Did you know that cob is one of the oldest building materials around? According to my guest, Dave Olsen, most cob houses are tiny houses because they take so long to build! Cob is a mixture of clay, sand, straw, and water that hardens into a thick, load-bearing, structure. Think curved, earthen walls and whimsical building shapes. Dave Olsen has been building with cob for over 20 years and has developed his own technique, called “Fast Cob”. Dave tells us about the benefits of Cob building, how to do fast cob, and more.
In This Episode:
- What is cob and how is it used?
- How cob insulates and lets the house breathe at the same time.
- Off-grid friendly, hardly any waste, and little home maintenance
- Traditional cob building and how it differs from the Fast Cob mixing method
- Does cob require any sort of framing?
- Natural plaster is made of what? 💩
- The best foundation for a cob house and how it's different from a regular foundation
- Where to find materials if you have to source them
- Cob and metal are a fireproof combination
Links and Resources:
Dave Olsen completed a cob workshop led by Ianto Evans in 1996 and has had mud (and sourdough) on his hands ever since. He began hosting Natural Building workshops in 2007, began instructing the revolutionary “Fast Cob” mixing and building methods in 2009, and turned 50 in 2013. Based on off-the-grid Lasqueti Island, he also hosts an apprenticeship that goes well beyond Natural Building, helping people develop responsible and environmentally sustainable lifestyles with enjoyment and ease. Dave has been very fortunate to have worked with many of the leading cob builders of our time and to have a dynamic, cob- and bicycle-loving daughter (and dogs!).
This Week's Sponsor:
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Tiny House Engage brings together tiny house hopefuls and DIYers to share plans and resources, learn from each other’s challenges and mistakes, and celebrate our successes so that we can feel less alone while we build faster, safer, smarter, cheaper homes and embrace the tiny house lifestyle. Whether you’re a tiny house dreamer who is still figuring out all the systems, plans, and everything you need to go into your tiny house, or if you’re actively building, Tiny House Engage has the resources for you. There are professional contractors in the community here to answer your questions about plumbing, electricity, and ventilation, and there’s also plenty of interaction between members. If you need some encouragement or just need to know how someone else solved a problem, you’ll get those answers in Tiny House Engage. I’m also very active in the community, answering questions and keeping an eye on things, so if you want to interact with me, this is a great way to do it. To learn more and register for Tiny House Engage, go to thetinyhouse.net/engage. Registration is open Tuesday, January 12th, and it’ll be open through the following Tuesday or when we get 20 members, whichever comes first! I can’t wait to meet you in Tiny House Engage and I know you’ll love your new tiny house community.
Workshops started as a way for Dave to get help building while teaching others how to build with cob
If your window doesn't need to open, you can set the glass right into the cob
Workshops are a great way to learn and have fun
And there are some great supervisors
You can see the foundation rocks at the bottom of the wall
Check out the mosaic designs
Smaller tarps help make the Fast Cob method less laborious
Sometimes timber framing is necessary
Dave Olsen 0:00
The way I build club is no posts at all period. I find that that's way more complicated way more resources than are needed. Cob walls are way stronger than any post could ever be.
Ethan Waldman 0:16
Welcome to the Tiny House Lifestyle Podcast The show where you learn how to plan, build and live the tiny lifestyle. I'm your host, Ethan Waldman, and this is episode 144 with Dave Olson. Did you know that cob is one of the oldest building materials around? According to my guest, Dave Olson, most cob houses are tiny houses because they take so long to build. Pn top is a mixture of clay, sand, straw, and water that hardens into a thick load-bearing structure. Think curved earthen walls and whimsical building shapes. Dave Olson has been building with cob for over 20 years, and has developed his own technique called Fast Cob. Dave is here to tell us about the benefits of cob building and how to do it fast with Fast Cob, and more. I hope you stick around.
I'd like to tell you a little bit more about our sponsor for this episode, an online community that I run called Tiny House Engage Tiny House Engage members are able to listen live as I record these podcasts and interviews and ask questions of our guests. So if you're a big fan of the show, it's a great way to get an inside look at the tiny house lifestyle podcast and get access to episodes weeks or even months before they go live on the feed. To learn more and register for Tiny House Engage, go to thetinyhouse.net/engage. Registration will open Tuesday, January 12 and it'll be open until we get 20 new members- or for one week, whichever comes first. I can't wait to meet you in Tiny House Engage and I know you'll love your new tiny house community. That website again is thetinyhouse.net/engage.
All right, I am here with Dave Olson. Dave Olson completed a Cob workshop led by Ianto Evans in 1996, and has had mud and sourdough on his hands ever since. He began hosting natural building workshops in 2007, began instructing the revolutionary Fast Cob mixing and building methods in 2009, and turned 50 in 2013. Based on off the grid Lasqueti Island, he also hosts an apprenticeship that goes well beyond natural building, helping people develop responsible and environmentally sustainable lifestyles with enjoyment and ease. Dave has been very fortunate to have worked with many of the leading cob builders of our time, and to have a dynamic cob and bicycle-loving daughter and dogs and Dave Olson. Welcome to the show.
Unknown Speaker 3:07
Thanks so much for having me, Ethan.
Ethan Waldman 3:09
Yeah, it's great to have you here. I feel like we've been following each other for years and years. And we've we've traded some emails, so it's great. I'm actually getting to see your face for the first time here on the Zoom.
