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cob house questions...

8K views 27 replies 13 participants last post by  mtngirl17 
#1 ·
My husband and I are considering doing this, building our own house out of cob (mud mixed with sand and straw). I was curious to know if anyone has tried this, or even seen one in person! I have only books to go on, and am dying for some real life info. So, if you've done it or know anyone who has, please share!
Thanks,
Rachel
 
#4 ·
we got the instructions in the book "build your own earth oven", by kiko denzer

yeah, it was very easy. we were measuring out the earth, sand and straw really carefully for the first batch or two but soon we were just throwing it together until it 'felt' like the right mixture. i have lots of pictures of it being built on my blog. just look at July 2006 for the story.the link is in my sig.
 
#5 ·
The front wall of our house is cob. I'm almost half way thru building it. The wall is 7.1m long by 3m high on the side of the front door I started on & it is 10.something m long by 3m high on the side of the front door I still have to do. It's way easier than I thought it would be. I have done it all on my own & managed to do my other day to day stuff as well. Where I am up to now has taken me 7 weeks to do.

I have read every single book on cob I could find & IMO the Becky Bee one is actually the best. It may not have the pretty coffee table book type pictures in it but I have found hers by far the most useful. She answers emails too. I built a stable wall first as a test wall. Then I went back & re-read all the books & so much more made sense in them.

I've got it so I have probably <1mm shrinkage around the side of the windows ( over the 7m wall ) & the wall is rock solid without any cracks. What I did was cut the clay with as much sand as I could fit in without it getting crumbly, then stuffed as much straw into the mix as I could. The way I worked out my %ages is started with the formula you need 15-50% clay to sand. I did a brick with just clay & sand & made it 30% clay to 70% sand ( 3 shovels clay to 7 shovels of sand ) It seemed way too crumbly to me. Then I tried 40/60 & that seemed to shrink a bit from the side of the brick mould. So I made a mix using the ratios that I am using now ( 4 buckets of clay to 7 of sand ) & that worked well. By trial & error, I've worked out a pretty good routine for mixing it all. I use those surfing bootees made of wetsuit material to mix it & a groundsheet.
 
#6 ·
OceanMomma, i LOVE the becky bee books too! i'm using her "you can build the best hot tub ever" book.

wow, 7m x 3m wall!? sounds like a big project! and all on your own too! congrats, it sounds wonderful. do you have any pictures to share?

we're thinking of trying something bigger after the hot tub. maybe a small building near the oven. my husband is a baker and would like a warm place to work close to the oven in the winter.
 
#7 ·
I do have days when I feel quite daunted by the whole thing. It's the other wall on the other side of the door that I am not looking forward to! I still have to find some windows to go in it but I am so tempted to get really really big ones so I don't have so much cob to do


I have some pictures but they are a few weeks old with one of the kids modelling doing the cob while I took pictures. The wall is up to the middle of the top sashes of the windows now. I get dh to cut it straight for me so it is also now alot straighter.

http://img.photobucket.com/albums/v2...Picture121.jpg
http://img.photobucket.com/albums/v2...Picture125.jpg
http://img.photobucket.com/albums/v2...Picture119.jpg
http://img.photobucket.com/albums/v2...Picture131.jpg

There are some real cool buildings or ideas for buildings here

http://www.simondale.net/house/
http://www.thatroundhouse.info/

I'd really like to do something small like a studio out the bush at the back with oneof those reciprocal roof things on it & maybe out of cobwood. I still have to finish the current project first so we shall see tho'
 
#8 ·
Oceanmomma-thank you for the pictures. I have been flirting with the idea of cob building for a long time. Is the rest of your house just a regular frame built, then? Was is easy to connect the two? Why did you choose to only do one wall cob?

I really like the accesablity of cob. Neither dh nor I have much construction experience so when we decide to build this will be a major factor.

We will probably (hopefully) be building in Northern Michigan, however, so climate may be a major downfall for building with cob. Does anyone have experience with cob in a cold cliamate?
 
#9 ·
The rest of the house is timber frame. It's on a hill so we did the east & north facing walls ( sunwise for us ) in cob that were on the flat bit. Here's a piccy of the rest of the house.

http://img.photobucket.com/albums/v2...7/DSC01815.jpg

No hassles so far with joining it up. We're butting the cob to the weatherboard & then going to put a flashing over the join somehow so it looks tidy & subtle.

As to the cold, depends how you define cold. I can't grow tomatoes outdoors here as it never gets that warm but we only probably get 4 or 5 frosts a year in the winter. I guess in Michigan it would freeze for a few months of the year? Cob did come from Britain where it does get cold too but the ground doesn't freeze for months. I think traditionally they started building when the birds started doing their nests & aimed to have finished by the end of the summer. Maybe email someone like Becky Bee or the cob cottage company or you could try some of the Pommie cob builders. They are all very helpful.
 
