I've done a few torch-down flat roofs when my crew included a welder who was quite used to dealing with scary amounts of heat. But I've seen too many flat roofs put down without an intervening protective membrane to feel confident in suggesting that method.

I plan to use 1/2 or 1 inch of polyico over the deck, then EPDM fully adhered to the polyico. In this situation, Would the color of the EPDM make much difference on heat?

Also, given the very small slope (1/8 inch per foot which could lead to potential puddling) do you think the seams in torch down would not hold up more than a handful of years?

1/8 inch per foot

Specs I've seen call for 1/4 in.

Worth, I agree. However, the house is 62 years old and they did things differently. Do you have any information regarding whether a torchdown would hold up over time?

Flat roofs, no matter how you do them, require slopes of more than 1/8". If the slope is less, you should make provision for drainage. (Commercial "living" roofs can be made theoretically watertight. But that's another matter.)

From the" EPDM Roofing Association FAQs:

"How can drainage be enhanced on a flat roofing installation or roofs with 1/8 inch per foot or less slope?

In addition to the number and size of roof drains, drains should be positioned in low areas to eliminate ponded areas. Also, crickets and saddles may be incorporated to divert water and reduce the accumulation of water. If necessary, tapered insulation may be incorporated throughout the roof or in localized areas where additional drainage is needed. "

Thanks Worthy. These are standard techniques for most commercial type installations. For a small residential roof, we are not going to be adding scuppers, special drains, automatic siphons, etc.

The slope of my roof (1/8 inch per foot) is lower than many roofing manufacurers recommend (1/4 inch per foot). Does anyone have practical experience regarding whether a torch down (modified bitumen) type roof would still work for a decent amount of time? (I am worried that there is some chance that after the installation described in an earlier messge, there will be some small amount of puddling; puddles perhaps 1/8 inch deep)

lower than many roofing manufac[t]urers recommend

Can you name one that says 1/8" is ok?

Instead of doing it wrong and worrying whether you can beat the odds of it failing prematurely, consider doing it right from the start and sleeping better.

FWIW, every contractor/inspector continuously comes across improper and substandard work that hasn't failed--yet.

Here is a link that might be useful: Building a slope on a small flat roof

Hi - My DH is a commercial roofer with 26 years experience. I'm typing this as he tells me what to pass along as his typing skills are ...

First things first. Yes!! You absolutely need to have tapered polyiso insulation added. Without it you're opening yourself up to a lot of problems, not the least of which is the added weight of ponding water on the structure.

As for you choice of products, much of it depends of the visibilty of the roof from the ground, upstairs windows etc. Most TPO roofs can look very nice, especially when there are no penetrations to have to flash. The draw back is it is not available to most contractors in less than full roll qty. It also requires the installer to have equipment/knowledge specific to this type of roof.

If visibilty of the roof is not a factor, a black EPDM membrane will be very serviceable. EPDM is more readily available in smaller sizes and so should be less costly. Fully adhered would be the best choice.

Torchdown, though effective, would be the least desirable IMHO. Playing with that amount of heat on an older structure is just not a good idea when other options are available. We just had an historical structure in our area burn to the ground from this very thing.

Sorry this is so long winded. My DH sees a lot of mis-applied roofs and fixes poorly detailed ones all the time. Make sure you choose a reputable firm and insist that you have a Certificate of Insurance proving their insurance coverages.

EPDM can go to zero pitch, and it installed this way all the time commercially.

It will even work with the small random puddling this produces without a problem.

The water will not accumulate higher than the edge of the roof.

Thanks all! You have provided me with a great education. It sounds like I have the following options:
1. Build up the slope from 1/8 to 1/4 inch per foot and use Torch down. (The reason I am still thinking about torch down is that the best local guy uses it and does not offer the newer materials and the skill and attention of the installer is most important. Also, it is about half the price of EPDM).
2. Build up the slope from 1/8 to 1/4 inch per foot and use EPDM.
3. Do not build up the slope and use EPDM, thereby saving $1,100 from number 2.
4. Do not build up slope and use either PVC or TPO (in order of quality), since these materials can withstand ponding for many years.

Considering that none of the local roofers I spoke with offer PVC, and TPO is 17% more expensive than EPDM (based on one quote), EPDM is probably the choice. I now need to decide:

(a) If it is worth spending $1,100 for the tapered polyico insulation; (Brickeyee says this would be OK, if I understand correctly, but Danvirsse implies that I should increase the slope)
(b) Whether the heat gain from the black color of EPDM is significant, or just exagerated? (I'm told that the white EPDM does not last as long, as evidenced by the warrantee being only 10 years vs. 20 for the black); and
(c) Is it OK to put the polyico over the existing tin roof without tearing it off? This would be followed by a rigid decking material such as 1/2 inch plywood, then fully adhered EPDM.

I tend to use something that's flat when I am constructing a flat roof.

Hi, my house also has a flat roof. I have to renovate the hydro insulation this spring, but I would like to be able to install a decking in the future. Is EPDM strong enough, to endure a permanent load on top of it, even in hot days? I was thinking to put a bitumen, but I am not so sure any more of which is the best choice. If it makes any difference, I can say that the previous insulation was double-component (cemet-looking powder, plus some white liquid). Thanks