Unknown Speaker 3:22
Yeah, I'm so glad to finally connect directly.
Ethan Waldman 3:25
Likewise, likewise. So we're gonna have to start with with the real basics. What is cob?
Unknown Speaker 3:34
Cob is a mixture of sand, clay and straw that you mix together with water. So it's a it's a very simple creation. Some people might say that it's that you have to have a specific ratio of each of those ingredients. I don't the the one ingredient that's unbelievably flexible is the clay portion. And you can have as little as 5-10% I don't know exactly how little you can go all the way up to 100%. The the smallest amount is the amount that is needed to make the sand stick together. And the straw.
Ethan Waldman 4:16
Okay, so when you say percentage, you're referring to the percentage of the clay in the soil.
Unknown Speaker 4:23
Yeah, the material that you're using to actually build the walls - the percentage of that material. So anywhere between five to 10 to 100% clay. I say 100% - I've never built with 100% clay only because a wonderful man who came to one of my workshops, told me about it and showed me books and in Korea, they've been building clay houses for hundreds of years. So maybe even 1000s of years so it obviously works. The but if a cob specifically is designed to be the material is meant to have sand in it. So. So, you know, if you don't have very much sand, that's okay, you have a lot of clay, that's okay. But if you have a lot of sand and not so much clay, it has to stick together, of course, otherwise, you're not going to have a building that stands out. So, you know, very nonspecific answer, because at least certainly in the workshops, but in my own personal experience, we just experiment with what we have to make it as easy as possible. Because that's really the goal of this is to not only make something that's unbelievably resilient, long lasting, non toxic, unbelievably, hugely, outperforming any other building that I've ever known. But just to make it as really quick and easy and simple as possible.
Ethan Waldman 5:59
Very nice. So I guess my follow up question, we've got the kind of literal definition of what is cob? Right. I guess what is? How is cob used in homebuilding? What do you what do you do with the cob?
Unknown Speaker 6:16
Yeah, great. So literally, like you can see, right, sort of up there, that those are called walls. So in the building that I'm sitting in, that I live in, the walls and the floor are all made of cob. Certainly don't recommend building a roof out of cob. Simply because cob will absorb water. And when it does absorb water, it will loosen or lessen its strength. And so building a dome out of cob is would be a foolish thing to do and the climate I lived in, live in. And I don't know of any climates, actually where it would be suitable. So I wouldn't try that. So certainly, some non cob materials are needed for any building that you do build. But the vast majority of the material for this building, this house is cob because the walls are a foot to 18 inches thick, and run from floor to ceiling. And the floor is completely cob. The second floor is all wood, I considered putting a cob floor on top of a wooden sub floor. But the same principle even though it's inside, very likely to stay perfectly dry. But if it doesn't, or if there's a lot of vibration, I just haven't tested a second floor cob floor. So you know, that's out of my realm of experience. But, but ya know, to lessen the cost of any building, if you build it out of cob. It's guaranteed to lower the cost. Because, yeah, literally cob is dirt cheap. So
Ethan Waldman 8:04
I love the pun and I invite you to make as many cob puns as you wish in this interview. Are there any climates? I was going to ask what climates does cob work in? But it sounds like almost I should ask the opposite. Like, are there any climates that cob doesn't work in?
Unknown Speaker 8:25
I would be surprised if there was a climate that doesn't work. In really hot climates it's amazing in terms of keeping the building cool. Because it literally, it's just a totally different kind of building than what most civilized people are using. Right? We're used to often wooden or metal buildings that kind of try to trap the air, at least for heating. And even for cooling. I imagine cob doesn't do that cob breathes. It's constantly breathing. It doesn't it's not drafty, you can't feel it. Breathing, the air can get through the walls. And it's a very, very slow transfer. So you never get sick building syndrome and a cob building which is really nice. And the way that it performs is it it's like a thermal battery. So when there's heat in the air around it, it will absorb that heat and hold it basically until the air around it is cooler than the cob and which case then it releases heat. So it really moderates the temperature, especially of the inside part of the building, that of any building that's made out of cob so and that's what I'm just enjoying in our climate here. We have a climate where in the extreme parts of the summer it's quite warm, it can get up to 30 degrees Celsius, and probably over 100 degrees Fahrenheit. And it's never uncomfortably hot inside our home ever. Doesn't matter how hot it gets outside. In the winter, we we don't have a deep freeze at all. So that makes building foundations here easier. But it still gets to be about freezing, and between zero and 10 degrees Celsius all winter. And so, and it's very humid. So it's still quite cool in terms of human living. And so we have a rocket mass heater that heats our floor, our cold floor, which then emanates that heat throughout the home. And so our feet are always warm, our bodies are warm. And the where cob comes in is overnight when the fire is out the cob will emanate warmth back into the building. So even though it can be down to zero overnight, in the morning, it's still 16 degrees inside the house, right? Even though it was only maybe 20-22 degrees when the fire went up. So very little heat loss. And because it's a thermal mass, and the rocket mass heater is heating that thermal mass, it stays warm for days. Like if we were not to have a fire, say we went away for the weekend, we come back or something like that, and the space would not be the same temperature is outside, it would be significantly warmer, probably at least 10 degrees warmer. So and yet, the air circulates the air breeze, it's not a sick building syndrome, there's no special ventilation system that has to be installed. To make it livable. It just all naturally works.
