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ASCE 7-05 Section (#4) clarification needed

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I need an interpretation to note number 4 of ASCE 7-05 Section which states:

“Where the flat roof snow load, Pf, exceeds 30 psf (1.44 kN/m^2), 20 percent of the uniform design snow load, regardless of actual roof slope.”


This seems to conflict with itself. My first interpretation is that if the snow load for a flat roof (say ¼” in 1-foot) slope or a shed roof exceeds 30 psf then you would add 20% or 6 psf to the roof dead load. However, the last section of the statement reads “regardless of actual roof slope” in which case I would interpret the 20% of the Snow Load exceeding 30-psf to be added to any sloped roof.


How do others interpret this statement. If the roof is flat should 20% of any Snow Load be considered whereas only 20% of the Snow load exceeding 30-psf be used if the roof is pitched?


Dennis S. Wish, PE


Dennis S. Wish, PE

California Professional Engineer

Structural Engineering Consultant

La Quinta, CA 92253