I’ve searched the archives but cannot find the specific answer to my question.
I’ve framed a low-slope roof for a portico (plywood is not on yet). It’s pitched 1.5″ over 4′. The roof will exposed to the sun for half the day. I understand the tapered insulation could have been used for the slope but I did this with the joists.
My plan is to cover the plywood with Ice and Water shield, potentially add a layer of fiberboard insulation and then a a top layer of synthetic rubber (EPDM). I have two questions:
1. Is the purpose fiberboard insulation to protect the EPDM from contact with the plywood or underlayment? There is not a conditioned space underneath so I’m wondering whether the insulation is needed given that it is already sloped to drain.
2. I will use copper as the drip edge. I’d expect the copper to be fixed to topmost layer below the EPDM and then the EPDM would fold over the edge of the drip edge down the fascia as shown in the attached pic. I’ve seen details where a batten is used with the EPDM folded over insted of a drip edge. Is there a reason I shouldn’t use the attached detail?
I’m not a professional but have done several traditional roofs that are neat and leak free after many years. This is the first time I will do a flat/low-sloped roof and want to do it properly. Any help is appreciated.
Thanks
Replies
Glad you asked first! Lotta corrections to make.
First - do not waste your money on the ice and water shield. It is not compatible with EPDM. off gassing from it may be damaging to the EPDM which is intolerant of many bituminous products. Further, if you did develop a leak in the EPDM, the moisture would be trapped between and never dry, leading to other problems.
So just nail down a base sheet of 30# or coated 43# under your fiberboard.
It is also possible to just glue the EPDM directly to a good smooth plywood surface.
For the edge detail, the EPDM drops over the edge first, then the metal is fastened, then the neoprene flashing is glued and caulked of=ver the metal, but6 not dropping down the face of it.
Welcome to the
Taunton University of Knowledge FHB Campus at Breaktime.
where ...
Excellence is its own reward!
Thank you for setting me straight on this one. It crossed my mind at one point about possible incompatibilities between the materials.
Whoever you are buying the EPDM from should have plenty of detail information too.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
I also recall from yesterday, the way your detail is drawn, it would be possible for water to wick from the bottom edge of the cooper in behind to the plywood sheathing. plan to use a rainboard 1x2 as in mine, or use a longer face on the copper trim
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
yes, I saw that detail in your drawing and was planning on using it. I'm using Azek for the fascia and will add a piece for this.
Thank you
here is an old drawing from my files
Welcome to the
Taunton University of Knowledge FHB Campus at Breaktime.
where ...
Excellence is its own reward!
What is the purpose of the fiberboard insulation in respect to an underlayment for the EPDM?
I take it the asphalt coating would be laid face down against the ply sheathing?
Is the fiberboard mentioned the same as asphalt impregnated fiberboard commonly made by Celotex?
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. snorK*
"Hope and the future for me are not in lawns and cultivated fields, not in towns and cities, but in the impervious and quaking swamps." -Thoreau
No asphalt at all! EPDM is not compatible with a lot of asphaltic or bituminous products.The fibreboard is or should be one of several specifically made for underlayment on roofs and for EPDM. It is firm enough to walk on, adds a slight bit of thermal protection, ( roofs get a very hot surface and can move more than underlying substrate, stressing bonds) and acts to some degree as a slip sheet barrier if there is structural movement under the roof surface. Additionally, it helps if a nail in the roof sheathing turns out to be a shiner and finds a way to back out. The head of said nail would be worrisome for the EPDM princes and princesses.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
The 1/2" insulation should be screwed down using special plates for insulation attachment then this acts as a good base for a fully adhered membrane to be adhered to.
Some folks omit it with a good plywood deck, but it's used on almost any overlay.
Walter
To help get the ball rolling....
I suspect that one purpose of the fiberboard is to cushion the rubber. Rubber on plywood might be more susceptible to damage. But this is my own suspicion...I have no memory of reading or hearing it anywhere. Also, demo of a rubber roof that is glued to fiberboard which is screwed to ply sounds a lot easier than demoing rubber glued to ply. Given the relatively small cost of the fiber board, it seems silly to forgo it.
Your edge detail lacks the termination bar. It would go on top of the rubber that is hanging down. The one problem might be that the term bar screws in contact with the copper might be susceptible to corrosion. There may be alternatives to a term bar, but I am not aware of them.
I would consider the Ice & Water shield to be superfluous. If you do the rubber right, there is no need and if you do the rubber wrong, the Ice & Water doesn't make it right.
Rich Beckman
Coming to the Fest? Don't forget pencils!!!!!!!!!!!!!
No termination strip is necessary if this is a glue down.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!