Sandy - Green Roof

ademink(z5a-5b Indianapolis)June 18, 2006

Ok, I'm into this green roof idea. I have a few questions. Do you have to install a specific type of roof in order to do this? I'd love to eventually do this to my garden shed roof but it will have to be down the road. Do you have to plan for it in construction or can you pretty much "retro fit" a roof for it?

Do you have pics of yours?

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Me, too, Sandy! I want to hear and see more!


    Bookmark   June 18, 2006 at 9:02AM
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pondmaninfl(z9 FL)

By "Green Roof", are you refering to having grass growing on your roof? I would imagine that you might need to beef up the roof trusses and decking.

I've never done it but have seen pictures and what I'm saying is from a carpenters veiw point. I'm not a carpenter but I am a woodworker and have been around construction all of my life. I have built my own workshops when I lived in Alabama and designed the roofs to handle the weather that they would be subjected to in that area. If I was going to have a green roof, I would use trusses constructed with 2x8's with a 3/4" sub decking using pressure treated plywood then concrete backer board. Then I would put on a layer of rubber roofing and then a layer of landscape fabric. Make sure that you leave a ridge on the edge of the roof to keep the sod from sliding off. I say sod because you might have a problem with keeping topsoil on the roof until the grass could fill in.

This is just the way that I would do it. I'm not saying that it is the right way.


    Bookmark   June 18, 2006 at 11:14PM
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sleeplessinftwayne(z4-5 IND)

Hi guys. This is going to be lo-o-ng.The Greenroof construction was completed last summer and it is beautiful. The project was originally a gleam in the eye of our Ext. Agent and Master Gardener leader who had been reading about the movement in Europe. The only place possible to put it was on the roof of the garden shed behind the Extension building which is on the campus of IUPurdue. I was given the project because I was likely to be the only one crazy enough to try it and also because I lived in an Earthshelter house for 20 years. I don't know how that translated into a retrofit Greenroof but that seems to have affected his reasoning.
The first thing I asked was if the shed had a foundation. The answer was no so I wasn't too positive about getting past that little problem but said I would see what could be done. After about 300 hours of research and 350 pages of printout, construction details,plant selection and math problems I gave the project report and proposal to Our Leader and he presented it to the IUPurdue Committee that has the last word on things like that. They wanted more info. I supplied it. He presented it. They wanted a picture. I painted it. He presented that and they gave their approval. That was what happened the first year.

The next spring I hauled lumber, tools, rubber roofing material (45 mil EPDM by the way), adhesives for rubber roofing, bales of perlite and soilless potting mix and snowfencing in my poor mistreated Geo Prism. The 4x4x10 timbers and concrete almost defeated me. I also had to purchase a multi-purpose folding aluminum ladder. The first step was to reinforce the shed so it would not collapse under the weight of the new roof covering. We(I had the willing assistance of several other MGs who wound up doing the major part of the physical labor while I tried to make sure everyone was on the same page) sank the 4x4s into concrete at each corner of the shed, tied them into the corner studs and installed 6 crossbars between each and every truss. This was truly exhausting as each piece had to be measured and cut individually. Fortunately, the man doing the cutting and measuring is OC so that turned out better than I expected. No nails were used in the construction. Everything was attached with coated exterior grade screws. We used up several bits but they are cheap when it come to this kind of retro fitting. It took several days to finish that part of the job but it was the most important part.

A 2x6 was installed on top of the 4x4s and a bench was built between the 4x4s to add to the structural stability. After we couldn't think of any more ways to beef it up we stripped off the shingles, removed a roof vent and patched the hole, painted the roof with rubber adhesive, built a frame on the outside edges and top of the roof with 2x4s. The inside of the frame was caulked with butyl caulk and the EPDM (roofing rubber) was laid after a second application of adhesive. It was rolled with a brayer(fancy term for a rolling pin) to remove any air bubbles. A layer of capillary cloth was laid down and a frame of PVC was placed inside the wood frame to hold the layer of landscaping cloth that went on next in place. At that point I decided to devise a drain that would carry off excess rainwater and telling my construction crew how to use a hole saw and what a boot does was probably the hardest thing to explain. But, despite the strange looks they gave me, it works fine and looks fine after the PVC pipe was painted to match the shed. Cold weather was closing in so we had to neaten up things and close the project down so the planting mix was left undone till spring. To prevent anything from blowing away we did install the snow fencing and put a finishing edge on top of the whole thing. In the spring we had a line of MGs mixing the perlite and potting mix, filling buckets and passing them to other MGs on the roof who poured it through the snowfencing and spread it out. Some of the more energetic MGs planted sedums, coleus and moss roses through the holes in the fencing and it was done(except for some trim that I can't seem to get cut). Most of the sedums survived the winter but our busy MGs added more this spring. The annuals of course have to be replaced but, they were just for the extra color.

