[GSBN] Steel mesh in clay plaster (?)

[Graeme North]

My 2c worth

Unprotected steel in clay plasters - don't do it.

In the NZ Earth Building Standards steel reinforcing is to be galvanised or painted with zinc rich paint or asphalt as a "belt and braces" approach even though we have little evidence of reinforcing steel rusting or otherwise in clay, but we were influenced by observations already made about how quickly steel tools rust if clay is left on them.  

For plasters we are now using light polypropylene meshes such as Cintoflex D - or C if we want a heavier mesh. Its  much easier to use than any steel meshes I have seen, is compatible with clay, very cheap, and corrosion free.
For any horizontal reinforcing inside earth walls we use heavier polypropylene geogrid square or triaxial  meshes, and shake table tests seem to give great results.

cheers

Graeme  
   

Graeme North FNZIA
Graeme North Architects
49 Matthew Road
RD1
Warkworth 0981

www.ecodesign.co.nz




On 26/08/2013, at 10:49 AM, Kyle Holzhueter <nihondaigaku.kairu at gmail.com> wrote:

> I think it depends on the soil and climate.  Rule of thumb in Japan is to avoid contact of earth plaster and metal.  In cases where it can't be avoided, cover the metal lath with a alkaline plaster first.  As Andre suggested, you'll notice how trowels not cleaned will rust differently when working with earth and lime plasters.  I've also noticed that my trowels will rust faster in Japan than North America.  I suspect that soil pH may be one factor.
> Regarding natural reinforcement, in traditional Japanese earthen storehouse construction, there is a practice called tarumaki (barrel wrapping) that involves embedding straw rope in wet plaster:  Vertical rope on roughly 20cm centers, more plaster, than horizontal rope on roughly 20cm centers secured with bamboo nails. Repeat depending on thickness of wall.  There's an interesting instructional video series on this practice that used to be for sale.  If anyone is interested, I could see if the videos are still available.
> I've attached two photos of an improvised non-traditional version on a straw bale wall using palm rope.
> 
> Kyle
> 
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