Is there a product out there for unballasted coal tar roof?
Brett,
Your question is rather vague. Please explain further.
Thanks
I’ve been asked to specify a coal tar pitch low-slope roof. Very antiquated but anyway. But the client does not want any gravel surfacing so I am looking for a coal tar roof with some type of mineral cap sheet or other surfacing material. I’ve never heard of such a thing. We are trying to talk him into a 2-ply mod. bit. instead but he is hung up on the coal tar. so then we suggested specifying the coal tar as an alternate just to look at pricing. Nope, he now wants us to specify the coal tar as a contractors option to the mod. bit. In the end I think it will be a futile excerise.
I spent a couple of years doing full-time onsite observation of coal tar and asphalt built-up roofing.
Coal tar is nasty stuff. The fumes make your throat and lungs hurt and leaves your skin with a sunburned appearance.
Aside from that, it is just about the best low-slope roofing. I’ve examined 50-year old coal tar roofs that are still in good condition. Probably have asbestos fabric flashing too.
Koppers, the only manufacturer of coal-tar I know that is still in business, says that because of the low melting point, you must have an aggregate surface. Even on a cool day you can’t walk on it without picking it up on your shoes and it is darned near impossible to get it off anything it gets on.
I have seen a couple of built-up asphalt roofs with a flood coat surface. Walking on them can be a little dicey on a hot sunny day.
The cooling effect of light-colored aggregate surface probably adds a lot to the life to the roof.
Another comapny I found is called Durapax. Both Durapax and Koppers are out of Pennsylvania. Both require gravel surfacing for heat control and UV resistance. I may have run into a dead end.
Coal tar has two unique advantages (as opposed to, say, asphalt)-- one is that it is insoluble in water. (Asphalt is slightly soluble, due a totally different chemistry.) And the other – due to its low melting point, it’s self-healing; it will flow at normal roof temperatures to plug any leak that might develop. Of course, that trait also makes it necessary to cover it up…
It may be more than the Owner has in mind, but in the past I think I’ve seen coal tar used under Styrofoam in an “Irma” roof, with a paver walk surface over that. The foam tends to keep the tar from getting as hot and sticky, and the pavers keep it off your shoes. Used to be a company that coated Styrofoam with a thin layer of concrete for a walk surface.
And I’ve heard that the old Gulf Building in downtown Houston had coal tar on top of a concrete roof slab, and was in turn covered by another concrete slab. Encapsulated in concrete, if you will. That roof has lasted from the 1930s – pretty long for a roof membrane.
Well, OK, those are both ballasted, but at least they’re alternatives to loose gravel…
“Used to be a company that coated Styrofoam with a thin layer of concrete for a walk surface.”
It is now called Lightguard or Heavyguard by TClear Corporation out of Hamilton Ohio. Formally by Dow called Roofmate CT.
Yes, TClear–that’s the name I was trying to remember…thanks.
Last I heard, coal tar roofs were pretty much banned because coal tar is a known carcinogenic.
I know it was officially banned in NYC and I don’t see any coal tar roofs in California.
I think I heard on the news recently that coal tar roofs are not banned yet–they just can’t be labeled “light” or “low tar” anymore…
Back to Brett’s original question…seems I heard a few years ago that there was a coal-tar-based modified bitumen membrane system. Is that still around? Anyone remember who produced it? Koppers? Allied Chemical?
How about Hyload’s “CTEM” (Coal Tar Elastomeric Membrane) technology, which offers the benefits of coal tar in a cold-applied application? The coal tar is bonded to DuPont Elvaloy (KEE) membrane, which has uncoated selvages that are heat welded. This system combines single-ply membrane & coal tar in a single product.
I have spec’d the waterproofing version of this system. There is also a roofing system available, which I understand can be covered w/ aggregate surfacing, liquid coatings, or left alone.
These are some great products you guys. Thanks so much for your input! Maybe it could work after all.
Allied Chemical stopped making modified bitumen sheets with coal tar in the late 90’s.
Having placed a coal tar roof on my house I am interested in the technology. Did some digging and low and behold Garland is listing “Millennium Coal-Tar-Based Technologies” as a product they offer.