The (second) reciprocal roof frame is on!

by ziggy on September 18, 2008 -- 3 comments -- Follow

reciprocal roof frame

What an incredibly arduous past two days, but oh the excitement! Yesterday I made a mad dash to transport twelve new black locust poles for my roof to my building site, and then I spent the entire afternoon (and into the evening) stripping bark. My body was aching, to be sure.

This morning I finished stripping the last of the twelve poles. At 8:00 a.m., I began dis-assembling the original reciprocal roof frame with the help of Tony, Tamar, Mark, Apple, and Arrien. It was easy work – much easier than putting the thing together. We jammed the charlie stick (the support post) back under the first rafter, and worked backwards to slide each rafter out. It went quickly and smoothly.

Then we re-positioned Charlie and started lifting the newer (and much beefier!) black locust rafters into position, tying them together with wire at the top as we went along. They were a little slippery, and slid around a little bit once they were in position, but they couldn’t go too far with the wire at the top and some wire around the butts at the wall.

By the time we were ready for the last rafter, the inner ring of the frame was already tight, and we pried the last rafter in with a bit of leverage at the butt end. They slid right into place and the roof was done. We took out the charlie stick and the roof stayed put – it didn’t drop at all since the construction was already so tight.

reciprocal roof frame (wide)
(The reciprocal roof frame from afar [it looks like some sort of alien structure!])

Overall, it went great. The new rafters are much stronger than the old ones and I am very satisfied with the integrity of the structure.

I plan on writing at length about this process in the near future. In the meantime, enjoy these few pictures!

(Tony was brave enough to climb the frame for a little photo opportunity)

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  • Rushin

    great work! Just came across your article researching these roofs. As I understand, the pressure of the rafters pushes the walls out instead of straight down, as in force aspect? What type of roof coverings is acceptable – green roofs?

    Any suggestions would be truly appreciated.

    Have to start on my sandbag home and having second thoughts in regards of the roof type – thinking of reciprocal roof with layers of straw and epdm as a membrane with soil topped at 6-12 inches. Would this type of roof withstand that much weight with some snowloads in the winter? What do you think about this with a combination of sandbag walls (with barbed wire in rows)?

  • Actually, I believe the pressure is supposed to be straight down on the walls, and not out. Due to the irregular nature of the reciprocal roof, covering it with soil is perhaps the easiest way to finish it. You can build a reciprocal roof with dimensional lumber, however, which you may be able to finish with something like tiles or shingles.

    I can’t really answer your engineering question. It depends on the span of the rafters, the thickness of the rafters…

    If you have a good way to join the roof to your sandbag home, it shouldn’t be a problem.

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