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I’m having my house re roofed. The main roof is shingle 5/12 pitch that has a flat roof connected on the north side. The flat roof has a modified bitumen that is cracked and has some leaks. The contractor is going to go over the existing flat roof with mineral roll roofing. My question is should I allow him to use cold tar or would a hot mop treatment be superior? I should mention that I live in SW Fla. Hot,hot hot!
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Rastagard,
Re-roofing over an existing roof that has failed is, in my experience, a questionable practice.
Likewise for mineral roll roofing over an existing roof.
I'm not saying it won't work, but you might well be better served in the long run by removing the existing roof, flashing the building properly, and going with any of the recent innovations in membrane roofing, such as torch-down with a reflective coating or EPDM. Some of these roofs carry a 50 year manufacturer's warranty.
In any case, on the basis of what you've posted here I think a second opinion from a qualified roofer is in order.
Good Luck,
Dave
*About 15 or so years ago the tar that is used by roofers was changed considerably, particularly the material that comes out of Mexico. I was at a workshop this week in San Antonio with roofers and roofing supply people. When I brought up this subject, they all agreed that what they are getting now isn't holding up as well as the stuff did from 15+ years ago. One MAJOR supplier at the training session stated flat out that this is the reason that sheet goods and built-in-place elastomeric membrane roofs are becoming more popular - they do a good job (some better than others), and they are predictable. In addition one doesn't have some of the other issues related to operating a hot kettle - not a concern for most home owners. With a built-in-place elastomeric roof you can also get lighter colors which will help considerably with your energy bills. A study done in Austin, TX, showed that at noon on a clear, windless day, a black roof typically achieves a surface temperature of 190 degrees F.. On that same type of day a white elastomeric roof will have a surface temperature of approximately 110 degrees F.. It doesn't take a rocket scientist to figure out that an 80 degree temperature difference is going to make a significant difference in cooling requirements.Good luck,Cliff.
*I would be concerned about the additional weight of any roofover on a flat residential roof. With a 5/12 on the main roof and a flat roof atthached to it, I am thinking "addition". What size framing members, what is the span, spacing and sheeting? Lots of questions would need to be answered, but the minimum would be a tare off and then answer the question of what type of repacement.Dave
*:-)brian
*Comparing a cold applied mineral roll roof to a hot mop built up is like comparing an '88 Yugo with 175000 miles (yeah, right) to a 2002 Mercedes 500S. Cold applied mineral roll roof is a joke. Choose the hot applied or reinstall new modified bitumen. Silver coating the roof is critical in hot sunny climates.
*Thanks ya' all, Modified bitumen it is. I am i extremely grateful for this forum. I suspected this would not be the best move. It didn't make sense to put on 30 year shingles with a roof that my limited experience tells me wouldn't hold up nearly as long. Your good sense and experience definitely helped me make a well-informed decision.