[GSBN] Plaster thoughts

Thu Mar 22 21:33:52 UTC 2012

Very well put, Tim, and thank you.

And thanks to all of you who offered help & suggestions.  We'll keep  
you posted.

Greetings to all baleheads from a sunny day in the San Juan islands of  
Canada/USA aboard the ferry from Here to There.

Bruce King
bruce at ecobuildnetwork.org
(415) 987-7271

On Mar 22, 2012, at 12:10 PM, Tim Owen-Kennedy wrote:

> Thank you all for your thoughts.
>
> Obviously this is a way more complex problem than can respectfully  
> be solved, or even thoroughly discussed, over email. I'm really  
> aware of most of the challenges - chemistry, climate, mechanical.  
> but I've also had lot's of success with lime over earth and lime in  
> earth. And have invested a lot of time in understanding why it's  
> successful sometimes and not others. Hopefully this process will  
> yield more understanding of failure modes at least and has more  
> potential to find a successful way to meld the modern desire for  
> cement finishes and the value of preserving traditional structures.  
> At the very least a whole new group of concerned cement geeks (and I  
> say that with the utmost affection) now have a much deeper  
> understanding of the value of earth and lime, and the challenges of  
> cement and especially how they work or don't work together.
>
> Our primary goals are to match a super flexible, durable, and vapor  
> permeable top coat that won't easily delaminate on the traditional  
> wood and earth walls in Kenya. Most likely through the right mix  
> design of a good intermediary material as well as the the design of  
> the top coat itself.
>
> I'm still much more a fan of an earthen solution. But the PR problem  
> of Earthen Building as an antiquated high maintenance peasant  
> material is one that I don't have the skills or funds to over come  
> quickly. So if we can find a way to have earthen structures  
> experienced as modern by giving them a functional modern "skin",  
> Then we can save a lot of great existing natural buildings from  
> being replaced by buildings with huge ecological footprints. And may  
> even encourage some doubters in the conventional building world to  
> wade slowly into our Deep Green waters.
>
> Until then, please feel free to share your wisdom and experience as  
> you have time and desire. It is always welcome and helpful.
>
>
>
> Tim
>
> I delivered the first four test panels yesterday. so hopefully we'll  
> be able to keep you posted soon.
>
> On Mon, Mar 12, 2012 at 8:36 PM, Rikki Nitzkin <rikkinitzkin at earthlink.net 
> > wrote:
> hi,
>
> I agree with alex's comments 1 and 2, but I would be careful about 3.
>
> I know that using oil as paint makes the house water-proof, but also  
> (almost) unbreathable.
>
> If you live in a place as dry as Alex (Didn't you say it rains once  
> every 10 years?) it is so dry that there is almost no humidity to be  
> trapped in the walls... but in many other places it could be a  
> problem.
>
> As for lime over clay, sometimes it works, sometimes it doesnt. I  
> find that Mixing lime with clay is often enough (between 1/6 to 1/2  
> parts lime depending on the type of lime and quality of clay). And  
> if it is not enough, you can always add a lime plaster on top. It  
> will stick better if there is a bit of lime in the coat below.
>
> Even so, I avoid the use of lime. I would add cow or horse excrement  
> to the finish plaster, and/or wheat paste, or even a SMALL amount of  
> oil (no more than 4% in volume)... and make the mix plenty of time  
> before you use it so it ferments. The fermentation helps a lot. That  
> is usually enough if there isn't a lot of wind-driven rain or hail  
> (which seems unlikely in Kenya).
>
> good luck, rikki
> -----Original Message-----
> From: "Alex Cicelsky (Kibbutz Lotan)"
> Sent: Mar 4, 2012 12:44 AM
> To: Global Straw Building Network
> Subject: Re: [GSBN] Plaster thoughts
>
> Dear Bruce, Tim and Mark,
>
>
>
> Three points:
>
> 1. Not knowing what the climate is there (in particular humidity),  
> type of sand (silicate or crushed lime) or clay mineral type, I can  
> only share the if it’s dry and the sand is silicate then my  
