​Hold on to your seats. I’m about to blow your mind. I’ve just witnessed the most stunning clay plaster I’ve ever seen. It’s on an earthbag house too, which I can tell you is one of the trickier substrates to achieve a decent finish on.
 
The masterpiece in question is courtesy of the wonderful Geeli Mitti community in northern India. Geeli Mitti was founded by Shagun Singh, who is pretty much as incredible as her houses. What she has created up there near Delhi is nothing short of a dream. 

​This earthbag house is the latest in a number of revolutionary architectural projects at Geeli Mitti. Shagun and friends love experimenting with different kinds of natural building, and have perfected clay plasters to such an extent, I’d rate it as some of the best out there. And that’s no exaggeration.
 
I’m a bit lucky because Shagun is a member of our private Facebook group, so I was able to get some details on how these colours and finishes were achieved. It’s all surprisingly simple.

​I originally assumed this was a clay paint finish, but I was wrong. “No paint used,” explained Shagun. “It's the finish plaster coat itself on the exterior. We used red clay soil dug out from a nearby land, and similarly some whitish-yellowish soil that had been dug out, then added some yellow oxide minerals to it to achieve the colour.”
 
Yes, amazingly and wonderfully, this beautiful result wasn’t achieved by importing a bunch of materials, but by searching out and using clays in and around the structure itself. This is so often possible. Unless you’re at the beach, it’s highly likely you have many different types of clay in your neighbourhood, and it’s worth hunting for them because you don’t need huge amounts for a finishing layer of plaster.

​“On the inside, we lime washed the walls with the yellow oxide added to lime,” says Shagun.

​But what about this truly eye-opening Shiva sculpture? How was that finish achieved?
It's actually a clay, sand, dung mixture sculpted into shape. Then, once the sculpture was completely dry, it was sanded smooth with sandpaper. After that it was coated in linseed oil for sheen, hardness and weather protection. Nice huh?

This guy is a real masterpiece. I wondered how Shagun and friends achieved the milky finish. “This finish plaster was a mix of our site soil which is 60% sand, some clay to balance it, cow dung and very little lime. The lime to rest ratio would be 1:6 and then once the plaster was still slightly moist, not completely dry, I burnished with crystals using small circular motions. So lots of elbow grease needed,” says Shagun.
 
As you see, the mixture itself is incredibly simple. It kind of proves why I’m skeptical about adding a million things to your earth plaster. The application technique, along with perseverance and  effort, is at least half of the story.

Over the course of time, some of the Geeli Mitti team have become real pros. "I'd love to mention the name of one of my oldest team members, Ganesh," says Shagun. "He has worked with me throughout on all the plasters and finishes showcased in the article, and has become quite the plaster wizard now!"

​If you think Geeli Mitti is content to rest on its laurels here, you’d be wrong. They’ve already got another ground-breaking project organised for the end of May. What’s next? A bamboo geodesic dome! So if you’re in northern India and want to experience the Geeli Mitti natural building phenomenon, I’d sign up for that course quick.
 
More about Geeli Mitti
You can find out more about Geeli Mitti from their Facebook page or their website: http://geelimitti.in/
Do check out “The Team” page on Geeli Mitti. I love that the animals are placed at the top of the team, and the cooks are second. Sounds exactly right:)

Are you building or planning to build?
If this is you, consider joining The Mud Home Facebook Group. It will no doubt save you a bunch of money, as many have already commented. You also have the chance to connect with some amazing natural builders and off-gridders. The numbers for that group will be limited to 100 so that I can give the proper attention to each project.

Do you enjoy The Mud Home?
If you find these articles inspiring or useful please consider joining us on Patreon. Your support pays for the running of this website, my virtual help, and my sustenance. A big thank you to all The Mud Sustainers, and everyone chipping in and keeping these posts and articles coming.

Can you put earth plaster on drywall or gypsum?

​We have some very inspiring people in The Mud Home Facebook Group; and a variety of artisans and building techniques. For the house renovators, Camilla MacDonald's and Erhard Groneth's work in Germany is going to be very interesting. It’s been wonderful to watch this farmhouse transform from a bunch of dust and brick like this...​

to this:

And finally become this cosy, airy abode:

And it happened so fast!
 
Applying Earth Plaster to Difficult Surfaces
 
What’s a difficult surface for earth plaster? Any surface that isn’t porous and doesn’t breathe is going to be tough for clay: Portland cement, drywall and gypsum all fall into this category. What can happen is that because those materials don’t breathe, humidity collects behind the plaster and pushes it away from the wall.
 
