Green Roof Reno

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April 2, 2008

The Meeting

Finally we met with our structural engineer, “Bob,” an old timer who seemed to know his bricks from his beams. Bob was recommended to me by a friend in the construction business who talked about him as someone who “knew how to get things done in Brooklyn.” We had chatted on the phone so he had a good idea of what we were after.

Bob was a wealth of information – both practical and historical. Although typical homes in Park Slope allow for a load of about 40 lbs/sqft, Bob said that sometime around 1950 they realized they didn’t need quite that load and resized things down a bit to 35 lbs/sqft. Since our building is from 1920 we should theoretically be able to handle more weight than some newer construction, but I guess we would also have to factor in the age of the beams. One thing we didn’t think of was that the ceilings of our apartment have to be factored into the load calculation, as they hang off the roof beams. Also included in that number should be the roofing material, of which there may have been three or four layers applied throughout the years.

I was beginning to think my green roof modules were doomed! At roughly 15-20lbs/sqft when saturated – could these work on our existing roof? Bob had a lot more questions, for instance - Where are the load-bearing walls? What size are the beams and how far apart are they?

His thought was that our type of building, a 29ft x 60ft building with a central staircase, would typically need to be supported by two load-bearing walls in order for the single wood beam to span the 29 ft across without sagging. A quick trip to the basement confirmed that our building had load bearing columns each about 10ft offset from the side walls of the building. See the image below for the 1936 basement plan with my annotations – my trip to the DOB was worth it after all!

Essentially what this means is that we could cut through the roof and build up from that load bearing wall to create a low wall, or parapet, in the middle of the roof. We could then frame the deck off that wall and the side brick parapet. Obviously the next steps are contingent on the investigation of the beams, but Bob’s feeling was that the green roof modules would be okay! Let’s hope those old builders in the `20s overcompensated on their structural load calculations.

Without original building plans, we will have to do some investigating into the beam size and spacing. So . . . we’re looking forward to cutting a hole in the ceiling! We always wanted to see if we could ever raise our ceilings higher – now here’s the chance. We’ll let you know how that goes . . .

We were also a little surprised to learn that architect, engineer, and permitting fees could be close to $5000 for even something this simple. In most cases, design and permitting fees should be between 10 and 20 percent of the total construction cost. So these projected fees definitely have us concerned, as they could be more than we’ve planned for. In any case, we’ll feel better about having it permitted, both for our own peace-of-mind and ease of resale somewhere down the line.

While this meeting was productive in moving the process forward, we still felt left with more questions than answers. Until we do our own investigations (i.e. the pending hole in the ceiling) we won’t really know anything. We also left feeling that we wanted a general cost comparison between using and not using steel on the roof. All you structural engineers out there - feel free to weigh in right about now!

Although we don’t want to get into specifics on finances, we understand it may be difficult to budget for these types of projects, so we will answer your budget questions by email. Also, we know how hard it is to find good people, so . . . we would be happy to share additional info about our structural engineer and other friends. Drop us an email at greenroofguy@gmail.com.

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Comments

I think you're asking for trouble, like the old house next to new construction. You never know what could happen when substantial weight is added to an old structure that has not been tested for a very long time. I go passed such buildings and see the facade cracked or the the wall nearest the new construction slipping downward--subsidence.
My point is you may be satisfied with what you can see, but have you considered the hidden underpinnings, the footings, for example? Have you tapped on the cellar floor to determine if the soil is still in place or has it been quietly washed away.
BTW, have you calculated the added weight of two-inches of frozen saturated soil, a sheet of ice with accumulated snow on top of that?
Good luck.
Paint your roof white with a quality product and you'll get 75-80% of the benefit of a 'green roof'.

Posted by: guest at April 2, 2008 4:48 PM

Yes . . . anytime you do new construction or renovation there are opportunities of uncovering things you didn't expect to find. I think that's just part of the process. We have had both a home inspector and a structural engineer look at our apartment and our building to verify its structural capabilities. I'm not really sure what else we should do given that we are not trained in structural engineering.

What we do know is the fact is that green roofs have been tested and vetted over the last 35 years in Europe and otherwise. Empirical data proves the validity and reliability of both intensive and extensive systems.

