[GSBN] lime plaster over compressed earth blocks

Bruce EBNet bruce at ecobuildnetwork.org
Mon Apr 7 15:45:51 CDT 2014



Thank you all for your thoughtful replies -- VERY helpful.

This is not a design job, but an investigation of an existing group of buildings.  Near Kerrville, Texas, built 7 years ago by Kevin Coleman, and actually a pretty good job.  A few cracks and delaminations, but mostly large expanses two stories high of unblemished plaster over blocks, both inside & out with every solar orientation.  Impressively few problems, really.

My takeaway from all your posts is that potassium silicate can be pretty useful, but -- per Graeme's caveat -- there ain't no perfect system.  As in construction in general.  As in life.

Which is to say:  rock and roll will never die.  But GSBN is great.  Thanks again!

Bruce King
www.ecobuildnetwork.org
(415) 987-7271
Skype: brucekingokok
Twitter: @brucekinggreen 
http://bruce-king.com/





On Apr 6, 2014, at 2:43 PM, Graeme North <graeme at ecodesign.co.nz> wrote:

> Thanks Frank,
> 
> The issue that I have seen with impressive samples like the birthday cakes is that they are not a real building with large walls which have pesky people living inside them generating moisture and wanting windows and doors and openings and inevitable cracks and pinholes in the coatings, and nasty ol' moisture that moves in and out of walls. There are real experts on this forum that know a lot more about this dynamic moisture movement stuff that I ever will.  Maybe they have an answer.  I can only go on what I have observed around the traps over many years.
> 
> I wish it were otherwise, but I have now looked at probably hundreds of earthen walls in particular, to see if there is one where an impressive magic goo coating has actually stood the test of time. I really would like to find one I could have faith in.  I really would. In most instances I must repeat that I have had to conclude that nearly everything that I have seen so far has not come anywhere near reliably replacing good primary weather protection offered by appropriate design  (whatever those fantastic weasel words may mean).  I call the resultant degradation of plaster surfaces skin cancer.  And the surgical cures can be just as extensive and transformational.    
> 
> Using magic goos as a back up I have no issue with, and will, and do, sometimes specify them for use over earth and over s/bale plasters.  As Frank says, they can offer some great back up help. Its all made so much more complex by having such a range of variable substrates and site conditions - hence the "nearly" everything above as sometimes there are earthen mixes that seem bomb proof in themselves anyway.
> 
> And even if durability issues are resolved, there often are leaks caused by wind driven rain.  Dealing with the latter (by rain screening) is usually an over-riding feature of real building design concern in my part of the world anyway, as clients often get grumpy when their buildings leak.  For some reason the sense of humour often goes first.
> 
> 
> 
> Graeme
> 
> 
> 
> 
> 
> 
> 
> On 5/04/2014, at 12:40 AM, Frank Tettemer <frank at livingsol.com> wrote:
> 
>> Here's a story that might help address your query, Bruce.
>> 
>> I agree with Graeme that design is the first solution. Design and plan to keep the walls as dry as possible.
>> 
>> With climate change comes stronger, windier weather.  Now we have to plan on the walls becoming wind-blown with rain, (in between periods of drought).
>> 
>> In addition to adequate roof overhangs, eavestroughs, and proper site orientation, I do believe there is a good use for the magic of silicate dispersion paints, either from Bioshields in the States, or Eco-House in Canada.  I'm certain there is an outlet in Europe, since that's where that technology came from.  I've used it a number of times, as a colourant top dressing to plaster. The specs claim it to be vapour permeable and water resistant, (Like gortex for plaster). I'm a skeptic, so I prefer visual, tactile  test results.
>> 
>> Here's an inadvertent, but likely valuable test result:
>> In 2004, we completed a straw bale home for a client in Ontario, Canada; a climate of high humidity, and frequent rain through the Spring, Summer, and Autumn.
>> Tina Therrien and Camel's Back Construction were on site, plastering, when someone discovered that over the weekend Cheryl and I had both quietly passed our birthdays.
>> Tina and her crew made two "birthday cakes" for us, out of the plaster. They were so cute that we took them home, and set them on the deck to admire.
>> 
>> When obtaining a series of samples of different colours of Eco-House silicate dispersion paints, Cheryl decided to paint the "birthday cakes" with a variety of these pastel paints, as a colour sample.
>> 
>> To make a short story longer, I set these samples out in the weather, (in 2004), on the deck, where they have remained to this day.  Slightly chipped, and with the red colours slightly faded, these samples are perfectly intact today.  See the attachment photo of them, that I took this morning ... yes, that's still three feet of snow in the background, with a shovel handle sticking out as a depth gauge.
>> When it rains, the water beads up and runs off the surfaces of these samples, and appears not to be soaking in. When covered with snow, frost, ice, the samples have remained intact.
>> 
>> I've liked these "cakes", so I've never immersed them into a tub of water, or attempted the "soak test" like Bill's friend, Paul Salas. I think they would turn back into the plaster components that they came from, and get pretty soggy. But standing up on the deck, in direct sun and rain, they have survived over Ten Years.
>> 
>> So too have all the SB homes survived that we've treated with this silicate paint over the past decade. It does wear, yes, and probably will need a touch up coat after ten years.
>> It's no real replacement for good overall design, but I am a believer in the help that they offer in the form of rainscreen cladding.
>> 
>> For what it is worth,
>> 
>> Frank Tettemer
>> Living Sol ~ Building and Design
>> www.livingsol.com
>> 613 756 3884
>> 
>> ....................................................................................................................
>> 
>> 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.
>> But
>> 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.
>> 
>> 
>> Cheers
>> 
>> 
>> 
>> 
>> 
>> Graeme
>> Graeme North Architects
>> 49 Matthew Road
>> RD1
>> Warkworth 0981
>> tel/fax +64 (0)9 4259305
>> 
>> www.ecodesign.co.nz <http://www.ecodesign.co.nz>
>> 
>> 
>> 
>> 
>> On 4/04/2014, at 1:54 PM, Bill Christensen <lists at sustainablesources.com <mailto: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 <http://www.ecobuildnetwork.org/>
>> (415) 987-7271
>> Skype: brucekingokok
>> Twitter: @brucekinggreen
>> http://bruce-king.com/
>> 
>> -- 
>> 
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