Coal Tar Pitch Vs Asphalt For Dead Flat Roof

 
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Old 07-27-2017, 11:43 PM   #1
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Coal Tar Pitch Vs Asphalt For Dead Flat Roof


I've read a few posts on this forum mentioning Tar and Gravel as still being a good choice for a durable roof vs the newer tech stuff like torch down and TPO. I currently have a 41 year old 4 ply dead flat CTP roof that's still holding its own, even though it has about 2" of water pressing down on it for 3 months of the year in winter. I've agonized over the different re-roofing choices, all of which require adding a 1/4" per foot slope, which is not a trivial undertaking. After reading an article from the Whole Building Design Guide (WBDG) explaining how CTP doesn't have solvents that dissolve in water like asphalt, I'm thinking why argue with proven success.

I'm just beginning the process of finding a contractor, there's still a few up here in Northern Idaho that do BUR, but I'm not getting a very comforting feeling. When I asked the first guy for CTP, he didn't even know what I was referring to while claiming he's been in business for 25 years and still does numerous BUR using type 2 and 3 kegs on dead flat roofs. I also contacted Durapax about local distributors of their CTP products, but no luck. So my question for you pros is this: how bad of a choice would 4 ply asphalt/gravel be for my situation? I don't expect 41 years, but would 25 to 30 be out of the question? I can still get the CTP shipped by Durapax, but I'm going to guess that just the shipping cost of 1300 SF of 4 ply is going to be prohibitive. Thanks!
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Old 07-28-2017, 12:00 AM   #2
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Re: Coal Tar Pitch Vs Asphalt For Dead Flat Roof


Better beef up your framing.
where are you at? What type of contracting do you Do?


I'll give one bit of advice here. Tear it off and taper with insulation.

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Old 07-28-2017, 01:36 AM   #3
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Re: Coal Tar Pitch Vs Asphalt For Dead Flat Roof


I just had my roof done with spray foam, doesn't require a perfectly sloped surface.
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Old 07-28-2017, 08:12 AM   #4
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Re: Coal Tar Pitch Vs Asphalt For Dead Flat Roof


1300 sf?
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Old 07-28-2017, 12:38 PM   #5
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Re: Coal Tar Pitch Vs Asphalt For Dead Flat Roof


Sorry folks, I wasn't very clear with my question, sometimes too much detail clouds the issue. What I'm asking is, from your experience, would asphalt tar provide a reasonable life, say 15 to 20 years, on a properly applied 4 ply dead flat roof with gravel? I already know that coal tar will do it, but I may have a problem sourcing it in my area. And if I can get away with not having to slope my existing roof, I've reduced the amount of work needed by a ton.

Thanks to those who responded so far. I'm in a rural area, north of Sandpoint, Idaho. I'm a project manager for a mechanical supply and installation company, mainly sawmill and mining related. Don't need to strengthen my roof joists, any new material will be the same or less weight than what I have now. Spray foam isn't going to work, about 450 SF of the 1300 square foot total is over my attached garage, and I have a hot tub up there, so there's some regular foot traffic.
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Old 07-28-2017, 12:54 PM   #6
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Re: Coal Tar Pitch Vs Asphalt For Dead Flat Roof


Quote:
Originally Posted by SilentR View Post
Sorry folks, I wasn't very clear with my question, sometimes too much detail clouds the issue. What I'm asking is, from your experience, would asphalt tar provide a reasonable life, say 15 to 20 years, on a properly applied 4 ply dead flat roof with gravel? I already know that coal tar will do it, but I may have a problem sourcing it in my area. And if I can get away with not having to slope my existing roof, I've reduced the amount of work needed by a ton.

Thanks to those who responded so far. I'm in a rural area, north of Sandpoint, Idaho. I'm a project manager for a mechanical supply and installation company, mainly sawmill and mining related. Don't need to strengthen my roof joists, any new material will be the same or less weight than what I have now. Spray foam isn't going to work, about 450 SF of the 1300 square foot total is over my attached garage, and I have a hot tub up there, so there's some regular foot traffic.
Tear it off and install a tapered insulation system and a fully adhered single ply

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