I've been clicking through many many websites about green roof systems, but haven't yet found the crucial piece of information I'm digging for.
1) Does any one know whether or not (or how) you can use a green roof system on a wood roof structure?
2) Any suggestions of good concise websites about green roof systems?
whistler
Apr 14, 08 11:43 am
A good option for green roofs over wood frame is www.liveroof.com more of a container style system but a good choice depending on the specific circumstance of the project. You can still build up the green roof as per typical specs but I am a little more wary over any wood structure and the potential for leaks in the membrane roof system.
zigfromsa
Apr 14, 08 12:17 pm
I went to a "Liveroof" demo not too long ago, it's pretty neat stuff, basically a box that has the flora pregrown in a greenhouse. All you do is build up the roof and plonk the boxes down. The install could be made over wood because you first need to build up the roof with rigid insulation and membranes, plus if a leak develops all you do is lift a box up, patch the leak and put the box down again.
Steven Ward
Apr 14, 08 12:36 pm
tectagreen has a similar system. can work with local nurseries to grow the plantings for the modular baskets. AND you can coordinate it through your roofing contractor instead of having a separate vendor.
best news: compared with an 'intensive' green roof, this modular 'extensive' type system can weigh less than conventional roof ballast = no special structural requirements!
zigfromsa
Apr 14, 08 1:34 pm
Steven are you talking about the tectagreen or the liveroof, because I was told that liveroof adds about a 20lb/sqft dead load to the structure.
R.A. Rudolph
Apr 14, 08 2:23 pm
We have done one on a wood roof - on our own house. I think somewhere in another thread I listed the components, but here's the basics:
1. wood framing for a load of 80 lb/sf (we have done 2 green roofs here in socal, both engineers wanted to use 120 lb/sf but we got the engineer to reduce the load for our house). this required a ton of extra structure, in fact so much that we would not do a green roof on top of wood framing again. we have also done it on a concrete block structure w/concrete deck, which makes a lot more sense when you see what is required of the wood.
2. sbs modified bitumen roof (expensive but somewhat standard type of roof) - the roofers would not warranty the roof because we were planting on top, but we did it anyway. on the green roof over concrete block the contractor had a waterproofing company do a liquid membrane - we could not get a reasonable quote for anyone to do it over wood so we went with something our regular roofers could do.
3. 1" rigid insulation (for protection of roof)
4. epdm pond liner
5. J-drain drianage mat (plastic cups w/built-in root barrier)
6. 8" soil - lightweight green roof mix blown onto roof (it has compacted over time to 6")
ckp
Apr 14, 08 3:10 pm
The live roof system seems pretty cool.
I guess they don't have much specific information online because they want you to hire one of their "designers".
Hmm, I wonder what it takes to become one?
whistler
Apr 14, 08 4:48 pm
We've had a lot of buy in from developers on the live roof because of the system approach, the liveroof part is a separate definable thing and if it needs to come up to fix or get at something then its not nearly the issue it is if you have to dig out the soil medium with a shovel, and you don't loose the green roof it just gets relocated temporarily.
It just seems to be a more straight forward approach, not cheap but has some real effective, practical improvements than the traditional route.
I've spoken with this company , they are surprisingly helpful over the phone answering installation questions. This website is pretty thorough, cad details etc.
spark
Apr 14, 08 10:55 pm
we're planning to use LiveRoof on a project set to start in the next few weeks. top to bottom...
live roof (12" x 24" pre-grown units)
slip sheet/membrane
epdm roof membrane
1/2" insulation board
8" SIPS
pre-engineered Wood trusses (doubled up at 48" o.c.)
As long as you account for the load of the green roof (about 30 psf for LiveRoof), you can put it on wood framing.
Call the LiveRoof rep. They were very helpful. They are also coming up with some deeper units that we are going to use to have a taller border so the green stuff is visible above the parapet.
Non Sequitur
Aug 27, 14 9:46 am
I am not a fan of green roofs. Yes, they might add sex appeal to your building but they cost a shit ton of money + annual maintenance... and let's not forget the risk of fire. You can design a well insulated roof with little impact on your structure or construction budget and hit all the LEED points without having to stick soil and cabbage on your roof.
But because laymen everywhere equal green anything with sustainability, this is all I hear at public open houses.
Stephanie Braconnier
Aug 27, 14 10:34 am
The liveroof system is what we are using on one of our projects. I've also seen it implemented on other buildings in Toronto (most recently the Fort York branch library). When I had questions about stormwater retention within the green roof system, I sent an email to the Toronto rep and he got back to me with quite detailed info. I'm sure you could ask about the wood structure and get a response without having to hire a designer.