And yes, the 17lbs/sq ft number is a "fully saturated" number (snow, wind, rain or otherwise) for four inches of soil plus plants and drainage materials. This information comes straight from the manufacturer but I could also point you to numerous resources that verify this data.

In regards to painting your roof white . . .uhhh no - that would be silver. And silver would do a lot to lower your buildings reflectivity and thus general heat absorption, but as discussed on his blog previously, that is not the primary advantage of green roofs.

The benefits of green roofs are numerous, from extending the life of your roof from two to three times to the insulation benefits of having vegetation on your roof (an R8 value for all you energy nerds.) In Park Slope, perhaps none is more important than the issue of stormwater retention. Are you aware that anytime we get more than a tenth of an inch of rainfall our storm drains combine with our sewage in CSOs and go directly into the Gowanus Canal?

When you begin to think long term, typical roofs do not even begin to compare to green roofs. You just have to ask yourself: Do I want to build a Roman cobble road that lasts for a thousand years or do I want to build a typical American asphalt road that needs to be replaced every five years?

I hope that with the advent of global warming into mainstream consciousness our country has begun to move beyond the need for immediate gratification and begin to look towards the long range plan. Idealistic, maybe. . . Possible, definitely.

Posted by: Green Roof Guy at April 3, 2008 12:03 AM

I hate to say this, but if you were surprised about the architect, engineer and permit fees being near $5,000 then you have a very steep learning curve. This is going to end up being more expensive than it's really worth -- that's why the are so few roof top projects. 12:03 has a good point. There are cheaper ways to get most of the energy savings and there are also cheaper ways to enjoy your roof without building a deck. Think seriously about using playground pads as a simple easy base (they're made of recycled rubber), then use selected plantings for greening your space. You'll be sitting in your roof garden in a few weeks (no permits required) enjoying it instead of battling surprises. Just my two cents.

Posted by: guest at April 3, 2008 12:17 AM

Well, the truth is we live in a co-op. So everything that goes up there would have to be permitted anyway. There's no getting around paying for that.

And as to the idea of of playground pads? It's not a bad product but the way your talking about using it seems really boring. I've seen many a playground pad "garden" in Brooklyn and I guess that just doesn't do it for me. We are the type of people who care about a well-designed environment.

We also know that if we do ever want to sell our place the investment in the roof should bring quite a significant return.

Posted by: Green Roof Guy at April 3, 2008 8:23 AM

FYI, the roof may require some railing.
Another factor to the load may be leveling the roof because I'd hate to be the guy walking on wet slopy grass without railing on the edge of the building

Posted by: guest at April 3, 2008 11:17 AM

Hi Green Roof Guy,
Playground pad guy here again. i just wanted to thank you for your measured response to my playground pad post. I know these blogs can attract an awful lot of negative criticism and I didn't want mean add to that noise. Personally, I think green roofs are very important and the way of the future. I also like the roof top lifestyle and wish you good luck and much enjoyment with your project. And thanks for working hard at bringing more green to Brooklyn.

Posted by: guest at April 3, 2008 2:46 PM

Just a note on playground pads vs properly supported decking: the former will not distribute the weight of any plants you put on them. Any plant in a 10"+ planter is going to outweigh your 40lbs when wet. You may be able to put the green roof trays on the roof, but any larger garden plants should be on decking that will distribute their weight. Sounds like your plan will cover this.

I went up on my deck for the first time in weeks today. The forsythia is blooming. The strawberries, blueberry bush, hardy kiwi, sedum, and many other plants are starting to sprout. The view is fantastic. I don't know if I'll see a monetary return on my investment upon selling my apartment. I am sure, however, that I get more joy out of the roofdeck than I do out of the kitchen and bath I redid.

Posted by: guest at April 3, 2008 4:46 PM

What if you raised the level of all bearing walls above the roo and placed a grid of steel on top of them, followed by a metal decking system (Supported by the steel girders) and your green roof above that?
Would it still be a green roof if it were not directly on top of the roof, but raised a cmu block higher? Then if you get any leaks, you could remove the decking modules and get ot the roof. If you're interested in working with me on this project, I can show you some sketches I have. Just list your email and I'll get back to you - thanks, unemployed architect

Posted by: guest at April 3, 2008 5:33 PM

We love doing this blog and we love to see people commenting and giving their own two cents - whether we agree with it or not. Playground Pad Guy - thank you for your sensitive post. You're right, its not always easy to take the criticism - but I do know it comes with the territory.