Ethan Waldman 12:07
The house, the house is able to breathe. It's not even though you're you are making this kind of dense mixture of clay and sand and hay and water. It still is able to breathe.
Unknown Speaker 12:20
Exactly, yeah. And I'm just gonna say it's not hay, it's straw. Yeah, that's a unbelievably common thing for people to say. But the difference is if it will just get technical per moment, straw is a tubular type of material. So it's a stronger and hay is a solid material and bacteria, especially anaerobic bacteria thrive in hay, so straw is highly recommended, and typically used whereas a is rarely if ever used.
Ethan Waldman 12:54
Got it. Have you ever heard of anyone building a cob building like to passive house kind of standards, which is kind of this standard that the building can generate a lot of its own heat?
Unknown Speaker 13:09
Okay, well, the way I advocate designing any house, but especially a cob house is passive solar. With the passive solar design in mind. I don't live anywhere near any grid. So I, but I do recognize that most buildings in civilization are built on a grid on a road grid, typically. And it doesn't matter where South is, if you're in the Northern Hemisphere, and it doesn't matter where north is if you're in the southern hemisphere, which doesn't make any sense from a practical building a passive, smart home point of view. So yeah, our home, as you can see, has tons of natural light coming in. So whenever the sun does shine here, we get a lot of passive solar gain in the winter. In the summer, we get passive solar gain, but again, the way that the cob performs, it just sucks up that heat. So it's not an issue, even though it's 30 degrees to have the sun shining inside our home. Which, you know, wouldn't be the case in a more typical boxy home. Did I answer that question?
Ethan Waldman 14:25
Yeah, absolutely. I was. You've definitely extolled some of the benefits of cob, I think we've touched on, you know, the thermal mass and the heat and the cost is very inexpensive, the breathability. Are there any other you know, benefits of cob that you that you like to talk about?
Unknown Speaker 14:45
Well, cob is in general, yes. In the sense of waste. So when most typical building sites have to have like a dumpster or you know, some some sort of large bin to put all the garbage in with a cob house, I didn't even, I don't think I even called a bag of garbage away in a 900 square foot home that I built in five months, if there's no garbage, because any excess cob just melts into the ground. Anything that you trim off, you know that you might change to take down a wall or something, a radical or different things like that. You just reuse the material, you don't have to throw anything away. So that's, for me, huge, absolutely giant. But for the typical own user, thing that's quite remarkable to me is almost no maintenance. If you've built your building, while from the beginning, you might need to plaster once every 10 years, maybe in the high wear areas. Before I moved into this home, I lived in a 64 square foot, tiny home and for 10 years. So that was a very vertical oriented place because I had a loft that I could sleep in above the kitchen, essentially. And in that home, I was building other buildings. So I was in and out all the time. Hard wearing, you know, construction zone for 10 years, basically. And after 10 years, I kind of looked at it. And I was like, "Oh yeah, I guess I should plaster around the doors." That was it. That was all the the ear that it endured. And so it's they're remarkably resilient outweigh the thing about the technique that I use myself, and that I teach, though, compared to what most people probably know, of cob, is the speed of building. I call the technique that I've developed in Fast Cob, because it literally is fast. And not only is it faster than regular cob, it's dramatically faster. And I've had at least one professional carpenter come to our workshops, and he has given me the confidence to say this technique is as fast as any technique that exists for building a building.
Ethan Waldman 17:34
I don't know what my listeners' exposure to cob is, you know, it's it's something that I'm sure people have seen because there are tiny houses made of cob. But maybe you could cover you know, what the traditional cob building process is? And then, you know, I'd love to learn about the fastcob process and what is different about it.
Unknown Speaker 17:59
Oh, for sure. Yeah. Yeah, most cob buildings are tiny by necessity, simply because the the traditional, if you will, West Coast, I call it traditional technique that Ianto taught me It works. But it's so exhausting and slow. Because let's see if I can describe it verbally very well, in a say a 8x10 tarp, you've got maybe a couple of wheelbarrow loads of material on it. And the way you mix it is you dance on it, add straw, add water while you're dancing. And typically it's two people
Ethan Waldman 18:46
dancing or literally like with your feet.
