Downward (Positive) Wind force on Roof Overhang

[WoodDesignCat]

I'm an engineer in California, and when designing large overhangs I check them for the same components and cladding load as the main roof in the downward direction, and check them for the increased overhang load in the upward direction. But looking at ASCE7-10 and CBC 2013 I see no requirements for checking an overhang for a net downward wind force at all.

One of my superiors at work says he uses the increased overhang force in both directions, which I know is incorrect.

Are there any requirements for components and cladding for a downward wind force on an overhang? It seems like there should at least be a suction force value on the soffit on the leeward side of a building for a gable roof, and you would have a downward force on and overhang on the top end of a monoslope roof on the leeward side.

 

[Guastavino]

Don't have it in front of me, but isn't there the minimum 10 psf regardless of direction for components and cladding?

 

[DaveAtkins]

I think you are correct. Overhangs only see uplift. I think the same may be true of all open structures--soffits, etc.

DaveAtkins

 

[BUGGAR]

I design in CA too and also noticed that with all 376 different wind load conditions and combinations, there is no net downward wind load on overhangs. But I just went to Pier One and they sell these swinging cocoon "love seats" that you hang from your eaves, so we here have to consider those special California loads.

 

[WoodDesignCat]

After njlutzwe's comment I looked for a minimum pressure harder and found this. It looks like the minimum is 16PSF in each direction. I will continue using the same CC values as for the main building.

CBC2013

ASCE7-10