We have run into this a few times. It takes a call to the AHJ. If the beams are more than 22" deep I would say you should maintain a 1" deflector distance below the beams. I believe that the concrete twin tee rule is only thing that allows greater than 22". The 3 ft rule has been in 13 forever (I think) and doesn't make much sense. It is even in the concrete twin tees. A strict interpretation would require a head in every pocket if the beams are less than 3 ft. on center. Maybe when this happens it should be treated like a smooth ceiling?
The last project we had this on was concrete twin tees 34" deep with the stems 18" apart. The AHJ agreed that we should stay within 1" of the bottom of the tees. Ron Fletcher Aero Automatic Phoenix, AZ -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Dewayne Martinez Sent: Friday, May 11, 2012 8:36 AM To: SprinklerFORUM Subject: Obstructed construction NFPA 13 (07ed) section A3.7.1 (1) When beams are less than 3 ft o.c. do the rules for obstruction construction still apply or does the pocket between the beams become small enough to treat it like unobstructed construction and place the sprinkler deflector 1-12" below the beams? Thanks, Dewayne Martinez Design Build Fire Protection 262-784-7900 (w) 262-784-8401 (f) 414-349-0468 (cell) -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://fireball.firesprinkler.org/mailman/private/sprinklerforum/attachments/20120511/0cdf6405/attachment.html> _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum
