Green Roof Reno: February 2008
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February 13, 2008
Making Progress
The Meeting
So we finally had a chance to sit down with the co-op board last weekend. We brought a brief project introduction and a couple of drawings to illustrate the conversation. Things went well and they seemed responsive to a lot of ideas we brought up. We explained our project and talked about the tax and energy benefits to the building . . . which of course they loved.
We presented our preferred option; a 200 sq ft wood deck with a 550 sq ft green roof. It’s economical for us and energy smart for the building. The way we construct and install the deck, however, depends entirely on the structural engineer. If they say the roof can’t hold the weight of the deck and green roof, then we need to lay down steel I-beams. The steel would extend from parapet to parapet (or from side property edge to edge and essentially across my neighbors half of the roof) and we would build the roof deck on the steel. Our neighbor would have to okay this, of course, which is another story in itself . . . Steel would allow us to do almost anything, which could be fun but, will most definitely be major expensive.
Questions
We could only go so far in the co-op meeting -- all decisions for the roof now seem to rest upon a structural analysis. We have some real questions for the structural engineer at this point, like:
- Can the existing roof hold the prescribed saturated weight of the green roof blocks and the wood deck?
Green roof blocks = 17 lbs/sq ft (saturated)
Cedar deck = 30 lbs/sq ft
Ipe deck = 65 lbs/sq ft
- Is the staircase bulkhead a supporting wall and can we anchor-bolt wood beams to it as a support for a wood deck?
- If we need steel beams to support a roof deck and vegetation, how much steel do we need? How thick does it have to be? And where should it go?
Of course, the board did have concerns – they wouldn’t be a board if they didn’t . . . Apparently the building has had problems with the roof in the past (we’ve heard rumors of someone nailing decking directly to the roof membrane – ouch!). They asked some good questions . . . What would happen if the roof had to be fixed? How would they get to it? Would it invite people from adjoining rooftops to “vacation” on our deck? Would plant material get caught in the roof drain? Totally valid questions – some of which we’re still trying to figure out ourselves.
Stormwater
Oh yeah . . . We almost forgot to mention. It turns out that our building is having stormwater issues. We were sure to mention in our meeting how a green roof would capture a significant amount of the roof’s would-be stormwater . . . a perfect solution to their problem. We really seem to have gotten lucky with our co-op board; they have been very open and interested so far. . . fingers-crossed.
We'll keep you posted. Mr. and Mrs. Green Roof