Yeah, okay, smushing the material around trying to activate the clay with the water, mixing up the straw kind of thing. And but you're constantly also every minute at least bending over and pulling on that tarp. So that's a lot of weight that you're pulling back. And it's very exhausting on my back at least. And you're constantly you know, jogging or dancing. So you know, it's it's a serious physical exertion at least 20 minutes and then possibly 30 minutes until the material really starts to stick together. And the fast cob way of mixing, which was the genesis of it was given to me by that same Korean man so van who came to a workshop, he, we were teaching that technique that I just described. And early in the workshop, he just tapped me on the shoulder and said, "Dave, you know, I don't like this mixing. It's not easy", and I'm like, "I get it. It's not easy and it's your workshop to do what you like." And we had bonded over making food from scratch with our two year old daughter's at the time. So he took his noodle making technique, and literally transcribed it into a cob mixing technique. And so a couple days later he showed me and and we all did the four corner Korean noodle takeout method just for fun. And basically what he did was he shrunk the tarp down to maybe three feet by four feet, largest, maybe two or three, two by three, rectangular just to make it easier to access as a human. And now what I I'm not totally sure what we did at first. But what I do now is I squat besides that tarp, I put probably a couple of shovel fulls, maybe three, I usually put material from a wheelbarrow on the tarp so I'm not measuring, because it doesn't have to be exact at all. And I squat down beside it. And sorry, let me take a couple steps back. So now put out these tarps, at least 10, maybe 20. If the space allows 30 right beside each other, then I use a wheelbarrow to deliver the material on each of the tarps, a small amount like two or three will shovel fulls on each tarp. Then I go around with straw and I put the straw on those piles of material, then I have a hose with a sort of a sprinkler end on it. And I'll have that hose in my hand and I'll go in the squat beside the the first tarp. And I squat down. And then within 30 seconds, I've mixed all that material with the straw and watered it down to enough so that all the clay will be activated and start to bond but not become like mush and just run off not too much water. So then after the 10 to 20 seconds of flipping and mixing by using the tarp that's a very valuable tool. I just rolled it up, fold it up. And then I start stamping on this what I call a brick that I've just rolled up and made. And that leads to the second half of the building process, because that's the first half the mixing, you have to mix material to create something to build with in our technique. So then I go to next tarp next tarp nxt tarp make all these bricks. So now I've made all these wet bricks. And by the time I've made all these wind bricks, they've had a chance to really activate the clay is activated device standing on them or jumping on them for 10 seconds, 15 seconds kind of thing I'm putting pressure on and so I'm really activating that clay, I'm dispersing the water so that there's no dry spots. And that bond is really starting already. Whereas with the method that I initially learned, that bond doesn't start until you somehow get all that pile of material onto a wall. Right, you somehow got to get it up there. And the fun way with that technique is you make little cob balls, if you will loads and you toss them from person to person, and the last person puts it on the wall, and then eventually kind of knead it into the wall. But with that technique, you could if you get a foot high, foot of height in a day of building, you're doing really well. Okay, with our, with our technique with the bricks, you've got bricks that have integrity already, and you bring them to the wall, you flip them, and you simply meld the two out the inside and the outside part of the wall. And you're done. So not only is it about 30 times faster than the first technique that I've learned, you can we can build at least three feet in a day without having any compromise in the wall integrity at all. So that's a huge, huge difference.
Yeah, so it's fascinating to me, I love I love that story that that you adapted a noodle making technique. Because I can envision I have made homemade pasta before and I'm like yeah, that is kind of how you make, you know, you put some filling in the pasta and you fold in the corners and smush it. But though these bricks that you're putting up on the wall, and I'm envisioning that, you know, especially if you have a group of people, and they're not all uniform in size, and they might be different in you know, somewhat different in their consistency in terms of like, how much water is on them. How do you how do you control for that? How do you account for that as the wall is going up?
Unknown Speaker 25:01
Well, thank you for asking that. That's an awesome question. And I wouldn't have thought to discuss that at all. That's unbelievably common, of course, especially during workshops. And when you're first learning your consistency is far from ideal. And with cob, and Fast Cob, in particular, it's okay, you can totally compensate. It's a, it's really I call it more of a common sense technique. Because if you end up with a dry brick, well, if it's really dry, and it doesn't hold together, you just, you simply have to add more water and mix it so it does hold together. But if you've got a brick that's not really wet, but it holds together, and then you've got another brick that's really quite wet, you can put them on the wall, one on top of each other, and they can just compensate for each other basically, as long as they're holding together, I'm not advocating that you put a bunch of dry sand on the wall, because it's not gonna stay on the wall. In terms of brick sizes, absolutely. Another regular issue is that the the brick size, if it's wider than the wall, well, we can just kind of mush it, or meld it is what I call it to size. And we've used bricks to build out walls. So if you got a whole bunch of bricks, and you put them on the wall, and you're not really paying attention, for whatever reason, and suddenly your wall is a lot thinner than you want it to be, well, you can use our technique to put a brick on and literally curve it or fold it over the side. And instantly you've built that wall back out to the width that you want, like. So because it's a wet brick that you're putting on work. So I know the word brick often implies, like these rectangular, very solid, you can't move them, once they're in place at all kind of things our wet bricks are very malleable. So you can squish them to size or fold them over to build out or even cut them up if you want. With by with your hands. You don't need any special tools. So that's the other huge benefit of building with cob, in general, is that the tools is minimum, maybe a couple $100 of absolutely brand new tools. Maybe a dozen dollars of use tools are necessary to start building. That's it.
Ethan Waldman 27:39
Fascinating, and it's actually helpful like looking, you know, behind you at your house and helping to prompt me with questions.
Dave Olsen 27:48
Ethan Waldman 27:49
So, you know, in a, in a stick built structure that is framed, you know, we have to frame a special structure around a window or door to help carry the load coming down from the roof so that it doesn't crack your window or prevent your door from opening. Is there any structural framing required in a cob house around like a window or a door? Like do you have to use two by fours? Or, you know, other lumber to do that? Or do they just go right into the cob?