> experience is that lime washes and thin lime plasters will peel off  
> after the first rains.  I’ve seen even small amounts of cement cause  
> good clay bricks to disintegrate - I assume because of the type of  
> clay mineral.  I hope that’s not what you’re finding.
>
> 2. For many years we mixed our earth plasters using clay (from dried  
> flood deposits and well drilling tailings), course - sharp sands (no  
> fines - wind eroded Nubian sandstones quarried from sand dunes) and  
> paper fibers -  newspaper, egg crates and cardboards soaked for 24  
> hours+ and broken down in a cement mixer.  These mud-paper plastered  
> structures, pseudo ‘earthship’ - tires filled with plastic waste,  
> have stood for 20 years with very little cracking and an amazing  
> ability to get wet and dry out without disintegrating.
>
> 3. the exterior coating that we like best is used cooking oil using  
> the ancient Steen 4 coat recipe: 100% oil (applied heavily with  
> rollers), 75% oil + 25% turpentine, 50-50 and finally diluted to 25%  
> oil with 75% turpentine.  We apply them one after another without  
> waiting, best when it’s hot and Always after the clay/sand plaster  
> is completely bone dry.
>
>
>
> We’ve found that maxing the sand  component in a final, thin plaster  
> coat without straw creates the hardest protective layer - that’s  
> particularly appropriate where people (kids) come in contact with  
> the wall / bench (otherwise they pick at the straw).
>
>
>
> Good fortune and feel free to drop in since you’re already on the  
> continent.
>
> Alex
>
>
>
> Alex Cicelsky ~ Director of Research and Development ~ Center for  
> Creative Ecology ~ www.kibbutzlotan.com/ga
>
> Kibbutz Lotan ~ D.N. Eilot 88855 Israel ~ Tel: +972-(0)54-979-9009 ~  
> Email: alex at klotan.co.il
>
>
>
> Have an iphone/ipod/ipad and want to ‘green’ your home and  
> lifestyle?  Download the Free Eco Guide App www.tinyurl.com/ecoguideapp
>
>
>
>
>
>
>
> From: GSBN-bounces at sustainablesources.com [mailto:GSBN-bounces at sustainablesources.com 
> ] On Behalf Of Bruce King
> Sent: Saturday, March 03, 2012 19:10
> To: Global Straw Building Network
> Subject: Re: [GSBN] Plaster thoughts
>
>
>
>
>
> Marks, funny you should ask!
>
>
>
> Tim Owen-Kennedy and I have been roped into working in Kibera  
> (Nairobi) Kenya on the Human Needs Project (http://www.humanneedsproject.org/ 
> ), one part of which involves renovating earthen huts in the  
> shantytown that is Kibera.  The renovations mostly involve applying  
> a nicer and more durable finish to the badly eroded wattle-and-daub  
> walls.  You can see pics on the website;  their main thing is to  
> build a community center that provides clean toilets, potable water,  
> and solar-powered charging stations for mobile phones.
>
>
>
> For the earthen walls, our client came to us already wedded to a  
> cementitious system based on PVA fibers that bond to cement and give  
> concrete/stucco huge flexibility and crack resistance.  Tim's and my  
> job, which we're in the middle of right now, is to devise and test  
> PVA-cement mixes that can bond to the earth & stay put.  We are  
> going to test for delamination in a weather chamber that wildly  
> fluctuates temperature and humidity.  We are acutely aware of the  
> innumerable previous problems all over the world  associated with  
> cement-over-earth, and know we need to have as much vapor  
> permeability as possible,  So far we imagine using only large,  
> course sand (no fines), minimal cement, the PVA fibers (they look  
> like bleached, finely chopped straw), and possibly some lime.  As  
> usual, we have very little time or money to play around.
>
>
>
> Well report back to everyone as we progress over the next few months.
>
>
>
> Bruce King
>
> bruce at ecobuildnetwork.org
>
> (415) 987-7271
>
>
>
>
>
>
>
> On Mar 3, 2012, at 8:20 AM, huffnpuff at q.com wrote:
>
>
>
>
> Mark and All,
>
>
> I am sure you will be aware of some of what I suggest, as it's  
> common knowledge in the earth plaster world. Too much clay, too  
> little sand/aggregate, the size of the sand/aggregate (too fine  
> sand) can all cause excessive cracking. Removing clay, adding more  
> sand/aggregate or upping the size of the sand/aggregate could help.  
