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Re: CBC 2007 Wind Load

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You and Scott are correct that it is in the combination listed as OR with Snow Load.

Stacked roofing material I can see as being a live load. At code level forces, I would think that whatever is stacked (say tile) would get blown off one by one by the wind (thereby reducing the live load) since it's just sitting there unfastened.

The project is in San Francisco, low wind zone, no snow load.

This is a 6:12 wood roof and the rafters will not even come close with this requirement. I usually just consider the wind as an uplift on roof members (using method 2) since I don't come across Gable shaped moment frames too much where I'd use Method 1 in UBC...

It also appears that 16psf Roof Live load is adios for sloped rafters...


On Dec 19, 2007 9:14 AM, Dmitri Wright <dmitri(--nospam--at) > wrote:
I think this load combination is targeted primarily for Wind + Snow
combinations.  Remember the old 1/2Wind + Snow and Wind +1/2 Snow?  This has
been replaced by the simpler 0.75Wind + 0.75Snow (or 0.75 Lr).  For the
low-landers who do not have big snow storms, I have personally been involved
with a number of buildings where the roof drains plugged (wind borne debris)
and the roof filled with water while the wind was howling.  I have also seen
several projects where roofing materials were stacked on a roof (rafter
component live load), and remained there throughout a windstorm, because the
roofers were smart enough to stay off the roof during the storm.

Dmitri Wright, PE
Cascade Engineering, Inc.
2459 SE TV Hwy, PMB #202
Hillsboro, OR  97123-7919

>Who/what is on the roof causing live load during a wind event I ask?

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