# Mystery Roofing System



## rmacleod (Jun 14, 2010)

I am preparing drawings for a roof replacement project and the test cuts of the roof revealed a material that no one can identify.

Under the existing EPDM membrane and a layer of ISO is the original built-up roof. Below this top surface of the built-up roof there is a black foam material that varies in thickness. The roofer that performed the test cuts had seen it before, but could not identify it by name. I can’t find anyone else who has seen it before.

It is a very ridged material (it can’t be bent or depressed without breaking) that breaks up into small pieces fairly easily. The structure is open celled and it has a very strong smell of sulfur. It was applied over a paper barrier that was laid over the metal deck.

The building is almost 50 years old and is in Massachusetts.
I would appreciate it if anyone can help me solve this mystery.


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## BornaRoofer (Oct 28, 2008)

Cinder concrete is a low-quality, light weight, structural concrete that utilizes cinders as the primary aggregate. A commonly employed mix is one part cement, two parts sand, and five parts cinder. Cinder aggregate is a by-product of coal combustion and it is highly porous and cellular in nature. Cinder concretes have also been used as sloped fills over normal-weight concrete. Some cinder concretes have high sulfur contents, which are deleterious to steel.
Hope this helps.


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## rmacleod (Jun 14, 2010)

This does not look like a concrete based product. It is easily penetrated with a screwdriver and looks like a hardened black foam.


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## BornaRoofer (Oct 28, 2008)

Correct. Its more like a pumice or slag. It was used back in the day as way to slope/insulate flat decks cheaply.
If you see in my last post most of the material is cinder or slag not cement.
The sulfur smell is from the coal byproducts. I have seen it many times here in detroit on the car plants under coal tar roofs unfortunately.


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## rmacleod (Jun 14, 2010)

Ok, I can see this as being some sort of slag. It does looks a lot like pumice. If there is sand in it then the grain of the sand must be very fine or it has been dissolved in the manufacturing process -- there is no sand or any aggregate type of material visible.

I will add a photo so you can see it.
Thanks for the help.

You mentioned that this material is deleterious to steel. What damage should I expect when we remove the system? There is a paper separation sheet between the slag material and the metal deck so hopefully it has been spared, but we do have dunnage that would be in contact with it as it penetrates the roof system.


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## rmacleod (Jun 14, 2010)

*Mystery Solved:*

The Product is Foamglas. It is manufactured by Pittsburgh Corning and is made up of small glass cells. It can operate in extreme temperatures and appears to be mostly used for industrial insulations, although it looks like it is used in building construction in Europe.
http://www.edcmag.com/Articles/Cover_Story/0bfaf305e7697010VgnVCM100000f932a8c0
www.foamglasinsulation.com/
http://www.urecon.com/applications/industrial_field.html


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## BornaRoofer (Oct 28, 2008)

That foamglas is a different than what I had originally pictured. 
Im glad you figured it out.


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## Ed the Roofer (Sep 15, 2008)

Foamglass was big 30 or so years ago for fire ratings and also the tapered system they provided.

It will chew the chit out of your clothes, gloves and any knives you use.

The last on I worked on was on an Illinois Bell telephone building housing all of their computers and had a concrete deck and we use a Bobcat to scoop up the tear-off from the deck.

Every one of those old foam-glass jobs were mopped with coal tar pitch instead of asphalt for the roofing felt plies, but they were mopped in over a primed deck with asphalt.

It smells like rotten egg sulphur too.

Watch out for getting it in your eyes. It's very abrasive.

Ed


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## SinglePlyGuy (Jan 7, 2009)

fartboard!


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## RooferJim (Oct 20, 2008)

FoamGlass. that stuff was used on a lot of the roofs around Boston "smells" . There are a lot of strange insulation types out there. ever ripped cork board ?

RooferJim
www.jbennetteroofing.com


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