> I've found that the more/longer straw added can eliminate higher  
> clay content cracking. I've used a 1:1:1 ratio of clay, long straw,  
> masons sand for a very sticky, super strong, low/no cracking  
> application to stick as a base over foam, lumber and plywood  
> (placing some of this mix on the surface, tack mesh to subsurface,  
> place more mix, for an added mechanical bond).
>
>
> When you start adding lime and cement to a mix sounds like what we  
> do in the US. If it doesn't move, get a bigger hammer. It's not  
> better living through 'bigger hammer' chemistry. Often less is more.  
> I think you'll find some of your answers to cement earth plaster  
> ratios in a study by the U. of Penn as they attempted to do some  
> repairs to the mortar on ancient ruins in the Mesa Verde and Chaco  
> Canyon adobe structures.http://repository.upenn.edu/cgi/viewcontent.cgi?article=1044&context=hp_theses 
>  You'll find test results on "tensile strength, modulus of rupture,  
> water vapor permeability, and water porosity (respectively) (and  
> freeze/thaw) vs. volume-percent of Portland cement for amended  
> mortars" .
>
>
> Also, you might check out Stabilized Compressed Earth Block sites  
> (adobe block on steroids...it's what happens when engineer types  
> make adobe block). My limited experience with SCEB's is they only  
> use about 6-12% cement...lime may be substituted, but don't quote  
> me. Check out the Auroville Earth Institute  www.earth-auroville.com  
> for mixes using cement. Maybe others can chime in here with  
> knowledge on substituting lime for cement. Of coarse, different  
> areas have different clays that react in varying ways so  
> experimenting with different mixes/ratios would be prudent.  The one  
> advantage of using cement amended earth mixes is that it hardens  
> much faster so the results of your experimenting is swifter.
>
>
> For a shameless plug for the Conference in Sept. 2012 http://www.strawbaleconference.com/index.html 
>  the Auroville Institute will be represented at the conference by a  
> presentation by Richard Presley.
>
>
> If the locals insist on using cement additives to the earthen  
> plaster mix, visiting the information on these two sites should help  
> with your educated guess as to ratio's. I did some extensive stone  
> work this last summer and wanted to use an earthen mortar. I used a  
> 9:1 mix of my earth plaster mix/cement. My mason buddy thought I was  
> nuts. Eight months later, 4 feet of snow and lots of freeze/thaw in  
> our Colorado winter climate and that mix seems to be holding up  
> amazingly. There's little to no degradation of the mortar.
>
>
> For those interested in pre-fab straw bale walls and those using  
> cement stucco's these amended earthen mixes may be worth noting.
>
>
> Hope this helps Mark...Regards,
>
> Mark (see you in September) Schueneman
> Colorado Straw Bale Association
>
> 303-444-6027 hm.
> 303-591-9841 cell
>
>
>
>
>
> From: "Mark Jensen" <markj at redfeather.org>
> To: GSBN at sustainablesources.com
> Sent: Saturday, March 3, 2012 3:44:05 AM
> Subject: [GSBN] Plaster thoughts
>
> Hello et al,
>
>
>
> I am in Kenya right now working on two straw bale buildings,  
> stacking for both Monday and Tuesday. I am struggling with plaster  
> thoughts. I guess the last plaster they did was clay, sand, cow  
> dung, chopped straw, lime, cement and water. Nobody knows the  
> proportions but they had severe cracking, like a dried up lake bed.
>
>
>
> Now they want to do 1 1/2 bags of lime, 1/2 bag cement, 4  
> wheelbarrows of sand, chopped straw and water. This seems like a  
> recipe for disaster to me. They are on a very short budget. I  
> suggested harvesting clay and just doing a earthen plaster, it's  
> free other than some labor to harvest.
>
>
>
> Any thoughts on the recipe above?
>
>
>
> Your input would be appreciated.
>
>
>
> Asante Sana, Thank you very much,
>
>
>
> Mark
>
>
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>
>
> -- 
> Tim Owen-Kennedy, Owner
> Vital Systems, natural building & design
> P O Box 751, Ukiah, CA 95482
> www.vitalsystems.net
> 888.859.6336
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