[GSBN] building in Haiti LOE

[Rene Dalmeijer]

Kim,

First I have very little hands on experience with LOE, but have read a lot from various resources based on this I would like add the following.
Based on the difficulty of successful long term LOE I do not advocate its use in the Netherlands. Then again there is quite an extensive tradition in the surrounding countries and even in the Dutch province of Limburg of LOE. I am a firm believer in power of natural selection meaning that this tradition tells me that there is some merit to LOE.

As I understand it the mechanics for successful LOE is sufficient mechanical keying of the Lime plaster to the earth plaster subsurface. Looking at various traditions I see all kinds of techniques, downward slanting stick pocked holes, stones (including horizontal continuos thin slabs) severe scoring and finally lots of projecting fibre. The techniques when studied often have a local logic to their use ie the availability of straw reed, flat stones etc. Basically the problem is that when severe wetting takes place the earth plaster softens specifically at the interface with the lime plaster. Because of the lower permeability of the exterior lime plaster this sometimes leads to catastrophic events taking place well after wetting took place. 

Another option is a very thin exterior lime plaster wash working as a protective rain screen for the more susceptible earthplaster. This type of application does require regular but simple maintenance. 

Basically I have an LOE partway between a full lime plaster and a lime wash in my bathroom. It is a stucco lustro (lime plaster with Marseille soap) of roughly 1-2mm thickness giving a much smoother finish then the earth plaster could have given over a very thick earth plaster backing. No specific mechanical keying was done besides an open surface but the last layer of earth plaster had a very small addition >2% of lime making it much more resistant to wetting. I don't think it would work on an exterior but I do think that the addition of lime in at least the last layer of earth plaster can make quite a difference.

Slathered in mud in the reclaimed swamp at the mouth of the Rhine
Rene Dalmeijer

On Mar 2, 2011, at 04:20, kim thompson wrote:

> We have been doing various lime over earth experiments here in the Maritimes over the last six years or so.
> One system that has had good results in this "very hard on any kind of building" climate of Nova Scotia is
> to add a small i.e. 5% amount of lime to the final earth layer then leave this coat rough (or as with a scratch coat)
> to give a mechanical bond for the lime and sand plaster (1-2 coats). My theory is that adding some lime to the clay makes it
> more "compatible" for the subsequent lime layers, but this is purely conjecture. Would love to do more serious testing on this.
> 
> Indeed we have found that just adding the lime putty to the clay does amazing things to making it more water resistant. Hose tests
> and 6 winters confirm this. Getting this recipe right is likely relative to type of clay etc. so maybe challenging to standardize, or it may
> be that it is more forgiving than I think.