Plasters made with clay are beautiful, durable, and made from inexpensive and non-toxic ingredients. Clay creates a breathable finish material with a natural capacity to regulate moisture and temperature in the surrounding air. Clay naturally absorbs excess moisture in the air, helping air to feel more comfortable in summer, while its high thermal mass creates a battery heat (or cooling) storage that helps to maintain constant air temperature. Materials can often be found on or local to the building site, making the ingredients dirt cheap...literally. Or you can use dry bagged clay from a pottery supplier. Clay naturally occurs in a variety of colors and clay plasters can be pigmented with mineral based pigments in every range of color. Techniques for mixing and applying are simple and the plaster is extremely forgiving, even for beginners of any age.
Below are instructions for wall preparation to apply clay plaster on drywall or on clay substrates, followed by my favorite finish clay plaster recipe. At the very end are my 3 favorite plaster books. Have fun playing in the mud!!
Drywall Preparation
sanded primer for drywall application of clay paints (from Keely Meagan’s article in The Last Straw: www.thelaststraw.org/bonus-articles/earthplaster.html)
- 10 parts wheat paste
- 1 part coarse sand
- 1 part clay
Covers approx. 40 SF
Wheat Paste
Bring 1 quart water to boil in a non-aluminum pot. Meanwhile, mix 1 cup flour with 1 cup cold water until smooth and lump free. (If you can’t get it lump free, run through a strainer.) When water in pot is boiling, slowly add in flour/water mixture, stirring constantly. Bring back to almost a boil, stirring constantly, until mixture thickens. Remove from heat and allow to cool completely. Use wheat paste within a day or two; it goes rancid after a few days (faster in warm weather), and becomes smelly and usable.
Makes approx. 5 cups of wheat paste.
Clay-Over-Clay Preparation
Dampen clay substrates prior to application of clay paints or plasters. I recommend dampening clay substrates the evening prior to application, again in the morning before you begin to mix your material, and then again about 20 minutes prior to application. Thick cob walls generally require more dampening than clay plaster surfaces. Be sure to allow your water to completely absorb or you will create a water slick that prevents plaster from adhering to your substrate. Continue to dampen the wall as you work.
Kaolin Clay Plaster
beautiful white or off-white, creamy plaster that can be pigmented as desired
- 1 gallon water
- 1 (5)-gallon bucket kaolin clay putty*
- 2-½ (5)-gallon buckets fine sand**
- 1 cup wheat paste per 5-gallon bucket of material (clay and sand)
- Pigment, mica, or chopped straw, as desired
**typical is mason’s sand though finer grit sand may be used; the finer the sand, the smoother the wall surface without buffing with a finish trowel
- Mix all ingredients together thoroughly. You can use a cement mixer or you can mix materials on a tarp (flipping often & mixing with your feet). Final consistency should resemble creamy mousse. More water may be added to achieve desired consistency.
- If adding pigment, save some pigmented plaster with no wheat paste for later patches or repairs. Add wheat paste after pigment.
- Apply plaster to desired texture, typically using trowels, onto substrate that has been prepared as above.
- When leather hard (slightly firm), smooth the surface by buffing with a damp tile sponge, rinsing the sponge frequently. Or, for a super smooth finish, run a final sweep across the dampened surface with a very flexible trowel. Mist clay surface slightly as desired as you buff with the flexible trowel.
Resources
If you are plastering over strawbales, read our other plastering posts:
"Clay Plastering Strawbales - FIRST COAT"
These are the most useful books I've found for information on making & applying clay plasters.
Clay Culture: Plasters, Paints and Preservation by Carole Crews, Gourmet Adobe Press, 2010
The Natural Plaster Book: Earth, Lime and Gypsum Plasters for Natural Homes by Cedar Rose Guelberth and Dan Chiras, New Society Publishers, 2003.
click the book covers above for more info or to purchase
Using Natural Finishes: Lime- & Earth-Based Plasters, Renders
& Paints, A Step-by-Step Guide by Adam Weismann and Katy Bryce,
Green Books Ltd, 2008
Clay Culture: Plasters, Paints and Preservation by Carole Crews, Gourmet Adobe Press, 2010
The Natural Plaster Book: Earth, Lime and Gypsum Plasters for Natural Homes by Cedar Rose Guelberth and Dan Chiras, New Society Publishers, 2003.
I don't have any words to appreciate this post.....I am really impressed ....the person who created this post surely knew the subject well..thanks for sharing this with us.
