Has anyone tried cob constrution?

[ladywolf]

My husband and I are interested in cob construction and I was wondering if anybody has had any experience with it. We are going to build a "garden room" to get a feel for it and see if we like it.

Thanks for the input.

[farmer mama]

I have experience working with cob. It is fun and user friendly, but very labor intensive. It creates beautiful, sculptural spaces and is thermal mass, but not very insulated, so it doesn't have the insulating value of something like strawbale. Have you checked out the book the Hand Sculpted House? Also the cob cottage company in Oregon gives workshops www.deatech.com/cobcottage/.

[ladywolf]

I have checked out the website and am waiting on the books.

[farmer mama]

Oh good. Do you have any specific questions? I think a little garden room would be a great start, and could easily be completed by one or two people in a relatively short amount of time.

[ladywolf]

Not really any specific questions. I just was curious to know if any one here had tried it. I figured this would be a good place to ask

I am very curious and interested in sustainable architecture. I like the idea of strawbale very much but I like the idea of the more human (woman/child) scale of cob. My husband and I thought that a cob garden room would give him the hobbit hole he wants and I can learn some building techniques

[farmer mama]

My brother lives in a cob house, so that is where I got the bulk of my experience. I also really love those cob ovens. Again, sounds like a great place to start. I think I already mentioned this, but The Natural Plaster book has a lot of great ideas, especially for the artistic element of working with cob (sculpting cob, natural pigments in plasters, etc.) as well as the practical stuff.

[OceanMomma]

I built one of the walls in my horse stable from cob & am going to be building part of our new house in cob. Probably starting within the next couple of months. I have sleepless nights about it I can tell you !

What I found the most important thing to do is practise. Observe how what you do turns out. Keep of where you got the dirt from & the recipe you used. Read the book again as you go along & it all makes so much more sense. Cob is essentially sand glued together with clay with straw acting as rebar. The idea is to get a mix that is sandy enuf not to crack but not so sandy as it crumbles. The reason this is important is that you need all your doors & windows to fit properly. You can plaster over cracks but it helps to only have very small surface crackling.

What works in a test brick cracks on a wall. ie you need a much sandier mix on the wall. Do a sample run of cob wall on a board or something like that first to see how it holds together, how much it shrinks or cracks etc. Be flexible. The soil where we live varies wildly. If I had a fixed recipe, it would work sometimes & others not. You get to be able to tell the feel of the mix with your feet.

I had an old pair of windsurfing bootees which I use as my cob boots. More sensation & control than gum boots but way less foot damage. I used rubber gardening gloves for my hands.

By all means take advice from ppl, but I found a lot of them did not really have that much experience. eg my architect. Who I actually think had none before the house they built on their propertly. & you should the many massive cracks in it! Other ppl with supposedly lots of earth building experience do things like add cement which totally misses the point of earth building IMHO. So, basically, aks lots of questions & then get out there & practise yourself until you get it right.

Cob might be a sustainable building method but it needs lots of very unsustainable concrete in the foundations for the authorities where we are to give you building permits. One thing I noticed in the handsculpted house is they talk about how to get around getting a building permit. Which is all fine, but we still needed to think of resale value.

One last thing. Don't be tempted to leave out the straw. The afore mentioned architect did as they had a mismash of adobe bricks they were padding out with cob. THe straw strengthens everything & if cracks do develop it stops them getting too big.

[ladywolf]

Thank you so much! The practice you are talking about is exactly why we are doing a garden room. What that really is, is a less then 100 square foot structure that will fulfill my husbands needs for a hobbit hole. And needs for digging! He is so much more relaxed when he works outside. And I can play with cob. I am also very interested in strawbale and light straw-clay. I have arthritis so the thought of slinging stawbales around is extremely overwhelming but maybe a bit at a time.......

[OceanMomma]

I was initially very interested in doing a straw bale house but I read the ultimate straw bale book or something like that & it put me off. I also realised that straw bale is a very new construction method. I think it is very quick, but here you have to put so much stuff around it to get building permits, it would be very costly. Now I may do a straw bale chook coop one day as I do need to move the chook coop in the next couple of years. Cobwood is another thing I think is interesting.

I've not read much about light clay straw but it looks interesting too!

[ladywolf]

Look up econest.com (?). They do their building with light straw clay. It allows them more flexibilty of form then strawbale. It actually has been a form of construction for a similar length of time as cob has been. It is similar to cob except more clay, less sand, and more straw.

A chicken coop sounds like a good way to try strawbale. Then you can decide if you wish to deal with all the permitting issues.

[wemoon]

I personally, hated doing cob. It is A LOT of work. We started doing a cob wall for our house, then changed it to wattle and daub because it was faster and you don't need nearly as much sand, clay and straw. But wattle and daub is not as thick so we had to insulate the inside.

[OceanMomma]

I can also say cob is a lot of work but you have the complete wall when you are finished. No need to insulate, add linings, weatherboards & so on. I s'pose you do need to earth plaster but that is great fun so doesn't really count as work. The way I look at it. I used to pay good money to go to the gym & pump iron. I used to spend hours aimlessly running around the neighbourhood getting exercise. This way I get something back

I doubt I'd ever build a whole straw bale house. They are changing the law here very soon so that only qualified builders can build houses. Thankfully dh is a builder so we are always covered if we feel the desire to build another house when we finally finish this one. If there is a next time I think it will be in a much warmer area & I am going to stick to timber as the concrete foundations & all the other drama they make you do for permits are too much for me.

[madrone]

I've been meaning to come back to this thread and haven't. We've been experimenting with small things. One thing we have learned from someone else near by is that you have to get a roof up first here. Otherwise, you might lose your work to a storm. We are using wattle & daub for a room we are adding on. We didn't put enough straw in one batch and that has a nice crack. We figure we'll be fixing it with our next layer.

Not quite sure what else to say since we haven't built a cob home yet and would build a home from several different natural building techniques if we build a new home for ourselves one day.

[MihrDanae]

My husband and I have built several cob ovens over the last few years- I love the idea of building on a larger scale but cant imagine doing it without the help of a LOT of friends. Its very intense work- though lots of fun! I recommend the small project of building an outdoor oven. They make the BEST pizzas ever and will also bake or dry anything that a conventional oven would.