Not sure about the weight issue mentioned - 20lbs/sq ft is probably when the trays are sopping wet. Your roof should be able to handle snow loads anyways (at least, in Canada they should ;p), so a green roof system is peanuts compared.
In reality, green roofs are less effective at offsetting the urban heat island effect than white/reflective roofs. But they are better for evapo-transpiration and drought reduction. Anything is better than asphalt/shingle. Most green roof failures (dead plants, no retention capability) occur because the planting medium is too shallow and the plants used are unsuitable for the climate.
mightyaa
Aug 27, 14 6:34 pm
Google "Chicago Green Roof" ... lots of information, links, and reasons to do it particularly in a urban environment.
@ Non Sequitur... Fire? What is your thinking there?
Non Sequitur
Aug 27, 14 6:37 pm
mightyaa, we've had a few fires on green roofs in my area... that's why I mention it.
mightyaa
Aug 27, 14 6:59 pm
Like grass fires? lol... I could see that as an issue. 8" of soil doesn't retain much water and some folks won't put in irrigation to maintain it (or proper access). Dirt roof construction if you don't maintain it...
Personally, I love them as part of a roof plaza; Commercial setting.
Carrera
Aug 27, 14 9:37 pm
Love the idea of green roofs but as a principal owner (former) I hold up a wood cross. Roof technology is a major problem in our industry and putting anything on top of all of these questionable systems is a sure liability. Do what you must to respond to owner wishes but better be savvy when leaks occur…you’re sure to be suspect for the implant.
3tk
Aug 28, 14 9:35 am
Also, unless you want it choked with invasive weeds, proper maintenance is necessary. So many of the NE ones seemed to be filled more with weeds (mugwort, ragweed, etc) than the initial planting.
Non Sequitur
Aug 28, 14 10:35 am
Carrera, I've got a large (was largest in my city at time of design) green roof and our RFP demanded an electronic leak detection system at all vegetated roofs. We essentially have a electrified mesh somewhere within the deck insulation that will fail if moisture is to penetrate. Our P.engs had no idea what this thing was and everyone remains skeptical that this pirate treasure map style leak identification system will work.
mightyaa, you got it. Bad maintenance and dry planting makes great kindling for roof bush fires. I found the discussion with our master shrubber (landscape architect) about flame spread ratings for grass coverings fascinating and damn scary.
mightyaa
Aug 28, 14 11:23 am
One that I'd designed a while ago (but got cut), I designed it intermittent. So, parts were pavers, other parts more of a planterbox, etc. Think of compartmentalizing it like fire separations so sitting areas and paths in pavers dissecting landscape areas. So you didn't have large expanses. That way, if there was a leak, you'd just have to demolish the box in that area.
Also, having done so much litigation over concrete plazas... A live growth roof is so much easier to repair the leak. With concrete, you have to cut (which if they aren't good might cut too deep). And the patch concrete will never match the original. Selective demolition with dirt is a ton easier as well as patching back landscaping so the repair is undetectable.
Carrera
Aug 28, 14 3:40 pm
Non Sequitur, your leak-seeking concept sounds interesting and I guess that locating the leaks can be a big problem with everything piled-on. But my point is directed to whose fault the leak is; here are some questions that will come up:
Where is the leak?
What caused the leak?
Who pays for the labor to investigate the cause?
If it’s the roof membrane, does the roofer pay for the removal/replacement of the green features?
If it’s the landscapers fault, does he pay for the roof repair? (I guess so).
In the eyes of the owner during and after all this who do you think he/she will blame for the disruption? (He’s going to say to himself “Who’s idea was this?”, and my point is that it better be him not you).
With a simple membrane roof its 99% the roofer and his manufacture that addresses these issues with one phone call. Adding green to a roof turns it into a “treasure-hunt” with you leading the expedition at your expense. It’s been awhile since I’ve read a manufactures warranty but based on my experience with these guys I can’t imagine them covering the residuals involved.
You guys are the experts not me but if I was involved I would be writing one hell of a spec with a 15 page warranty narrative where I got paid to play.
mightyaa
Aug 28, 14 4:23 pm
I've yet to ever see a warranty on a complex project ever avoid the "not my fault" finger pointing. It is the manufacturer holding the warranty once out of the typical 1-year GC warranty period. They love to blame the installation. And honestly; they are usually right. In all my litigation, I've rarely really seen a product failure... usually it's the intersection or installation.
Some are easy as hell to identify. A shovel punching a roof membrane is hard to mistake for a product failure. Also, there are manufacturer's who understand reputation is more important than a couple thousands bucks and will assist you find the problem and fix it.
So if you are specing a product, try to use those that require certified installers and have a process in place through the manufacturer to verify proper installation. That helps establish that the roof condition was good prior to the next sub doing his thing.