ReplyDeleteLondon Plastering
Thanks so much for your kind words! I'm so glad that you found the information to be useful!!
ReplyDeleteVery timely for me to find as well as am planning a clay plaster over drywall this Spring in the urban Victorian I am fixing up from a vacant condition. First step was, find a substrate recipe! Thanks!
ReplyDeleteI'm so glad to hear that! Best of luck with your plastering project. Sounds like fun.
DeleteMany thanks for your advice Sigi. I tried your recipe "Drywall preparation" and to other materials such as drywall, for example: wood board, concrete, lime plaster, lime-sand bricks, even old painted wall and I was pleasantly surprised adhesion to the substrates.
ReplyDeleteUse this recipe and the old plaster in houses or old houses? Or use another method? What is the preparation of such a wall please?
Thank you very much
Erik from Slovakia - Europe
Hi Erik, I'm so glad to hear about your experiments with the sanded primer recipe. I've never tried it on concrete or brick and am so glad to hear that worked! For your question about wall preparation, can you be more specific about the existing wall surface...what is the wall made of, is it painted (and with what type of paint), are there cracks to repair, etc.??
DeleteThanks!
Hi Sigi,
Deletewall in the flat is composed of brick, the first layer is cement plaster, the second layer is a soft lime plaster and two coats of paint on a natural basis, small cracks.
Today I tried the recipe directly on the paint. I will send a message what is the result.
Over paint is the only surface I've had problems with. Especially if it is a latex or plastic-based paint. Be sure the adhesion of the sanded clay primer is really good when it dries, and then make sure it doesn't have any signs of flaking off or cracking. Definitely let me know how your test area goes! Fingers crossed... :-)
DeleteHow were my tests? Your recipe keeps well for concrete and also the lime-sand bricks and of course the drywall.
DeleteThe recipe has not adhered to the old paint, while creating good skin, but is not connected to the base, so I had to remove all the paint.
That makes sense...should work best on absorbent surfaces, which includes the concrete, brick, and drywall. Thanks for letting me know your results!
Delete... and your recipe keeps well on wood
DeleteSigi,
DeleteThank you so much for all information given. Is there a primer/base that
can be used on a painted wall?
You should be able to use a sanded primer (ie, paint with gritty sand in it). That will give you a textured surface that you should be able to plaster over. Do a test area first, to be sure all of the materials are indeed compatible.
DeleteHi Sigi, I've got a question about this article. I'm planning on using this recipe on a wall in my house over drywall. It's close to 100 sq ft. How large is the "part" in this recipe that says it covers 40 sq ft?
ReplyDeleteHa! Thanks for catching that! So you are talking about the wall prep sanded primer recipe. The "part" is 1 cup. Also, this won't stick to existing paint, only to raw drywall. So if you are planning on refinishing an existing wall that has paint, you will need to use a different sanded primer. Good luck with your project!
DeleteIt had wallpaper on it and was never painted, not even primed. We have it mostly down to the bare wallboard. I think it will work okay, though I'll do some tests, hopefully this weekend. I'm really looking forward to a unique finish.
DeleteIs it a cup (part) for the kaolin plaster as well?
DeleteYup, exactly, so 10 cups wheat paste, 1 cup sand, 1 cup clay. the clay doesn't necessarily need to be kaolin. I actually mostly use site clay for this. But then you need to test your clay/sand proportions and adjust the quantities accordingly...
DeleteFor your wall prep, as long as you removed the wall paper and there is no paint, you should be fine. Definitely do a test area to make sure your sanded clay primer sticks without flaking off. If it does stick with good adhesion, you are good to go!
DeleteIs there an alternative for wheat paste for those who have wheat allergies?
Deletewheat paste shouldn't effect a wheat allergy, but you can use anything that is sticky like pudding...or just skip this ingredient
DeleteThis comment has been removed by a blog administrator.
ReplyDeleteCan I use clay over brick and plastered wall?
ReplyDeletedepends what the surface is. You need surface area to create a physical key for the clay plaster and you need an absorbent surface for the clay to bond to. Often this means you need to apply a sanded primer or sanded bonding agent of some kind. Best bet is to do a test area.
DeleteWonderful information you shared. Thanks
ReplyDeleteplaster walls
you describe really very useful Article..you describe the method for making clay plaster is very useful.Clay is very important ingredient for plaster Thanks for sharing with us.!!