Unknown Speaker 28:19
Yeah, again, right in? another great question. Thank you. The way I build cob is no posts at all period, I find that that's way more complicated way more resources that are needed. cob walls are way stronger than any post could ever be. Assuming that you're building foot wide walls or bigger. If you're building eight inch walls, they're still more than strong enough, you know, a foot in diameter posts might be stronger. But I'm not an engineer. So I don't know. And I don't care, I just do it. And I've built at least a dozen buildings of varying sizes, varying complexity and different types of roofing systems. And I've had some failures. So I've learned what doesn't work. And I know firsthand that you don't need posts. So that's the first answer. The other answer is around windows and doors. You can frame them in. But again, that's just another waste of resources really and time. Because what I've learned initially because the technique to build was so much slower. You could literally put windows and doors in to where they go and build up around them. But I've learned with our technique, you don't want to do that because it's just too fast and the material is super heavy. Of course it's sands primarily and also clay with a lot of water. All those materials are super heavy. So that kind of weight will break windows and twist doors and whatnot. So what we do now is we build holes, we literally leave a hole in the wall, or for a door or window and build that with cob. Let it set so that it's not going to move much. So in the summertime, that's at most a week. In the fall or the spring, that might be a couple of weeks of waiting time for the water to disperse, evaporate, and wall to really settle. And then we put the window in. And literally just cob it in just with minimal amounts of probably like six to eight bricks, depending on how big the window is. And same thing with the door with the door, you haven't put a door in without a frame, that doesn't seem to make any sense to me just because as strong as it is it is brittle. So if you're, if you've got a an area where you're literally pounding that part of the wall, it will degrade for sure. So like if you just were to have a door slamming against a cob wall without a door frame, I've got metal door frames, and I've got wooden door frames. I haven't tested this because I haven't bothered to try my intuition is the wall would just degrade and then you'd have to maintain that more frequently than we are which is not at all. So so the metal or wooden doorframe would take that abrasion and has and even though it's surrounded by cob, trying to think of a doorframe that has needed repair, just the plaster around the doorframe has needed repair. And that's just from abrasion of walking in and out and carrying stuff through the doorways all the time. But in terms of doors that have been, you know, slammed a lot, or at least closed hard or just not treated gently. I haven't even had an experience with one door coming loose in the cob. So so at most, you need a frame for a door in the wall. But for windows, you don't need frames. If you want a window open, you need a frame, of course so that the window has something to attach to or slide in or something like that. However you want that window open. But if you don't have an opening window, you don't need any frame at all. You can just simply put glass in.
Ethan Waldman 32:50
Amazing. You've mentioned a few times plaster. Can you talk about you know what? What do you mean when you say plaster? Is that something that you're putting on the inside on the outside on both and what does it do?
Unknown Speaker 33:06
Plaster in our experience, and our use of it is both outside and inside. And the reason for it in a cob building on the inside is really to minimize the dusting. It's a sand building and building made of sand Of course. So depending on the clay content, if it's a high clay content in the wall, it doesn't dust very much of course, because there's a lot of glue holding all those sand particles. If there's a lower clay amount in the wall, still enough to make it strong and stick together. But minimal clay, I've built quite a few walls with minimal clay. If you touch that wall, it's gonna dust off if you will. And I don't know how long it would take a couple of centuries to continually rub that wall for it to wear right through. So it's not like a structural issue that dusting but you know practical living kind of issue. You don't want to have to sweep or clean your counters constantly because it's always been dusted on so we've plastic and we use a natural plaster because it's a natural building. And so our plaster is in South Africa they have a special name for it in their language. It's called the tamer and it's a mixture of cow manure and clay. Mostly commonly 80% cow manure and 20% clay and it is amazing if you the reason why we use cow manure is cows have a special enzyme in their digestive system. So what it manifests practically for plastering is it It goes on super smooth, and it hardens up really, really nicely.
Ethan Waldman 34:52
Does it smell?
Dave Olsen 34:52
It does initially Yes. when it's wet it smells as soon as it dries. There's no smell like anybody that comes into this building has never ever guessed that there's coming around the walls. So, so yeah, that that can be an issue for some folks if you can't deal with the smell, but you can also use horsemen or it just doesn't have the enzyme. And I haven't really used horse manure to compare it. So I know I remember using it at one point I just didn't perform as well. So I just didn't even bother anymore. So. So that's our plaster, you put it, you can put it on the outside to again, to prevent the erosion of the building. Most of our buildings we just haven't gotten to, because we've been building and now we're finishing this building. We're just about finished. So. So the next evolution in our building life gear on the day to day basis will be getting the outside parts of the walls finished now. And we're going to do mosaics and things like that as well. So you can really see, we're going to sculpt it, and we're gonna make reliefs and have some fun with it.
Ethan Waldman 36:08
Nice. What kind of foundation is required for cob building? Like, can you just put it right on top of the earth? Or is there something you need to do to prevent moisture from the earth from, you know, coming up into your cob?
