Flat roof replacement dilemma!

I’m sorry. Technically it goes beyond my grasp. So I am very grateful for professional input. Are you saying 2 ply Mod-Bit torchdown for the gutter? Would it help if I posted the bid here?

Need a SQ FT price on deck replacement in that estimate.

Thank you! Is there an ISO your would recommend?

Not sure what your total insulation needs are, but always use 2 layers staggered to reduce thermal breaks. Iso has an R rating of 7 per inch.

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We never install only GTA over base sheet. Our standard torch applied roofing system is nailed ventilated certainteed yossemity base, and one layer of sta (smooth torch applied) then coated. Our recommended roof is 3 ply, 1 base, 1 smooth, and one GTA (granulated torch applied) cap sheet, no maintenance required.

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If it were mine I would definitely go with the EPDM. I would tear off old roofing material down to ISO board then anywhere there was evidence of a previous leak I would tear on down to the decking to check for structural damage. You want this roof to last for 30 to 40 yrs. why chance putting over a deck that could fail in the near future. With that being said, if you got 2 or 3 places leaking dont really see the point in tearing all that ISO board off until the most likely areas are assest. I would not use the torch down for more then one reason. Torch down doesnt last as long and to get full life it will need to be painted white or silver. The potential of a fire. I was on a job one time and unknowingly at the time a nail head was heated, the nail smoldered in the wood for 5 or 6 hours before bursting into flames about 9:00 pm. That’s what the fire department determined the cause as. With the rubber roof lengths and widths you can purchase it in, you could possibly cover the area with no seams.

A torch applied system lasts as long as any other modified roof system. With granulated cap you also don’t need to coat it with aluminum. If you use APP you can also get granulated cap sheets but smooth caps which need coated are more common.

Insulation R-value is 5.7 per inch for ISO. It used to be 7 a long time ago but they keep lowering it. 4 inches gives a total R-value of 22.8. If you spend a lot on heating and cooling you will notice the difference with more insulation. You can skip it completely on the garage unless it is heated.

Really didn’t want to get into the LTTR - off gassing calculations or the whole R value make up starting with the interior air film. You get a little better rating with a foil facing.

Wow, this gets technically way over my head. I am so sorry. I don’t even have enough technical base knowledge to ask intelligent questions, much less evaluate the responses. I was sort of just hoping for point-and-shoot consensus, but with so many options, I guess many preferences and viewpoints are to be expected.

In layman’s terms, I can only say there doesn’t seem to be much up there. Maybe that’s expectable for mid-century modern “post-and-beam” architecture. I remember my mom saying, if the beams ever went, it would be the end of the house. So when they tear off the roof, I’ve thought I should have the beams checked.

Core sample results were: “You have your EPDM membrane, then below that you have 2.5” of ISO board, then you have your tongue-and-groove ceiling inside/next.”

ISO choices given on the estimates were 1/2, 1", 2" or 4". Should I add one of these to the estimate?

Thank you.

When you get into the specifying end of it, it can get technical. Live / dead loads, wind loads, bar joist span, deck profile / gauge, Total R calculations, interior humidity, heating / cooling degree days, yada yada yada . Lifetime roof would be a 60 mil reinforced epdm, fully adhered with solvent based adhesive, vapor vented, over iso insulation. I can get a 40 year NDL warranty with that system.

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Here are photos, if it helps!

Very nice. Love the back yard!

Thank you! My father was a mid-century architect. He built the house in 1958. It is small by today’s standards, and land values around here are such that if it changed hands it would be a teardown. When I die, it will go to my sister, who is pledged to preserve it. There’s also a very tiny studio house my parents built in 1950 and lived in before building this house, and it needs electrical update, HVAC, flooring, etc. And there’s a free-standing garage. All of which need roofing!

I feel great loyalty to my father’s memory and pressure to preserve his dreams intact. However, I don’t have much money to work with, and can’t afford expensive roofing mistakes.

Sorry…more information than needed probably, just background info, for what it’s worth…


You can do most, if not all of that work…

Mod bit is fine. But the danger of fire is high. The roofer would need open flame insurance and that’s REALLY expensive so some guys don’t get it. Stay away from them. If you want a 40 yr roof go with 60 mil EPDM fully adhered over 4” of ISO foam insulation. R value is about 5.5 per inch. Try to hire someone who is EPDM certified by the EPDM manufacturer. Also, write in the contract that you’ll be holding back X number of dollars for a month or so. This way you’ll have time to make sure the job is done properly. Make sure they show proof of liability insurance as well.

One nice feature of EPDM is that if it does get damaged or punctured by a branch or something it can be patched in a few minutes the same way you patch a bicycle tire tube. It’s a good roof as long as the installer is good.

If someone handed me a contract that said I had to wait 30+ days for payment to see if my roof was done properly I would tell them to find another contractor. They should do their due diligence to make an educated decision and then pay their bill. That is why they should hire contractors with a good track record in their area. The longer customers hold your money the more reasons they try to find not to pay their bill.


They would have to pay at least 90% immediately but a hold back of about 10% is normal. Around here, in a commercial situation, often they’ll give a deposit but the balance doesn’t get paid for 30 days anyway. No reason a residential customer can’t do a small holdback considering how many loser hack roofers are out there. As for finding a good and competent roofer to begin with, it’s often difficult. Many times people are told to hire this company or that one, only to end up going through hell with them. How is a consumer to really know?

No , its not.

No reputable Roofing company would do that.
Unless they were willing to work for a general contractor/ new construction/ remodeler which does everything to hold back your money because they are always broke needing a draw to pay you…

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