due to pre existing conditions & a bank of three windows that I cannot change I’m participating in the unthinkable here in the Northwest
I’ll have a 14′ X 17′ section of flat roof coming off the side of a house then 4 in 12 slope off three sides ( two hips )
thinking EPDM but have never used it on roof ( not a walking deck )
what say you & is there a combo 1/2″ cushion insulation layer one can put between plywood sheathing & the epdm to help w/ its durability etc..?
should I do two layers? built in UV protection ?
thanks, John
Replies
We use them a lot here in MN. Never heard of doing two layers. One would last a good long time. When the first one went bad, how much would you really gain having a second layer under there? It isn't like you could just sit and watch the top layer disintigrate. You'd want to change it, but you'd have to pull both. Plus, not even sure how well it would work. When fresh contact cement hits rubber, it stretches from the solvent. So if you put contact cement on the first layer, it would expand some, and then you'd probably have wrinkles. I dunno for sure, but it just doesn't seem like a great idea.
We often put down a layer of fiberboard (aka beaver board, insulite, builtrite) and glue to that. This outfit has a how-to booklet somewhere on their website.http://www.rubberall.com/
I think he is confused. When edpm is installed it requires a layer of cushion between it and the wood. At least that is how I interpret the post.
>>>>When edpm is installed it requires a layer of cushion between it and the wood.Not necessarily. EPDM can be adhered to fresh plywood or osb. The cushion is added for reroofs if there might be splinters, nails or other imperfections in the sheathing.View Image
Not according to the guys that used to sell me roofing, of course that was years ago>G<
EPDM only needs a clean smooth solid surface to adhere to.The word 'cushion' bothers me as it should not be too soft or cushy. deflection from walking on it should not happen or that degrades the roofing.recovery board or insulation boards get used more often when there is old material sheathing or the presence of bituminous stuff left over that is incompatible with EPDMBut it is not a definite requirement.I can see an installer making it a requirement on all his work if he had been bit one time by a bad substrate
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It may not be an absolute requirement, but I would require on a roof I would do.>G<
>>>>>>>>>is there a combo 1/2" cushion insulation layer one can put between plywood sheathing & the epdm to help w/ its durability etc..?
You can use 1/2" "recovery" board which is typically used under membranes on reroofs to protect the membrane from any imperfections in the old sheathing. Or for insulation, polyiso sheets are available for this application. I'm not sure if 1/2" is available (I've never used it), but 1" is as well as tapered if you need to increase the slope.
>>>>>should I do two layers? built in UV protection ?
I wouldn't do two layers initially. If the top layer fails, then water will collect between the two layers and degrade the bottom layer quicker.
edit: my epdm rep's name is John Harkins.
Edited 9/12/2008 8:41 pm ET by seeyou
john,
EPDM has a high degree of UV resistance and among the common modes of failure, UV deterioration is not one of them. So two layers isn't going to provide you any benefit for UV protection.
Assuming this roof won't see any significant traffic, I would use 1/2" wood fiberboard, mechanically fastened, as a substrate, then glue the membrane to the FB.
1/2" Polyiso is available as a recovery board, but in practice, it can easily compress and break under normal construction traffic during installation.
You cannot convey tone in an email.
what is looking like my best bet is promoting GenFlex TPO
thermoplastic polyolefin single ply roofing systemswith a name like that it is lookin like it is meant to be
thanks, john
Sure, sure, get me all excited about EPDM and then switch hit onme....!;)how's a name like Ethel Propel Diene Monimer grab yah? ( er something like that)
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it can easily compress and break under normal construction traffic during installation.Yes indeed.....unless you've got a really good plan to get it on, and get the roof on, and keep everyone other than the roofers away, and have really good roofers, you can end up with a whole lot of dimples ion your new roof......that often have to be fixed to keep the warranty...
don't ask me how I know this....
Two layers - my guess is you're wasting your money there.
Putting the roofing over insulation is standard ... up to 10+ inches of rigid insulation.
EDPM and hypalon roofings are made for sun exposure ... no worries w/ U-V issues.
A small roof like yours may be done in a single sheet ... yay!
It's not unthinkable in the northwest, either ... done ALL THE TIME ...
with that acronym I get nothing but looks of cluelessnesstwo layers of torchdown is common approach and to find someone conversant in singleply membrane is a reach
thanks to everyone for their input
We do a little TPO. It's a little slicker than EPDM and will have more seams in it.View Image