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spray foam roofing

mdler

discuss

 
Jan 13, 09 8:53 pm

i like replacin' it.

all that stuff put on in the 80s played havoc with steel decks - especially the stuff that turned corrosive when exposed to water.

Jan 13, 09 9:10 pm  · 
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Janosh

If you are talking retrofits on existing buildings: Not so good. Although it offers a quick fix for failing built-up roofs and doesn't require landfilling the old plys, once a leak occurs it is very difficult to locate the source (the water can migrate great distances). Facilities people and our waterproofing consultant hate the stuff.

On the other hand, it is very popular with building owners looking to sell...

Jan 13, 09 10:07 pm  · 
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mdler

i was thinking for new constrcution. It seems like it would be a good system; +/- 12" of foam insulation would prevent water from getting through your roof, wouldnt it?

Jan 14, 09 1:39 am  · 
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binary

if you doing flat roofs for commercial... do epdm... i was a roofing inspector for 2 summers and worked on epdm roofs and they are easy to install and clean compared to coal tar pitch and whatever else ish is out there.


you would be surprised how many trees i have seen on roof tops of coal tar roofs.... once you get a crack/crease/etc any little seeds will harvest and grow. not sure on the density and hardness of the spray foam stuff.

Jan 14, 09 2:06 am  · 
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Janosh

Mdler - I think most agree that SFR works great until they start leaking. Pipe penetrations and curbs all just disappear underneath the goo, so detailing is easy. Construction is easier since slopes can be created with just additional foam, so no goofy tapered insulation, sloped framing, rip strips, etc. That said, the leak migration issue is a concern for new construction as well.

Jan 14, 09 2:39 am  · 
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on roof installations, i listen to the more conservative of my clients. e.g., the facilities guys will no longer allow foam on their jobs.

check out the variety of membranes out there. don't just assume epdm. we've had some beautiful epdm jobs; makes for a clean roof. but it's thin and, unless you go for the fiber-reinforced, it can puncture a little more easily than other membranes.

there is, by the way, a white-faced epdm out from firestone now. i'm sure others have it, where it's not a coating but an integral lamination of the material.

check out tpa or similar elvaloy based white membranes. we're liking those right now.

if it's to avoid tapered insulation that you're considering the foam and it's new construction, why not slope the structure? i agree that tapered is too expensive if it can be avoided. sloped structure can make for a little more work in defining bearing elevations sometimes but if you're working in 3d software, even that issue kind of goes away.



Jan 14, 09 7:39 am  · 
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wurdan freo

Steve. I think you mean TPO. There are several manufacturers who make this product. tpo roof system

Jan 14, 09 12:34 pm  · 
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el jeffe

there is a TPA membrane.

Jan 14, 09 12:41 pm  · 
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mdler

how do the foam roofs tend to fail? It seems that the foam would create such a thick barrier that failure would be a non-issue..unless, of course, there is a huge crack

Jan 14, 09 7:38 pm  · 
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yep, that's what i'm talking about, el jeffe. tpo's can be okay, wurdan, but i prefer the ones like tremco's tpa. some of the tpo brands are of the same makeup. just had 'flex' on one job and it's pretty good.

mdler, the foam roof gets a sort of shell at the top surface. the shell is very hard and pretty thick, but it can be penetrated by a nail or a boot heel or a branch - or it can just crack. under that shell, it's all just voids, like a hardened sponge. once the shell is penetrated, water can filter through the voids and, to complicate matters, it doesn't go directly down but can travel some distance and come to the deck in a completely different place.

Jan 14, 09 9:02 pm  · 
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isn't that foam just absolutely dangerous to the environment?

Jan 14, 09 9:10 pm  · 
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le bossman

i thought you were talking about spray in. it can work pretty well with new construction for a roof because it's like make-your-own-sip, and the framers don't have to deal with positioning a heavy-ass sip panel for the roof. if you want to make a sip-panel house, always substitute the spray in cor-bond stuff for the sip. and you don't need to vent it. the framers will marvel at your genius, and you'll save money. some types of foam are dangerous to the environment. others, like icynene, supposedly aren't. but either way the energy performance makes up for the one-time chemical pollution thing to me. thousands of years from now, people will have a completely different concept of ruins when the only thing that remains of our architecture is the foam that once existed in the cavities.

Jan 14, 09 11:10 pm  · 
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mdler

le bossman

have you had a lot of experience with SIPS???

Jan 14, 09 11:24 pm  · 
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asiatic

Spray foams like icynene aren't as bad installed, but there's still plenty of debate about the manufacturing and all the crap that goes into making that stuff...

That said, we use spray foam for roofs all the time in new construction-commercial & residential-obviously to increase the R-value and to reduce thermal breaks. No complaints so far, but then none of our contractors have built shoddy roofs that leak. Have heard though that the foam will pull away from the framing members and that when used with wood framing members the shrinking and twisting of the wood over time may have an impact on the effectiveness of the air barrier.

also, who would put only insulation (spray or rigid) on top of a roof structure w/o a membrane...you should get a new roofing contractor or waterproofing consultant, sounds like you have bigger problems than what type of insulation to use

Jan 15, 09 12:12 am  · 
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Janosh

I think we are talking about Sprayed Polyurethane Foam (SPF) systems, right Mdler? These are intended for use a total insulation and waterproofing system w/ no membrane, and can be applied either directly over deck or in retrofit situations over existing roofing. Icynene is purely an insulation product.

Jan 15, 09 12:54 am  · 
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monkeyboy

wow mdlr!

"+/- 12" of foam insulation would prevent water from getting through your roof, wouldnt it?"

you should know better.

Jan 16, 09 5:52 pm  · 
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le bossman

mdler

i've worked on a few sip-panel homes in my day. why?

Jan 17, 09 2:25 am  · 
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