ReplyDeleteHi Sigi, I am surprised to know that a clay plaster will adhere to drywall! We were going to use peg board for an interior wall, but now am considering the drywall.
ReplyDeleteActually, would like your thoughts on using peg board as we want to curve the shower walls...
ReplyDeleteI'm confused...sorry. How would you curve the pegboard? And do you mean to use the pegboard as backing for clay (because of the holes)? Or do you want pegboard as your shower walls?
DeleteEither way, a shower wall should NOT be drywall. It should have cement board or greenboard that can handle the damp conditions in the shower. You can do drywall in the rest of the bathroom.
Also, I wouldn't do clay plaster inside the shower, as it will erode over time. You can do clay plaster in the rest of the bathroom, but the shower should be a lime-based plaster instead.
Hi Sigi, yes we'll use lime plaster on the shower walls. We were going to use cement board, but we were thinking we may be able to some how curve pegboard, slightly.
ReplyDeleteHi Sigi, yes we'll use lime plaster on the shower walls. We were going to use cement board, but we were thinking we may be able to some how curve pegboard, slightly.
ReplyDeleteI wouldn't use pegboard in a shower...either as the finish or as the substrate. Picture everything should be able to get wet...
DeleteInteresting information about Clay Plaster and recipes. Nice blog
ReplyDeleteInteresting information about Clay Plaster and recipes. Nice blog
ReplyDeleteI have drywall that has been painted with drywall paste, not paint, will the primer recipe stick to that? Or could I just apply the clay and would it stick? Thanks, great article, very informative!
ReplyDeleteNot sure, depends what the paste is made out of. I would do a test area and see. You should not be able to scrub the primer off with your hand. In order for the clay to stick, you need texture on the wall. And you need a substrate that is compatible with the clay. I have no idea what the drywall paste is made out of, so no idea about compatibility, but I'm guessing it is smooth, not textured. So do a test to see if the primer recipe above will stick. If so, then you are good to go. If not, then you can use any primer paint with sand added in to paint texture onto the wall.
DeleteHi Sigi,
ReplyDeleteI think I have interpreted your recipe incorrectly. Here is my translation: one part water, five parts putty, 12 1/2 parts sand. Is that correct? I'm ignoring the wheat paste as when I do it I will use a dollop. When I try it, it rolls off the wall as particles of sand. Should the sand be 2 1/2 gallons (instead of buckets) or does 2-1/2 mean from 2 down to 1/2 buckets? Thanks!
You definitely need more sand than clay. But I can't speak to your exact recipe. The thing to know is that first, there are so many different types of clay, and different clays have different stickiness. The more sticky, the more sand you need. Second, the sand is crucial. It must be gritty, toothy sand and it should be 1/2 as big as whatever thickness you are putting on for your plaster. So if it's a thin coat, you need gritty sand, but screened fine (usually 1/8" or smaller). In terms of wetness, it should be about like sour cream or whipped cream. Too thin, and you can't plaster with it.
DeleteMy recommendation is to make some tests with slightly different mixes until you get a consistency that feels both sticky and gritty, and that is solid enough to plaster but is still creamy enough to spread.
Hope that helps.
Hi Sigi
ReplyDeleteI have tried your clay plaster recipe with an oxide powder for colour on a cob wall and it is lovely. i think it will be perfect for the internal walls of my garden structure, but my question is, could I apply lime wash over the plaster to make it more weather resistant on an external wall (I live in Australia so the wall iwon't get constant rain on it, but may be subject to heavy, driving rain from time to time). Thank you.
sortof...the limewash will wash off over time and you will need to reapply it and if the wall gets heavy rain, the limewash will not prevent erosion
DeleteThank you for your answer, Sigi. Much appreciated. It's a small section of wall that isn't protected by the roof, so regularly lime washing might be the easiest and best option to prevent the cob eroding. if there is heavy rain I might just need to physically cover it temporarily with a tarpaulin or something. I guess my main concern was that maybe the clay plaster with wheat paste and the linewash might be incompatible, but it sounds like it should be ok.
ReplyDeletejust to clarify again...limewash will not prevent erosion...at all...
DeleteBut the materials are definitely compatible
Excellent your work ... God bless you, to see when they bring these techniques to the countries of South America , there are places where people do not have resources for the construction of houses. They left the old techniques and is now more expensive. Greetings from Venezuela.