#10 ·
wow, Oceanmomma, you are lightyears ahead of me-I am in awe! Have you taken a workshop or anything, or just going from books? The workshops are kind of pricey for me, though I'm sure they're worth it.
Whereabouts do you live? Region is fine if you don't feel like being specific. Have you had any trouble with building codes or inspectors or anything? We would be building in Louisiana, not sure if the climate is right for cob... I'm going to check out the Becky Bee book, thanks for all your info!
Rachel
 
#12 ·
I live in New Zealand & I do have a building permit. It was a slight hassle to get but we managed it. I never did any workshops as there weren't any to do. I probably would have thought it was a good idea but you can work it out yourself fairly easily. It's just a matter of practise, re-reading the book & thinking about all the more subtle points in there, more practise, observing how your cob looks & feels & so on. The real issue you will have is the actual physical task of keeping at making all that cob. It's kind of like knitting in that you need to keep at it. You can't let the top of the wall completely dry until it is finished & if you do too much in a day, it bulges & you have to cut half of it off to get the wall straight!
 
#15 ·
That's only really a small part of the view. It's way better than that IRL but we do get alot of not so gentle sea breezes to contend with. Our architect is american btw, I chose him coz he was the only decent architect I could find who was into earth building & by earth building i don't mean adobe blocks with cement in them! He does the heavy timber frame stuff too with mortice & tenon joints.

I wanted to share this url with you. http://www.buildsomethingbeautiful.com/
Just in case anyone thinks cob is a slow way to go. The two story house they have photos of called Keppel Gate was built over a summer by 3 people. I did hear on the grapevine that these people use a tractor to mix cob & forms for their walls, but then I am on the other side of the world from the grapevine so it may not be the case. Me & dh were looking closely at the pictures the other night to see how straight the walls were so we could decide if they had used forms or not.

I do have a cob building book by some other english cob builders & they reckon you can mix 12 tonnes of cob a day with a digger. I am guessing they mean metric tonnes? If I can borrow a digger ( dh is a construction builder ), I am mulling over mixing the cob for the other half of the wall like that. It would save me a stack of time but I am also feeling like I would be cheating. I am enjoying mixing it by foot.
 
#16 ·
We're building a cob cottage right now. It will be small and cozy - about 250 sf of cob downstairs and about 200 sf stick framed upstairs. We went to a one-day workshop to get a feel for things but for the most part have worked from the books. We reference different books for different things. At first I really like the Becky Bee book I love her checklist for different stages of building. We then moved on to The Hand Sculpted House. That book is falling apart.
We have building with cob and reference it from time to time but these days we mostly prefer a book called Building Green. The authors built a hybrid guest cottage - each wall was a different building technique with cob being one of them. It is so clear and explicit in it's descriptions and and it has lots and lots of photos - not drawings. We wish we had bought in the beginning. You can preview it at google books.

We tried mixing cob with our tractor but weren't happy with it. It was loud, tedious, and we just didn't feel we could get a good mix. We were anxious to move more quickly than by foot, though, so we mix the earth in a bucket with a paddle attached to a drill (described in Building Green). Then we stomp the straw in on tarps by foot. We've developed a system in which dh mixes the mud, I stomp it then put it on the wall. Other tasks have naturally fallen to one person or another as we have different preferences and skills. Sometimes the kids will join in but quickly get bored and move on to playing nearby. I'm trying to keep a healthy kitchen but we rely a little more on prepared foods than usual.

We're about 2/3 done with the cobbing. Overall we've enjoyed the process but I must say the details are frequently overwhelming for me. If I could I'd like to just not think and keep cobbing. But I get bogged down with details - installing windows, plumbing, electricity, waste water, niches, etc. Keeping up with whether my walls are plumb, thick enough, not too thick, trimmed properly. Some days I was really into it but others I was just ready to scrap the whole project.


We live outside of the city limits so we only needed a simple development permit from the county. If you will need to get permits cleared but think you will have trouble I have a link somewhere in which Ianto Evans gives info about an inspector or somebody who is willing to help you out. Let me know if you want it.

The most important part is your planning stage. Really think about what your structure needs to supply, how it needs to perform. You may decide that a hybrid type house will do better. Cob is great but it is labor intensive. Building will go a little slower probably than what you are used to seeing in stick frame homes. We had a couple of false starts with out house but once we buckled down we've really been pleased with out progress. We try to do something every day even if it's just stomping in straw to batches of mud.

You can probably find a large part of what you need in other supplies - windows and whatnot - on freecycle and craigslist but that's time consuming. We started to go that route but just decided we couldn't drive an hour one way to get something to probably wasn't just what we wanted. We've compromised in a lot of areas. I'd love to have used all recycled/reclaimed stuff but it just wasn't practical in our situation. We do it when we can but don't stress about when we can't.

Do you have any specific questions? I imagine my post is kind of vague in the details. I'd be happy to address anything you're curious about. However, right now I need to get outside and get some cob up on the walls.
 
