[GSBN] Lightweight concrete roofs

Mon Jun 21 16:29:04 UTC 2010

This is an aside on the topic of lightweight concrete roofs - My grandfather, Jim Waller, was a civil engineer and innovator in the use of concrete (he built the first concrete boats for the admiralty during the 2nd world war). The reason why I mention him is that in the 1950s he developed a building system that has similarities with the Nez roof. His system was called Ctesiphon after the ancient arch in Iraq, and basically involved building a temporary structure based on a series of inverted catenary arches as ribs and covering them with an envelope of Hessian fixed to the ribs. The hessian was covered with thin coats of a cement slurry (no latex in his day) This was designed to sag between the ribs causing corrugations which gave the shell its structural integrity. The trick was that the arched forms could now be removed and reused, leaving a self supporting lightweight concrete shell.
The system was used for grain silos in Egypt, emergency housing in India and a whiskey storage shed in Ireland among other projects, but never took off in a big way and has remained an interesting byway. As soon as I followed the link to the Nez roof I was reminded of my grandfathers work - it seems they would have had a lot in common.

Thanks
Jim

Jim Carfrae
PhD Research Student

Room 119, Reynolds Building
University of Plymouth
Drake Circus
Plymouth
PL4 8AA

jim.carfrae at plymouth.ac.uk
07880 551922
01803 862369
________________________________________
From: GSBN-bounces at greenbuilder.com [GSBN-bounces at greenbuilder.com] On Behalf Of Paul Olivier [paul.olivier at esrint.com]
Sent: 21 June 2010 16:51
To: (private, with public archives) Global Straw Building Network
Subject: Re: [GSBN] Lightweight concrete roofs

Mark,

Please forgive me for asking dumb questions about something you have written:
It sounds as though there is plenty of resources for the mix so I won't address that too much now...it's not rocket science. You basically use the latex as you would water for a cement mix with sand. You can use as little latex mixed with water as seems effective...more latex (50/50) to water for the initial coat. I can attest that the system works well and can be low cost. It is easy to learn and quick to build.
I am keenly interested in use of latex with cement,
and I would like to find a good summary of the steps involved.
We will soon start building outhouses in a ferro-cement over urine-diverting toilets,
and it is critical that moisture does not penetrate the structure over time.
This effort is summarized at: http://www.esrla.com/pdf/toilet.pdf
Today we are putting up the first ferro-cement structure as depicted in this presentation.
We must get it right, and your advice would be greatly appreciated.

Thanks.
Paul

On Mon, Jun 21, 2010 at 9:47 PM, MARK SCHUENEMAN <huffnpuff at q.com<mailto:huffnpuff at q.com>> wrote:
Greetings All interested parties,

The 'Nez' Roof system has certainly progressed beyond the experimental stages. The are many roofs around the world thanks to George and Al Knott. The reason George didn't return your email is probably he just returned from training folks his roof system in Uganda where they did a roof for a performing arts center. I know there's Nez roofs in Afghanistan, Kenya, Rwanda as well as many other working demo structures in the Denver area and the mid west US. He has trained his roof system to many folks , including myself, and we've built the system many times around the world. His model of 'roof first' makes sense. He was working with a minister in Afghanistan after their earthquake when all they had was tarps. Snows would collapse the tarps when they could have built his roof with mostly salvaged materials and used the tarps and more salvaged materials for walls. Recently he's been in conversations with some folks in Haiti, so he could get you in touch with them.

George is a wonderful man with a vision and plan and energy abundant for a Ninety year young fellow. Mr. Nez started doing disaster relief work for the federal Government in Central America years ago. He has always been more than happy to share his knowledge with anyone interested. As a matter of fact, you may want to make a pot of tea for a conversation with George. He is a most knowledgeable resource when it comes to disaster relief. If you have a project going somewhere I'd guess George is a suitcase packing away from joining you for a demo of his roof system, as would I, or to discus your project.

His system is more about the shape of the structure and the latex coating but the 'fabric' for the roof has been an evolution. He used to weave a fiberglass netting for the latex parging but has worked with and tested regular old cotton fabric (or even tarps) with chicken mesh. These materials seem more readily available in most parts of the world and cheaper. The frames can be made of salvaged materials and spliced effectively. The latex for the concrete parging can be old left over (or oops) paints, if you can live with the color. It sounds as though there is plenty of resources for the mix so I won't address that too much now...it's not rocket science. You basically use the latex as you would water for a cement mix with sand. You can use as little latex mixed with water as seems effective...more latex (50/50) to water for the initial coat. I can attest that the system works well and can be low cost. It is easy to learn and quick to build.

The latex parging seems very durable, flexible (elastic), waterproof and enduring. The material itself is not that difficult to work with other than that it doesn't lend itself to a great esthetic. My guess is that if you're homeless, cold or hot and wet, you could care less about esthetics. Once you apply the parging with a few strokes of a brush or trowel further strokings only drag, ball and/or tear. I got some on my vehicle and missed cleaning it until the next day and when I removed it some paint came with it...it's sticky. Clean your tools soon and often.

If interested please feel free to write myself or George geonez at peoplepc.com<mailto:geonez at peoplepc.com> or call me with your thoughts or inquires.

Regards,
Mark Schueneman
303-444-6027 hm.
303-591-9841 cell

> From: bob at bobtheis.net<mailto:bob at bobtheis.net>
> Date: Sat, 19 Jun 2010 22:57:55 -0700
> To: GSBN at greenbuilder.com<mailto:GSBN at greenbuilder.com>
> Subject: Re: [GSBN] Lightweight concrete roofs
>
> We've been considering this technique for work in Haiti, but I never
> got a reply to my email to George Nez, asking, among other things,
> whether the technique has progressed beyond the experimental roof at
> the University of Colorado.
>
> Does anyone know of further work with it? I'm especially wondering if
> someone has tried making corrugated or folded plate panels.
>
> Bob Theis
>
> _______________________________________________
> GSBN mailing list
> GSBN at greenbuilder.com<mailto:GSBN at greenbuilder.com>
> http://greenbuilder.com/mailman/listinfo/GSBN

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--
Paul A. Olivier PhD
27C Pham Hong Thai Street
Dalat
Vietnam

Louisiana telephone: 1-337-447-4124 (rings Vietnam)
Mobile: 063 399 7256 (in Vietnam)
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http://www.esrla.com/