Unknown Speaker 36:23
Absolutely, yeah, called will wick up moisture from the earth. So if you just put it on the ground, and water hits that wall, it will wick it all up, and eventually degrades, and you can control it, you can even collapse. So definitely, you need a foundation. What kind of foundation? Well, I've used stack rocks here, because we have rocks here. I don't like concrete or cement, any cement products, this house, including the shower room, has zero cement in it at all. And so we back to the foundation, I stack the rocks, one over two and two over one is the mantra there so that you don't build towers that can not be tied together, or that are not tied together and therefore could move. Because that's the other main function of the foundation is to keep the building from shifting and moving. And that's the that's needed any building, especially, but just just as relevant in a cob building. Although I have a feeling and I haven't tested this out, that if the foundation moves the cob walls probably wouldn't move. Because they're this monolithic mass, they're just so strong. But I'm not advocating testing that out. So but what we do, yes, stack rocks, you could, again pour cement, if you want, it's just a concrete, concrete foundation made of cement. But cement is made an unbelievably high temperature and often they throw in toxic chemicals, because that's just a nice way to get rid of them. Seemingly get rid of them. But of course, there's that residue. But ecologically speaking is far from benign. Whereas stack rocks, it's just a bunch of human labor to move them. Or at least here it is, you might even have a machine somewhere to move them to make it easier. We don't but so it's a very human scale, technique and very, can be beautiful, and very effective. So yeah, I think that's it. And then the other detail, I guess is that the stacked rock foundation typically is knee high, my knee is quite higher as taller I guess, than many. So I don't build up quite to the height of my knee. But you know, a couple of feet is more than adequate. And what the other role there not only are you trying to prevent water from wiking up, you're also trying to prevent water from splashing from rain. So if you've just got a six inch Foundation, for instance, the splash will splash above that. And depends again, on your location, your weather, whatnot. Over time, it will wear the wall away. In which case there's some maintenance to do. It's not going to be catastrophic if there's splash, but if there's running water to your building, it could be catastrophic because there's a constant source of water that's constantly being picked up. But with a knee high foundation and you wouldn't have any maintenance at all for hundreds of years.
Ethan Waldman 36:38
So when you're talking about a stack drop foundation Are you is this like for the entire floor of the building. So like you're making if you would say we're building a round cob house This is a big circle of rocks or is it just are underneath the walls?
Yeah, just underneath the walls. Okay. Sure.
And so you can do a cob floor, right on the earth?
Yeah, absolutely. Well, again, it depends, right? So you're building site is it in the path of water that will run to it? If it is. So if you're on this hill, on the top of a hill, and you've got a roof over your building, and every side slopes away from your building, then yes, you can put that cob flow right on the on the earth, if I think the vast majority almost probably close to 99% of cases is there's going to be water running towards your building from at least one direction, just the way that life is on planet Earth. And so you'll need to either build a swale to divert that water around your building, or a French drain underneath the foundation to allow the water to fall to the bottom of the foundation and then be directed around the building that way as well. So in whatever way you're going to get, the vast majority of the water can be non coming into your home, and you still want to have the floor, not susceptible to disaster or just getting flooded in some ways. So what I do is I excavate down to the bedrock because there is bedrock to excavate here to some places, you wouldn't be able to do that, of course, excavate enough, and then put either a drain, if it's very likely that water is going to enter your home, a drain pipe, at the bottom of that excavation to allow the water to get into the pipe. And then the pipe facilitates its exit, for sure. He put many pipes in if if needed. And then cover those pipes with canvas or newspapers so that the holes in the pipes don't allow the material to get into the pipe. And then put round rock, drain rock on top of those that allow the water to fall with gravity through those rocks into the pipes, which then are exited. And then you would put finer material on the cover the drain rock so that the finer material doesn't get allowed to get into the drain rock. And then you put the finer you say gravel on top of that. And then you can build your sub floor. And that's another magic thing aboutcob. Cob, some floors just magically grow and are built when you mix inside your home that you're building or inside the building, you're building. Inevitably little bits of cob are falling off your tire. And they over time, just build a nice inch or two sub floor. And then once that sub floor is done, then I pour a layer of finished cob floor on top. And it's only about a half inch. Should we keep going on the floor thing?
Sure. So let's finish the floor out.
Unknown Speaker 43:23
Yeah, okay. So once and you for the cob floor you, I pour it so it's a liquid mess mixture, because then gravity is helping the level. And then once it's dry, which can take a while because it's so wet by linseed oil. And initially I tried four layers and I didn't find that adequate. So now I put seven applications of linseed oil on and then if you want to, you can wax it with the half beeswax and half linseed oil mixture. And that makes it waterproof. So you can spill anything you want on it and it doesn't get absorbed. It wears after about six months of heavy use, it needs to be reapplied the wax, but the linseed doesn't wear out. And we can dance on our floor we can drop things we can do whatever. And it's not a hard like concrete floor. That's the other amazing thing about cold floors is that they feel like they have some gift even though I can't believe they're giving anything up when you walk on them. But they're you don't I my legs just don't get tired standing and working on a floor. Whereas in an hour or two on a concrete floor. I can notice that I'm on a concrete floor. Yeah. Well,
Ethan Waldman 44:50
I definitely want to make sure we have time to talk about kind of how to learn calm and the workshops that you offer. But And one last question on the building process. Where do you tell people to find the materials? You know, like if you know I want to go out in my backyard and I want to build, I want to build a cob pizza oven or I want to build a little cob structure. Do I just get a shovel and start digging in the ground? Are there places to source the materials?
