Vaulted Dome Roof Project

After the earthbag walls were erected and coated with an adobe/paper/lime render, it was time to get underway with the roof. First I made a scale model of the building and the proposed arching trusses which were fabricated from 5/8″ rebar. The model shows 2D trusses but for stability the actual trusses were three dimensional as shown in the photos that follow. The design is actually a series of intersecting vaults.




A note about the image above: burlap didn’t end up being the roof coating. Instead we used expanded metal lath over stock panels and wired on using bailing wire. That was coated with a 3/4″ embedded layer of non-shrink construction grout modified with chopped pva fibers. (pva = poly vinyl acetate). In retrospect, using sand and portland cement would have been much less expensive, as the sand can be ordered for about thirty dollars a ton and a 94 pound sack of portland cement costs roughly ten dollars here in 2017.


Here, the “X” trusses have been placed. Note the pins of rebar extending upward from the walls- these are welded to a steel ‘top plate’ which is concealed in the final layer of render and runs along the tops of the walls. The pins extend about four feet into the walls, and the rebar trusses, etc. were welded to these.


Each X section is comprised of four ‘legs’ which join in the middle at the pipe, shown above.


Above, a truss is laid out and welded together on a plywood table treated with borax to prevent it from burning. It smoldered but never caught fire. 37 truss sections were welded upon this table, each about the size of this one.



With zero noted deflection even with this minimal amount of truss work in place, we pressed ahead confident that the engineering was sound. The gentleman seated above is a close friend and provided the final design, engineering (complete with animated 3D stress loading), and both off and on-site fabrication almost for free- he’d had a series of strokes and only had the full use of one hand and wanted to find out if he was still capable of such a project


Here the sections of truss were being welded to the heavy guage pipe.




Sunsets in Arizona can be spectacular.


DSC07401 DSC07509


Above, all trusses in place and welded. After this, rebar purlins were welded every two feet in order to define the shape, and stock panels were laid and attached to that.



Above: stock panels being attached to rebar purlins and trusses. Note area near my friend who is standing upright- large open spaces are evident here because stock panels have not yet been placed in this area


Above: View looking down from atop the roof structure. Silver/gray metal is stock panel. Only sturdy enough to walk upon the rebar areas without deflection at this stage.

Insane trusses!



Above: expanded metal lath has been attached to entire roof surface.


Wire lath placed and attached to stock panels. Open square at center is where cuppola will be placed.


The material I have begun applying to the roof structure is high strength, non corrosive, non shrinking grout modified with 3 ounces of chopped PVA (poly vinyl acetate) fiber per 50 pound bag (dry weight). The reason I’ve gone with this option is that I can afford to purchase the grout piece meal, and have found that when wetted down, cold joints blend well without cracking. On a small test structure I found I could use this material in much thinner application than traditional ferrocement, and can control the stiffness of the mix to allow placement on the steepest sections of the roof without it sloughing off- at the base of some of the arches the angle approaches 90 degrees. It is hoisted in five gallon buckets to the roof through the openings for the cupolas using an electric winch, and the material is poured out upon the mesh and worked with a gloved hand.



Above: thin shell formed.



Above left are the domes from inside.  Above right: Roof coated except for cuppolas. Domed Roof Detail

Domed roof detail, above.


December sunset from the property.

steel framed glass block cuppolas with vents

Cuppola with swirled ferrocement roof
Cuppolas finished, with lightning rods.


Above: the structure circa 2012

In monsoon season, the grass grows very fast!


The grass grows too well here.

Even with daily driving, the space on the road between tire ruts is filled with grass between three and four feet high. Some of the grass to the sides is seven feet high- its all the nitrogen that falls to the ground during lightning intense storms that we get in the summer. It makes for excellent fertilizing of plant life.

If you want an easy address to remember this site by, type this to see it. No, really…


10 thoughts on “Vaulted Dome Roof Project

  1. Hi Jon,

    I have been having fun perusing your website and the incredible FC, truss roof structure you have come up with. Your last comment asks about using a wire feed welder to attach the expanded metal lath to the stock panels. I have not done this and would be interested in hearing the outcome should you or anyone else do this. At least it seems like a way to tack the lath in place.

    What I and others have used is a pneumatic C-ring tool a.k.a. a hog ring tool. The right size ring tool will easily fasten lath to stock panels. If you are interested let me know on the side and I can get you a good price.

    I also would like to invite you to join the free FC discussion group/listserv hosted by the Ferrocement Educational Network

    keep up the good work,
    Paul Sarnstrom, director

  2. I’m an experienced welder/fabricator. I have worked with expanded/perforated metal over framework. It is fine to MIG weld the two together. In your situation, I would use .030″-.035″ flux-cored wire. You’ll have better luck than with gas-shielding (wind gusts, etc.). I’ll also offer this: when welding two pcs. together that are very different in size, i.e.; thick frame to expanded metal, start the weld on the thicker piece. Then carry the weld into the thinner stuff, paying close attention not to burn through the thin stuff. Good luck!

  3. Hi John,

    I have friend that worked for Fibersteel, a ferrocement, boat manufacturing facility that operated in Sacramento. He told me they had an arc welder that was fitted with two balls from tariler hitches, one ball on each lead of the welder. They would position two pieces of lath so they were touching and then touch the ball leads from the arc welder, one ball on each side and it would spot weld the mesh tpgether. I don’t know what amperage they used. If anyone successfully does this I would like to hear the details.

    Paul Sarnstrom

  4. We did the whole roof of the round house with a ‘hog ring’ tool (thanks Paul) and it went waaaaaaay faster than by hand! Its come in handy for a number of smaller ferrocement projects since then, as well. I haven’t tried the arc welder idea but am definitely curious.

  5. John, These places are awesome. It was great talking to you today. It would be really fun to make something in my backyard. It great to be working with someone who has similar interests. see ya at the shop.

    Quinn Scheibal

    ps the wife likes the structures too, she is a trained sculpter, she wants you to come over for dinner to talk more.

  6. Hi John,

    For various reasons I want to replace the metal roof on our strawbale house and your techniques with the grout or ferrocement would be perfect. Would you tell me the exact products I should use?

    I’m sure there’s a lot you could say about the material and your methods but any really important bits of advice you have would also be appreciated.

    Thanks, Stuart.

  7. I am a journeyman lather who has tons of experience literally tying metal lath. We used nippers to tie the wire to metal lath. That is the fastest way. I could do thirty tie a minute with no problem. Trying to weld panels that are galvanized and different thicknesses could be a problem for a mig welder. We did arches and vaults with black channel iron ran through radius bender. I loved doing that type of work. It is becoming a lost art. Thanks for showing.

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