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Roof Decking Being Used For Support

Roof Decking Being Used For Support

Roof Decking Being Used For Support

During an inspecting of a commercial project I noticed the acoustical ceiling contractor had screwed fasteners into the roof deck for his supports. I can not find anywhere in code that doesn't allow the contractor to support the ceiling grid system from the roof decking however I can't imagine this is acceptable. I have been on many projects where the Design Professional stated this in the Structural Notes or in the specifications however I can not find anything listed like that for this project. I have researched the IBC, SDI and ASTM 636 (ceiling grid installation)with no luck. The decking is 20ga and maybe its allowed however on most jobs I inspect the contractors always use the bar joist for support.


RE: Roof Decking Being Used For Support

There was a thread here recently that touched on this topic thread507-450112: Interior stud framing

If there is nothing in the specs that prohibit this, then I don't think there is much you can do unless someone is willing to pay the contractor for the re-work. I would be taking a close look at this though, particularly the fasteners. What fasteners did they use and do they have a pull-out capacity for 20Ga steel? Was the deck designed for the additional dead load?

RE: Roof Decking Being Used For Support

Not only that, but what about the length of the fasteners and their effect on the roofing material above?

Mike McCann, PE, SE (WA)

RE: Roof Decking Being Used For Support

a) Acoustical ceiling is pretty light so load capacity on the deck isn't an issue
b) Screw fastenings to the bottom flange of the deck don't extend 1 1/2" (or the deck depth) to extend beyond the upper deck flange.
c) I've seen this done many times and have never seen a note stating it is not allowed.

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RE: Roof Decking Being Used For Support

From a delegated designer's point of view, the decking is "Structure by EOR," so unless there is something in the general notes or specs that limits the attachments to the deck (as Canpro said), it sounds like you're stuck with it. If you have access to the older CISCA documents (I believe the ASTM 636 is based on these older documents), there are some prescriptive options for attaching to metal deck - because it was shown there, it has become standard practice by the framers and they won't hesitate to anchor to a metal deck unless they are directed not to.

Msquared48's comment is a concern; for this reason we try to avoid attaching to metal deck when we can but sometimes we aren't left with very many options.


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