using adhesive-backed
flashing material. Place
flashing around each
jamb, overlapping the
sill flashing.
Place adhesive-backed
flashing across the
header extending up
and over the jamb
flashing.
Step 2:
Assemble or fabricate a
Sill Pan to fit between
the jambs and set on
top of the sill. We will
illustrate a fabricated
pan, but the steps apply
to a pre-formed pan.
Do not anchor with 
fasteners through the
pan to avoid a leak
path.
Fix the sill pan to each
jamb using the head of
a roofing nail, as shown
below. Seal with caulk
Step 4:
Place a bead 
of caulk on the
flashing or the
backside of the
mounting flange. 
Next set the 
window into the
opening. Using a
framing square, to
plumb and square 
the window 
carefully. 
If you need to shim
before anchoring
(Step 5) use 
plastic, flat, 
stackable shims.
Never use tapered
wood shims.
Sill Pans
If you’re not using a pre-formed sill pan, you can create
the effect by installing a 1 x 2 to create a backdam before
applying the flashing. 
If you choose a preformed sill pan, do not nail through
the materials as it will create a water path. Mount it to the
jamb with nails sheetrock nails so the head of the nail
secures the pan without needing to puncture it, as shown.
You can level the sill under the pan with plastic shims.
Window Fitters Guide to Window Installation 
98               ©2022 AWDI, LLC Do not reproduce without permission
Step 1:
If WRB has been applied
to the wall prior to
beginning of the window
installation, cut the
house wrap in such a
way to be able to fold 
it back, and tape it 
out of the way. Using
Adhesive-backed
Flashing Material place
flashing over rough sill
extending 5 inches
down the front, and 4
inches up each side.
Roll it secure.
Be careful not to tear or
buckle the membrane.
Flashing (Method B)
SAMPLE MANUAL

View this content as a flipbook by clicking here.