All said there are a few things I would have done differently but they are minor. Our Leader is happy because our roof is the first one in the state. Others are now in the planning stage. The roof has made the local news once and shortly will be shown in a small magazine. I have no idea which one. I couldn't attend the interview. I love to see the faces of people seeing it for the first time during garden walks and tours. It really does terrible things to my already inflated ego.

Problems we ran into were few. The worst was my inability to delegate anything. I would be an instant bankrupt as a contractor. I have to remember there are many ways to the same goal but it is really hard. The second is the time it took. I am a physical disaster and the others are all volunteers who could only be there a couple of hours a week so that slowed things down.

You all are going to force me to finally learn how to use that digital camera. I've managed to put it off since I got hurt but I guess I'm out of excuses. Sandy

    Bookmark   June 19, 2006 at 2:46AM
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zinniachick(southwest Ohio)

Yay Sandy! I've been dying to hear about that since you first mentioned it last year. Thanks for the details. Now, pictures! Is there a website we can check?

Do you think if a shed is built on a slab, that would be enough to hold up a green roof? Given that the roof would have to be entirely reconstructed for this purpose, of course.

    Bookmark   June 19, 2006 at 9:59AM
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jeanner(SW Ohio - Z6)

If you don't get out that camera I might just have to drive up there and get some!

I would like to hear more about your earthshelter too as we need a shed really bad and the only places we have are on a slope so I was thinking of building the shed into the hill rather than on a deck.

    Bookmark   June 19, 2006 at 10:53PM
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sleeplessinftwayne(z4-5 IND)

Lol... You know you're getting old when you make excuses to avoid learning something new. I promised to start posting pics last year and never did get around to it. I will learn how to transfer pics to the computer. Cross my heart.
Jean, it is certainly a do-able project and it has been done for centuries. One of the best current sources I have seen is a manual put out by the U.S. Army. It is amazing the kind of information they put out. The manual I am thinking of is about all sorts of structures a soldier or two can construct for shelter until they can be rescued. They range from the simple to the sublime and all the details are there. It may take a while before I can remember where I put it 5 years ago. (I don't throw away anything that is so interesting.) The only thing I found disturbing was where they thought those soldiers were going to get milled lumber and construction grade plastic sheets if they were lost behind enemy lines. Sandy

    Bookmark   June 20, 2006 at 2:30AM
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hi, sandy! i have also heard of using the metal roof set up and chicken wire to keep a lightweight soil mix in. is this no good? i cant' remember what the wire was attached to exactly.

    Bookmark   June 20, 2006 at 4:13AM
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sleeplessinftwayne(z4-5 IND)

