ASCE 7 C&C Pressures: Wind uplift on EPDM Roof

[FoxSE14]

A few questions about wind uplift on roofing systems:

1. Are roofing systems, specifically EPDM fully-adhered systems, required to conform to the uplift pressures determined by the Ch. 30 (Components & Cladding) in ASCE 7-10? I assume the adhesive for the EPDM layer and the mechanical fasteners anchoring the insulation layer are both indeed bound by these requirements.

1a. If not, what building code provision would govern their uplift anchorage?

2. What basis would a roofing manufacturer have if they were to claim that their system conforms to wind speeds of approximately 50-60 mph, when code requirements for C&C are based on wind speeds of 90 mph (ASCE 7-05 Category II bldg/ASCE 7-10 "service level speed")? 50-60 mph seems terribly low to me. Just wondering, based on others' experience, what a mfr might with such low specified speeds might be hanging their hat on.

Thanks in advance for your thoughts.

 

[JAE]

Some links to read:

Factory Mutual's discussion on their requirements

http://www.roofingcontractor.com/articles/85396-understanding-wind-uplift-ratings

An applicable article: "Roofing wind Speeds: ASCE 7, uplift Ratings, and warranties"

http://rci-online.org/wp-content/uploads/2014-CTS-chamberlain.pdf

"Basic Wind Uplift Design,Factory Mutual and Alternative Criteria"

http://www.ronblank.com/courses/usp07a/usp07a.pdf

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[spieng89]

Typically, I have had roofing material manufacturers provide an assembly certification letter that stated that the specified system would meet the max uplift required for the building designed. I would then have them alter the warranty to state this information. If you just look at their standard warranty most situations wont be covered. Now, I don't know if manufacturers would do this for just everyone. I was working for a major roof installer at the time with clout in the industry.

 

[Ron]

JAE's links are good info.

I also require similar to raspivey.....I require that the membrane manufacturer provide the warranty to include wind uplift to the code mandate for the area.

The roof is a form of cladding, so should conform to the requirements for components and cladding. Most manufacturers have their systems rated to comply with Factory Mutual (FM) and Underwriter's Laboratories (UL) requirements for insurance reasons. Both of them have stringent requirements for attachment and performance.

In general there are 3 zones on a roof that require attention. The more critical is the corner zone....usually it is rated at 2 to 3 times the "field" zone of the roof. I have done many membrane uplift tests (both "tripod" and vacuum chamber) on a variety of roof systems and the corner uplift pressures are sometimes difficult to meet, particulary in my area of practice (Florida).