[GSBN] lime plaster over compressed earth blocks

Graeme North graeme at ecodesign.co.nz
Fri Apr 4 02:37:53 CDT 2014

for what it is worth

I have looked a many many walls treated with just about every magic potion known to man where people have tried to remedy what really is poor design in an attempt to try and reduce water ingress into earthen materials.  Small samples of some potions can give impressive short term results, esp  potassium silicate brews. 
In nearly every case, when dealing with a whole real building over several years, it also reduces moisture outfiltration (to reuse a great word) and the very least result, in by far the majority of cases I have looked at,  is delamination of the treated surface layer, whether stabilised or not, if not more severe degradation, or leaking issues.  

If there already is a plaster delamination problem caused by moisture I would not be brave enough to suggest that any magic potion alone will solve it. 

The best performing surface treatments over natural earth are earth plasters, but they are prone to erosion, closely followed by lime plasters.  Whitewash will also delaminate over natural earth.

Keeping most of that darn rain off with roof overhangs appropriately sized for the conditions  and /or rain screens is THE surefire treatment that really works.

I really wish that there was a magic potion  that really really worked. And that I had $10 for every time someone had asked me to name them one.  


Graeme North Architects
49 Matthew Road
Warkworth 0981
tel/fax +64 (0)9 4259305


On 4/04/2014, at 1:54 PM, Bill Christensen <lists at sustainablesources.com> wrote:

> Dang, I'm just catching up on my GSBN email tonight.  Sorry we missed you! Alert me directly next time, will you?
> Paul Salas out of UNM told me about potassium silcate at one point, and gave me a quick demo as we passed through Santa Fe one time.  He was looking into the same, and I believe he was trying to figure out if/how it was chemically changing the soil.  It was definitely effective in reducing water problems - he had a small adobe that had been treated and another of the same soil which hadn't, and when he dropped them both in water the untreated one came apart.  The treated one came out whole.  
> I suspect a brush-on application would help the plaster hang together as a monolithic sheet.  It would also reduce water infiltration, I believe.  Of course, it might also reduce outfiltration...  If it holds water in the untreated interior, well, I don't need to spell out for you what could result.  You're a smart guy. 
> On 3/26/14 9:59 AM, Bruce EBNet wrote:
>> I'm trying to help a builder near Austin, Texas with a delimitation problem on a 7 year old building.  He says he has since learned to use potassium silicate as a brush-on stabilizer for the blocks, helps the plaster hang on.
>> Thoughts?  Experiences?
>> Austin folks:  I'm coming into town tonight.  Dinner?
>> Thanks,
>> Bruce King
>> www.ecobuildnetwork.org
>> (415) 987-7271
>> Skype: brucekingokok
>> Twitter: @brucekinggreen 
>> http://bruce-king.com/
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