# Snow loads are not live loads under a code definition



## mtlogcabin (Jul 29, 2013)

Snow loads are not live loads under a code definition

2009 IRC

LIVE LOADS. Those loads produced by the use and occupancy of the building or other structure and do not include construction or environmental loads such as wind load, snow load, rain load, earthquake load, flood load or dead load.

I would be happy to hear the answer and how we apply the "snow loads" to the prescriptive tables in the IRC specifically Table R503.2.1.1(1).

Being in a heavy snow area I have always used Table R503.2.1.1(1) to determine the minimum roof sheathing required based on the roof snow load. I find out today I may be wrong and have no idea how to determine the minimum roof sheathing based on the snow loads. I have always been taught the snow load is a live load but according to the definition it is not. Any help would be greatly appreciated.


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## jar546 (Jul 29, 2013)

Snow loads can be converted to a live load using ASCE 7.

I get submissions from RDPs on occasion this way but we ask for a copy of how they arrived because it can vary based on a few conditions, around 3 that affect the result.

I think it is easier for them to do calculations on live load rather than ground snow load but that is just speculation.


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## Mac (Jul 29, 2013)

New York State has determined that for a 'prescriptive' project, where the components and loads are taken right out of the ResCode, the roof snow load must be no less than the ground snow load. Architects and engineers may be able to calculate lesser values, in accodance with the Building Code.

Truss certifications must confirm the design loads including unbalanced loads - like when the wind blows one side of the roof clear and the other side has five foot drifts!


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## Architect1281 (Jul 29, 2013)

Does it matter ? and why - ? it is a snow load, it has all kinds of conditions., considerations, full, alternate, drift, sliding, impact, duration factors.. n on n on..

if an architect says the ground snow is 30 the snow is 30 just like a live load; Im done I'm outta here the answer is wrong.


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## Architect1281 (Jul 29, 2013)

Without going back to the AWC (APA) sheathing the ply is in reality based on near 100 psf tl fot its diaghpram design standard, trouble comes in when roof planes (steps) exceed 2 feet vertical and in places like valleys and around dormers, snow loads drifting etc increases.. Single story garage next to a 2 story frame say that 8 foot height effects the next 16 feet of the projecting roof plane you should generally not see the same rafter/ truss/ engineering documentation for the area adjacent to the step... the condition is a triangular type increase over the lower roof could be a 60 to zero on top of the base ( here in RI thats base 30# pluss a graduated 60# to zero # over 16 feet (L= 2H) (Lenght  = 2 X Height DIff )

Whn I specify it Right and the Lumber yard orders the roof over the phone by span length they really PO'ed when I suggest the foward the plan to the truss fabricator so that it comes back correct.


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## Gregg Harris (Jul 29, 2013)

jar546 said:
			
		

> Snow loads can be converted to a live load using ASCE 7.I get submissions from RDPs on occasion this way but we ask for a copy of how they arrived because it can vary based on a few conditions, around 3 that affect the result.
> 
> I think it is easier for them to do calculations on live load rather than ground snow load but that is just speculation.


I would agree


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