Re: [SB-r-us] wear and tear on earth plasters
- I agree with David. I was the one who talked about Rain-Sil. One thing we also added to our earthen plaster as we mixed it was the powdered wallpaper paste. I found that mixing flour & water, cooking it, etc., was a definite threat to my desire to continue the project at all, so found the powdered paste, added it to the water for the plaster, then added the rest of the ingredients--clay, sand, and straw. My test patches told me this definitely added to the strength of the plaster over not using it. Our weather wall, very similar in overhang and it sounds like weather patterns, is still hanging in there enough to where I am not worried about having to re-coat right away.
We put 32 ounces (four 8-oz boxes) of the powder into each cement mixer full of finish plaster. This makes a nice, sticky, smooth plaster. That seems expensive, I know, but boy, it really made a difference in my test patches so we think that's worth it since we didn't have to make nearly as much finish plaster as infill plaster, of course. (It would be $20 or less per mixer full.) The brand I bought is available through Ace Hardware or online. Here is one site, but you might shop around for the best price on Golden Harvest Wheat Paste (get the powder, not the stuff already mixed up):
One other thing that comes to mind is that since the worst wear on your wall is at the bottom, do you have a splash guard there that might help with splashing rain from the roof? (Don't know if you have gutters or not.) Or some other kind of guard to protect the bottom edge of your wall. Perhaps a rain screen of some sort would help. We are committed (resigned might be a better word) to having to replaster at least the weather wall from time to time, but we are in our fifth year without having to do so just yet. Perhaps another year or two before it's really needed. For the record, we did add short chopped straw (two or three times through the leaf chopper) in our finish coat.
----- Original Message -----
From: Nancy or David Gray
Sent: Friday, November 30, 2012 3:42 PM
Subject: Re: [SB-r-us] wear and tear on earth plasters
Have you looked at recipes that include wallpaper paste, aka flour and water, added to the mix? It doesn't take much on a volume basis and the result from small areas I've seen is very strong. I would still put on the siloxane.
Limewash sounds feasible, but I have no experience with it. You could try it on the most exposed side you have, say halfway up the wall, as an experiment to see if it stops erosion. If it doesn't work you could cover it with the wallpaper paste amended coat.
Earth plaster is so easy to work with that I would keep it and not replace it. You probably should put chopped straw in the outer layer too, along with the paste.
--- On Fri, 11/30/12, cynshrn <cynsharon13@...> wrote:
From: cynshrn <cynsharon13@...>
Subject: [SB-r-us] wear and tear on earth plasters
Date: Friday, November 30, 2012, 1:02 PM
I have a load-bearing strawbale house plastered inside and out just over two years ago outside of Santa Fe, NM. We applied 3 coats of earthen plaster (total thickness about 2-3"). The last coat had no straw, just horse manure. We tried several stabilizers, but found them very hard to work with in our samples, so ended up sealing the walls with a product (Rain-Sil- a siloxane coating)recommended by someone on this list-serve. The problem is that the plaster seems to be wearing/washing off, even though we get only about 7" of rain annually and we have 30" overhangs around the whole building. I think the main culprit is that we get extremely strong winds (often over 40 mph) and it picks up the loose sand of the desert and abrades the walls. After two years the top 2' of wall looks virtually untouched, the bottom two-thirds has lost most of its finish coat, and the bottom edge shows water drip-marks/abrasion through the thickness of the brown coat.
Having read all the horror stories about lime over plaster, I'm totally confused about what to do. I know some people have had no problems with lime over plaster, but others have. So it seems like my choices are 1) reconcile myself to doing maintenance every year, 2) put a lime plaster or lime wash (I have gotton conflicting opinions) over the earth plaster and hope for the best, 3)try another earthen plaster sealer, perhaps linseed oil, or--the most drastic-- 4)take off the earth plaster and re-do it with a lime plaster.
I suspect that the posters who have talked about how young our field is are correct and that in another 40-50 years we will have a much better understanding of which earth plasters work with which lime plasters, but in the meantime I feel like I have nothing but conflicting advice. So of course, I am soliciting a little more! Any help is appreciated!
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- Hi, we started out with lime plaster over earth plaster- and it delaminated on two walls. We removed it and went with straight lime. We have one wall where it didn't delam because the lime layer was much thinner. That wall gets the full force of wind- up to 80mph. It looks as you describe and we also figure it's the wind abrasion. We do not have 30 inch overhangs and we get considerably more moisture than you (snow too). However we have done several moisture tests, especially around windows, and the bales are DRY DRY DRY. So you should perhaps not worry while you figure out a solution! :-)
One idea we got from this list and we considered it carefully. You might find it workable for you as well. Have you considered Rain Cladding? Are you experiencing the wearing on ALL sides or just the prevailing wind side? If it's one or two sides hanging some rain cladding might do the trick for you. Our problem wall is ONE wall facing the wind- we solved most of the problem by stacking our firewood along that side- thus having a very thick 'rain cladding' with no construction required! :-) (however our long term solution? we will be removing all the plaster on that wall eventually and replacing with lime plaster. The other walls are wearing beautifully and we are happy with the results. Just have to talk ourselves INTO the project first!)