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Old 07-10-2010, 10:46 AM   #1
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EPDM - flat roof to sloped roof transition


Here is my situation. I have a 12x40 rectangular flat roof that is met on all sides by a slate roof. I want to install a new EPDM flat roof. The water runs off the long ends...that is flat roof is highest in the middle and slopes to the 40 foot sides.

Here is my question: how do I properly terminate/flash the epdm flat roof where it meets the sloped slate roof? My first thought had the layering of material like this: wood plank roof deck, ice/water shield, insulation board, copper flashing 4" on boar, 4" on slate roof, EPDM. Problem is the EPDM would now be adhered to copper and don't know how to properly terminate it. Concerned that it will peel off the copper over time (will clean copper with acetone first, as per Firestone EPDM guidelines).

Another way to flash would be to put the copper ON TOP of EPDM and then use lap seam over the EPDM and copper with lap sealant, but problem here is that given slope of roof, this would create a "mini-dam" as water would run off and meet the lap seam and thus pool.

Any thoughts??? Thank you in advance!

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Old 07-10-2010, 11:28 AM   #2
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EPDM - flat roof to sloped roof transition


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... layering of material like this: wood plank roof deck, ice/water shield, insulation board, copper flashing 4" on boar, 4" on slate roof, EPDM...
First, I would start by leaving out the ice/water shield. You don't need it; it's an unnecessary, huge expense; and you'd be creating a double vapor barrier.

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Old 07-10-2010, 11:41 AM   #3
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EPDM - flat roof to sloped roof transition


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First, I would start by leaving out the ice/water shield. You don't need it; it's an unnecessary, huge expense; and you'd be creating a double vapor barrier.
I don't mind the expense and at a minimum, should I use it at the perimeter, say 3 feet from the edges?? if water ever did find it's way under epdm and beyond the flashing, this would protect from leaks, no??

thanks!
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Old 07-10-2010, 02:27 PM   #4
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EPDM - flat roof to sloped roof transition


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I don't mind the expense and at a minimum, should I use it at the perimeter, say 3 feet from the edges?? if water ever did find it's way under epdm and beyond the flashing, this would protect from leaks, no??

thanks!
I'm not sure I'm visualizing your application correctly. But, for the flat roof section, ice/water would be unnecessary anywhere. Typical installation would be: roof deck; board insulation (as much as possible/practical is better) and the EPDM.
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Old 07-10-2010, 02:45 PM   #5
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EPDM - flat roof to sloped roof transition


You don't want the I&WS under the EPDM. Any asphaltic material will degrade the EPDM.

If I understand your dilemma, you've got a slate roof in place with a new EPDM roof being installed below the slate. You need to remove several courses of slate, lay the EPDM and re-install the slate over it. You could use a copper flashing under the slate and over the rubber, but you'd have to remove slate to install the copper correctly and then strip the copper onto the rubber with uncured tape so there'd be no backup under the copper. Just more steps and materials for the same results.
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Old 07-10-2010, 04:23 PM   #6
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EPDM - flat roof to sloped roof transition


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You don't want the I&WS under the EPDM. Any asphaltic material will degrade the EPDM.

If I understand your dilemma, you've got a slate roof in place with a new EPDM roof being installed below the slate. You need to remove several courses of slate, lay the EPDM and re-install the slate over it. You could use a copper flashing under the slate and over the rubber, but you'd have to remove slate to install the copper correctly and then strip the copper onto the rubber with uncured tape so there'd be no backup under the copper. Just more steps and materials for the same results.

Actually, it is the other way around. the flat roof is the highest point and water sheds down on to the slate roof. at this point, order I am considering is roof deck, ice water shield, insulation board, copper flashing and finally epdm. I would lap the ice/water shield over the slate and the copper flashing would cover it and top slate. the epdm would adhere to the copper. this is my problem. I know that having the epdm adhered to copper with no termination is probably not best way to do this but have not come up with better alternative.

one idea i had was as stated in first post: adhere epdm around and under the edge of the insulation board, then copper flashing over this and hanging down over the slate roof and then use lap seam to join the copper flashing and the epdm layer under it. problem here is that it will create a "mini-dam" as water runs off this edge onto the slate roof.

i have looked online for hours and have not found anything on how to do this. must be better way than my ideas. currently, there is a metal galvinized roof that hangs over the edge and to this layers of torch down roof have been adhered. the edge is also not terminated per se but it has held down and not lifted off the metal roof. not sure i'd have same luck with epdm sticking to copper flashing.

many thanks for suggestions!
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Old 07-10-2010, 05:36 PM   #7
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EPDM - flat roof to sloped roof transition


Don't put I&WS under EPDM.

The proper detail for this is: Sheathing, insulation or recovery board, EPDM fully adhered and cut long enough to lap over the top of the slate. Install the copper transition flashing screwed or nailed through the epdm and recovery board. Then strip the flashing back into the epdm with flashing tape. I'd also use seam tape under the copper flashing.

Nail copper strips through the slate just above where the bottom of the transition flashing will be. After the flashing is in place, bend the strips back around the bottom of the flashing by 1/2" or so. Solder or rivet them to the flashing to secure the bottom.
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Old 07-11-2010, 08:19 AM   #8
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Don't put I&WS under EPDM.