You know I read the reno blogs here religiously before my wife and I had the opportunity to write own own story, so I definitely had an idea of what I was getting into.

Brooklynites feel passionate about their home and real estate. It is a true passion that runs deep - like the overeager father who can't help but yell at their kids on the sports field.

Posted by: Green Roof Guy at April 4, 2008 12:04 AM

Sounds like the green goblin roof maniac is condesending as well as conservationist.
I've read the posts' above, but can't find where the other posters sound like the overeager father types?
This is an open forum where you posted your issue for others to post their comment. If you write - two cents whether we agree or not - then you're not getting this forum.
Alternatives are necessary and the guy signed unemployed architect has an alternative.
Oh and sounding surprised to hear about $5K in fees is a surprise for me. Did you just wake up from a 20 year nap? There is a thing called inflation

Posted by: guest at April 4, 2008 8:38 AM

Just to add to the comparison to overeager fathers yelling at their kids. That is nothing to aspire to, there is nothing positive about that except stoking the ego of the shouter. Maybe the money spent on this could be put to better neighborhood greening.This has the potential for a very interesting blog as Mr. Green Roof Guy seems unhappy with questioning comments.

Posted by: guest at April 4, 2008 11:33 AM

I love the discussion about alternatives and costs and I don’t mind the questioning, or the open discussion about how we should spend our money. None of that bothers me.

I would love to hear some info that isn’t hearsay or conjecture about costs and fees . . . Can anyone share their direct experience with getting a project (roof or otherwise) permitted? What percentage of the total construction budget were the architect/permit fees? Thanks.

Posted by: Green Roof Guy at April 4, 2008 11:59 AM

On small projects, I have typically seen fees in the 15% range (low of 10% and high of 25%) for architects fees.

On interior projects I've worked on, the permitting fees were roughly 1% of the construction cost, but exterior work requires more paperwork and fees.

One thing for unruly posters:

Posted by: pHdesign at April 4, 2008 1:47 PM

Debating the advantageous vs hype of a green roof can go on forever. Bang for buck, they are not always the most effective energy efficient solution for a project, BUT for your personal roof, I see no reason why not. You will get insulation, runoff benefits and more importantly, you will simply enjoy the 'greeness'.
I have a question - are you just going to do green roof modules over the entire area? Or are you also planning a deck?
I am looking into roof deck option as well on a place just purchased in Bed Stuy, probably around 1890's. Even in the archtectural field, I remain perplexed on the process..seems some people just throw them up with no problems, but I have concerns on permitting, load capacity, ect.
Your post was very helpful though!

Posted by: spaderdam at April 21, 2008 12:05 PM

Green roof guy,
Check out the below link about my DIY green roof in Red Hook and my post on the Reclaimed Home website as well (link in below post).

http://www.brownstoner.com/forum/archives/2007/10/green_roof.php

The sedums have returned from the winter and have covered more of the modules. I am adding 100 more modules this year using gaiasoil, a medium made from recycled styrofoam cups in the the Bronx.

Please e-mail me at yash7@aol.com to let me know what you think.

Posted by: ohiise at April 21, 2008 2:56 PM

We're still considering whether we will do green roof modules or a more integrated green roof system. We're leaning toward the modules
because of the flexibility of removal in case of a leak and the ease of installation.

I like working with my hands and getting into the soil so I am less inclined to get the "full package" that many places offer with pre-mixed and pre-grown plant material. We definitely want control over the plant selection, design and installation.

Working with modules - for both the green roof and deck may be the way to cut down on the time and cost of installation.

Posted by: Green Roof Guy at April 23, 2008 11:15 AM

Green roof guy,

Can you please call me? 917 501 4263 04 email me off line
debra@408group.com.

THanks

Posted by: guest at May 8, 2008 11:14 AM