We'll see how it works. The roof membrane is actually kind of extraordinary. Not a product I've seen before. And the plants are in their own little interlocking cubicles that are set on top of dense padding. So uncovering the roof in an emergency is pretty quick. There is some R-value aspect that plugs into the overall equation, but there isn't much really.
I'd say just from watching the install of both the roof membrane and the plants that the sort of thing that would create a leak would be the sort of thing that would create a leak even if the plants were not up there.
Jorn,
Are you going for the manicured lawn look or a wild prairie look? Either way it will be pretty cool looking.
Mike
Mike Noble
I'd like to hear about the advantages, etc for this type of roof, why you went in this direction, etc.
SPP
As I was looking down, from my closet-sized hotel room, on the green roofs of Munich office buildings, my benefit-of-the-doubt meter swung from experimental to established. Acres of green roof in a place that gets that much precip tells me someone has figured out the weather proofing.
Dan Fuller, local bicycle enthusiast
Hey Pete
Originally the roof itself was going to be made of cross laminated timbers - basically 3-5 layers of 2x4's laid cross-ways to each other and machined into interlocking panels that would make the entire roof. Over the top of that would be the membrane roof layers while the underside would be finished and sealed to create a nice wood ceiling. The advantage of that structure was a built-in finished ceiling and wide expanse of unsupported (no columns) space with a relative thin profile roof.
However, we didn't like the look of the finished product from the company whose product fit our overall budget, and to get the look we wanted, we'd have to spend way too high a percentage of overall budget for the roof materials. Having a roof that was effectively solid was also creating some issues with running wires, roof drainage, calendar and other things. Cement floor and solid roof - where do you put the rest of it?
So instead, the GC, architects and engineer sat down and worked out a conventionally framed roof that had nearly the same thin profile, required only a small handful of columns that could be made into a design element, and solved all the other problems in the meanwhile.
Using a flat roof is because of the design. The roof, however, isn't really flat. The pitch is from a central point and runs in all directions. There actually have to be diverters on the roof to keep the flow of rain and/or melt water away from areas like exit/entry doors so people don't get drenched. So the flow is really very good off the roof - either off the outer lip or through the internal gutter system.
The roof was sheathed over the framing, that was covered with a black material (a type of house wrap material I think?) & a layer after that I believe, then this white membrane material that is super strong and (on one side) super sticky. That was rolled out over the roof on one of those "okay just roof today no one else" tense kind of work days, fixed in place and seam sealed. 3 layers total over the wood unless I mixed up the ordering. The advantage to this roof material was that the weight fit the engineering requirements for what we were doing inside the house, plus it met the hydrostatic requirements for freeze/thaw wind/rain in our zone with a relatively flat roof with X% slope etc.
On top of that layer goes ballast (small rocks) along with water diverters & ballast retainers (these either under the white final layer or covered by pieces of white membrane and sealed,) drip edges and gutter covers. The gutters are built-in to the edge of the raised center platform of the roof (there is the edge section of the roof which varies from ~15' to 1' in width and then a raised square platform that covers the area of the roof above livable space below & holds wiring & insulation) and sealed with membrane and drained by built-in downspouts routed through the outer walls and slab of the house to spots about 20' out where they daylight as future wet spots in the landscaping. The gutters and downspouts are all thermal taped to prevent freezing, and the gutters have a custom designed cover to keep leaves and pine needles out (but I'll still need to do periodic cleaning.)
The roof plants all cover this raised plantform. There is a drain/cushion fabric that protects the roof and allows movement of water to the gutters, then the interlocking modular trays of plants go on top of that material. The advantage to using the plants is that they provide a bit of r-value relief to the thermal build-up on the roof, they are cooler temp-wise than rock ballast and the plants are all zone-rated for our seasons, are low water succulents and require relatively little maintenance. I will have to do some regular weeding, particularly to keep trees off the roof. There are all sedum varieties, and we got an assortment rated as "hardy" but also "showy" as they all like to send up flower stalks. They surround the pop-up room on the roof, which is my wife's office, so she's got a nice view.
