Flat Roof Sloping Curb Membrane
ACRYLIC DOME ON A CURB
Caulking is often used to try and seal a skylight…
and then more caulking… and more caulking.
Domes often end up with condensation
Acrylic domes cannot be sealed to each other. They have a tremendous amount of expansion and contraction which makes it impossible to make a perfect seal between 2 layers of acrylic. (Only Glass can have a perfect seal and have argon gas added between the panes of glass) Because of this they often end up full of condensation between the 2 layers of acrylic. The large amount of expansion and contraction also causes them to make strange popping sounds sometimes.
A Curb of proper height is required
Having a curb that is too low does not raise the skylight up and off the flat roof. The skylight ends up sitting in the rain water and snow. The proper curb raises the skylight off the flat roof to keep it out of the snow and rain so that's it's not vulnerable and so the snow doesn't keep it covered in the winter and block the light from going through the skylight.
ROTTED ROOF PLYWOOD
Caulking a skylight is not a solution
Caulking a skylight is often viewed as a simple and hopefully effective fix. Sometimes the caulking will stop the leak for a short time and as it breaks down the leak shows up again, it is never a permanent solution. The result of caulking over and over and chasing the leak is usually badly rotted plywood underneath)
Replacing all rotted plywood is important.
NEW SLOPING CURB
A curb with a slope to allow a flat glass skylight
The sloping curb allows the flat glass skylight to drain off rain and snow from the skylight. Flat glass skylights are much more energy efficient than domes. Because a perfect seal can be made between the two layers of glass and argon gas can be inserted in between the 2 panes the result is what's called LowE3 Glass. LowE3 Glass
New Base membrane
Primer to curb
Applying primer to the new wood surface of the curb so that the roofing membrane bonds properly and provides protection from the flame.
NEW 2 PLY MEMBRANE
New Cap sheet membrane
The top of layer of the 2 layer system is called cap sheet. It has a granular exterior surface to protect It from the sun.
Top of curb Membrane
The cap sheet goes all the way up the curb and down and across the flat of the roof to give a complete new seal of the skylight curb and surrounding roofing. The top of the cap sheet stops at the very top edge of the curb, then a soft self-adhesive membrane covers the very top part of the curb and over the edge of the cap sheet. This provides the best seat for the new skylight to sit on.
Because the new sloping curb extends the existing light shaft interior finish is required. Drywall could be added to the inside of the new curb and then plastered into the existing drywall and then painted. A simpler and more cost effective alternative is to install a white wood trim on the inside. Although it is a bit different in appearance than drywall would be it allows for the interior to be addressed at the same time as the skylight installation work. That saves the homeowner from the extra cost and scheduling of drywall work.
GLASS SKYLIGHT ON SLOPING CURB
The new LowE3 energy efficient glass skylight provides a much more comfortable interior space by blocking out the heat in the summer and giving UV protection against fading.
Most of the old skylights on flat roofs are domes. Domes are cheaper to install because they don't require a sloping curb and also provide a bit more light than a sloping glass skylight would because of the curvature of the acryl;ic that bends light in. But, that same curvature also creates a magnifier effect with heat often making the space below unbearably hot in the summer. We've often heard from clients that have switched to glass “Now the A/C works Upstairs”.
90 Esna Park Dr. #17/18
Markham, ON L3R 2R7