Snow Loads
Snow Loads
(OP)
My local building code states the following:
1608.1 General. Design snow loads shall be determined in accordance with Section 7 of ASCE 7 using the ground snow load values determined by Table1608.1, but the minimum flat roof snow load shall be not less than that determined by Table 1608.1. The design roof load shall not be less than that determined by Section 1607.
The code is a state modified version of IBC 2006. The building is double pitched at 1:12 slope.
Table 1608.1 Ground snow load (pg) = 30psf
Table 1608.1 Minimum flat roof snow load pf = 30psf
There is an argument in my office on how to interpret the section of the code.
1: Calculate the snow loads based off Chapter 7 of ASCE 7. If they are less than the minimum of table 1608.1 then use the minimum of 30psf. If they are greater then use the greater number you calculated in accordance with ASCE 7
2: Calculate the snow load based off Chapter 7 of ASCE 7 replacing the minimum snow loads in section 7.3 of ASCE 7 with the 30psf described in 1608.1.
The question then basically comes down to the definition of a low sloped roof in section 7.3.4.
Which method would the community interpret as being correct?
1608.1 General. Design snow loads shall be determined in accordance with Section 7 of ASCE 7 using the ground snow load values determined by Table1608.1, but the minimum flat roof snow load shall be not less than that determined by Table 1608.1. The design roof load shall not be less than that determined by Section 1607.
The code is a state modified version of IBC 2006. The building is double pitched at 1:12 slope.
Table 1608.1 Ground snow load (pg) = 30psf
Table 1608.1 Minimum flat roof snow load pf = 30psf
There is an argument in my office on how to interpret the section of the code.
1: Calculate the snow loads based off Chapter 7 of ASCE 7. If they are less than the minimum of table 1608.1 then use the minimum of 30psf. If they are greater then use the greater number you calculated in accordance with ASCE 7
2: Calculate the snow load based off Chapter 7 of ASCE 7 replacing the minimum snow loads in section 7.3 of ASCE 7 with the 30psf described in 1608.1.
The question then basically comes down to the definition of a low sloped roof in section 7.3.4.
Which method would the community interpret as being correct?






RE: Snow Loads
Dik
RE: Snow Loads
RE: Snow Loads
Basically it comes down to method 1 yielding 30psf for a roof snow load and method 2 yielding 21psf for a roof snow load.
It appears what you guys are saying that the calculations should be performed in accordance with method 1 above and end up at 30psf?
I have a call into the local building official and to the state...... nobody is there. My tax money hard at work.
RE: Snow Loads
But it is interesting that your local Code essentially ensures that ASCE 7-05 flat roof snow load will never control. The local (arbitrary) value of 30 psf will always control.
DaveAtkins
RE: Snow Loads
In the end, they said the purpose/intent of the code was to use a minimum roof loading of 30psf.
RE: Snow Loads
I remember in some areas (Oregon?) they would allow you to use the calculated roof snow instead of specified minimums for checking drifts and unbalanced snow.
RE: Snow Loads
When would you end up greater than the 30psf? How about when considering snow drift?