Hey everyone. There are so many sources added to the internet listings since I did the original research that it's hard to point to a short list. In addition, many of the sites have been changed to the point where they are no longer helpful. The most useful site originally was It had some great pictures of the finished sheds they constructed for the research project but most of those have been removed or changed dramatically.
Since shed retrofits are not common I had to do a lot of detail by extrapolation. I couldn't find a civil engineer or local builder to advise me on such things as "load bearing" or "resistance to torque pressures" but since there is more interest in living roofs now that tax incentives are involved you may be able to find someone to help you with that. I erased my list of favorite sites last year and don't have my notes here so I will have to get that info for you later. I did not have to worry about such things as building permits since the shed is on University grounds and they can get away with things a private citizen can't. I would recommend you check your local building codes.
There must be some sort of foundation or reinforcement of the structure if none exists. A slab would be sufficient if the ties to the frame were adequate. Our shed was the cheapest possible construction so we had to do a lot of extra work. The determination of adequate depends on the weight of the load (That is the weight of the planting medium, the weight of the water it holds and the weight of mature plantings per square foot). I can tell you I worked with a figure of 1 1/2 lbs per sq. ft. at 4 inches deep for the weight of the dry planting mix plus a pound for the plant material. The planting mix is 1.5 parts perlite to 1 part soilless potting mix. How much water it holds depends on the materials you use in what proportions. We used mostly sedums. Grasses would more than double the weight load.
We used the 3/4 inch plywood that was the original roof since it was in good condition. The studs and trusses were separated more than normal since it was a cheap shed which was another reason for all the fuss over reinforcement. I didn't see any metal roofing used, FTM. I doubt it would be practical because there might be a chemical reaction with the planting medium and it would be difficult to build a lower rim to prevent sliding. But just because I didn't see it doesn't mean it wouldn't work. Menards carries a rubber roofing system that was perfect for our purpose. They even have a video at $4.99 that shows how to do it although it shows a flat roof and we were working with a pitched roof.
In just about every system I saw there were options on how the construction was done. No two were alike. The only constant was there are three layers.The first layer on top of the rubber is a material that allows for the flow of water UNDER the planting material. I used capillary cloth which just might be flattened by the weight above it. The second layer prevents the bottom layer and the top layer from getting mixed together. I used porous landscaping cloth. The third layer is the planting medium. In addition most systems need something to keep the planting medium in place. That was where the PVC grid and the snowfencing came in. Now obviously plastic snowfencing and capillary cloth, not to mention the EPDM didn't exist when the first sod roofs were built so you can see there is almost an infinite number of ways to do things. So put your imagination to work.
Lots of info when you do a google search on greenroof. Sandy

    Bookmark   June 21, 2006 at 3:26AM
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thanks, sandy! i didn't even know that rubber roofing existed. this was several years ago when i read on metal roofing. i agree with the potential for a reaction. it is possible that the project was only for a mailbox green roof, since i do recall seeing one, and my brain converted it to my shed :)

    Bookmark   June 21, 2006 at 5:11AM
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zinniachick(southwest Ohio)

Scroll down to the links at the bottom of this University of Michigan page. With this utterance I am compelled to add, "Go Buckeyes!"

Here is a link that might be useful: UM greenroof

    Bookmark   June 21, 2006 at 10:36AM
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sleeplessinftwayne(z4-5 IND)

Zinnia, that is a fantastic new (for me)site. The research on the plants is something other sites just skipped over except for one on the west coast that researched only plants for west of the Rockies. UM has often been out front in technologies like this. Thanks for the link.
I thought the Buckeye state was Ohio. :D Sandy

    Bookmark   June 21, 2006 at 2:37PM
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zinniachick(southwest Ohio)

You couldn't expect me to acknowledge something nice about U.M. without concluding with GO BUCKS, now, could you? :)

I never would have thought to put sedums up there. What a cool idea. Someone (was it Jeanner?) recently told me about a home-made hanging sedum ball for the porch. You take two of those coconut-fiber trough liners, fill them with potting mix and then stick them together, wind chicken wire or hardware cloth around them and then poke holes in which to stick sedum plugs. Hang it with a chain.

    Bookmark   June 22, 2006 at 9:07AM
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That is a GREAT site, ZC! This whole topic is interesting. :)


    Bookmark   June 22, 2006 at 10:38AM
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zinniachick(southwest Ohio)

This is an aside, but here's something I'm really interested in. Boy would I love to do away with our driveway and replace it with this lawny, driveable stuff. I'd have just a footpath from the street to the porch, and the rest would be Grasspave. Wouldn't a neighborhood be so much more pleasant if everyone did that? And the runoff we'd spare the storm sewer system... I just get all tingly.

Here is a link that might be useful: grasspave

    Bookmark   June 23, 2006 at 10:12AM
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ademink(z5a-5b Indianapolis)

Oooh, nice!!!!

    Bookmark   June 27, 2006 at 3:04PM
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