Snow Load In Valley

Have you tried searching this forum? I know there was a past thread on this topic. I use the requirements from the 97 UBC and kind of average the snow out over the area.

I too, was surprised that the current ASCE 7 does not address this issue more specificily. Snow accumalates in valleys and may be a major design concern. One reason may be that the current unbalanced snow load provisions for gable roofs is much higher then what was required by some codes in the past. In practice I found, when a building only has a single valley on one side of the roof, the unbalanced snow ussually governs.

However if you have a building with valleys on both sides of the roof the snow in the valley may govern.

So, then, how did they handle the drifters in "The Big Valley"?

Sorry for that...it's Friday... My ex-bank gave me a snow job today, so I'm gonna drift outa here.

Mike McCann
MMC Engineering

Geez... I hope you're kidding. If not, good luck with that Mike; I find banks are pretty ruthless and cold hearted when not being inept. Good luck!

On topic: Most codes don't give you complete guidance; And I hope they never try! They're already plenty thick enough, and as often mentioned, don't add much more utility in the added pages.

Personally I calculate snow based on slopped roof sliding and take 1.5 times the added effect above flat roof. Might not make sence for your code, but worked in OBC, NBCC and now in the NZBC - AS/NZS 1170.

Cheers,

YS

B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...

I always say if you want to know about snow ask a Canadian. "ANYONE!!! IS THERE A CANADIAN IN THE ROOM!!!" "Someone help this poor engineer!" [Use a high pitched woman's voice for that last bit]

On the serious side, we've been using 1.5 but sooner or later someone is going to start asking questions... That's all I've got, I'll shut up now.

Actually, the Canadian code does provide guidance for the snow load in valleys. You could check it out in the Structural Commentaries (supplement to the main National Building Code) or, an even better reference for snow loading is a publication put out by the Canadian Sheet Steel Building Institute called:

NBC 2005: Snow, Wind and Earthquake Load Design Criteria for Steel Building Systems

It gives the same basic info as the Commentary, but with a couple of really good, worked examples.

The uk code "BS 6399-3:1988 Loading for buildings - Code of practice for imposed roof loads" gives guidance on valley snow loads and other drift cases. It may be of help.