An earthbag dome will likely have a longer lifespan and require less plaster maintenance if it’s protected by a durable roof. (click to enlarge)

An earthbag dome will likely have a longer lifespan and require less plaster maintenance if it’s protected by a durable roof. (click to enlarge)


Attach rafters to braces that are embedded between courses of earthbags. (click to enlarge)

Attach rafters to braces that are embedded between courses of earthbags. (click to enlarge)


Nailers help hold braces in position. (click to enlarge)

Nailers help hold braces in position. (click to enlarge)


As discussed in a previous blog post the other day (see link below), dome roofs protect domes from moisture damage, shade the structure, reduce plaster work and capture rainwater. If you’re building in a rainy or snowy climate, your dome will likely have a longer lifespan and require less maintenance if you have a durable roof.

The drawings above show my recommended techniques using either wood poles or milled lumber. Wood poles are less expensive (or free), although they’re more tedious to work with. The basic ideas shown above can be altered to meet your needs. For instance, you could use purlins instead of roof sheathing. You could leave a gap between the roof and the dome for ventilation, add a skylight, gutters, etc.

Previous blog post on Roofed Domes


Comments

My Suggestions for Roofed Domes — 7 Comments

  1. i looked at the kelly hart article about the small dome in cold climate. this seemed like a good idea for a cold weather like in the northeast u.s.

    are you now recommending putting a roof on, or will a concrete dome suffice in cold/rain/snow?

    do you think reciprocal roof frames would work well in an earthbag dome in a high snow climate?

    would a reciprocal roof frame work on a rectangulare or square earthbag structure?

    • Roofed domes would be more durable in your climate. Cement plaster always cracks. Water will get into the cracks, freeze and expand, and gradually degrade the plaster. In areas with strong freeze/thaw cycles, it makes sense to build roofed domes for more expensive structures to protect your investment. The final decision is up to homeowners. Some may want to keep the dome shape, keep it really simple and worry about maintenance later. You could add waterproof coatings (elastomeric, etc.) to increase durability.

      Reciprocal roofs are highly recommended if you have long, straight, strong poles and low cost labor. You can use reciprocal roofs on most any shape, including domes, squares and rectangles that are nearly square. The main limiting factor is size. This method works best on small, simple shapes.

      Best info on reciprocal roofs: http://small-scale.net/yearofmud/

  2. This is a very elegant solution to the problem of leaky domes, as a roof this steep sheds water immediately. You might even leave a hole open in the tip of the dome, a steel car tire rim as a window frame in order to maintain the strength of the dome, then this framework & roof. This hole would allow hot air to escape out of the dome naturally in summer, and could be sealed up in winter with a home made decorative plug. That would of course entail building an additional small roof over that hole, but if you’ve gone through the trouble to build an earthbag house, that last part won’t be a big deal.

    Another idea worth considering is concrete canvas. Build a dome, then this wooden roof framework, then stretch a layer of concrete canvas tightly over this framework, and you’ve got a roof in days, rather than weeks. Given that a roof is usually the most expensive and difficult part of building, this type of roof would be quite inexpensive, and it’s guaranteed to last ten years before you have to repeat this process, which just entails laying down a new layer of concrete canvas.

      • My mistake then, Owen, I didn’t realize it was an overly expensive product, given that it’s just canvas and a small amount of concrete – if it’s anywhere close to metal sheathing in price, you’re right to go with metal, as I think manufacturers now warranty it for 30 years or more.

        I’ve recently become interested in the use of rebar, wire walls and a thin shell cement to create interior walls, roofs, fences, etc… in conjunction with earthbags for the house. If I find a winning formula ( cheap & strong ) I’ll let you know.

  3. I am in the process of getting an appointment with FAU reference my garden shed project. Geeze Louise, It’s just a shed for goodness sakes! I’ll keep you posted. Thanks for this post and blog, amen!

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