EPDM roofing in Canada?
October 3, 2015 5:41 PM   Subscribe

We are creating a new roof on a small 100 sq ft house addition with a slight slope, almost flat but not quite. Should we go for an EPDM roof?

Where I come from, most people get flat roofs torched on, but I've heard of EPDM products that just unroll and stick...

Would this kind of product work in a GTA climate?
Does it require special installation techniques?
Is the GAF brand a reasonable product?
posted by ovvl to Home & Garden (7 answers total)
 
Response by poster: (oh, with spray foam insulation on the ceiling)
posted by ovvl at 5:46 PM on October 3, 2015


I know GAF more for residential shingle roofs than single-ply, and it appears they don't make EPDM (at least for the US market), but do make TPO and PVC. I'm in Wisconsin, and we use TPO and EPDM all the time. There are versions of each that are self-adhering. TPO will most definitely involve some special construction methods, and is probably out of your league.

Here's the webpage for Firestone's self-adhering EPDM product - you can go to the "specs" tab and download the application to see what installation involves.

One thing you may want to consider is that you'll only be using a very small portion of any product you buy. TPO at least comes in 10'x100' rolls, EPDM should be about the same. Both are intended for very large roofs where the speed of their installation makes them much more economical than an asphaltic (tar, torchdown) type of roof. I don't know that going with EPDM over asphalt really gets you anything.
posted by LionIndex at 7:46 PM on October 3, 2015


Best answer: My climate is nothing like yours, I am in the SE US, but I am involved with quite a bit of roofing work as a design professional. Most of the reputable roofers won't do a torch down modified bitumen roof on a wooden structure. (ModBit is the kind that is torched down. It can also be adhered with adhesive or installed with hot asphalt - think stinky asphalt kettle.) There is also a "peel and stick" Mod bit. One thing all have in common is multiple plies, even the peel and stick wants a nailed down base sheet.
It is a good sturdy system, tolerant of abuse, not tolerant of poor drainage or slopes of less than 1:48.
ModBit has been loosing market share to single ply membranes - of which EPDM is one, for many years as the single piles are cheaper - fewer layers. The other advantage is the single ply membranes tend to be more tolerant of standing water from poor slope and drainage.
Down here in the south we don't see much EPDM because it is black. Heat gain is not something we want. I understand it is much more prevalent in the north. It is a good system as long as it is an adhered system - the failures I have seen were ballasted (held down by stones) systems. Seaming can be an issue and is where it typically fails. It takes care to get a decent adhesive bond between the pieces, and the material shrinks a bit as it ages, causing strain on these lap joints. If it is covered with rocks, it is hard to find the bad seam. GAF is a respected manuf. of this product, as is Carlisle and some others.
In these parts, PVC is most prevalent now. It is heat welded together. If done properly, the seams are stronger than the material.
You can get it in colors but for obvious reasons big commercial jobs here use white. It can be glued down, or mechanically attached. The 60 mil thick sheet is the way to go. Don't use thinner, thicker is a waste of money and hard to work with. One really great thing about PVC is it is easy to roof difficult details.
I have a couple of small areas on my house, a porch with a bitumen roof of some kind, and an addition with shingles that doesn't slope enough for shingles. Both are going to get PVC when the time comes.
The installer should be certified by the manufacturer for the system they are installing, what ever it is. And crews that are good with one type of system may not be so good with something they don't use as much.
Make sure that the membrane covers the edge of the wall - if it is a drip edge situation, PVC has PVC coated metal that can be welded to - therefore your guarantee is what is called "edge to edge" If a parapet wall situation, run the membrane up and over the parapet, then you can install metal trim. I strongly advise against TPO roofing - which is sold as a cheaper version of PVC.
Insist on "edge to edge" in the warranty - make the installer provide you with a sample warranty with this specific language in it. The installer should warrant the system for at least two years, I call for five. After that, the manuf. has to pay the installer to fix it, up to the end of the warranty period. 20 years is a typical manuf's warranty. Owner is responsible for any physical damage, properly maintaining the roof (not much there), etc.
Also, get language that the warranty will not be voided by emergency leak repairs.

Spray foam insulation - I hate the stuff, but that's me, it won't affect the the membrane. It will cause higher temperatures in your substrate, and plywood glue has been known to let go over years of elevated temps. It will also mask any leaks, keeping that moisture in your deck. Unvented wood decks are not something I think is a good idea, but spray foam seems to be all the rage now. Consider that somewhere between the cold outside, and the warm interior with all that moisture - people breathing, washing clothes, dishes, themselves, somewhere in that roof/ceiling assembly, it is at dew point temperature. The vapor barrier needs to be as far towards the inside as you can get it. With a roof membrane, now you have another vapor barrier right at the exterior. Not good. In my view, the stuff in between needs to be able to breathe - i.e., be vented.
posted by rudd135 at 7:57 PM on October 3, 2015 [3 favorites]


I stand corrected - I had thought GAF was selling EPDM, but I see that isn't correct. Carlisle sells it, Firestone did and may still.
Again - I strongly advise against TPO. The US Army Corps of Engineers just released a directive that none of their facilities were to use this material unless the facility would be sold or demolished within 10 years.
Here's why
posted by rudd135 at 8:05 PM on October 3, 2015 [1 favorite]


Response by poster: What Is the simplest cost-effective approach for a small flat-ish roof in a Northern Climate?

I know that there are some peel&stick products available, but they might not be the most perfect solution. But if they might work, please recommend.

If the torch is really the only final way to go, then tell me.
posted by ovvl at 9:33 PM on October 3, 2015


That is a really hard question to answer without seeing and knowing the particulars. Like I said, torch-down is not a good choice for wood decks because of the fire risk. We don't know what deck you have, your wind loads, the slope of the roof, and what the local roofers are good at doing.
If you want a good, unvarnished opinion, best path is to find a local roofing consultant who isn't making money form selling you a roof see the "find a member" tab on the right side of the screen.
posted by rudd135 at 11:20 AM on October 4, 2015 [1 favorite]


Response by poster: Thank you for the advice. Where I live in Canada torching is frequently done for flat roofs. There are always risks, but a decent contractor would try to minimize the risks, like sopping down hot spots and keeping an eye on things for a while after the job is done. (there is actually a sad/hilarious story I heard about this, but for another time...)

It's worth hearing a skeptical view about spray-foam, which is a fairly popular recent construction trend here. This project space doesn't have any plumbing, so hopefully moisture issues will be at a minimum. But it's worth keeping in mind.

Thanks for the RCI link.
posted by ovvl at 6:33 PM on October 4, 2015


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