Old Gypsum Roof Deck

[PSUEng11]

Hello all,

We came across a project where an older commercial structure had a roof failure after a high wind event. I went to look at it and found that it had about 25% of its newer EPDM roof that had pulled loose. The EPDM roof was fastened directly to a gypsum roof deck. The thing that struck me as odd was that the gypsum deck was not the typical poured decking. Instead it was a paneled decking, with approximately 36"x18"x4" panels laided tight against one another. The panels spanned 3' to the bulb tees, which spanned approximately 6'-8" to the bar joists. The EPDM roof was fastened directly to the gypsum panels throughout the roof.

Does anyone have any technical information on this style gypsum roof? I am trying to determine a true method of failure. I am not sure what kind of guides or design information is out there for this product, but any help would be greatly appreciated.

Thank you for your help

 

[bridgebuster]

How did the roof fail? Did the roof pull away from the gypsum or did the gypsum pull away from the framing?

I don't have anything to offer on the gypsum per se, however in 1991-92 I was resident engineer for a similar type of roofing project. The building was an old theatre, constructed in the earlier 20's. We put down 40,000+ SF of EPDM roofing. More than half of the roof deck was gypsum. We replaced a number of sections in-kind, using panels between the purlins then poured gypsum. I don't recall the thicknesses of the panels or gypsum, perhaps 1/2" & 2", respectively.

The membrane was fully adhered to rigid foam insulation. The insulation was attached to the roof with screws. Prior to installation the contractor had to conduct pull out tests of the screws in order for the roofing manufacturer to develop a fastener pattern. The pull out capacity is what's important.