This probably didn't answer your question. I just started typing. So let me know. Also I can get brands, material names, etc.
Last edited by j44ke; 05-01-2020 at 01:38 PM.
I think the company whose design we are using originated in Europe. The company we deal with is a franchisee out of CT. Really very well run. And our contact is a super nice guy.
Probably going to be a mix of these photos taken from our landscape architect's website. No mowing. Any grassy areas will be a mix of native thyme, moss and sedges. The landscape architect works with a group of botanists who did a plant survey of the property to compile all the native species naturally occurring on the property. Then they divide up the house site into similar climate/soil features and the landscape architect and her gardeners get together and design the plantings. So we have an old gravel pit on our property and that matches the septic area in terms of soil composition and sun, so it will get a lot of plants found in the gravel pit area. We have a nice stand of hemlock, and there are a couple shady areas around the house, so that will get plants from the hemlock stand. Birches and aspens, striped maple, shadblow, musclewood, witch hazel, hophornbeam will all be used to create a mid-story to contrast with the wall-o-pines that surrounds everything else. Should be fun. The gardeners are our across the valley neighbors and really nice people - which is good because the project will take about 3 years! Oy.
Last edited by j44ke; 05-01-2020 at 01:53 PM.
Very cool. I love e the idea of how those flower stalks will look from the office...
SPP
Jorn...in the industry, we stopped using the term “flat roof” and now call them “low slope”...brings a lot of clients back from the edge of their chairs. Green roofs require research and homework and when the application is appropriate as it is in Jorn’s case, they are a great approach in dealing with insulation, roof membrane life cycle and stormwater management.
rw saunders
hey, how lucky can one man get.
That's what I needed - thanks RW. All coming back to me now. Must drive the architects crazy. Them: "We designed a low slope roof." Me: "We're getting a flat roof only it isn't flat." Them: "We enclosed surface mounted insulation & topped it with a green roof to increase life of the roof membrane and help with storm water management." Me: "We get pretty flowers on our roof!"
I'll take some more photos this weekend. They went nuts this week with site clean up and grading prep so our earthmoving maestro and his Volvo excavator can begin working his magic on topography and the drive. I tried to put a stake into the ground where the trucks have been parking for most of the job, and I broke it in half. Plants aren't going to like that. Needs some loosening work with a thingee.
Last edited by j44ke; 05-01-2020 at 02:20 PM.
They have several bee hives on the “low slope roof” of the Pittsburgh International Airport Hyatt, that you can see from the people mover...you need one up there, Jorn.
rw saunders
hey, how lucky can one man get.
Have you picked out a name for your roof-goat yet?
Geez - I was just going to say we're getting a goat instead of bees. Really I was just looking at goats the other day (though not for the roof - more for brush control.)
Bees would be nice, especially since most of the plants will be flowering plants. And chickens, though I think that would just be a form of bird-feeder for the coyotes.
Last edited by j44ke; 05-01-2020 at 02:28 PM.
Funny that airy light filled store turned into a cellar.
Jorn, interesting. what’s the plan for maintenance? Any plans for irrigation?
My last commercial project included a green on a portion of an office building. The install was very similar to what you have.
During my one year warranty inspection, the lovely green roof had turned into a dreaded brown roof. I was told their maintenance crew disabled the irrigation system. They ended up replacing the plants with pea gravel.
Rick
If the process is more important than the result, you play. If the result is more important than the process, you work.
The plants are mixed sedum varieties similar to the mix below, and they are cold hardy, even able to be buried under snow. But they are also drought tolerant. Our architects have a similar mix on their roof a few miles away, and they haven't watered it once since it was installed two years ago. It dies back a bit initially, but then it gets its equilibrium and grows just fine.
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