UBC 97 Question

[SpiderM]

I am doing some calculations for a client who is fighting an insurance claim. Long story short, I need to show that the original decking was inadequate; which I have proven. But, I would like to be certain that I have performed my calculations correctly.
The code for this particular city is the '97 UBC. Table 16H - Pressure Coefficients (page 2-29) in section 3 of the table indicates a 0.5 value to be added to the above coefficients. I am not clear as to when this applies. I think I know, but I would like some other opinions.

Thanks in advance.

 

[SpiderM]

I need to ask one other question. Deflection limits. The limits are for total load and live load only. Is the live load, in this case, roof live load only, roof and wind loads, of a factored combination of roof and wind? I have never had this completely clear in my head.