Snow Drift on Lower Roof

[jopalu]

Ground Snow = 35 psf
Roof Snow = 30 psf.

The lower roof, above an entrance, extends 10' beyond the building. The upper roof,(lu>150')which is 13' above the lower roof, extends 8' beyond the building. Thus, the lower roof extends 2' further from face of building. With the 8' overhang above the lower roof, will a drift occur?

Thank you!

 

[JAE]

I wouldn't count on an upper roof overhang to reduce a lower roof drift. While there is some logic in saying that blown snow will drop mostly beyond the lower roof, with swirling winds, complex behavior, and silence on this matter in the codes, I'd take the conservative route here.

 

[TheBlacksmith]

If you leave your car window open one quarter inch, even with one of the popular aftermarket wind/rain deflector installed, snow will blow in under the right conditions. Be conservative, do not count on a shadow effect.