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Drifting snow on small canopy

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We are reviewing structural calculations for a small (5' perp. to bldg face and 8' parallel to bldg. face) flat canopy over a door for which the engineer has not included any snow drift.  The distance from the high roof down to the canopy is 13'-6" and there is a 2'-6" high parapet.  The main roof is flat and at least 140' wide.  The engineer's position is that it is too short or too small to get any drift from the upper roof.  I seem to recall someone telling me that if you had a roof projection less than 15' long, that you didn't have to consider show drift against it, but I don't know where this might be in the code - (might have been in BOCA, but is not in IBC?)  If the canopy had not already been constructed, this probably would be a no brainer - just make it a little stronger to be able to handle the drift, but, unfortunately, it is already constructed.  Anyone sure that we do or do not need to consider snow drift?  The balance snow height is about 1'-3".  Thanks for your help.
Best regards,
Kenneth S. Peoples, P. E.
Lehigh Valley Technical Associates, Inc.
1584 Weaversville Road
Northampton, PA 18067
Phone: 610-262-6345
Email: kpeoples(--nospam--at)