The plywood or other exterior grade material needs
only to be 1/8” - 1/4” thick. The level of the sill
should be checked when the opening is measured 
so the addition of the plywood can be determined to
be necessary and its thickness can be accommodated
in the sizing of the new window.Installation of the
plywood should be adequately caulked
underneath with a bedding sealant, and
the plywood should be covered when
capping the finished installation on the
outside.
2. The Opening Must Be Square. Because there 
is no gravity to help the sash operate smoothly, the
squareness of the opening is more important for a
slider so that the operating sash do not bind up. 
Be careful to install the slider in a “relaxed” state. 
Don't push the window against the blindstop or
anchor to the opening in a manner that might force
the window to rack or twist.
Other considerations when installing 
Sliding Windows.
A. The sill must have uniform support across 
the whole sliding window, and the support must 
be greater than the width of the tracks.
B. Any exterior finish work must not cover nor
impede the operation of any weep holes which 
allow drainage of any accumulated water from the
operating tracks.
C. No anchor screws should be put through the
sill/track of a slider. This may cause water to get
under the window and cause water damage to the
opening or leak in the house. 
D. Be sure that the full perimeter of the window 
is adequately insulated under the master frame.
NOTE: Further information that will be helpful in installing
Sliding Windows is found in this book in the sections on
Frame-Out Method for Replacing Old Aluminum and Wood
Windows, and Installing Windows in Masonry Openings.
Window Fitters Guide to Window Installation 
58                ©2022 AWDI, LLC Do not reproduce without permission
Proper
Sash/Frame
Reveal 
must have 
A equal B 
and the
window 
plumb and
square 
Seal the
Exterior
but do not
cover the
weep holes
Underside
of Slider
SAMPLE MANUAL

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