barrier and siding is key. In replacement, as the photos
illustrate, removing an old door can either destroy the
integrity of the old sill, or expose the fact that there was no
integrity in the first place. Filling the old sub sill with mor-
tar or even the same thin set as used with tiling floors, can 
create the sealed, level and strong sub sill a successful
door installation requires.
3. Proper Sill Pan/Drainage. In heavy winds,
water can literally blow under the door and up and over 
the back part of the door’s operating track. In wind above
150 mph the water can “climb” upwards of 2 inches and
over the sill into the room. 
The first inclination is to seal the front of the operating
track to prevent water from penetrating under the track
and into the room. Doing so prevents another key function
of the sill under the track - drainage. Proper technique
requires a sill pan (see illustrations) to be placed under 
the track to allow water than may get into and round the 
opening to drain out. Creating the proper balance between
protection from wind blown rain and sill drainage is 
difficult, but necessary.
Some manufacturers make a two piece sill/track to 
accomplish the goal, but in most instances sealing the
front edge of the track, but leaving two 2-inch gaps in the
seal, will protect against the window blown water, but allow
drainage from the sill pan when necessary. Judgement can
also be used considering  location. If the doors are set back
on a large porch, there is less worry about window driven
rain. If the doors are near a corner of a balcony on a high
floor, there is more concern for blocking wind-driven rain.
Summary: Make the sill smooth and level, use a sill pan
and use clips/straps or conventional installation as shown
in the window section. Be as mindful of flashing, sealing,
and mounting hardware as for window products. 
Finally, as with most door products, be sure to follow 
manufacturers’ instructions as they have most likely
designed their sill and track systems to comply with the
requirements of the door’s application.
Window Fitters Guide to Window Installation 
108                ©2022 AWDI, LLC Do not reproduce without permission
SAMPLE MANUAL

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