Our green roof project --- turning a flat garage roof into a roof garden

Before you start with the new, you must deal with the old:

This project actually started 9 years ago, when we bought our house. The house has an attached garage --- with a flat roof. When we bought the house, the garage roof was sealed with asphalt, and covered in pea gravel. The first winter we were in the house, the roof leaked. Actually, there were indications (water stains) on the roof joists indicating that this was NOT a new problem, although there were no leaks during summer rains.

As a result, during the following summer, we removed the asphalt roofing, and replaced it with a fiberglass-reinforced EPDM membrane. At that point, I had the brainstorm that we should make that hot flat roof part of our living space by turning it into a Mediterranean roof garden.

We brought in a licensed engineer; reinforced the roof framing; added a jack post and a steel I-beam; had a railing fabricated to our specifications; and put down concrete pavers. We covered the roof deck with a second EPDM layer (used fabric from the roofing supplier, laid on top without adhesive, as a barrier from friction, penetration, and UV). Our original intent was to fill the roof space with containers and planters, and install drip-irrigation. Well, this worked OK, but there were a few problems with the original plan.

One, the roof was still very hot, even in our Northeastern US location. We had patio furniture on the roof, but rarely used it. The pavers retained a lot of heat, making evenings pleasant but mid-day almost unbearable.

Two, the drip irrigation worked well, but the roof deck surface did not drain especially well, nor especially completely. This resulted in long-lived puddles, algae, mosquito larvae. We had laid the pavers directly on top of the membrane (the friction barrier layer), and swept sand into the pavers as though it were a ground installation. This worked really well --- but drainage through the pavers and sand was not very fast. The pavers and sand remained moist most of the time, and we developed a great crop of moss, algae, and liverwort.

Three, the drip irrigation system (from DripWorks --- great folks, BTW) also worked well, but it did not withstand our summer sun and winter freezing very effectively.

Four, the original installation of the railing had the "feet" (the railing is supported by 4" steel posts at the corners and about every 8 lineal feet. Each post has a 6 or 8" square steel plate) UNDER the pavers. My thought at the time was that the pavers would lock the posts in place, and provide additional stability. What this really did was enable the steel plate to rust badly, since the sand/pavers rarely completely dried out.

So, we decided to lift all of the pavers; sandblast and powder-coat the railing; install a drainage fabric (a Carlisle product designed for green roof installation); re-install the railing and pavers; and then plant the entire roof surface with succulents. Our roof garden will become a green roof!

The renovation project began in earnest on 30-April-2005. Once I figure out how to post pictures to Blogger, I will post photos of the project. My intent is to describe every step of our project, from vendors, to the reasons for our choices, to plant species used in the garden.

At this point, the roof is covered by the drainage fabric, and the refurbished railing is being installed today. I've got 8 x 72 cell flats of various sedum species rooted and growing in the greenhouse. We should begin the re-install of the pavers tonight, weather permitting.

Photos soon. I promise.