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Window Design Pressure

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cuxcrider

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I am in a 165 mph wind zone in Colorado and am building an addition to my house. My structural engineer has this table in the plans:
View attachment 11980
I am looking at a 20 sq ft. sliding window that has a CW-30PG rating in a Zone 4. Am I correct that the rating I need is 0.6*-50.9 = 30.54? And does that mean my 30PG window doesn't work or is there flexibility?
 
cuxcrider said:
I am in a 165 mph wind zone in Colorado and am building an addition to my house. My structural engineer has this table in the plans:
View attachment 11980
I am looking at a 20 sq ft. sliding window that has a CW-30PG rating in a Zone 4. Am I correct that the rating I need is 0.6*-50.9 = 30.54? And does that mean my 30PG window doesn't work or is there flexibility?
Click to expand...
Sorry about that, I’ll the image again.
 

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Hmmm ...

So you have a structural engineer, and the engineer put a table from a reference standard on the drawings rather than provide actual parameters that are specific to your project. In a nutshell, IMHO your engineer is passing the buck to the builder and asking the builder to make determinations that are supposed to be made by the structural engineer of record. I would not have approved those plans.

You should be asking the structural engineer this question, not us.
 
Fair enough, but he put the table there, all I did was multiply by 0.6 so I can calculate any opening I need to calculate. My question I feel is more of a code question. If the window is DP30, but the calcs call for 30.5, do I in fact have to bump up to a DP35 window? Or does DP30 cover anything below DP35? The engineer obviously will say 30 < 30.5, but who knows how the DP ratings work? If the window fails at 32 for example, it would be fine for 30.5 but maybe it gets slapped a DP 30 rating?
 
The only answer I can offer is what one of our former State Building Inspectors used to hammer into us when the state still had live in-service training for code officials (per-COVID-19 pandemic). In this state, only the State Building Inspector is authorized to interpret the code. Local BOs can only enforce -- if anything is unclear, we have to refer it to the SBI for interpretation.

With that as background, what he used to say in just about every class was "The code is the least you can accept and the most you can require." 30.5 is more than 30. I think you answered your own question, but your AHJ may take a more flexible view.

What is a “DP” rating? Is it like a “PG” rating? | Lyndale Glass

A “DP” or “design pressure” rating is a numerical value given to a building component that represents its ability to withstand a given amount of wind load. DP ratings represent three performance…
www.lyndaleglass.com www.lyndaleglass.com

 
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