ASCE 7 Section 7.3.4 (Min. pf) 2

[STR04]

A bldg 20'x40' with a hip roof on a 3:12 slope shall use what pf (min) according to 7.3.4? My pg=50psf so this really hurts me if I have to use pf=50psf. I want to say use the ps=Cspf (Eq. 7-2) but I've seen others use pf=pg. Since my 3:12 slope equates to 14.03 degrees which is greater then (70/W)+0.5=7.5 then do I go to Section 7.4 (eq. 7-2) ps=Cspf or use the pf=50psf? My slope is less than the minimum 15 degrees but it says for monoslope roofs. Please help.

TIA

 

[warrenw]

STR04
Since no one answered you,I'll give it a try.
This is the way I read it;

Eq.7-1 Flat Roof Snow Load:
pf = 0.7(Ce)(Ct)(I)(pg) where pg = 50psf
but not less than 20(I)

Your slope(hip roof) is 14.03 deg. which is greater than (70/W) + 0.5 = 7.5
Therefore use Eq. 7-2 Sloped Roof Snow Load:
ps = (Cs)(pf)
where pf is from Eq. 7-1 above.

Why use pf = pg?

 

[sfatz]

warrenw,
To answer your question, some local building department offices require it. I recently did a project in Douglas County, CO (near Denver) where they required that pf = pg.

 

[STR04]

Thank you both for the clarification. Then based upon ASCE 7 section 7.3,7.4 your load can only be one of the following three choices whether it’s flat, hip or gable:

1) pf=0.7CeCtIpg
2) pf=Ipg or 20I
3) ps=Cspf

This does not include pf=pg unless your local building official requires this. Agree or not?