Living Roof

I was told the roof would be too heavy.

Even heavier than a gravel roof?

I'll have to do some additional research. I'm sure their must be a way to use less soil for less weight than gravel.

kevin

Any idea what the pounds per square foot is for a gravel roof?

I've been looking into the living roof more and have found out that the weight of a roof with 4" of soil and plants is between 25-27 pounds per square foot.

We are big fans of 'Living Roofs'. When you visit the San Francisco California Academy of Sciences, be sure to visit the living roof.
here's a link to the roof info.

http://www.calacademy.org/academy/building/the_living_roof/

They used four different plants, but it appeared to me that one of the plants will soon take over the total 2.5 acre (100,000 square foot) living roof. On the roof is a display showing the multiple layers of materials used in the roof. I would lie awake nights if I was responsible for keeping the water out. You look, and tell me if you think it will work 'long term'.
The San Francisco roof is sloped, which avoids the water build-up weight problems. The roof also has a rock layer under a filter fabric to facilitate drainage. For an Eichler, the weight, especially wet, would be enormous. Putting the weight so high would really work against the Eichler structure in an earthquake. Eihler roofs sag under the weight of a tar roof. The sagging creates ponding areas. These ponds get leveled with gravel, filled with water and get deeper. Jarom Feriante in our office (my son) is an optimist. He says a living Eichler roof could become very accessible after an earthquake, since it would be on the ground. Jarom has a Construction Engineering Masters from Stanford. Jarom also says that Eichler roofs are ideal for 'growing electricity' and that Eichler owners should stick to using their roofs for this.
Randy from Dura-Foam Roofing and Solar Center

Thanks for the info Randy. At present I have one of your companies foam roofs. It's served us well all these years. I'm convinced that foam is a better option than tar and gravel, but want to look at other options as well, hence the living roof idea. If I could afford to put up solar panels I surely would but the cost even with rebates puts it out of my budget. I found a company out of Santa Maria that has living roof panels that a home owner can put in place and they claim that their system with 2.5" of soil and other organic material has a weight of 15-17 pounds per square foot.

Thanks again Randy.

Kevin

Kevin,
I did not look this up, but I believe the Eichler roof is designed for a 'live load' of 20 pounds per square foot. This is common. Also, consider this; One square foot with one inch deep water weighs 5.2 pounds. If your flat roof had three inches of soil, saturated with water it would be quite heavy.
Another consideration: A thin soil layer would dry out easily....requiring a lot of water. Even four inches of soil would be considered 'thin'. This would take special consideration re. hardy plant types.
You could get some engineering advice and consider putting a narrow planter right over one of the big beams. You could have the look of the 'green' roof without the punishing weight.
Don't worry about weight hurting your foam roof. Our foam roofs can take 45 pounds per square INCH without even denting. This means you could load 6,480 pounds in one square foot. (bad idea)
If you are serious about the living roof, you should only consider an installation after your roof is recoated. Then you would have at least 20 years of use without considering more coating. We like to do the original recoat when the roof is 5 years old. It is still very clean and the new coatings stick to the surface better. It is also easier to clean and has less staining at 5 years. This keeps the recoat labor costs in the ideal 'low' range.
Randy from Dura-Foam Roofing and Solar Center

Is there any way to spread the load over the roof with a more firm and solid base like a metal or perhaps reinforced plywood? It sounds like the potential problem would be when the living roof gets saturated, it would be too much weight. I'd call a roofing specialist to see what options there are?