Unique Roofing System

[Guastavino]

See below pics. Any ideas on the specs/type of system that is? Bulb tees at 32" o/c over Steel wide flange beams. Mid-atlantic state in US, likely 20-30 years old. I DON'T think it's tectum, but I could be wrong if they had some old system.

From Below at a roof opening. You can see the panel edge cut, a bulb tee and the typical underside.

From above

Also, the original roof was a built-up ballasted roof. They removed and replaced with a spray on roof, see below. It makes me think that these panels may not have the uplift capability anymore too, as the original designer likely counted on the ballast to hold these light-weight panels down? Anyone seen this system before?

 

[XR250]

Might be a gypsum panel product. I encountered that on a job a few years ago in RTP area of NC.
Can't remember the details

 

[Guastavino]

XR, I bet it's in the same cluster of buildings because this is in RTP too.

 

[jike]

I could be a gyp. roof. The ones I worked with typically had bulb tees at 32" oc. Only way to confirm would be to core thru roof. Should have form board + gyp.

 

[Ron]

Agree with jike. Probably poured in place gypsum on formboard between bulb tees. Uplift resistance was pretty good on those systems.

The SPUF roof "covering" is not a good combination for gypsum decks. Both will hold water and SPUFs are notorious for leaking a long time before it shows......increases load!

 

[EZBuilding]

I agree with what has been posted before. I still don't understand how uplift wind loads are transferred to the bulb tees from the gypsum deck. Friction appears to be the only available mechanism.

Had a couple of renovation projects with this type of roof deck recently. Here are a couple good links to get you started:

http://d3110379.u38.hosting-advantage.com/wp-content/uploads/2013/12/NRDCA-500.pdf

http://rci-online.org/wp-content/uploads/2012-10-hogan.pdf

 

[XR250]

XR, I bet it's in the same cluster of buildings because this is in RTP too.

Nice. We should have lunch sometime

 

[jgailla]

Were they still using gypsum roof decks in the late 1980s?
I thought gypsum was mostly phased out by 1980. Almost all of the gypsum decks I've seen are between 1950 and 1970.

 

[Guastavino]

@XR250, haha yes...
@jgailla, turns out I was wrong on the date. Your timeframe is more accurate I believe.

Thanks to all.

Lastly, they butt-welded the curb support angles to the flange of the W8x10 beams. Does anyone else spec RTU frames that way? I typically require welding a plate in.