ReplyDeleteHi Sigi. Thanks for the info! I have some leftover plaster from a friend's project that is a bit stinky thanks to the wheat paste. Do you know if it will continue to smell after it dries? Or is it really unusable?
ReplyDeleteoooh, yes, the wheat is anaerobically decomposing...there's no return from that. When I use wheat paste, I only add it to the plaster I'm using, never to plaster that will be stored. Also it may create black blotches on the wall. I would ditch it and make new
DeleteThank you so much for this information and the recipe! I'm renovating a traditional danish timbered, thatched country house, where the walls are made of only timber and raw clay. So I expect this will work like it was meant for it :) I really like the idea of making the plaster white with kaolin and then add some pigment. Do you have any recommendations regarding type of pigments,or where to read about it (also 'recipes). I'm very much appreciating you using your time and effort on answering questions here.
ReplyDeleteGreetings from Denmark, Mona
I order mineral pigments from a US company...probably not the best resource for you, though. I don't really know companies to specifically recommend in Europe. Sorry! But I would look for natural mineral pigments. Does that help?
DeleteForgot to ask, if you have tried painting on this type of plaster with paint? I use a transparent kind of paint, based on beeswax, called lasur. I've often seen it used in Waldorf schools etc. I was thinkint it would look good on this kind of plaster.
ReplyDeleteyes, for sure! :)
DeleteThis comment has been removed by the author.
ReplyDeleteHi,
ReplyDeleteThanks for all this info!
Would you be able to give me a little advice about making the kaolin putty? It's a pretty difficult/ interesting material mix; similar to cornstarch but much stronger.
Thanks,
Jake
First off, I have no experience with clay so I apologize if the answer is obvious.
DeleteWhen mixing the kaolin clay (powder) with water, not sure how to determine the amount of water to add because the way the material changes when it's worked - the harder you work it, the more firm it gets, while it gets more fluid if you're gentle with it. Seems like it's meant to be mixed well and left alone and in time it will absorb the water/ break down - as you said soak it for at least 24 hrs...seems like the key word is "soak."
Thanks!
Jake
Directions are above and the process really is that simple. Put some water in a bucket, slowly pour in the dry powdered clay, mix as you go. Make sure there is no powdered clay clumps and then make sure you have some water on top. Then simply let it sit for at least 24 hours. Time will do the work for you. Hope this helps.
DeleteHi, thanks for your knowledge! What are your findings with longevity?
ReplyDeleteThanks!
Jason
extremely good :)
DeleteThanks! Would you know if granular clay work rather than powdered clay?
Deletenot sure what granular clay is...but any clay can be used to make plaster if it doesn't have unnatural additives. Note, however, that the recipe above is specific to powdered kaolin clay. If you use different clay, you will need to re-calibrate your recipe.
DeleteMy wife and I are so excited and have started experimenting based on your suggestions! This is great! Some questions that have come up...
Delete1. how much water to add to the (100% kaolin) clay powder to make the putty (it seems one can add any amount and pour off the excess after 24 hours, correct? Or is there an easier way?)
2. Do have a supplier for the clay putty?
3. Our wheat paste turned out lumpy although the cold water/wheat mixture was smooth. Did it need more mixing while on the stove?
Again, we are more than grateful for the information and looking forward to passing on your blog to others!
Jason
great questions!
Delete1) if you make the putty at least a day ahead of time, then the putty will settle down and water will settle to the top; in this case you can skim the water off the top as needed. If you make it the same day, you'll have to experiment a bit to get the exact proportions, but usually it's around 20% water to 80% clay powder (start with the water in the bucket first, and add the powder)
2. you can get powdered clay from any pottery supplier. I happen to be near Baltimore MD, so I use a supplier there. Not sure where you are, but you should be able to find a pottery supply store near you (or one that ships).
3. Sounds like you didn't stir enough or there was too much water. Feel free to add 50% more water to the recipe above. the thinner the paste, the easier it is to work with. (But you'll have to adjust your recipe to add more paste since each cup has less flour in it)
Hope that helps!
Hi Sigi,
ReplyDeleteDon't think my last comment went through so will try again. Thank you for your helpful article and recipes. What would be the approximate ratio of sand to primer for preparing drywall for plaster. Had some sand delivered to protect pipes from getting cracked by rocks when backfilling, would that kind of sand work? It has been out in the elements for a while so would I need to wash it somehow? Is only one coat of clay plaster required for drywall coverage? If more than one coat is required is there any special finish you need to do for the second coat to adhere to the first? About how thick should the coat(s) be? Many thanks, Kathryn
gosh, I'm not sure...I usually just have sand on hand and add as needed. The goal is to turn your wall into a rough sandpaper texture to give your plaster something to grip to. My favorite sand is concrete sand, with some larger aggregate.
