Return to index: [Subject] [Thread] [Date] [Author]

Snow Loads & the Building Official

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Recent posts regarding snow loading have recommended contacting the building 
official.  While that may give you the snow load that the building official 
may require, it may be nowhere near the actual snow load that may occur.  
While the building official may give you a *minimum* snow load value, it may 
not be anywhere near what you *should* use.

While many may think of Arizona as devoid of snow, we have a large variety of 
conditions from warm desert to high, cold mountains.  Pima County, in the 
southeast part of Arizona has elevations that range from less than 2,000 feet 
to over 8,000 feet.  The Flagstaff area and the White Mountains in eastern 
Arizona are in the 7,000 ft plus elevation range and are subject to 
considerable snow loads.  In the early 1970's, following the lead of Oregon, 
the Structural Engineers Association of Arizona published an Arizona Snow 
Load study that showed the snow loads that would be expected in a 30-year 
return period.  ASCE 7, in the Appendix, shows that for a 50-year return 
period, the site-specific ground snow load for the Palisades Ranger Station 
(35 miles from downtown Tucson but at an elevation of 8,000 feet in the 
Catalina Mountains) of 125 psf, yet the County Building Official was 
requiring only 20 psf for construction in the area.  The Tucson Chapter, 
Structural Engineers Association of Arizona, recommended that this be changed 
and submitted recommendations based on the Arizona Snow Load study for snow 
loads in various elevation ranges.  It is unknown whether the recommendations 
were adopted by the building official.

I have had a couple of recent projects in the White Mountains area where the 
ground snow load was 50 psf.  Drift snow loads, using the UBC appendix 
procedures, had maximum drift loads of 130 psf.

A. Roger Turk, P.E.(Structural)
Tucson, Arizona