In April, FM Global published an updated version of its Property Loss Prevention Data Sheet 1-52 (FM 1-52), "Field Uplift Tests." If you are involved with roofing projects that specify compliance with FM Global's guidelines, you should be aware of FM 1-52's changes.
The most significant change to FM 1-52 is field uplift testing no longer is recommended for new roof covers that are mechanically fastened directly to certain roof deck types provided the roof cover fastener spacing is verified as adequate; FM Global indicates fastener spacing can be verified by visual examination or nondestructive examination. According to FM Global, the roof deck types with this testing exemption are steel (minimum 22 gauge), wood, cementitious wood fiber plank and structural concrete (minimum 2,500 pounds per square inch of compressive strength).
For wide rib steel roof decks where the test pressure exceeds 60 pounds per square foot (psf), FM Global now allows an additional 1/4-inch deflection from the previously allowed deflection limit for each 60-psf increment of test pressure. If an intermediate or narrow rib steel roof deck is used, FM Global now permits the allowable deflection limit to be twice the previous allowable deflection limit up to a maximum 1-inch deflection.