DeleteHI Sigi,
ReplyDeleteThanks for sharing all this info. I am trying to figure out how much kaolin clay to order, and Im wondering about how many .lbs of dry clay makes 1 5- gal of the clay putty?
Thanks!
Sara
depends a bit on the clay, but typically 50-lbs = about 10 gallons of putty
DeleteHi, can you let me know how thick a clay plaster can be applied to drywall? I am hoping to add thermal mass on my walls and ceiling with the plaster, so I want it as thick as possible ... I just don't know how far I can take it.
ReplyDeleteAlso, pardon my ignorance, but should something be put over the screw heads before applying the drywall preparation - or will the preparation formula stick to them ok?
Thank you so much for your time and this wonderful resource.
I would stick to 1/2" or less on drywall. Maybe maybe maybe 3/4", but only if you have a really really gritty surface painted onto the drywall. The issue is that the plaster is hanging on the drywall like a little rock climber...and at some point the weight is too much and the hold is not enough...and then it all falls off. For preparation of drywall, it would be exactly the same preparation at screws & joints that you would do if you were going to just paint.
DeleteThank you, as ever, Sigi for your clear and empowering info!
ReplyDeleteWondering if you have any tips on learning more about those mineral based pigments? (as a launching point to experimenting with colouring?)
And where do you get your pigments?
... I've ordered the "Natural Plaster Book" you recommended, maybe such details will be in there....
:) with gratitude,
Jenna
Hi Jenna, and thanks for your sweet note. Here are my favorite pigments sources:
ReplyDelete1. https://www.earthpigments.com/
2. https://shop.kremerpigments.com/en/pigments/
3. https://www.naturalpigments.com/
4. http://www.bioshieldpaint.com/index.php?main_page=index&cPath=1
Hope that gets you started! Let me know if you are looking for something more specific.
fabulous! That's a great help, thanks :)
ReplyDeleteI am building a straw bale house and plan on using clay plaster as you have so wonderfully explained. I am working alone and have some long walls to plaster. Is it problematic to stop plastering and resume the next day. What are the procedures for such a scenario? Many thanks for your help!
ReplyDeleteFor base coat plaster (ie, not the finish plaster), you can start and stop. Just be sure to dampen, always, the seam really well as you go. For finish plaster, you will always see a start-stop point. So you'll want to create stopping places. One option is to make a gentle squiggle edge, or some other defined shape that highlights your stopping point intentionally. Then it looks like a feature as opposed to an "oops, couldn't finish that wall". Or get someone to help you
DeleteThat is what I thought but could never find a definite answer. Good to know. Many thanks!
ReplyDeleteglad that helps :)
DeleteRegarding your Kaolin Clay Plaster, it says the recipe would cover 100sq ft. That seems way too little for the four 5 gallon buckets of material being used. Can you confirm Sigi? Its so great to have a calculation to help with knowimg how much material to source. Your website is the only one i found so far with numbers! Thank you.
ReplyDeleteWell it depends a bit on thickness of your application. I would take 1 gallon of plaster, apply it in the thickness you intend, and see how much coverage you get. That will be more accurate. But yes, generally I get about 5 SF per 1 gallon of finish plaster. I also always make an extra bucket of plaster, but wait to add any pigment or wheat paste....then if I need it, I have it quickly
DeleteI love this info. Thank you. I do have one question if I have premixed mud can I add arkansas dark red clay...It's dry and I would have to get the lumps out but I wanted to combine the two for paneling...would it work...I did my bathroom but without clay...without trowel...by hand...chunk looks great.
ReplyDeleteI'm sorry I don't understand what you are asking...
DeleteThe general point seems to be about eliminating chunks from a finish plaster. I always sift materials through at least a 1/8" screen (or sometimes smaller) if I am using the clay for finish plaster.
Hi Sigi, I am trying to understand if natural plasters such as these when applied over concrete blocks would trap moisture within the walls, creating mold over time. Thank you for all of your info!
