I'm at the friendster, I'm at the myspace, my doppelganger's at the combination facebook and twitter.
Jamie Schwesnedl
Side note- there was movement in town 10-15 years ago to get more green roof gardening going, but despite infrastructure, environmental, health, & social benefits, the City refused to allow rooftop gardens without counting them as an extra story, so higher taxes, and/or code restrictions on stories.
Challenges - Increased upfront cost. Reduces the storage space you'd have under a pitched roof. It's hot as hell up there - sedum, walking onions, milkweed and native grasses have done great; anise hyssop, echinaechea, and other plants not so much...
The roof of a detached garage is NOT a great place for vegetable gardening - you need a complex irrigation system, possibly with a pump, and to climb a ladder, so it's inconvenient. And it's HOT. Peppers do well, strawberries did okay. No luck with tomatoes or most other things when I tried...
Benefits - keeps the garage beneath about 10 degrees cooler in the summer. Provides a butterfly and pollinator-friendly plant-scape. Can retain about 1500 gallons of rainwater. Offsets urban heat island effect. Looks pretty.
Cost - immediate cost was about 2x a pitched roof bc of needing trusses that could support the weight, paying a licensed engineer to sign off on the design, the underlying waterproofing and green roof drainage system, and needing a crane to dump an average of 8"soil cover up there, plus plants...
Durability - data didn't exist when I put this in, but it's estimated the roof will last at least twice as long as a conventional shingle roof or rubber flat roof, because the soil protects the surface from hail and sun. Needed a new house roof after the hail storm 3 ago, but not on this garage...
Maintenance- recommended 2x a year checks +weeding to avoid anything that could puncture waterproofing from taking root. If you let it go too long, you may have to do some extensive tree digging and pulling-I have to dig out a couple biggies, plus a cute little christmas tree! (pink circles in pic)
I wouldn't recommend such an extenive and deeply soiled green roof on a detached garage or other less accessible space. But if they city provided incentives and reduced barriers, I'd totally recommend a 2 - 3" deep system of mostly sedums...
