Ask Uncle Mud is a natural building and rocket advice column. You can submit your own question for inclusion in the column here.
"Anyone have any experience using a masonry sealant on cob? Specifically, I'm interested in cob tub/hot tub applications. I've seen the old video of the cob hot tub attached to the wood fired oven....but this seems to be the only recorded application. I'm sure there are more. I'm curious about long term water exposure and using possibly some portland in the final layer then sealing as you would a concrete hot tub or pool. Benefit would be a "more" natural process and the ability to sculpt the product more than straight concrete would allow. Thoughts? Experience? Photos?"
Cob expert Miguel Elliott (way above my Uncle Mud pay grade) responded when I asked him this exact question years ago:
I live in the sandhills of Nebraska. Are our extreme high and low temps are going to be conducive to building a cob cottage here. What are your thoughts on this? We max at 130 degrees and bottom at -30 all before wind factor. Oh and its fairly open prairie but there are some trees and hills.
Your area has a few interesting tie-ins to Natural Building you should be aware of. East of you in Gotherberg Nebraska I came across recreation of the "Soddies" our pioneer ancestors lived in because (A) there wasn't any timber, and (B) it was too cold and windy to live in a timber house comfortably if you could afford to build one. Here's a link to a short clip about my visit to one a couple years ago https://www.patreon.com/posts/22384870 the takeaways for me were: Build with what you have, and building low to the earth with thick walls takes the bite out of the wind in your climate. (NOTE: Amanda later told me her great, great, great grandmother lived in a sod hut her first winter in Nebraska. What a wonderful connection to the land).
Marilyn From Utah asked: "How Much would it cost to have a 1000 square foot Natural Building constructed for me?"
People often come to Natural Builders saying to us something like "I heard so-and-so built their house for $25 per square foot." So much of what we want to do depends on how much money it costs, and we spend most of our time in pursuit of that money so "how much does a natural house cost per square foot" is a perfectly reasonable question that it is surprisingly hard to answer in an equally reasonable fashion. The short answer is "It depends."
#1 can you build with cob in colder climates? (SW Missouri)
#2 how thick do the walls have to be?
1. Can and should are two different things. Before the advent of modern insulation cob houses were among the most comfortable because the heat from your fire warmed the wall, and the the thermal mass of the wall kept warming you long after the fire went out. More importantly, unlike brick or log houses which also had relatively high mass, cob houses didn't have a thousand tiny cracks letting cold wind blow through.
I need to find out about any zoning or building issues I might have with building a 12x36 tiny house NOT on wheels in the M------ area.
The more time you take to research now, the easier things will be down the line. A lot of people's tiny or natural house ideas run into trouble when they go to get permission and it is best to eliminate hostile areas from your search before you invest in property. Zoning (size, placing of house) is generally done by city or township. Building code (materials, foundation, framing) is generally enforced by city or county. Zoning generally excludes manufactured housing less than 16' wide and less than a certain number of square feet in order to exclude the perceived low end "single wide" trailers.
Most municipalities have their zoning rules on their website to save their code person so much answering the same question over and over. They will also post their code person's office hours so you can drop by and ask questions and get a feeling for how receptive the town will be to your ideas. I have had good success for cottage builds by calling during business hours and asking about rules in an area I was hypothetically looking to buy and build in--not an exact address in case I wanted to do something without undue attention, just a general area so the code person could give me the zoning for the area.
My partner has a lot in North Seattle with a roughly 40 foot wide and 100 foot deep backyard where she hopes that we can build a 20 ft square, two story small home, and rent out the current home.
We have time and energy to do this, and cob looks great, IF it can work for us. We don't know yet about Seattle city planners opinion on this building style, or if we can use our local dirt as the main raw material.
I'd really like to connect with locals that are already building this way, and assist them to build something first.
Please do your homework. Consider saving yourself a lot of headache by hiring a consultant who knows the local laws. A cob cottage in your back yard is a wonderful thing, and before you put your love and time and money into it you need to be clear what the laws are in your community. Buildings are regulated at state, county and city levels. There are relatively few places in the US where there are no codes. A few more have lax code enforcement. Cannon County, TN for instance, has codes on the books but no code enforcement office.
Rene Suarez writes:
I'm building a cob oven in a temperate climate, and I'm trying to avoid unnecessary work. My resources suggest digging/laying the foundation below the frost line. That would be 4 feet deep here. Is this really necessary for a 4x4 oven?
For those who are just joining us, in temperate climates the winter cold will penetrate into the ground, freezing the water in the soil. That wouldn't be such a big deal except the little oddity of water that when it freezes it expands. Its a very small amount of expansion, but "frost heave" is a very power force. It can push soil and cement pads and houses out of their place by up to a few inches. Since it does so unevenly along the length of say a 40' house, it can break your foundation or cause your house to settle out of level. To keep this from happening we can dig down below the deepest depth frost is expected to penetrate (the "frost line", which in my area of Ohio is about 48" down) and back fill with gravel or concrete so the water drains away and the house doesn't shift. That would be a lot of work to go to for a pizza oven.
Fortunately the ground around a structure as small 4'x4' tend to freeze and thaw pretty evenly, and it isn't essential that a pizza oven stay perfectly level like your kitchen counter, so it will ride out the "heaves" with little chance of damage even if your gravel footer was only a foot deep or so. This is called a "floating foundation". If your soil is reasonably well-drained and certain precautions are taken a floating foundation will even work on larger buildings like Rob Roy's two story cordwood house in upper New York State.