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.
Hello, I purchased a round house with a defective tension ring that was made out of wood. I want to replace it with a metal one like the one shown. Can you possibly email me the specs so I can revise it to fit the one we are trying to make?
Thank you,
Dan
I have no more information about this than what is shown on the blog post.
Owen, I’ve recently purchased a home composed of three octagon wings. The builder used a similar compression ring system as above with about 30 rafters for each octagon structure. The home is needing some major renovation and we would love to remove some of the walls and vault the ceiling to the rafters and show the folded plate details of the rafters. I’d love to pick your brain regarding removing the walls and ceiling joists. Each octagon/compression ring was built with a central support of 2 vertical steel poles, so the roof/rafters are supported both centrally and by the outer walls. We just want to ensure there’s no potential for “kick out” from the weight of the rafters/roof on the exterior frame. Thoughts? Each Octagon’s sides are 12 feet. Compression rings measure 3 ft in diameter.
Well, Owen died a couple of years ago and I am doing the blog full-time now. A roof system with radiating rafters like you describe generally relies on a very stout tension band around the outer walls to keep them from kicking out (like with a yurt). The fact that there are central supports and bearing walls could suggest that there is not tension band, in which case removing the supporting walls could be a bad idea. I suggest that you carefully discover whether that band exists or not. If there is an adequate tension band, then the interior supports should be removable without harm. You might need to create a proper tension band.
Does this compression ring design work with a flat or near flat roof on a 20′ diameter roundhouse using 6″ round vigas? I’d rather not have a center pole.
I think it would work, although it’s pushing the limit. You’d want to draw it out to scale to see if the vigas would actually fit. They may need a little trimming on the ends or make the compression ring slightly larger. This is not hard to do. So get some graph paper, do the math and draw the roof plan so you know for sure how everything will fit together.
Hello Ms Kelly H. Would you have any idea why a compression ring roof dome not be covered by a insurance companies roof leaks?
I see no reason why this couldn’t be covered by insurance.
can you email me drawings of your compression ring? Looking at building an octagonal structure and would like to incorporate your ring into the design.
Thanks for your help
Looking to build a covered round horse riding pen 60′ in diameter. Planning on polygon with 16 12′ sides. Looking for a good detailed compression ring to handle the design.
Consider engineered trusses.
Hi, i’m interested in using a compression ring for a round roof on load bearing adobe walls with an 8 meter diameter. Is that possible? Would i need a tension cable as I’ve read about in yurt designs? And could I see more detailed designs of the compression ring?
Thanks!
I just emailed Robert. Is this the same building? He said his was 9′ DIA. The inside diameter changes things.
For larger designs such as 8 meter DIA you’ll need to build a bond beam. And yes, my compression ring design will work for that size.
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
Thanks. Did you see my earthbag roundhouse Instructable?
http://www.instructables.com/id/How-to-Build-an-Earthbag-Roundhouse/
Yes, you’ll need to support the compression ring until it’s bolted together.
I use the word culm to refer to sections of bamboo. Not sure what you’re referring to.
Do you have any pictures or specs of the compression ring?
Email me for details. My address is at the top of the page under About Us.
I cant find info. Im building a house and i need more info on where i can get compression ring and plans. Anybody help?
Email me.
Main gole of this ring
It holds the roof together without a center post. No center post means more space inside the home.
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.
Yes, this works perfectly. I’ll send you a better drawing.
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?
Please email for suggested details. Every project is different.
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.
Hi there to every one, because I am actually eager of reading this website’s post to be updated regularly. It carries nice material.
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?
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.
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…
Take a look at these brackets: http://www.alibaba.com/product-gs/336472068/Metal_bracket_MF_148.html
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.
I love it! Didn’t have more to say about it.
Maybe I would use bamboo. Do you see any problems with that?
If you mean bamboo rafters, then sure. That would work fine.
If one would use bamboo. Would it be better to clamp them to the ring insted of bolt them. For strength in the bamboo?
The standard way is to fill the culm next to the bond beam with cement. Simply drill a hole and inject cement into the void. (Use a bag for the cement like pastry chefs or masons use.) Then you can bolt the bamboo to the bond beam as shown in the drawing.