Tar & Gravel Vs. Modified Bitumen ($13k Or $7k) ?? - Roofing/Siding - DIY Home Improvement | DIYChatroom

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Old 10-06-2006, 11:34 PM   #1
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Tar & Gravel vs. Modified Bitumen ($13k or $7k) ??

I got two bids on new flat roof in S.F. Calif and I am puzzled.
1st is 4-ply class A, one layer Malarkey UDL modified base sheet and 3 layers#11 Type IV fiberglass ply sheets hot mopped together. All walls are 2 ply with the Malarkey base sheet and a single layer Certainteed Poly SMS sheet also hot mopped together. The roof will be surfaced complete with a coating of hot asphalt and new gravel. (this is the type roof I have now 20years old & leaking).
2nd is New Mop on Modified Bitumen Roof System, 1 ply Glas Base sheet 28lbs (nailed or spot Mop)per 100s/f area, asphalt solid mopping 25lbs 100s/f and 1 ply Flintlastic roll roofing 100lbs (Granule one side of Membrane).
Both systems will have new metal galvanized flashing, drain outlet, roof jacks and chimney set installed.
The tar & gravel will give 5year guarantee, cost is $13,375. Reputable firm.
The Modified Bitumen give 7 year guarantee, cost is $6,960. BBB Honor Roll.
My question is which is a better roofing system?
Any help would be greatly appreciated.


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Old 10-07-2006, 08:41 AM   #2
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That is a 3 ply. The base sheet does not count as a roofing ply.

Flintastic is not roll roofing. It modified bitumen.

IMO, the Built up with gravel is a much better roof if properly installed. Asphalt BUR's can klast 40 years with proper maintenance, once again, if properly installed. Usually, the flashings will fail first (around 20 years) and must be repaired. But, if the field was done right, and excessive leakage has not deteriorated the substrate, can be repaired back into service.

I would suggest that biannual maintenance be performed to clean debris from the roof, check for possible problems, and remedy small issues before they become big issues. Lack of these checkups is one of the biggest contributors to the need to replace a low slope roof. The reason for the price difference is in the quality and the $$$ needed to 0btain it. You could do a BUR once in 40 years, or that mod bit spec 2-3 times at a lower rate today.

With inflation, the cheaper roof is usually more expensive overall.


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Last edited by AaronB; 10-07-2006 at 08:50 AM.
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Old 10-07-2006, 09:29 PM   #3
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the BUR is much better. have you considerd going single ply such as EPDM ? that has taken over the northeast, and the weather can be pretty bad here.

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Old 10-09-2006, 03:42 PM   #4
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Thank you for the good advice. I'll get a few more bids and make a decision.
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Old 10-09-2006, 03:43 PM   #5
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I don't know what EPDM is but I will look in to it. Thanks
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Old 10-09-2006, 04:52 PM   #6
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Originally Posted by Roscoe View Post
I don't know what EPDM is but I will look in to it. Thanks
It's a "rubber roof".
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Old 10-10-2006, 08:34 AM   #7
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What Aaron said.


Maintenance, Maintenance, Maintenance.

Without it a 20 year roof will last maybe 10 before problems develop.

Then you'll be calling your contractor complaining that he sold you a 20 year roof that's leaking at 10.

A good commercial contractor will tell you that maintenance is key to best performance.

Whenever I sell a re-roof, a maintenance package is offered at the end of the job.

"why should I pay for maintenance when I just paid you $$$$ for the new roof?"

See Above.


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