The proper detail for this is: Sheathing, insulation or recovery board, EPDM fully adhered and cut long enough to lap over the top of the slate. Install the copper transition flashing screwed or nailed through the epdm and recovery board. Then strip the flashing back into the epdm with flashing tape. I'd also use seam tape under the copper flashing.

Nail copper strips through the slate just above where the bottom of the transition flashing will be. After the flashing is in place, bend the strips back around the bottom of the flashing by 1/2" or so. Solder or rivet them to the flashing to secure the bottom.

Thanks for the advice. So you think that stripping the copper flashing (which sits ON TOP of epdm membrane) is better than adhering to copper from top?? My issue is that if I strip the copper flashing on flat roof, it will create a "mini-dam" as residual water will not shed off flat roof. I assume I would also use seam caulking at this strip, further raising the "mini-dam". My concern is that water will pool at edge over time. This is definitely more secure, but will not allow water to run off. Compare to this order at the edge:

sheathing, ice/water shiuled, insulation board, 1 foot strip of epdm over and adhered to slate, copper flashing, epdm lapped over edge of flashing and adhered to flashing. I'd also put a bead of caulking over edge to further hold epdm to copper and prevent it from lifting up.

so trade off is "mini-dam" in your methodology compared to epdm coming up off copper in my order. which is the lesser evil do you think??

thanks again for the input!
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Old 07-11-2010, 12:59 PM   #9
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EPDM - flat roof to sloped roof transition


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Originally Posted by emtaboy View Post
Thanks for the advice. So you think that stripping the copper flashing (which sits ON TOP of epdm membrane) is better than adhering to copper from top?? My issue is that if I strip the copper flashing on flat roof, it will create a "mini-dam" as residual water will not shed off flat roof. I assume I would also use seam caulking at this strip, further raising the "mini-dam". My concern is that water will pool at edge over time. This is definitely more secure, but will not allow water to run off. Compare to this order at the edge:

sheathing, ice/water shiuled, insulation board, 1 foot strip of epdm over and adhered to slate, copper flashing, epdm lapped over edge of flashing and adhered to flashing. I'd also put a bead of caulking over edge to further hold epdm to copper and prevent it from lifting up.

so trade off is "mini-dam" in your methodology compared to epdm coming up off copper in my order. which is the lesser evil do you think??

thanks again for the input!
Only one manufacturer (Mulehide) approves the detail you want to use. All others require doing it as I described. I have tried the method you describe for the reason you're concerned about and have had trouble with it over time.

I repeat "do not put I&WS under EPDM" without venting the epdm with one way vents.

And the slight "dam" that you'll be creating will hold maybe what? 1/4" of water? The rule of thumb for a low pitch roof is anything that will evaporate in 48 hours is acceptable.
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Old 07-12-2010, 10:03 AM   #10
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EPDM - flat roof to sloped roof transition


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Only one manufacturer (Mulehide) approves the detail you want to use. All others require doing it as I described. I have tried the method you describe for the reason you're concerned about and have had trouble with it over time.

I repeat "do not put I&WS under EPDM" without venting the epdm with one way vents.

And the slight "dam" that you'll be creating will hold maybe what? 1/4" of water? The rule of thumb for a low pitch roof is anything that will evaporate in 48 hours is acceptable.

thanks again for your input. why is putting i&ws under the insulation board be a bad thing?? I realize that it is a vapor barrier that will slow the flow of heat out of attic but how is it a bad thing?? will it cause the epdm to bubble?? having an almost water-proof layer under the insulation board would be a good thing to have I would surmise, notwithstanding fact that water should never get there if flat epdm roof is installed properly.

thanks again for your time and for sharing your expertise!
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Old 07-12-2010, 10:16 AM   #11
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thanks again for your input. why is putting i&ws under the insulation board be a bad thing?? I realize that it is a vapor barrier that will slow the flow of heat out of attic but how is it a bad thing?? will it cause the epdm to bubble?? having an almost water-proof layer under the insulation board would be a good thing to have I would surmise, notwithstanding fact that water should never get there if flat epdm roof is installed properly.

thanks again for your time and for sharing your expertise!
There is asphalt in the I&WS. As it dries the asphalt gas it releases will condense on and degrade the EPDM from below. Belt and suspenders is good in some cases, but not this one. If you want to use a second layer of defense, use a synthetic underlayment, but not I&WS.

Venting is required if EPDM is installed over any sort of asphaltic product.
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Old 07-12-2010, 10:46 AM   #12
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EPDM - flat roof to sloped roof transition


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There is asphalt in the I&WS. As it dries the asphalt gas it releases will condense on and degrade the EPDM from below. Belt and suspenders is good in some cases, but not this one. If you want to use a second layer of defense, use a synthetic underlayment, but not I&WS.

Venting is required if EPDM is installed over any sort of asphaltic product.

I see....very good info to know! Thanks again. Given what you have told me I think your method is the best to follow!!
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Old 07-14-2010, 01:12 AM   #13
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EPDM - flat roof to sloped roof transition


the epdm runoff will burn untreated copper edgings,I would recommend using zinc coated copper if you`re going that route

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