Unknown Speaker 45:23
Well, that's what I would advocate is exactly what you said, get a shovel, start digging, see what you find, again. So what I, I use almost exclusively, two summers ago, we went to Alberta to build a giant cob oven, it was nine feet wide, eight feet tall and 7 feet deep. It was a showcase as well as a practical pizza oven. So in that case, I was in a town where we, the it was a restaurant and surrounded by parking lot, so I couldn't just go and dig the ground. And we also had time constraints. So I had to source it. And I went to a landscape company and sourced it. So getting the clay is not usually very easy in civilization, because everybody builds with concrete. And clay doesn't allow concrete to work. It interferes with the process. I don't know the details, but that's what I'm told. So nobody has clay to sell almost anywhere. So in this town, I had to almost beg a landscape guy to talk, the whole place was was built on clay, like everything is clay. So if I had the ability to get a backhoe or shovel and just there digging, we would have had an abundance of clay. But we had to get it sourced. And then we also got the gravel or the sand, easily sourced, that's easy, that part's easy. But if you're just going to experiment and start building on your own, I highly recommend digging where you're going to build because you've got your material right there if it is usable material for this house. Again, I'm we're building on bedrock primarily here. So we just didn't have the material to dig up. So I had I sourced it on different places, excuse me on the island, most of this building was built just a couple of blocks, I guess, away. And so I had a friend with an excavator dig it out of a gravel pit. But it was the stuff they didn't want, which was perfect for cod because it had enough clay. And it was very, very Sandy, very coarse sand. So that's the ideal coarse sand. And enough clay, maybe 25%. That's what Ianto always told me, that probably is ideal, I trust his scientific approach. But it's not necessary. Again, you just need enough. So if you dig in your backyard, and you've got a pile of material that you suspect is going to work, put it on a tarp, mix it together, make a brick and let it dry and see what it does. If it holds together and has some strength, you've got your material. If it doesn't, if it doesn't stick together, then you're probably going to need to source some clay. That's my guess, to add to that material to make it sticky enough. But in my experience on this island, anything that has that's been dug out of the ground that sub soil not doesn't have any organic topsoil in it is what I call ready mix. And so it's ready to mix.
Ethan Waldman 48:47
It's got it's got the right balance of sand and clay in it.
Yeah, yeah. And again, that right balance is a giant range.
Yeah. Well, we were talking before, before we started rolling about baking bread and how it's like, what works for me, works for me, but like, if you tried my technique, it probably would fail. And if I tried yours, it probably wouldn't work. And it sounds like with cob. You know, there is some there is something to it being so hyper local, like, what is that material that you're working with right there on site and whose hands are mixing it and all that kind of stuff.
Unknown Speaker 49:27
I agree in the sense that Yeah, different materials are all over the earth. And the beauty of that is all those buildings that are going to be built are going to have their own unique characteristics for sure. But in terms of buildability, and strength and durability, and all the critical components. I can't say everything's gonna work, but I would be surprised if anything didn't work. That's how flexible this technique is. You do not need To go and get, you know, 75%, sand and 25% clay, you can do that it works. But if you dig some stuff out of the ground, it's likely to work too. So what's easier for you is that's always been my approach to building. What's easier for you, if it's easier to go and buy stuff, and have it delivered and you have the precise ratios that you feel comfortable with. So it's easy, you're not worrying, you're not thinking beautiful do that. If it's easier for you to dig in the backyard and make a test brick and not have to pay for transportation and pollute the air and all that sort of stuff. Then go for that. Right. Both work. Yeah, definitely. Yeah.
Ethan Waldman 50:46
Well, I just realized there's one more major topic that I didn't ask you about, before we talk about your workshops, which is the the roofing systems because and and the second floors, because that does look like it's the one place where you are placing timbers?
Unknown Speaker 51:03
Absolutely, yeah, I, again, I haven't wanted to test or experiment with cob, above people's heads. Ianto cautioned us to not even go there. And I just haven't gotten there because I don't see that being easy. Wood spanning is easy, right? So I'm trying to make correct and I don't even know how that could come close to being easy. So for roofing systems and second floors, I do have two posts in this building, because I just wanted to have a really open interior. And so I use a post two posts to hold up the second floor. But most of the second floors hold held up by cob walls. So if I had wanted to not use posts, very doable, it's just it would have been not as open concept of building. And there would be just more walls interior walls, which is totally fine. But the roof is all cut beams, cut and peeled beams that come from the forest right around the building. So we've done all of that ourselves. There's no milled wood. Oh no, that's not true. So after I put the rafters on, and the second floor floor joists on that's all round wood from the forest. And then I put milled wood on top of that to create a flat surface for the floor. And to create a flat surface for the metal roof that I put on this building. Very first two buildings that I built. I also hand split the cedar shakes. And so those buildings are completely natural. There's no human made materials at all that really like trees grew the roof and trees grew the rafters. And we dug out the soil from the earth and the metal. Initially I was thinking well, that's not necessarily natural, it's still out of the earth. And of course, there's a lot of processing involved to create that metal. But the reason I went to metal is it's completely fireproof. So this building is, is I can't imagine this building ever catching on fire. It's there's a ceiling, there's a ceiling that is made of wood. And the rafters are made of wood, but the top is metal. So any fire coming to the building from the top would hit the metal, I wouldn't have any exposure to wood and any fire from the inside. It might catch the ceiling on fire. But the building would totally be intact. And the rafters are substantial. They're you know, at least four inches. That's the bare minimum up to six inches in diameter so I have no worries at all about fire in this building. And so yeah, anyway get back to the roofing. The metal I've chosen to use because it's the half the price of cedar shakes and it's a 10th of the time or labor and it's just so much simpler and faster. So cedar shakes are gorgeous but in on this island now in this in the summertime it gets super super dry. So fire is a an issue or concern so far it hasn't been an issue thankfully. Um, if you're in California, obviously an issue. So yeah, metal roofs and cob. Make a heck of a lot of sense there.
