UL Wind Uplift Ratings

[garpe]

UL wind uplift ratings for roof assemblies only go up to 105 psf. What do we do if we have wind loads in corner and edge zones in excess of this? It is not unusual to have wind uplift values in the 120 to 150 psf range.

 

[Ron]

garpe...many building codes allow Factory Mutual ratings in lieu of UL ratings. The IBC and the Florida Building Code both allow this. FM has ratings up to 270 psf for certain membranes.

Check the manufacturer's test literature and see if they also have an evaluation report for the membrane system you are considering.

 

[garpe]

Thanks
I've looked at FM-28 for other projects. It looks like UL has responded to industry demands and only run tests for 90 psf. I did a quick calculation for a "typical" building this morning and found that for 100 mph, exposure C the highest pressure in the corners is about 90 psf.

 

[Ron]

garpe...I agree. I've commonly had to fight the membrane manufacturers who don't seem to understand that we want the membrane to stay in place up to and including the code mandated wind loads, without regard to what their sorry warranties state.

Uphill battle, but can be won. FM helps a lot since they are as widely accepted as UL and since they are an insurance-driven group, they have an interest in testing to much higher loads.

 

[MiketheEngineer]

Anybody can get a UL listing for the right amount of money... not entirely true - but you get my drift.

Say you buy a toaster and it has a UL label on it. Does that apply to the cord or the toaster?? Often, it only applies to the cord. How does the public know?? That is my problem with the UL label!!

 

[garpe]

My take on UL, for rated walls, wind uplift, is that the documented assembly is only good for the UL rating as assembled. What I am trying to get my client to understand is that UL can't be "extrapolated" and that there are other third party testing labs out there who can perform the test for their products. Not necessarily a bad move on the part of UL. The vast majority of the continental US can be covered by the 90 rating. By the way, if anyone is interested the FM-28 document has wind speeds for the Philippines, China, Mexico, Australia, New Zealand and Brazil. No information on Africa.

 

[Ron]

garpe...yes...testing is one solution to the UL dilemma. Have done a bunch of uplift testing on roof membranes in Florida.