Using Sod to Build a Green Roof

Learn how switching to a sod roof, the original eco-friendly roofing material, can help reduce your electric bill and protect the environment.

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    You can walk out from the second floor of this house onto the green roof/sod roof of the first floor, which creates a grass-covered patio.
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    Cedar logs along the eaves protect against insect infestation.
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    Sod roofs work best with a slope of no more than 4 inches of vertical drop per horizontal foot.

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Two young Plainfield, Vermont builders — Tim Rice and Steve Jacob — have decided that the time is right for a revival of the old-time sod roof. They just may be right. Sod roofs are largely free for the labor, the materials are easily found in most back yards, sod is one of the most fireproof materials going and it makes excellent insulation for all but the most severe climates (some Vermonters with turf-topped homes have seen 50 below with no complaints).

According to Tim and Steve, there's no reason why anyone building a house couldn't top it with sod . . . at least with a little advance planning. The stud construction of the typical frame structure, for instance, doesn't lend itself to sod roofing but log cabins and buildings of post and beam design are especially well suited for such a topping. The "yes or no" difference is in the amount of weight each type of structure will support.

Allowing for snow loads and your family gathering for summer breakfast on top of the house, figure that the beams and rafters under a sod roof will have to carry 100 pounds per square foot. This is twice as much weight as is supported by the corresponding beams and rafters under an ordinary roof.

Many early homesteaders selected the wood for their sod roofs' joists and supports by eye and used the by-guess-and-by-gosh method of calculating the timbers' dimensions. Such a trial and error approach can be pretty expensive and I don't recommend it . . . but if you insist on giving it a try, be dang sure to build your roof's substructure about twice as strong as you think seems reasonable. Better yet, forget such guesstimations entirely and get some professional help with the calculations.

If you live near a university, you can probably find an engineer who'll figure out the underpinnings of your house's sod top for a very small fee. Almost any reputable building supply house will help you with the calculations too . . . especially if the folks working there know that you intend to order materials from them.

Tim, who enjoys sharing his knowledge and experience with the construction method, advises that a sod roof works best when it has some but no more than four inches of pitch — or fall — to the foot. He says, though, that a perfectly flat roof can be made watertight if it is carefully planned. (EDITOR'S NOTE: Judging from the near-45° slopes on the sides of one of the houses shown here, a pitch of far more than four inches can also be made to work satisfactorily.)  

12/28/2020 12:30:35 PM

I am making a summer kitchen. It will be a stand alone structure. I would rather have an herb garden on top than sod. Is having exposed soil a non starter, no big deal? If it is a problem can you suggest a work-around? Also what soil depth would you recommend? Thanks

7/20/2018 6:31:51 AM

Dennis_276 if you are looking for a flat ecofriendly roof try we deal with white environmentally friendly duro-last products which are approved by the City of Toronto for their incentive program. With a white roof you can reduce your AC and electricity bill as well during summer months. We can also install a green roof on your existing roof or one of ours.

5/29/2015 12:50:30 PM

Where do you get service cement and what is it? How does this method compare to the pond liner approach? Labor, cost, durability.

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