sedum mat for green roof - source needed

19 years ago

Does anyone know of a source in the US for the type of lightweight sedum mats used in Europe for green roofs?

The material is planted with sedum starts and comes in rolls. You waterproof your roof with plastic, then roll out the sedum mat and fasten it down. Voila!

But I can only find mention of a project that used the sedum matting in a joint Us-Canada venture on some green roof installation at a border crossing. No source in US or Canada. Lots of English and European sellers, tho'.

Thanks.

Ginger

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Comments (7)

leftwood
19 years ago
Reading your bio, I can't imagine you would want preplanted sedums - ones that are not cultivars you picked out yourself. But for a business, what a cool and easy quick solution!

The lightweight material I suspect would limit the plant species used: only the most drought resistant, like cactus, semps and sedums. Unfortunately, don't have any sources.

We have one member in our Rock Garden Society who does have a green shed roof. Don't know what medium they used, but their species are much more diverse: sedum, sempervivum, dianthus, talinum, penstemon, etc.-alpines. It's complete with a small carved wooden goat. Most excellent. Anyone that may be coming to the central region Conifer Society meeting (June 24-26,2005) in Minneapolis will have a chance to see it.

Rick
abgardeneer
19 years ago
Hey, sounds like just the spot for roof iris, Iris tectorum!
Unfortunately, I didn't find them to be hardy here when I tried them a couple of times in the past - maybe zone 4 though?
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It must feel great now that you have set the wheels in motion! If your goals are to enjoy some of the enviornmental and personal benefits of planting something green on the rooftop without investing in and maximizing all the horticultural and engineering standards of a self-sustaining living roof, then any growing medium you use for sedums would serve the purpose and may be even succeed for the long-term. However, instead of using a mix of coir and compost, a simple mix made of 75% inorganic (of what you already have) and 25% organic components (or less, 7%) may proof even more advantageous since similar growing medium recommendations (b/t 60-80% mineral materials) have been corroborated by various academic and commercial sources for growing rooftop sedums and/or building an Extensive Green Roof such as yours (with less than 6" of growing media) based on my cursory read. Your final choice of growing medium made of all/mostly coir and worm castings are all organic and thus will compact and shrink over time unable to deliver nutrients and provide the needed aeration, drainage, and plant support while leaving the roots of plants exposed and causing plant degeneration or death. Moreover, many sedums do better in poor sandy soil and don't do well in fertile soil. A few studies also showed a few specific varieties of sedums thriving and covering a given area faster comparatively when less or a certain fertilizer was used. Any potential discharge of N, P, and other metals from green roofs is likely to be reduced considerably by using the minimal amount of fertilizer needed to maintain plant health when growing succulents such as stonecrop. A few green roof studies (using specific modular or commercial systems) published by Michigan State and Southern Illinois University may be of interest to you. There is one more academic source with similar findings as SIU which I can't recall at the moment. You may also want to reference the only internationally recognized German FLL guidelines for building and maintaining green roofs when looking for answers or suppliers and contractors. How high up are you? Will wind and water retention be relevant challenges in securing either your grower and potting mix in any way? You may want to consider using some type of a biodegradable, one-quarter inch mesh to cover the surface of the flat in the first year (or recycle plastic mesh you may already have). This material functions similarly to mulching and plastic cover or landscape fabric I mentioned previously and will hold the growing medium and also serve to prevent loss of water through evaporation and enhance nighttime condensation during the initial growing season. BTW, SIU found pumice to be the top growing medium out of four other types tested for growing two varieties of sedums when using a brandname modular rooftop block. Hope to see you succeed at the top :)
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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 http://hortweb.cas.psu.edu/research/greenroofcenter/research.html. 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
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leftwood
19 years ago
Even if they didn't bloom, the foliage of the Japanese Roof Iris is quite pleasing. Iris tectorum is hardy in zone 4a where I am, but doubt if it would be on a roof here. I had thought hard if there were any iris of any kind on my member friend's roof, but couldn't picture any. So I left it off the list. Even in zone 4 NH, I don't think tectorum would be roof hardy. A good, hardy pumila or setosa might do well, even though setosa prefers more moisture.

Zone envy, you, ABgardeneer to grow Japanese roof iris at all, me to grow it on a roof.

Funny thing about tectorum. I had the straight species and the alba form. A few years back in another snowless winter, the species croaked, and the alba was happy as a clam (I mean iris). Isn't Iris tectorum native to Japan AND Korea? I wonder if the alba was of Korean providence, and the species plant I had was of Japan(and less hardy).

Rick

P.S. Sorry about hijacking your thread, Ginger.
ginger_nh
Original Author
19 years ago
Rick and ABGardener-
Thanks for your answers. I found mention of a sedum mat today trade-named "RoofRug" by a US company. It was mentioned on their site in a paragraph describing installations, but is no where else on their site. I e-mailed them asking about sedum varieties, dimensions, cost, etc. and am waiting for a reply. Other than that, no dice. This is a product readily available in Europe.

Most greenroofs are engineered to the point that they are un-doable w/o a lot of $$$and expertise. I'd like to figure out a simple, DIY methos. I am trying to experiment on my own garden shed roof, will be taking digital photos to record the installation and maintenance over a year or so. If successful, I would like to add the sedum roof to the services we offer in my gardening business. This would be greenroofing primarily for aesthetic purposes, for wildlife, and perhaps for insulation if the small building were a studio or other building that is heated or cooled.

In looking at the many photos of greenroofs on the WWW, I find that aesthetically I only like the low groundcover plantings for the application I have in mind. Other plants look too weedy. Also, sedums are comparatively low-maintenace and can withstand drought.

If the pre-planted mat works out, my next effort would be to set up my own system of moisture barriers and soil/medium layers, then plant with perhaps a single variety of sedum.

Anyway, the sedum mat seemed like a nifty idea. Hope I can locate a source somewhere.

I think roof iris would be a bit more fussy than sedums--needs more water, fleshier, heavier root system, hardiness is in question--you don't see it around here, Whereas sedums last forever here - they like benign neglect. Just right for a difficult-to-tend roof garden. Might be nice to try a few along the gutter edge, though.

Rick-
Does your fellow Rock Garden member have photos of his or her roof posted on the internet anywhere? I would like to see it. Sounds like Heidi's grandfather's cottage.

Ginger
leftwood
19 years ago
My roof growing (?) friends do not have a computer. And silly me, last time I was there I didn't have a camera. But in June I will be there for sure, and get lots of pics of that and other things I'll be posting. But it is a shed in the truist sense. No paint, very rustic.
Rick
ginger_nh
Original Author
19 years ago
Rick-
Thanks for the response. I will look forward to seeing the photos. Nice thread you started on troughs--maybe this will be the year I actually make a hypertufa.
G.
eden_in_me
18 years ago
Wonder how iris cristata would go on a roof. It is exceptionally fast growiing in the ground here.

Marie

sedum mat for green roof - source needed

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sedum mat for green roof - source needed

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