Preparing for building the reciprocal roof frame

by ziggy on August 11, 2008 -- 0 comments -- Follow

The past few days, I have been dwelling quite heavily on the roof design for my cob house. I will be constructing what is called a reciprocal roof, a self-supporting structure composed of pin oak and black locust poles. Reciprocal roofs are round and spiral-y, perfect for round structures. They require no center post and are apparently “simple” to construct, requiring no experience. Plus, they look great, too.

The only downside to building a reciprocal roof is the apparent lack of really comprehensive information out there on how to actually do it. Running a Google search for reciprocal roofs results in a few decent hits, but still, there seems to be a dearth of hard information on how to go about making a reciprocal roof from start to finish.

The best resource I have found thus far is Tony Wrench’s book, How To Build a Low-Impact Roundhouse. You can see some photos of his design here. Wrench has some good sketches and a decent amount of how-to information in his book (which, by the way, is pretty hard to find), but I’m still craving more. Perhaps because my case is pretty different from his and I want to be reassured that this thing is going to work.

The main difference being that my walls are load-bearing, with the reciprocal roof rafters resting directly on the cob walls. Oh, and my house is also not totally circular… That makes a big difference, too.

But anyway, here are a few other sources of images and information for the prospective reciprocal roofer:

  • The LessPress Snail Cabin has a reciprocal roof made with dimensional lumber. Also, be sure to check out their Excel spreadsheet for calculating beam lengths and positions for both circular buildings and otherwise
  • Zone5 has a brief description with some images of a Tony Wrench-style reciprocal roof construction for a roundhouse here and here
  • Check out a scale reciprocal roof model and design using dimensional lumber at Casa de Baro
  • Cae Mabon in Snowdonia of North Wales features several buildings with reciprocal roofs. Images here
  • Simon Dale’s ‘low impact woodland home‘ has a gorgeous reciprocal roof with gnarly rafters and beautiful slab decking
  • For math nerds, visit The Pavilion for a very technical description of how reciprocal roofs function
  • Design Forward has a very brief snippet about the history of the reciprocal roof design, which was invented by Graham Brown, who says: “The structure demonstrates a principle that is fundamental to life on this planet – a simple natural principle: All life is connected.” (Unfortunately, Brown’s website is down…)

This is mostly what I have been reading and looking at for inspiration. I guess the only way to determine if my own reciprocal roof design works is actually making this thing. Soon enough, I will know!

(Image from Zone5.org)

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