I just found this great technique for making ferrocement roofs at Steve’s Flying Concrete site. Steve explains how to make roof panels on the ground so you don’t have to plaster overhead. This eliminates the most difficult and awkward step of making ferrocement roofs. The panels can be hoisted in place by crane or with a crew of strong workers.
“My latest idea is pre-fabricated, arched triangle, roof panels. 12 -18 ft wide–On the ground you build arched triangles in a dish shape. Finish the inside of the dish, flip the dish over, set with a crane and this becomes the ceiling of the dwelling.–No overhead plastering. A row of tiles inside, finishes interior ceiling.
The panels can either be set in a circular pattern to form a “dome” or alternating in a line to roof a rectangular shaped room. Building triangular dishes– start with insulation then structural layer and then polish the inside of the dish. THE HARD PART–Turn the dish over and stack it in vertical pile until the crane comes to set 8 dishes. Crane –reality check– for these dishes on the first floor I’d say 4 hrs at $150/ hr is $600– or $75 X 8 panels. Set the dishes and stick them together in the valleys– form work very simple using plaster lath– mix this pour on site, (pour out of a 5 gal bucket) and vibrate from above. 1/2 yd should go a long way.”
More details at Flying Concrete
Great site! I was wondering if anyone had used ferrocement to cover an earthen dam? We had a muskrat dig through the dam and the dam partially blew out. Would also love it if there were no weeds growing on it so I would not have to weed eat the dam. Thanks so much for any helpful hints. I have wanted to try ferrocement for many years now. PS, I live in Indiana where it freezes if that matters?
It seems possible to cover an earthen dam with ferrocement that would hold up fairly well over time. I know that cisterns have been made with ferrocement before. I suppose that a muskrat could still burrow in from the side, but the cement covering should protect it from blowing out.
This is a very interesting way of making ferrocement roof panels, but does require some help from other people. The lines which have been made by the workers have to be perfectly straight in order for the panels to align.
This is very interesting. I wonder if it would be possible to mix pumice into the concrete and lay it on a bit thicker, thus insulating the ceiling as well as giving it shape, in one step. Rice hulls would be even lighter and if I understand things correctly would even temper the tendency of concrete to crack. This one is definitely worth following up on, given that roofs then to be the most difficult part of earth building.
Steve is a real pro. I would follow his advice first and then if you want to experiment you could gradually try different things. His method creates a strong shell at first with the insulating concrete put on top later. That makes sense to me.
I think roof panels have a lot of potential. If you make a small roof panel (1-2 square feet), they are called tiles, and combined with a vibrating table, they are produced very easily.
For larger roof panels, i would go with a vault profile to make them a bit more modular. Vaults have less waste on materials, too.
I wonder what these weigh? With Laminated Ferrocement, we can average 4-5 lbs per square foot, so it might be possible to make these in a size that could avoid renting a crane.
I covered micro concrete tiles on my Geopolymer Blog:
http://geopolymerhouses.wordpress.com/2011/08/26/cottage-scale-mcr-manufacturing/
http://geopolymerhouses.wordpress.com/2011/08/24/micro-concrete-roofing-tiles/
I like the idea of making the roof panels small enough that you don’t need a crane. $150/hour? No way that’s affordable for many people. I sure wouldn’t want to pay that.
yeah, $150/hr is out of my price range, too, but I think I could rig up a tripod to lift a 200 lb LFC panel (40 square feet).
Alternatively, you don’t have to raise it that way, you could just as easily raise one corner at a time.
Sometimes it’s worth paying for services like this. One time we paid $150 to get trusses up on a two story house
Would be easier and cheaper to find twp men with strong arms to trowel mix on.
Ive been thinking about this while looking at acrylic concrete as a way to put up a strong cheap roof on a dome.
You’re saying to trowel on the plaster from opposite sides? Or two guys working at the same time but on different parts?
I’ve done a lot of overhead troweling, and it is super slow and tedious. Much faster and easier to do it this way.
When you say “insulation”, what do you think they are using? I watched this video after you recommended the site a few days ago. I love you blogs on ferrocement. My wife was talking to my father-in-law the other night and mentioned earthbags and building with affordable materials that will last a life time, he said he has wanted to do something like this for years and asked her to get me to send him information on earthbags. When she mentioned ferrocement he said” they have made ships out of those, you can build anything with ferrocement”. I think I have another earthbag building blog follower lol.
Thank you, and keep up the topic of ferrocement, I think it will help alot of people figure out how to build roofs that will hold up to “anything”.
BTW the gentleman that helped Cody build his house called me back and is willing for me to call him and discuss how they build Cody’s house and the cost of the structure…stay tuned.
There are various ways to add insulation. Steve adds a layer of lightweight insulating concrete mixed with perlite. You could also insulate the attic (if there is one).
Great news about learning the inside scoop on Cody’s house. Please take notes and keep us posted. The details make all the difference: size and spacing of rebar, thickness of cement, how many layers of mesh, what size mesh, thickness of foam insulation, insulation under the floor, etc.
Here’s the link to ferrocement boats. Some are 100 years old!!! So obviously ferrocement is extremely strong and thoroughly tested. A boat would experience far higher stresses than a typical house roof. http://www.ferroboats.com/
He might be interested in my blog posts about seasteading:
http://geopolymerhouses.wordpress.com/2012/01/04/seasteading-with-floatable-concrete-houses/
http://geopolymerhouses.wordpress.com/2012/01/06/seasteading-part-2/
More ferrocement info is in the pipeline. There are step-by-step photos of Cal-earth’s vault building http://s1261.photobucket.com/albums/ii594/Milton1960/#!cpZZ1QQtppZZ20 and a story about ferrocement over pole roofs that I’m still writing. Coming soon.
please remember that Steve is in central Mexico, where much insulation is not required.
I forgot, thanks. So many readers would want to build a ceiling and add roof insulation.