Therefore it becomes necessary to measure the height of
the opening in three places: once at each side, and
once in the middle. Provide the smallest of these three
dimensions accurately to the nearest 1/16-inch.
Measurement 
of the width is 
handled the same
as double-hung
or sliders.
Installation of 
the casement or
awning window
can proceed
exactly as with a
double-hung. In
fact, substitution
of casements or
awning windows
for a removed
double-hung or
slider can add a
new architectural
design look to
any house. 
Installation
Installation
Screw
Screw
Caulking
Caulking
Caulking
Caulking
Window Fitters Guide to Window Installation 
55                ©2022 AWDI, LLC Do not reproduce without permission
As with any replacement, accurate measurement 
is the most important requirement to assure 
weathertight and trouble-free installation.  Look 
over the instructions for measurement for the type 
of window that will be replaced and carefully 
measure and order the appropriate casement or awning
window.  Make note of any factory cut-backs and con-
sider whether it is advisable to order exact sized or
opening sized windows.
There are three important considerations regarding
Awning and Casement windows that make them 
different to install than double-hungs or sliders:
1.  Casement and Awning windows do not 
use a head expander.
2. There may not be pre-drilled mounting
holes in the window’s side frames for 
screws to anchor the window to the jambs
3. There is no sloped sill or drainage 
accommodations
These conditions do not prevent easy installation
but they are conditions which change the basic way
Casement and Awning windows are installed.
Blind Stop Installation
Conventional installation for replacement windows calls for
“Blindstop” installation where the new 
window is installed in the opening against the 
blindstop, the window is screw-anchored to the sides of the
opening, and the interior stops are re-applied. 
Because the Awning and Casement window styles operate
with a “swing-out” mechanism, a head expander would get
in the way of the swing-out sash and spoil the appearance
of the window. This condition requires some fundamental
changes in the installation procedure. It is necessary to 
measure accurately and order carefully.
Remember, there is no head expander to take up the extra
space in the opening.  Normally Double Hung and Slider
replacement windows are factory ‘undercut’  3/4-inch to 
1-inch less  than the opening height. This is done to
accommodate the height of the stool  (1/2”) the new win-
dow must fit over as it is placed in the opening.   
Casements and Awnings still must be placed over the stool
and set down on the sill.  But, because there is no head
expander supplied, the window will be routinely undercut
at the factory approximately 1/4” less than the measured
opening height.  This causes the set-in process to become
very snug and difficult.
Careful measurement is extremely important so that
the Casement or Awning factory manufactured height is at
least1/4” smaller  than the opening height, but no more
than 3/8” smaller! If the height of the Casement/Awning
window is smaller than 1/4” less than the opening height,
it will not fit.  If it is more than 3/8” less, the window will
not fit the opening well enough to adequately seal out
drafts and moisture.
SAMPLE MANUAL

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