But it certainly can be done. And I have to say, just by applying earth plaster you can radically transform the feel of your home. 

​How did Camilla Plaster her Walls?
 
Camilla had a tricky surface to plaster. She enrolled in The Mud Home Perfect Earth Plaster Course, and her work has contributed to an extra section in that course. It’s an example of the beautiful results you can create when you know what you’re doing.
 
1. First Camilla tested a lot of different primers and plasters on small areas. I cannot stress how important that is, because no one else’s plaster recipe is ever going to be the same as yours. Your walls, your climate, your clay and the atmosphere of your building are never going to exactly mirror someone else’s.
 
2. She properly prepped her surface (or substrate). In this case it was gypsum plaster and drywall. For a totally natural primer for non-porous surfaces, you could use wheatpaste mixed with clay and possibly sand. But sometimes a number of variables will conspire, and that won’t work. In which case you can do what Camilla did and buy one of the professionally formulated primers on the market. In her case she used Superputzgrund. Mike Wye in the UK also has one or two primers.
 
3. Finally she applied layers of plaster to her walls, allowing each layer to dry properly before adding the next. In some areas she added just two layers, and in others the full three layers. Was there a difference?
 
“Good question,” she says. “There is no visual difference, as the clay paint top layer is identical. But I would say the air in the rooms with the thicker layers is nicer...”

Using Clay Paint

​One thing I love about this earth plaster job is the way Camilla has painted the walls. She used a white clay paint, and then added natural pigments to it. The result is original, light and airy. You may not have realised earth plaster can look this sleek. Her bathroom is quite a masterpiece. 

Do you really need to do a course? Can’t you just research a bit online and slap it on? It’s only mud, isn’t it?

Well, that’s what I did of course on my first earthbag house. And that’s why it took me nearly 2 years to get my plaster right. So yes sure, you can do what I did. If you’ve got plenty of time and patience, go for it :))
 
If on the other hand you want a simple but in-depth guide (with videos) on how to get your plaster looking great on a whole bunch of different substrates - earthbag, cob, strawbale, stone, or even drywall - then the course is going to be the easier and potentially cheaper option.
 
Here’s what some of the other course participants have said:
 
"Your course was invaluable." Cath Coffey, earthbag builder in the UK.
"Very informative and good instructions in the text and videos! Absolutely helpful, thanks for putting it together." Nanda Doornik, cob oven builder in Ireland.
"Atulya has the ability to make natural building very accessible, empowering the participant to believe in their ability to do it." Emma Batchelor, course participant.
"Through the third lesson and loving it!" Wynter Miller, course participant.

This online course will show you:

• How to know if you've got clay on your land or in your hand.
• How to mix your plaster.
• How to test your plaster and adjust your ingredients accordingly (extremely important).
• How to apply plaster to all surfaces from earthbag to strawbale, from stone to dry wall.
• How to cope with different climates.
• How to understand what is going wrong with your plaster and what to do about it.
• How to protect your plaster and maintain it.
• How to sculpt plaster and create mosaics with it.
• How to make clay paint, lime paint and fine plaster finishes.
• How to use earth plaster as a mortar.
• How to build with earth plaster.

Do you enjoy The Mud Home?
If you find these articles inspiring or useful please consider joining us on Patreon. Your support pays for the running of this website, my virtual help, and my sustenance. A big thank you to all The Mud Sustainers, and everyone chipping in and keeping these posts and articles coming.

​Earth and clay, in and of themselves, are not insulating materials. They have thermal mass, which means they store heat (or cold), but don’t reduce the transmission of heat energy from inside to outside (or vice-versa). Nevertheless, you can make earth plaster more insulating if you need to. More on how to do that, and how well it insulates, later in the post.

Before I get to the plaster game though, a quick overview of insulating houses in general: The first thing you need to worry about is not the walls, it’s the roof. That’s where 60% of your heat goes. High ceilings are notorious for energy wastage, as you have a fat layer of completely unused heat that skulks under the ceiling. Your floor is the next worst culprit for heat loss. This doesn’t mean you don’t want to insulate the walls. You do. Though sometimes insulating the north facing wall (or south facing in southern hemisphere) is enough. But insulating the walls without sorting out the roof is a bit pointless.
​

What is all this jabber about R and U values? If you’re a newbie builder you may be wondering. Insulation levels are measured in R values. Here’s a neat little infographic for US climate zones showing the kind of R values you would need for your roof, floor and walls for a conventional house in various climates. All building materials have an R value per inch, though be careful because calculating R values is a bit more complicated than just multiplying by inches. Some insulating materials work in different ways (for example, if you compress certain materials, or mix them into something like clay plaster, then you reduce their capacity to insulate). Nonetheless, the graphic gives a basic idea of what’s going on with R values.
 
