What type of roof decking is this?

[SteelPE]

Below are two pictures taken while onsite of some existing roof decking. I am wondering what type of deck it is, and if there are any available data as the the capacities of this type of decking?

The first picture is a cross section of the decking, the second picture is how it's attached to the structure.

I scratched the material with my fingernail and it has the consistency of gypsum, so I believe it's some type of panelized gyp decking. Any information is appreciated.

 

[RickyTickyTavi]

Gypsum roof decks I normally see in buildings from the 40's and 50's. I dont see them too often as, from my understanding, once theyve deteriorated and allowed for water infiltration; they deteriorate quite quickly thereafter. I'm not super familiar with the construction, but the two or three I've seen had a panel backer system,and then a poured topping, similiar to plaster of paris. subsequently, a roofing membrane was placed ontop. The few buildings ive seen it in, it was outright replaced. I know there are tables out there for its capacity as I have seen them in the past.. but I cant point to a specific place.

Here's a link I found on generally repairing it.

http://loadmaster.net/?page_id=754

 

[SteelPE]

It doesn't look like it was poured in place as there is nothing on the bottom of the panel that would have stopped the gypsum from falling through the roof (unless form work was removed). The little hooks of the panels to the beam make it look like the panel was place as a solid unit during construction (not poured in place). I would add that this roof is located in the North East of the US.

It looks almost exactly like the insulrock system in the attached document (see page 6). The clips look the same (although they look like the joist clips) and the tongue and groove system looks similar. However, my spans are about 6'-0" o.c. which is much greater than the allowable spans shown.

 

[Ron]

Pictures are a bit too close to get the context of the decking. Could be one of the panelized gypsum systems or a variant of a Tectum system with some coating on the bottom. Attachment clip is consistent with Tectum-like material.

 

[SteelPE]

I thought the pictures were pretty good. The entire roof is painted black so getting pictures is extremely difficult. It does look like some sort of premanufactured gypsum type decking. In picture #1 you can see the metal tongue and grove joint. The panels are approximately 2'-3' wide across the building.

 

[Ron]

SteelPE...Sorry...now I get the photo!

Here's a link to MidCon Products...they produce something similar.

MidCon

Also, two other potential sources....SlideRuleEra's website and US Gypsum's Website.

The clip showing is typical of these systems; whether, cementitious plank, AAC plank, gypsum plank or Tectum.

 

[EngineeringEric]

Gypsum Panel Decking. Do not walk on that roof... they can be very dangerous if the gyp has gotten wet at all. I have seen a guys leg fall through and stories of complete fall through leading to broken bodies.... i don't mess with it!

If you are adding load, don't add it to the decking. Give yourself a structure ontop of the roof down to the support and penetrate the gyp. at supports. Possibly recommend that they plan on replacing the decking before the life of the roof is up or really keep up on maintenance.

 

[SteelPE]

The roof panel system is in really good shape.... however, my work is part of a renovation that is taking weight off the roof (removing stone ballast and using an adhered system). They are also demolishing 1/4 of the building for additional parking. Code is IBC 2015 and IEBC 2015. I am going fishing to see if I can get them to replace the roof with a IEBC requirement (wind speed is 124 mph and they are re roofing so they need to comply with 403.8 of the IEBC.... and I don't thing the existing roof decking complies with this section as there is no diaphragm capacity in that decking).

We will see how it turns out. I am usually the bad guy in this situation.

 

[Ron]

SteelPE....being the bad guy is usually a good thing!