# green roof, EPDM, how much glue, and whatnot



## Sparticle (Nov 1, 2004)

Starting on the green roof. The joists are up, soon the plywood. The EPDM(pond liner) goes on the plywood. Wondering how much glue/adhesive to use. Some company folks say to use their special stuff($$$$$$$$) and roll it all over. I'm wondering if all that's necessary. The roof pitch is 5%. Where's the rubber gonna go? It's not gonna fly away is it? Why not glue and tape at the seems and liberal application in the middle and be done with it? Anybody used EPDM? Also, our EPDM is the kind with the fleece on one side. They call it fleece backed. It is supposed to be stronger, I think. What do you know? Thanks very much.


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## Darren (May 10, 2002)

Sparticle said:


> Starting on the green roof. The joists are up, soon the plywood. The EPDM(pond liner) goes on the plywood. Wondering how much glue/adhesive to use. Some company folks say to use their special stuff($$$$$$$$) and roll it all over. I'm wondering if all that's necessary. The roof pitch is 5%. Where's the rubber gonna go? It's not gonna fly away is it? Why not glue and tape at the seems and liberal application in the middle and be done with it? Anybody used EPDM? Also, our EPDM is the kind with the fleece on one side. They call it fleece backed. It is supposed to be stronger, I think. What do you know? Thanks very much.


The EPDM I've seen on flatroofs has to be glued down. Rolled. Then the next section is glued and overlapped. Then rolled. The differences in the warranty all pertain to how much wind resistance the installation has. Wider overlaps and more screws in the insulation underneath are some of the things that get a warranty of 20 years rather than 15 years.

BTW EPDM roofing is a system. You have to use their glue to get the warranty. Keep your receipts.


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## Sparticle (Nov 1, 2004)

Thanks Darren. We're gonna glue it down, just didn't know if it was reallt necessary to glue every square inch down or not.


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## City Bound (Jan 24, 2009)

I don't see why you would need glue at all. i would just drape it over the side and nail it down to side of the house.


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## Darren (May 10, 2002)

City Bound said:


> I don't see why you would need glue at all. i would just drape it over the side and nail it down to side of the house.


That depends on the size of the roof and the width and length of the EDPM used. Wind blowing over a surface will lift the material up. With a big enough sheet (no overlap/seams) you might get away with your idea until a bad windstorm rips the whole thing off.

Roofers who work with that stuff are focused on gluing every square inch and getting the seams right. FWIW, the EPDM goes up and over the parapet wall where it's fastened and they still glue the hell out of it. They also glue down reinforcements at corners and other places. On top of that they use a special caulk and seal all of the seam and reinforcement edges.

Roofing is a tough job. Getting it right requires dedication to detail.

The commercial systems like Firestone or Carlisle include everything needed to install a roof. The EPDM is only one component.


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## Curtis B (Aug 15, 2008)

Darren said:


> That depends on the size of the roof and the width and length of the EDPM used. Wind blowing over a surface will lift the material up. With a big enough sheet (no overlap/seams) you might get away with your idea until a bad windstorm rips the whole thing off.
> 
> Roofers who work with that stuff are focused on gluing every square inch and getting the seams right. FWIW, the EPDM goes up and over the parapet wall where it's fastened and they still glue the hell out of it. They also glue down reinforcements at corners and other places. On top of that they use a special caulk and seal all of the seam and reinforcement edges.
> 
> ...


:thumb::thumb::thumb: Spot on. If the op would like, I think I still have pictures of the roof of a building where they did not glue it down properly.

For the record, I hate fully adheared roofs, they never seem to last like they are supposed to.


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## Darren (May 10, 2002)

They can always be damaged. Flat roofs usually have walk pads in areas where maintenance needs to get to roof top equipment. Locally a wind storm tore a piece of sheet metal loose and it cut the EPDM roofing in over forty places on a school. Personally I 'd go with metal.