And membrane roofs... I like RA's suggested of a modified bit. Those while not self-healing, tend to tolerate a lot more than EPDM or Vinyls when placed below surfaces as well as patching is simplified..
Another hint if you want to bombproof it. Over the drainboard, put in a layer of gravel or sand, then the top soil. Part of that is so if you are planting and hit sand or gravel, you are too deep... I think I've read that over that sand, you could put in a layer of clay which helps retain water and minimize what gets through to the membrane...
I've been clicking through many many websites about green roof systems, but haven't yet found the crucial piece of information I'm digging for.
1) Does any one know whether or not (or how) you can use a green roof system on a wood roof structure?
2) Any suggestions of good concise websites about green roof systems?
A good option for green roofs over wood frame is www.liveroof.com more of a container style system but a good choice depending on the specific circumstance of the project. You can still build up the green roof as per typical specs but I am a little more wary over any wood structure and the potential for leaks in the membrane roof system.
I went to a "Liveroof" demo not too long ago, it's pretty neat stuff, basically a box that has the flora pregrown in a greenhouse. All you do is build up the roof and plonk the boxes down. The install could be made over wood because you first need to build up the roof with rigid insulation and membranes, plus if a leak develops all you do is lift a box up, patch the leak and put the box down again.
tectagreen has a similar system. can work with local nurseries to grow the plantings for the modular baskets. AND you can coordinate it through your roofing contractor instead of having a separate vendor.
best news: compared with an 'intensive' green roof, this modular 'extensive' type system can weigh less than conventional roof ballast = no special structural requirements!
Steven are you talking about the tectagreen or the liveroof, because I was told that liveroof adds about a 20lb/sqft dead load to the structure.
We have done one on a wood roof - on our own house. I think somewhere in another thread I listed the components, but here's the basics:
1. wood framing for a load of 80 lb/sf (we have done 2 green roofs here in socal, both engineers wanted to use 120 lb/sf but we got the engineer to reduce the load for our house). this required a ton of extra structure, in fact so much that we would not do a green roof on top of wood framing again. we have also done it on a concrete block structure w/concrete deck, which makes a lot more sense when you see what is required of the wood.
2. sbs modified bitumen roof (expensive but somewhat standard type of roof) - the roofers would not warranty the roof because we were planting on top, but we did it anyway. on the green roof over concrete block the contractor had a waterproofing company do a liquid membrane - we could not get a reasonable quote for anyone to do it over wood so we went with something our regular roofers could do.
3. 1" rigid insulation (for protection of roof)
4. epdm pond liner
5. J-drain drianage mat (plastic cups w/built-in root barrier)
6. 8" soil - lightweight green roof mix blown onto roof (it has compacted over time to 6")
The live roof system seems pretty cool.
I guess they don't have much specific information online because they want you to hire one of their "designers".
Hmm, I wonder what it takes to become one?
We've had a lot of buy in from developers on the live roof because of the system approach, the liveroof part is a separate definable thing and if it needs to come up to fix or get at something then its not nearly the issue it is if you have to dig out the soil medium with a shovel, and you don't loose the green roof it just gets relocated temporarily.
It just seems to be a more straight forward approach, not cheap but has some real effective, practical improvements than the traditional route.
I've spoken with this company , they are surprisingly helpful over the phone answering installation questions. This website is pretty thorough, cad details etc.
we're planning to use LiveRoof on a project set to start in the next few weeks. top to bottom...
live roof (12" x 24" pre-grown units)
slip sheet/membrane
epdm roof membrane
1/2" insulation board
8" SIPS
pre-engineered Wood trusses (doubled up at 48" o.c.)
As long as you account for the load of the green roof (about 30 psf for LiveRoof), you can put it on wood framing.
Call the LiveRoof rep. They were very helpful. They are also coming up with some deeper units that we are going to use to have a taller border so the green stuff is visible above the parapet.
I am not a fan of green roofs. Yes, they might add sex appeal to your building but they cost a shit ton of money + annual maintenance... and let's not forget the risk of fire. You can design a well insulated roof with little impact on your structure or construction budget and hit all the LEED points without having to stick soil and cabbage on your roof.
But because laymen everywhere equal green anything with sustainability, this is all I hear at public open houses.
The liveroof system is what we are using on one of our projects. I've also seen it implemented on other buildings in Toronto (most recently the Fort York branch library). When I had questions about stormwater retention within the green roof system, I sent an email to the Toronto rep and he got back to me with quite detailed info. I'm sure you could ask about the wood structure and get a response without having to hire a designer.
