reciprocal roofs

[Chuck Morrison]

When I was designing my house I came across what I think is the nicest roof concept I've seen, at least for round houses. It's called the reciprocal roof and is self supporting with a skylight in the center. I didn't use it because I couldn't get beams long enough. I barely was able to get them long enough for the straight to the center type of roof I did build. The photo below was lifted from an article on this kind of roof. A google lookup on reciprocal roof will show quite a few pictures and how to's. If the building is small enough (mine is a 40' diameter) and you enjoy a challenge and nice looking result, this might be the way to go.

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[Rob Beckers]

Wow! Looks beautiful!
Looks hard to frame/build as well though. Everything is cut at an odd angle...

-Rob-

[Brian Bruns]

Hey Chuck,

Do you think this could be used as an interior finish and then shore it up for a reinforced concrete cap poured over it for earth sheltered design? I thought perhaps cutting costs for forming up a dome and having the interior finished in the same step!!
What do you think? Brian

[Chris Lee]

We build a 10 ft diameter round building out of cob and put a reciprocal roof on it. It was hard to wrap my brain around. They seem hard to plan. The diameter of the logs you use and their frequency along the perimeter decides the pitch. I couldn't get the low pitch I wanted without fewer rafters and huge spans for the roofing material out at the eaves. My solution was to add rafters between the reciprocal rafters. It was a learning experience and a lot of fun, but I'm glad its done.
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