I'd also make sure I only used EPDM designed for use as roofing. If it's done right those roofs can last way beyond what you'd guess from the warranty.


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## Sparticle (Nov 1, 2004)

This is a green/living roof. It will have 3-4 inches of growing medium on it. We're gonna glue but I don't think we'll glue every square inch. They'll be insulation and a drainage mat on the EPDM as well.


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## PlicketyCat (Jul 14, 2010)

We did a green roof on project build and it was fully reclaimed materials. So the EPDM really was a salvaged pond liner  Ergo, no warranties and whatnot to worry about.

Anyway, we ended up using a rubberized contact cement on the sheathing, rolled out extremely thinly like you do with laminate. Took a lot of time, but not a lot of adhesive, so it didn't cost that much even though the adhesive was on the spendy side. We did overlap any seams at least 6" and slathered sealant under and over it. Then we fixed the edges with screwed-down cleats, but that was more to hold the growing medium in place than to keep the membrane from lifting up in the wind.


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## Sparticle (Nov 1, 2004)

Thanks PlicketyCat. We got the EPDM used to from craigslist. Its got the felt on it. Did yours have felt? Any other words of wisdom for first timers on a green roof?


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## PlicketyCat (Jul 14, 2010)

Ours wasn't fuzzy on the back, but it felt like there might be some sort of webbing embedded in it (for tear strength maybe).

My advice for green roofs, hmmm.

1. It's heavier than you think (unless you're using only perlite/vermiculite), make sure your roof framing and decking are up to the task. No way is a 2x6 rafter 16" oc with 5/8" decking going to hold up! Consider deeper rafters, thicker decking and/or adding purlins.

2. Consider your climate. If you have cold winters and aren't insulating the rafter bays (or need even more R-factor) rigid foam insulation beneath the EPDM will work MUCH better than any amount of insulation put on top of the membrane because wet insulation doesn't work well. Soil has marginal R-value in a thin layer, great retention when massed (berm/subterranean) but not so much a few inches thick on the roof where most of your heat gets lost.

3. Consider installing a soft underlayment first. Splinters, fasteners and hardware can easily snag, puncture and wear through EPDM. Bad enough to patch it during installation, do you really want to remove all the plants and soil to search for a tiny leaking puncture from a nailhead later?

4. And consider a root block over the EPDM or you might end up with the same problem as in #3 and a web of roots growing into your roof/through your ceiling!

5. Gutters and dams are your friends. You want a dam at the edge to keep your growth medium from eroding off the roof and to keep water from just rushing out of the soil**, but you need to design in breaks that empty into gutters so you don't have too much water standing on the roof or flooding over the dams and down the eaves.

6. Consider an **absorption layer over the EPDM that will trap a *small* amount of water under the growth medium so you don't end up having to water your roof all the time.

7. Plant species that are native to your area and tolerate your climate conditions, AND that don't require a lot of maintenance... you don't want to have to water/mow/prune/trim your roof all the time unless you have easy access and it's a pretty flat roof. Non-native Sedums are another option, as they are hardy, low water plants that tolerate full sun and don't growth very big.

8. If you plan to use or access your green roof a lot... design some hardscape paths so you aren't sliding on foliage, damaging the plants or compacting the growth medium.


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## Brady (Jun 23, 2011)

As a weatherization tech for Clackamas Co. in Oregon I installed many doz. EPDM roofs on manufactured homes. First we screwed down 3" foam boards over the entire roof. Then the rubber sheet(s) goes over the top. Then the entire perimeter is screwed to the vertical sides of the home with butyl backed metal strips. I have since moved on to greener pastures but have never heard of any of the hundreds of roofs the county has installed coming up or off. This was not felt backed nor was it glued down.


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## Darren (May 10, 2002)

Brady said:


> As a weatherization tech for Clackamas Co. in Oregon I installed many doz. EPDM roofs on manufactured homes. First we screwed down 3" foam boards over the entire roof. Then the rubber sheet(s) goes over the top. Then the entire perimeter is screwed to the vertical sides of the home with butyl backed metal strips. I have since moved on to greener pastures but have never heard of any of the hundreds of roofs the county has installed coming up or off. This was not felt backed nor was it glued down.


