Glazing a Custom Sunroom, continued
Assembling the Parts
Before installing any of the extrusions, we pressed the EPDM
gasket material into its intended raceways (Figure 3). Each
gasket should seal tightly against intersecting and adjacent
pieces. Therefore, it's a good idea to allow the gasket
material several hours' rest before final trimming to recover
from possible stretching.
Figure 3.The crew used soapy water as a lubricant
to help seat the gaskets in their raceways (left). Because the
gasket material has memory, or a tendency to shrink back to its
original form after stretching, it's important to install the
gasket strips long and let them shrink for several hours before
final trimming. The top perimeter bar is installed first, with
mitered ends, then the side bars (right).
The first extrusion installed is the head member, which runs
across the top of the openings, the full length of the glazing
area. We predrilled the base of the perimeter bar with a series
of holes, starting 2 inches in from each end and spaced 15
inches apart, for fastening the bar to the framing with the
#10x2-inch stainless-steel screws provided. The prescriptive
spacing ensures that there'll be no conflict with the cap-bar
screws that are installed later, on 12-inch centers. The
inscribed centerline in the underside of the bar helped prevent
the 7/32-inch drill bit from wandering off center. Each end of
the head piece gets mitered to the perimeter sides.
The perimeter sides are square-cut at the bottom ends, while
the intermediate vertical members are square-cut at both top
Bottom perimeter members are cut to fit between the mullions.
It's important to drill the required 3/16-inch weep holes, one
at either end of each bottom bar, before installation. Drilling
later risks punching through the extrusion and chipping the
glass edge. Nicking the edge of tempered glass courts disaster,
as the sheet may spontaneously shatter into thousands of
glittering "dice." The weep holes drain the interior gutter
system and prevent condensation from overflowing onto and
staining the supporting wood frame. Because of the importance
of positive gutter drainage, the Pro-Seal system should not be
installed on roof pitches less than 3 in 12.
With the complete base-bar layout screwed to the frame and the
gaskets set, we're ready for glazing. We use 1-inch insulating
glass, with a laminated interior panel and a tempered exterior
panel. If, by chance, the glass is hit and breaks, the exterior
panel will break into small, harmless pieces; a bonded plastic
sheet prevents the interior panel from shattering and catches
the fragmented outer panel, preventing harm to anyone below. We
ordered the interior panel with a low-e coating on the side
facing the insulating void, as much to help reduce interior
condensation as to control heat loss.
Pro-Seal uses a pair of 4-inch-long rubber setting blocks,
screwed to the bottom perimeter bar of each panel section, to
fully support the double edge of the glass panels. Neglecting
to support the entire edge of an insulating glass panel
— both the inner and outer panes — is a major
cause of seal failure in sloped glazing. If only the bottom
(inner) pane is stopped at the base of the panel, the upper
panel may "creep" downward and rupture the seal. Generally
speaking, thermal glass fabricators will not guarantee against
seal failure in sloped glazing applications, especially when
they're not in control of the installation.
The glazing panels are heavy as well as fragile; four of us
working together boosted them onto the staging and lowered them
into place. We used glazier's vacuum cup grips to handle the
panels (Figure 4). A pair costs around $150, well worth it if
you frequently install glass panels or mirrors.
Figure 4.Vacuum cup grips make large, heavy glass
panels easier and safer to move.
Because of the custom nature of each installation, flashing
isn't included with the glazing bars. Pro-Seal recommends using
minimum .032-gauge aluminum flashing to prevent rippling. We
bent the profiles on a 10-foot brake, using bronze coil stock
to match the system components. The manufacturer provides good
detail drawings in its design manual.
The eaves flashing goes on first, before the extrusions are
installed (Figure 5). After the glazing panels were in place,
we installed side flashings, which overlap the apron flashing
with a 45-degree end cut, giving the appearance of a mitered
joint. The overlap is set in silicone caulk and secured with a
few stainless-steel screws. The design manual offers two
methods for sealing the side flashing to the glazing system: by
running it flat beneath the side perimeter bar, or by making
up-and-over right-angle bends and clamping it under the glazing
cap and gasket. We decided to go with the second, more surefire
Figure 5.Because every overhead glazing job is
different, flashings are custom-bent on site. The first
installed is the eaves flashing (top), which goes on before any
glazing bars. After the glazing is in place, the side flashings
are installed (bottom).
The head flashing breaks up and over the top perimeter bar to
fully cover the glazing cap. A strip of foam-backed tape
between the flashing and cap bar closes any gaps and serves as
a backer rod behind a final bead of silicone caulk.
The gasketed glazing cap serves as the primary barrier to
water intrusion around the glass. Because you can expect
aluminum to expand in hot weather, the design manual requires
butt joints in the cap to have a minimum 1/8-inch expansion
gap, to be filled with silicone caulk. However, the EPDM gasket
must be cut long to bridge the gap and butt snugly against
adjacent gasketing. The glazing cap gets drilled every 12
inches for the 1/4-inch gasketed stainless-steel machine screws
that connect it to the base extrusion (Figure 6).
Figure 6.Attaching the gasketed glazing cap makes
the installation watertight. A snap-on cover trim will hide the
A running depression in the cap creates a recess for the
fastener heads. The heads are finally concealed by a snap-in
trim cover strip that must be gently tapped into place with
either a wood block and hammer or a rubber mallet. A good grade
of silicone caulk on all the joints and intersections tops up
the glazing system.
The Pro-Seal design manual is detailed and clear. When
properly installed, the system will remain leak free for a long
time. We've been using this system for 15 years and have many
satisfied clients.John DeCiantisowns DeCiantis Construction in