Green Roof Reno

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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

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Comments

Doesn't building a green roof with Ipe kind of neutralize your effort to try to do something positive for the planet? Just something to consider.

Posted by: guest at February 14, 2008 9:26 AM

ipe?????

are you footing bill for entire thing? or are you hoping building kicks in? do they have a reserve fund that would cover this and still be solvent? how about increased insurance costs?

Posted by: guest at February 14, 2008 10:40 AM

there are environmentally responsible ipe loggers and suppliers. i suppose the carbon footprint of shipping is an issue as well. i don't think it neutralizes the benefits of a green roof. good luck.

Posted by: guest at February 14, 2008 12:21 PM

I am planning to post in the near future on sustainability and ipe . . . I still don't know how I feel about it . . .

12:21 is right . . .There are sustainable ipe loggers and suppliers. Also when calculating carbon footprint ipe may in fact be more sustainable than a lot of more local woods due to its incredible longevity and short, fast growing cycle . . .I am interested to hear if anyone knows any more about this . . .

Thanks.

Posted by: Green Roof Guy at February 14, 2008 1:16 PM

If your coop board has half a brain (and many do) they'll be fine with the roof once the structural and security issues are settled.

Posted by: guest at February 14, 2008 3:41 PM

I believe typical brownstone roofs were built to handle approx 45lbs/sq ft - but they were built 100 years ago and one would expect 30-35lbs/sq ft to be a more conservative estimate today. So it would appear that your deck and greenroof will almost certainly require steel support. I'd start making nice with your roof partner.

Posted by: guest at February 14, 2008 8:37 PM

Where did you come up with 65 lb/sq ft for the ipe deck? That seems really heavy... I believe your numbers for ipe and cedar are the weights per cubic foot, but you'd only be using a 1" board, I assume. I believe a ipe deck with non-ipe framing is actually about 11-15 lbs/sq ft, dead weight.

Or is that also factoring in furniture, people, etc?

Posted by: Heatherie at February 15, 2008 9:02 AM

I'm a research student working on the viability of installing green roofs (well, they end up looking red or brown here!) in the desert communities in Central Australia. I'll be reading your posts with interest to see how you solve any of the problems that pop-up throughout the design, installation and operation processes. Your blog is a valuable resource, thanks.

Posted by: guest at February 26, 2008 9:18 PM

Heatherie . . .your absolutely right. I mistakenly posted 65 lbs/sq ft instead of 65 lbs/cubic ft. . .and thanks for the ipe with a non-ipe frame calc of 11/15 lbs/ sq ft. I am not sure how to estimate for furniture and people. . . All questions for the structural engineer.

I found the ipe weight info here:
http://www.ipe-wood.com/tech.html

It seems like a pretty good resource. Does anyone have other sustainable ipe suppliers websites/contact info?

Also, I love the brownstone roof weight load information . . .Where is that info coming from? Even though our building is not a brownstone I imagine the width is similar/longer and the roof load similar . . .

To the previous poster: Did I catch that right? Are you in Australia? If so, thats awesome . . . comment, and let us know what you find out about green roofs in the down under.

Thanks

Posted by: Green Roof Guy at March 5, 2008 10:16 PM

There is a guy out of Brooklyn, Timothy Osborne , The Organic Gardener whom specializes in residential/ "urban" greenroofs.
I met him on the street in front of a project he was installing on Bond St. in Cobble Hill. He seemed very knowledgeable and passionate about the greenroofs.
www.theorganicgardenernyc.com

Posted by: guest at March 6, 2008 4:16 PM

Hi. I'm looking for a structural engineer for a green roof project. Can you recommend the one you met with?

Posted by: guest at March 11, 2008 11:55 AM

I'm interested in convincing my co-op to install a communal greenroof and deck. You mention the tax benefits in this post--could you tell me where you found information on that? I've been having trouble finding any city/state support for greenroof installations. Also, I'd love to see your presentation you made to your co-op, if you're willing to share.

Thanks!
lucishda @ hotmail . com

Posted by: guest at April 8, 2008 6:03 PM