My original response was based on a regular flat roof installation found on a non-residential structure. That's diiferent than what the OP is doing. Different situations. Different requirements.


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## jdhopkins (Aug 4, 2011)

Great thread! I am so glad I found this forum and also this particular thread as we're gathering details to possibly put a green roof on our new home. This has answered many questions already, but I know I'll have more!

Thanks PlicketyCat for the list of suggestions. I had overlooked/not thought of the need for an absorbing layer to hold some of the moisture. Good point


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## Sparticle (Nov 1, 2004)

What might work as an absorption layer? We're using Enkadrain over the EPDM.


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## PyroDon (Jul 30, 2006)

EPDM get the epdm contact glue no rolling needed cheaper than most glues and made for the stuff any decent roofing suppy should be able to get it for you they can also get you seam tape and primer . Do it right of you'll be wasting a lot of money. 
That sadi EPDM is a very simple system no need to make it harder than it is . 10x50 45 mi,, rolls here cost $215.00 including tax , glue is $100 for five gallons, seam tape $125 a 100ft roll,and primer $45 a gallon (goes a long way) 
I hate to think what your paying a square ft for pond liner epdm roofing run 20 cent a ft for 45 mil 40 cents for 65mil and 70 cents a ft for 65 reenforced .
glueing it down is simple lay it out where you want it fold half of it back over its self , roll out the contact glue on both the rubber and the decking ( heres a hint screw the decking down rather than nail it. nails work there way up and will cause problem in a couple years)once the glue is non tacky use a piece of pipe to roll the fold and glued rubber unto the decking. then you can either broom it dowm or roll it fold the other half and repeat the process .
Ive been putting this stuff on roofs for better than 20 years and never had a problem,even the first ones still look like they are new


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## PyroDon (Jul 30, 2006)

City Bound said:


> I don't see why you would need glue at all. i would just drape it over the side and nail it down to side of the house.


Because if you dont glue it down and wind ever does get under it you have one giant woopy cushion, Ive had to do repairs where DIYrs thought they would save the money and do without the glue.
drove in one drive way to see the entire carport roof looking like a huge bubble ready to pop but we were having 40mph winds that day


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## PlicketyCat (Jul 14, 2010)

Sparticle said:


> What might work as an absorption layer? We're using Enkadrain over the EPDM.


We used tight woven coir mats (doormats to be precise) for the absorption layer on our project building. Worked like a charm and are still going strong several years later.


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## Sparticle (Nov 1, 2004)

Thanks folks. Great information here.

Got the EPDM on the roof. The rolls are 10 foot wide. We took it up in 37' lengths and laid it down. Got 3 pieces up there, blocks and 2x12's holding them down, no glue at all yet. Had a serious storm yesterday, lots of driving rain and hail and wind. Didn't see any leaks, even around the Solatube! That EPDM is great stuff.


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## jdhopkins (Aug 4, 2011)

Continuing to do research for greening our rooftop over our car port. Love the idea from PlicketyCat about using coir mats. Had a couple of friends over who are Indianapolis roofing contractors yesterday and was talking with them about this idea. Our car port often shaded by the roof of other parts of the house so it doesn't always get the strong sun. Could the coir mats lead to a mold problem?


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## jdhopkins (Aug 4, 2011)

jdhopkins said:


> Continuing to do research for greening our rooftop over our car port. Love the idea from PlicketyCat about using coir mats. Had a couple of friends over who are Minneapolis roofing contractors yesterday and was talking with them about this idea. Our car port often shaded by the roof of other parts of the house so it doesn't always get the strong sun. Could the coir mats lead to a mold problem?


Update to my earlier post:After more research learned that coir mats are naturally resistant to mold. So this could be a great option!


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