Not sure about the weight issue mentioned - 20lbs/sq ft is probably when the trays are sopping wet. Your roof should be able to handle snow loads anyways (at least, in Canada they should ;p), so a green roof system is peanuts compared.
In reality, green roofs are less effective at offsetting the urban heat island effect than white/reflective roofs. But they are better for evapo-transpiration and drought reduction. Anything is better than asphalt/shingle. Most green roof failures (dead plants, no retention capability) occur because the planting medium is too shallow and the plants used are unsuitable for the climate.
Google "Chicago Green Roof" ... lots of information, links, and reasons to do it particularly in a urban environment.
@ Non Sequitur... Fire? What is your thinking there?
mightyaa, we've had a few fires on green roofs in my area... that's why I mention it.
Like grass fires? lol... I could see that as an issue. 8" of soil doesn't retain much water and some folks won't put in irrigation to maintain it (or proper access). Dirt roof construction if you don't maintain it...
Personally, I love them as part of a roof plaza; Commercial setting.
Love the idea of green roofs but as a principal owner (former) I hold up a wood cross. Roof technology is a major problem in our industry and putting anything on top of all of these questionable systems is a sure liability. Do what you must to respond to owner wishes but better be savvy when leaks occur…you’re sure to be suspect for the implant.
Also, unless you want it choked with invasive weeds, proper maintenance is necessary. So many of the NE ones seemed to be filled more with weeds (mugwort, ragweed, etc) than the initial planting.
Carrera, I've got a large (was largest in my city at time of design) green roof and our RFP demanded an electronic leak detection system at all vegetated roofs. We essentially have a electrified mesh somewhere within the deck insulation that will fail if moisture is to penetrate. Our P.engs had no idea what this thing was and everyone remains skeptical that this pirate treasure map style leak identification system will work.
mightyaa, you got it. Bad maintenance and dry planting makes great kindling for roof bush fires. I found the discussion with our master shrubber (landscape architect) about flame spread ratings for grass coverings fascinating and damn scary.
One that I'd designed a while ago (but got cut), I designed it intermittent. So, parts were pavers, other parts more of a planterbox, etc. Think of compartmentalizing it like fire separations so sitting areas and paths in pavers dissecting landscape areas. So you didn't have large expanses. That way, if there was a leak, you'd just have to demolish the box in that area.
Also, having done so much litigation over concrete plazas... A live growth roof is so much easier to repair the leak. With concrete, you have to cut (which if they aren't good might cut too deep). And the patch concrete will never match the original. Selective demolition with dirt is a ton easier as well as patching back landscaping so the repair is undetectable.
Non Sequitur, your leak-seeking concept sounds interesting and I guess that locating the leaks can be a big problem with everything piled-on. But my point is directed to whose fault the leak is; here are some questions that will come up:
Where is the leak?
What caused the leak?
Who pays for the labor to investigate the cause?
If it’s the roof membrane, does the roofer pay for the removal/replacement of the green features?
If it’s the landscapers fault, does he pay for the roof repair? (I guess so).
In the eyes of the owner during and after all this who do you think he/she will blame for the disruption? (He’s going to say to himself “Who’s idea was this?”, and my point is that it better be him not you).
With a simple membrane roof its 99% the roofer and his manufacture that addresses these issues with one phone call. Adding green to a roof turns it into a “treasure-hunt” with you leading the expedition at your expense. It’s been awhile since I’ve read a manufactures warranty but based on my experience with these guys I can’t imagine them covering the residuals involved.
You guys are the experts not me but if I was involved I would be writing one hell of a spec with a 15 page warranty narrative where I got paid to play.
I've yet to ever see a warranty on a complex project ever avoid the "not my fault" finger pointing. It is the manufacturer holding the warranty once out of the typical 1-year GC warranty period. They love to blame the installation. And honestly; they are usually right. In all my litigation, I've rarely really seen a product failure... usually it's the intersection or installation.
Some are easy as hell to identify. A shovel punching a roof membrane is hard to mistake for a product failure. Also, there are manufacturer's who understand reputation is more important than a couple thousands bucks and will assist you find the problem and fix it.
So if you are specing a product, try to use those that require certified installers and have a process in place through the manufacturer to verify proper installation. That helps establish that the roof condition was good prior to the next sub doing his thing.
And membrane roofs... I like RA's suggested of a modified bit. Those while not self-healing, tend to tolerate a lot more than EPDM or Vinyls when placed below surfaces as well as patching is simplified..
Another hint if you want to bombproof it. Over the drainboard, put in a layer of gravel or sand, then the top soil. Part of that is so if you are planting and hit sand or gravel, you are too deep... I think I've read that over that sand, you could put in a layer of clay which helps retain water and minimize what gets through to the membrane...