Take a look at this photo. One of you noticed that our specifications go above and beyond when typical roof drain flashing details.
Here, the tapered insulation detail used to provide slope to the drain - is sixteen feet (16') wide.
"A well-drained roof is not only more water resistive, but also more durable and structurally safer. A roof on which water ponds for long periods deteriorates more rapidly than a roof that does not pond."*
"Roofing materials have certain compounds that dissolve under sustained pressure of standing water, reducing the membrane's life."*
In addition to structural and durability benefits, a well-drained roof does not allow the deposition of windborne clay or silt on the roof. These deposits may lead to vegetation that may puncture the roof membrane.
The Best Practice to assure positive drainage is to specify and install a minimum slope of ¼” per foot across all areas of the roof.
The roof with the better drain detail installed, will drain better - and last longer!
*Roof Drainage - RCI Foundation - Stephen Patterson, P.E., RRC - Madan Mehta, PhD., M.Bdg.Sc.,B.Arch - J. Richard Wagner, P.E.*
*Roof Drainage - RCI Foundation - Stephen Patterson, P.E., RRC - Madan Mehta, PhD., M.Bdg.Sc.,B.Arch - J. Richard Wagner, P.E.*
- Tommaso Costanzo, CDT, RRO, LEED Green Associate
Some manufacturers accept details that offer less than the minimum slope - AND issue a 20 year warranty. I never understood why????? Everybody knows a roof that does not drain properly will not last 20 years.
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