Req'd Roof Obstruction Clearance to Prevent Snow Drift
Req'd Roof Obstruction Clearance to Prevent Snow Drift
(OP)
Problem: A duct run is to be placed on a roof of k-joists. The joists have very limited reserve capacity.
Given: The vertical depth of the ducts is 6'-0". Balanced snow height is 14".
Goal: Minimize the height of the duct run (for wind), but provide enough roof clearance that it is not subject to snow drift.
Question: What is the minimum bottom of duct elevation required to avoid snow drift?
I would ask for technical literature, but I don't believe it exists. I am asking for common practice. Guessing, I would say that:
[Air Space] = [6' Obstruction]/[2 T&B]
[Clearance] = [3' Air Space] + [1'-2" Balanced Snow Height]
But I would prefer to lower the elevation further.
Given: The vertical depth of the ducts is 6'-0". Balanced snow height is 14".
Goal: Minimize the height of the duct run (for wind), but provide enough roof clearance that it is not subject to snow drift.
Question: What is the minimum bottom of duct elevation required to avoid snow drift?
I would ask for technical literature, but I don't believe it exists. I am asking for common practice. Guessing, I would say that:
[Air Space] = [6' Obstruction]/[2 T&B]
[Clearance] = [3' Air Space] + [1'-2" Balanced Snow Height]
But I would prefer to lower the elevation further.






RE: Req'd Roof Obstruction Clearance to Prevent Snow Drift
Dave
Thaidavid
RE: Req'd Roof Obstruction Clearance to Prevent Snow Drift
This is based on a webinar I participated in years ago hosted by a gentlemen who did a lot of research into snow loads and contributed to the ASCE snow provisions.
I`ll dig up his name if you want to do some more research into it.
RE: Req'd Roof Obstruction Clearance to Prevent Snow Drift
RE: Req'd Roof Obstruction Clearance to Prevent Snow Drift
RE: Req'd Roof Obstruction Clearance to Prevent Snow Drift
Q1: What's the general standard on sharing webinar slides? Generally OK or generally discouraged?
Q2: If generally OK, how can I post a scan of the slides?
RE: Req'd Roof Obstruction Clearance to Prevent Snow Drift
Unfortunately, I believe that you are not supposed to share webinar slides on the internet.