Ethan Waldman 54:48
Well, you've been so generous with with information here and I want to make sure that we get to talk about you know the process for for learning Fast Cob Can you tell me about the workshops that you offer?
Unknown Speaker 55:03
Thank you. Yeah. Glad to. I first want to preface by saying, you know, the technique is far from complicated. What the workshops, what they do for people that come is they really help you learn a technique that absolutely works. Without question, you can see the results here and get mentored firsthand, so that you can really quickly deepen your understanding and skill level. But I learned all this on my own. I, you know, Ianto gave me the introduction to the other technique. And so I had a few years to sort of mull that around, I didn't build much because it was just too exhausting. And I didn't build really. And then finally, I had a place to build. And so I started having workshops. Because I needed help building. I had attempted to build a very small outhouse the year before I started hosting workshops. And my daughter was just born. So our first the first mix I made, she was sleeping on my shoulders and two months old. And that whole summer, I tried to build this very small outhouse. And I still have walls that are maybe three feet high at the most, I just haven't got back to that project. But it's kind of a testimony to the fact that that technique needed lots of assistance. And that assistance was going to come through workshops. But then so then came to the third workshop that I hosted, while teaching that technique. And he revolutionized my life by showing me the genesis of a new mixing method. And then since then I've created the new building method with the brick. So I literally don't need workshops to build anymore, it's way faster for me to build on my own than to build with helpers through the workshop. So that all of that to say, I love workshops, because the people that come are magical, like it's always a magical four or five or eight day session, people bond as much as the clay bonds to the sand, it's really lovely. And it's an opportunity to have everything ready for you, right materials ready, the project ready. And you get mentorship. So so that's the benefit of making the trip here. And it's not an easy trip, we're not easily accessible. So that's why I also say, you are keen, you can't make it here, try and do it anyway. And there's lots of, you could do the the slow, painful, what I call the slow, painful method by finding videos online, trying to avoid that I hope to one day have an online workshop available. I've just been sidetracked by life too much. So maybe in another year or two, I will have that available. But I think I still have some videos on my websites that give you an introduction, at least to the mixing. And then just try to make it your own if you if you can't come to a workshop, and if you do come to a workshop, you'll hear that all the time. This is how I do it. And I want you to make it your own. So So yeah, it's it's fun. It's fun if you come and go have fun if you don't care.
Ethan Waldman 58:41
Well, fantastic. One thing that I like to ask all my guests is, what are two or three books or resources that have inspired you that you'd like to recommend? And they could be about cob building or not.
Unknown Speaker 58:55
Okay, right on? Well, they're probably all not cob building. So the first book that always comes to my mind is john lead laughs continuum concept. And that's a book about a woman who is now dead. She was 25 when she wrote it, a New York based woman she was traveling in Europe, got invited to go look for gold and silver in the Amazon. And she transformed her life and many people's lives by going there and interacting with indigenous peoples that had not become civilized in any way. And she couldn't figure out initially What the heck was so different about these people and then she realized they're all happy all the time. There's no conflict at all, like all age groups, anytime any kind of situation like how could this be or any any of us growing up in civilization would not recognize Nice, isn't as a norm. So she came up with some theory, she went back there and tested those theories, because they had, she had got to know them well enough that it made sense. And for her to be there and wrote this book. And so basically, it's about how children are brought up. And it's not a parenting book. But if you're a parent, you want to read it because especially if you're planning to become a parent, because the keys are early in life, and it's just a fascinating read. And it's an easy read. Sure.
Ethan Waldman 1:00:40
Nice. Well, I really appreciate the recommendation and Dave Olson, thank you so much for for being on the show and sharing your your experience and knowledge and philosophy of cob building. I really appreciate it.
Unknown Speaker 1:00:55
Well, thank you so much for having me, Ethan, I really appreciate this opportunity. And I look forward to seeing more of your podcasts. I'm so glad that you're really a huge motivator for people to embrace the tiny home concept. And now cob can not only build Tiny Homes, but now it can build them quickly and easily.
Ethan Waldman 1:01:16
Yes. Thank you so much to Dave Olson for being a guest on the show today. You can find the show notes including links to Dave's website and information about his workshops, as well as some of my favorite photos of his cob buildings at thetinyhouse.net/144. Again, that's thetinyhouse.net/144. Don't forget to learn more about Tiny House Engage, my exclusive online community at thetinyhouse.net/engage registrations typically fill up in a few days. So if you're thinking about joining, head on over to thetinyhouse.net/engage. Registration is opening this coming Tuesday. And if you go to the website now, you can sign up to be notified as soon as registration is open. That way you do not miss your spot. Again, that website is thetinyhouse.net/engage. Well, that's all for this week. I'm your host, Ethan Waldman, and I'll be back next week with another episode of the Tiny House Lifestyle Podcast.
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