Natural Building Blog

Earthbag Building & Other Natural Building Methods

New Compression Ring Design

Compression rings are a key part of a fast, convenient roof building system that can utilize locally available wood poles.

Compression rings are a key part of a fast, convenient roof building system that can utilize locally available wood poles.

A roof like this can be bolted together with hand tools in one hour.

A roof like this can be bolted together with hand tools in one hour.

The compression ring I designed and had built by a local machine shop for our earthbag roundhouse worked perfectly. It costs me just $20 or so and used very few materials. The roof bolted together in one hour and, as reported previously, it was rock solid even with 4-5 workers climbing on it. Also note, roundhouses are the fastest, easiest earthbag shape to build and this type of roof works perfectly.

So why did I make this new design? For one, the compression ring on our roundhouse required tricky bending of steel at an angle. See photo of the beautiful exposed ceiling. Some shops may not have the skill or equipment to make one like this. I wanted something simpler that anyone could build almost anywhere at dirt cheap cost.

I was admiring the beautiful roof on the Superadobeserano earthbag house. (Again, wow! Great job on the roof.) They used a log section instead of a steel compression ring. That works fine on small roofs, but what about larger roofs? And then there’s a risk of splitting, non-code compliance and the inconvenient center pole. So I set out to combine the best features of both.

The new design shown above seems to meet all my criteria. The emphasis is on simplicity. It’s just a steel cylinder with brackets welded on. Every metal shop or backyard welder in the world can make this if you can’t. There’s a vertical piece bent into a circle, and circular pieces of plate steel welded on top and bottom. Steel brackets with pre-drilled bolt holes are welded on to support the rafters. Fabricate and paint the compression ring in advance so it’s ready when it’s time to build the roof. Then all you have to do is drill holes in the rafter poles and add bolts.

Note, the drawing is to scale showing 16 – 3” poles (at the tip) bolted to a 16” diameter compression ring. If you use different size or number of poles, you’ll have to adjust the measurements so everything fits.

Also note you can build two of these roofs — one above the other — to create a Double Pole Roof with space for lots of insulation.

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18 Responses to “New Compression Ring Design”

  1. Geoffrey Levens says:

    This is great! Planning a round, vertical walled, earth bag house about 20 feet in diameter and most likely this will be my roof.

    But I have no idea what a culm is and google only comes up with it as part of certain plants. Any clues greatly appreciated.

    Am I correct that you need to support the ring w/ a temporary pole while attaching the beams?

    Thank you

  2. Anders says:

    Do you have any pictures or specs of the compression ring?

  3. Jarad Barkeim says:

    I am building a circular roof like the one described here. We’ll be using 12 6″-8″ diameter poles that are around 20′ in length. So this is a lot of wood and a lot of weight. But there will only be the weight of the thatch roofing on top of it. Would you still go with the compression ring in this instance? If so, do you have a more detailed design or picture of the compression ring you used? I would like to get a better look at how you attached the poles.

    • Owen Geiger says:

      Yes, this works perfectly. I’ll send you a better drawing.

      • Jarad Barkeim says:

        Thanks for the reply Owen, maybe you can help me with a couple of other things. First, how thick should the steel in the compression ring be? Second, we plan to use an 8×8 wood bond beam for a tension ring. Is this ideal? How should we marry two ends of different pieces of bond beam. And should we have a metal strap around the wood bond beam?

  4. Owen Geiger says:

    Update: If you use thick enough steel for the ring (cylinder), you wouldn’t necessarily need the top and bottom pieces. That would save a little time and materials. Just be careful not to apply stress as the poles are being bolted on.

  5. William says:

    Hi there to every one, because I am actually eager of reading this website’s post to be updated regularly. It carries nice material.

  6. Zafra Miriam says:

    I wanted to reply to your “fill the culm next to the bond beam with cement” comment but there’s no reply button there. When you say the culm next to the bond beam do you mean to say next to the compression ring? or both ends maybe? I’ve looked extensively online for info on using bamboo for roofing (we have a ton of bamboo so we’re eager to make use of it) and have never seen anything about filling a culm with cement (except for making posts/columns). We’re fascinated by the idea – do you have any links or further information you can direct me to regarding that technique?

    • Owen Geiger says:

      I meant to say fill the culm next to the compression ring, but you should also fill the culm where the hurricane tie is attached.

      The idea is very simple. Search bamboo joinery or just follow the directions I gave. That’s all there is to it.

  7. Zafra Miriam says:

    Excuse my lack of imagination, but I’m having trouble visualizing the brackets. What are their qualities exactly? Thanks so much for taking the time to perfect this design – it might serve our needs perfectly…

    • Owen Geiger says:

      Take a look at these brackets:

      Similar brackets could be welded to the cylinder. The other end is bent downward to the appropriate angle. (22.5 degrees in this case.)

      I would fabricate the 1″ wide brackets out of the same steel as the cylinder for ease of welding. All you need is one bolt hole per bracket. A reasonable size would be about 2″ welded to the cylinder and about 3″ of length for supporting the rafter pole. Of course, scale everything up if you’re building a large, heavy roof.

  8. Robin says:

    I love it! Didn’t have more to say about it.

    Maybe I would use bamboo. Do you see any problems with that?

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