ReplyDeleteNo, natural plasters will not trap moisture in any type of wall. However, if you have an intrusion of water into the concrete block wall (for example, if the block wall is below ground with soil up against it), then you will have a persistently damp wall regardless of what type of finish you put on it. (And persistently damp conditions are where mold loves to live)
DeleteHi Sigi, I love your website and have found it to be incredibly helpful as I finish the upstairs bedrooms of our very old, but new to us, home. So far I have replaced a lot of the old lime plaster (it had plasticky wall paper which trapped moisture and got very mouldy so I ripped it all out) with clay plaster. I am just about to put our bedroom back together, but I started to worry about the dust from the new clay plaster walls with clay paint. They aren't terribly dusty, if I were to run a black cloth over it you would definitely see dust on it. Is it dangerous over time, to be sleeping and breathing this clay dust? Would you recommend something to finish it, a wax or soap or something similar? Thank you so much, I appreciate your knowledge so much!
ReplyDeleteIf your plaster or clay paint is dusty, it doesn't have enough binder in it. You can try to tweak your recipe to have more clay/less sand. Or you can add a non-shrinking binder, such as wheat paste. Or or, you can seal it with wax or hardening oil. Note that oils will usually darken the finish color and waxes can have a sheen. Hope that helps.
DeleteWhat kind(s) of wax or oil do you recommend? Does it still allow the plaster/wall to breathe? We are also having dusty walls, it feels like sand a light layer of sand brushes off when anyone touches the wall, sounds like we may need to add a higher proportion of clay and/or wheat paste (I did follow your recipe above, but our clay is probably a lower grade than yours, perhaps it has some sand in it already?), but I would also like some kind of compatible paint or sealer on the inside.
DeleteThe plaster recipe above only works for pure dry kaolin clay, purchased from a pottery supplier. If you used different clay, then you need to do tests to come up with a recipe that works for your particular clay. A sandy surface always means there is not enough sticky binder in your recipe. It is also an indicator that the surface will be weak and prone to scratching. You could make a clay paint, which is sortof like liquidy plaster and provides about 1/32" strong clay surface. I have a recipe on my blog here: https://buildnaturally.blogspot.com/2013/03/make-natural-non-toxic-paint-from-clay.html
DeleteOtherwise hardening oils will strengthen the surface of your clay to a degree (though they do darken the finish somewhat). Wax finishes diminish the breathability, and I only use them where I am trying to achieve a particular sheen or if I need a bit of extra water-proofing. I use a wax paste made by "Roman" brand. Hope that helps
Thank you! I have my jar sitting for the clay test now, still many more walls to go with this new information. I'm having trouble finding Roman wax but Biosheild offers this hard oil: Ingredients: Linseed Oil, Tung Oil, Colophonium Resin, Castor Stand Oil, Isoaliphatics, Lead-Free Dryers (Zircon, Cobalt Octoat), and Oximes (Anti-Skinning Agent).
DeleteAnd this wax: Ingredients: Beeswax, Linseed Oil, Orange Peel Oil (D-limonene), Isoaliphatics, Carnauba Wax, Larch Resin, Essential Oils, and Lead-free Dryers (Zircon, Cobalt Octoat).
Do those seem comparable to what you use? We just have one small wall on the outside that gets rain on it in storms (43 sq ft of plaster), would either the wax or oil be a good solution for that? or we were also looking at some kind of limewash
I can't say for sure if the products are comparable. You'd need to do an ingredient comparison. I mostly use oils from The Real Milk Paint Company. And Roman's wax pastes for the rare time I use wax finishes. I would avoid the lead dryers (which you have) but also the cobalt dryers because cobalt compounds can be radioactive (not sure about that particular one, but I would do some more research before using)
DeleteOh, I have some of their "half and half" tung oil and citrus solvent, does that work, or do you use the outdoor defense oil? None of them are specifically advertised for clay plaster, so I'd want to make sure I'm using the right thing. Do the oils affect breathability/or do I need to make sure to do the same treatment inside and outside the wall to make sure it's even, or does it matter? (Just I read on another strawbale website about making sure inside and outside of the wall have similar levels of breathability, its making me second guess what I thought I was going to do.)
DeleteThey actually have good customer service, so you could give them a call and ask what they recommend for your application. I tend to use the hemp oil (if anything) on plasters, because it's easiest to use (no thinning necessary). It's too soft for floors, generally, but fine for plasters. If you are doing 3 coats or less, the oil doesn't significantly effect breathability
Delete