Then there are U Values, which rate how energy efficient a given system will be. Me? I want to get back to earth plaster, but if you feel like geeking out on U Values as well here’s more info.
​

Ok, back to the plaster. First, let's be clear; Mixing insulating materials into your earth plaster alone isn’t going to cut the mustard in seriously cold climates. You’ll want to use the Other Ways to Insulate an Earthern Wall listed in the next section. But if you live in a temperate climate, or a place where you need a little extra oomph in the winter months, insulating plaster can work a treat.

• Sawdust/straw: If you mix a decent quantity of straw or sawdust into your plaster (instead of the sand), things are soon going get warmer in your mud world. Please note: That plaster needs to be pretty straw/sawdust heavy to have a decent effect.
• Cork granules: Ah, cork is a goodie. It has a very high insulating value, is also superb for sound-proofing, and, counter-intuitively, it’s relatively fire-resistant as well. But best of all, cork is sustainable. The cork tree’s bark can be harvested every 9 years. You can buy cork granules and mix them into your plaster instead of the sand.
• Paper adobe (R2.5-3 per inch): Paper adobe, as suggested by the name, is where you mix re-pulped paper with clay and earth to create a paper-rich adobe. Paper adobe has a high R value, so it’s worth experimenting with. 3-4 inches of this is going to help keep you toasty. To make it, shred lots and lots of newspaper finely. Let it soak in water overnight, then mash it with some kind of blender/mixer. Finally, when it’s a sticky pulp, mix it into your adobe.
• Perlite? I was a bit dubious about perlite, because I wasn’t sure you could compact it enough in the plaster for it to work sufficiently as an insulator. Perlite is a volcanic glass with an R value of 2.7 when used pure and compacted. It hasn’t been tested much in earth plaster, and the R value would certainly reduce depending on the ratio of perlite to plaster. Craig Ray's cob house in New Zealand (below) boasts a mix of perlite and paper pulp in the plaster with splendid results. He specified that he added two layers of plaster: the first is perlite-heavy, the second is a weather protecting layer with sand. His climate is very wet, with cool but not freezing winters. I’ve no idea to what extent the paper pulp was doing the insulating, but the house is snug.

Note: When using insulating plaster, you need to apply a thick layer (at least 3 inches). It's important to add the plaster to the exterior walls of the house for maximum insulation (though if you’re restoring a listed building, this may not be possible, in which case you’ll have to insulate the interior wall instead).

If you live in a climate which remains below zero for months at a time, earth plaster alone is not going to be enough. I'm not discussing whether or not you should have built a mud home in a cold climate here, nor going into massive detail. There are a few ways of insulating earthen houses. Most of these require attaching a light lath or frame over your wall, and stuffing it with some sort of insulation such as:

• Wool (R3.5 per inch)
• Cotton batts (R3.7 per inch)
• Cellulose (R 3-4 per inch)
• Slip Straw (see Sigi Koko’s nice FB post on this).

 
Alternatively, you can cover the exterior of your mud house in straw bales (R 1.45 per inch).

I'm sure there other natural, insulating earth plaster methods out there. If you've tried something else, feel free to add it in the comments.

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If you find these articles inspiring or useful please consider joining us on Patreon. Your support pays for the running of this website, my virtual help, and my sustenance. A big thank you to all The Mud Sustainers, and everyone chipping in and keeping these posts and articles coming.

Last week, as luck would have it, I ran into a two natural builders tucked away in the hills of central Portugal. Lucky me; they showed me around their fabulous cob creations (not to mention plying me with vinho frisante and humous).
​
Take a look at this wonderful cob oven with cob seating area Frenk and Nicole built. It's gorgeous. But that's not the half of it. It's also water-resistant. The area containing the cob oven and seat isn't protected from the rain. Yet the cob has stood its ground.

How did they do it? They coated the entire thing in 3 layers of linseed oil. I'd heard about linseed oil from a few Mud friends in India where the stuff is cheap and easy to find, but I'd never tried it myself, because in Turkey the cost was prohibitive, more than organic olive oil!

​Frenk is something of a rocket stove wizard, and has engineered another in his kitchen. If you want to look around it, check out the video. It’s very informative. The guy should have his own channel:)

Do you enjoy The Mud Home?
If you find these articles inspiring or useful please consider joining us on Patreon. Your support pays for the running of this website, my virtual help, and my sustenance. A big thank you to all The Mud Sustainers, and everyone chipping in and keeping these posts and articles coming.