Reciprocal roof on earthbag home??

Hello! I recently acquired an additional 5 acres and I would like to build a hyperadobe/earthbag home on it. I'm starting to get my plans together but one thing I'm having a hard time with is finding information on the roof. I would like to put a reciprocal roof on the home but I can't seem to find much information on how to attach it to the walls. I would prefer not pouring a concrete bond beam if I don't have to so what options are there? I've seen some people attach rafters to boards laid on the wall and then place bags in between each rafter. Would that work with a reciprocal roof?

What ways are there to insulate and waterproof the roof? I really like the way the roof looks from inside so I would prefer to insulate it from the outside. I don't mind spending a little extra on the roof, so I would be willing to hire someone if need be.

And the only trees available in abundance in my area are pines. Probably not the best to build a roof with. Any ideas where to get decent round wood to build with? Would magnolia trees or popcorn trees work? Should I dry anything I use for any period of time before building, or will they be fine if they are still "green" when we put the roof up?


Oh and some background info; This 5 acres is adjacent to where I live now, in Panama City, FL. I'm in no rush to move, so I can take my time with building. It will be me and my boyfriend doing most of the work and anyone else that is nice enough to lend a hand along the way. The main purpose of building this house is to build something that I love and then I can rent out the house I currently live in. Also kind of a fallback plan, since I own this land free and clear, but I have a mortgage on my house. If I ever lost my job, I would still have a place to live if I can't afford the mortgage...

[Quote Miranda] A I would like to put a reciprocal roof on the home but I can't seem to find much information on how to attach it to the walls. I would prefer not pouring a concrete bond beam if I don't have to so what options are there? I've seen some people attach rafters to boards laid on the wall and then place bags in between each rafter. Would that work with a reciprocal roof?

Yes that would work. You could also consider setting your rafters on a post and beam and bagging outside of that. The advantage is that you can tarp over rafters or deck your ceiling and cover with tar paper or tyvek or tarp and then be working in the shade. You'd have interior posts for easy various attachments. and still bag up without post and beam in the way. Maybe consider octagon?? If not then rest assured that earthbag are bomber and quite capable of bearing the load. Those Velcro plates you spoke of are handy to shim and spike and distribute a load. If you end up with an octagon or similar put a wooden top plate. If round an avoiding concrete bond beam then maybe head to a scrap yard and see if there is something that might just fit your diameter. What's your diameter and rafter spacing? I set a 16' diameter without a bond beam 2'OC 7 " pine on top of an ambitiously large dome - it firmed it up tremendously even before I spiked it or decked it or added weight on top or my FC bond beam skins under my plaster. I feel that using a reciprocal frame roof can (with appropriate diameter and rafter spacing) reduce bond beam requirements because they are strong without producing lateral thrusts and they typically sit on a strong circular shape. Spike them timbers down with rebar. And for Florida hurricane land get some strapping on them either poly or metal like seen on pallets of materials.

[Quote Miranda] What ways are there to insulate and waterproof the roof? I really like the way the roof looks from inside so I would prefer to insulate it from the outside. I don't mind spending a little extra on the roof, so I would be willing to hire someone if need be

I think most throw down rigid foam then edpm rubber then balluster with earthen roofing. If using rigid foam, I personally would rather fur it out an sheet metal (maybe shingling unprofiled metal roofing). or I'd frame a roof, a simple yurt style radial 2x rafter and blow in cellulose. Or some mineral material in your humid climate. I've put up a couple grain bins those roofs are dead simple... A square hip would also be nice if you hire help out with the hip Jack rafters
-Earthbag Chris

Thank you for the information! A lot to consider!

As far as diameter and rafter spacing; I am still way early in the planning process, I don't even know yet. I have drawn and redrawn the design several times over and I'm still not happy with it. It's hard to come up with something that combines functionality with aesthetics...

Miranda C.

Christopher S. :One of the most knowledgeable people with hands-on Builders experience, and specifically Reciprocal Roofs is Rob Roy, Who points out that

any flaw or miscalculation especially one that occurs early in the build; and this could be walls(!), Is magnified at every step in the rafter fitting process !

Rob Roy is a Prolific and talented Author, And anyone contemplating this type of build may want to take the 50% Discount for " Timber framing for the rest of us "

in the link below :

http://www.newsociety.com/Books/T/Timber-Framing-for-the-Rest-of-Us

This is a good book to have in ones Builders library and I have recommended it several times including sources where it was likely that the book could be purchased

2nd hand ( Amazon / Alibris ) but never at this great price ! For the Good of the Crafts ! Big AL
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