#18 ·
Quote:

Originally Posted by ChocolateNummies View Post

Do you have any specific questions? I imagine my post is kind of vague in the details. I'd be happy to address anything you're curious about. However, right now I need to get outside and get some cob up on the walls.

Wow, you are awesome! I have a feeling a lot of compromises will be made by us, too, both in the nutrition dept. and the recycling. I see old doors and stuff all the time but I really don't have anywhere to store a door for a year until we get building! It's hard to let it go, though. But even with the compromises, you are doing something AMAZING, remember that! What is your climate like? We would be building in Louisiana, I see you're in Texas so maybe the climates are similar... are you in a humid area?
Thanks for offering yourself for grilling...
Rachel
 
#20 ·
Quote:

Originally Posted by reepicheep View Post
What is your climate like? We would be building in Louisiana, I see you're in Texas so maybe the climates are similar... are you in a humid area?
Thanks for offering yourself for grilling...
Rachel
No problem. Sorry I'm just now getting back to this thread. I don't always get a chance to check in here at MDC.

Sometimes it's humid here and sometimes it's not.
Cob is actually not supposed to be the ideal structure for us since it gets so hot here in the summers and doesn't always cool down at night for the cob to cool down as well.

We may have done better with combo of straw bale and cob to help insulate us from the heat. We compensated by making use of doors/windows to capture prevailing winds, deep eaves/porches, and deciduous afternoon shade. We also bermed the house into a hill a little bit. One average the house is a bout a foot below grade. Of course that meant a taller stem wall. Our rock work really took its toll.


The cob should do great for us in the winter, though, since they are relatively mild. Plus, we live in an area where tornadoes are common so we wanted something we thought could withstand that type of severe weather. We're tired of worrying through each tornado season.

We also get driving rains so we had to make sure our stem wall was a little higher than normally recommended in the books to avoid splashback. The porches and eaves will help protect from that as well.

If you build in an area that has really cold winters, straw bale on the north side may be something to consider. It's more insulatory. Then the cob in the rest of the house can heat up during the day and let that off slowly through the night. You can also place windows to let light shine on a floor with some thermal mass (earthen, tile, stone, etc.) to make use of passive solar heating.

One idea is to consider hosting a workshop at your building site. I don't know how easy it is to schedule, but I think all you'd have to do is be able to feed everyone who attends and have room to accommodate them overnight - I assume in tents and such. Then you charge each person enough to cover your costs of food, professionals, etc. and you get free labor. I'm not sure what all these cob groups/builders look for in workshop sites.

A couple of links we enjoy looking at are this flickr photoset that chronicles a small cottage some guy built pretty much all on his own. He used a lot of reclaimed/recycled stuff, incorporated a rocket stove with heated bench, and installed a composting toilet. Kind of fun to see his progress:

http://www.flickr.com/photos/msstarr...107592/detail/

Then there's this site. This person is local to us and has photos of a number of projects she's worked on. I know on one project at least she and her crew rented a bobcat and mixed tractor cob. That was for a pretty big house, though, as cob standards go.

www.claysandstraw.com

Anyway, hope that helps. We're really pushing here to get our house roughed in before we get any freezes so I may not check in often. We want to get a roof up pretty quickly and we don't have much cobbing left to do. Then we are considering moving when the house is livable but not completely finished. That should be an experience.
 
#22 ·
Quote:

Originally Posted by OceanMomma View Post
I do have days when I feel quite daunted by the whole thing. It's the other wall on the other side of the door that I am not looking forward to! I still have to find some windows to go in it but I am so tempted to get really really big ones so I don't have so much cob to do


I have some pictures but they are a few weeks old with one of the kids modelling doing the cob while I took pictures. The wall is up to the middle of the top sashes of the windows now. I get dh to cut it straight for me so it is also now alot straighter.

http://img.photobucket.com/albums/v2...Picture121.jpg
http://img.photobucket.com/albums/v2...Picture125.jpg
http://img.photobucket.com/albums/v2...Picture119.jpg
http://img.photobucket.com/albums/v2...Picture131.jpg

There are some real cool buildings or ideas for buildings here

http://www.simondale.net/house/
http://www.thatroundhouse.info/

I'd really like to do something small like a studio out the bush at the back with oneof those reciprocal roof things on it & maybe out of cobwood. I still have to finish the current project first so we shall see tho'

okay, so I am completely foaming at the mouth now. wow.
 
#23 ·
I just came back to say we've finally found some windows for the last part of the wall so I can start it - yay! The windows themselves are beautiful. They are full clear leadlight windows which came out of a house which was built in the 1870s or thereabouts. I'm trying to be enthusiastic about the whole thing but it's 10.3m long by 3m high by 0.36m wide which is something like about 11cubic metres of cob minus 2 window holes


To be honest, the cobbing itself is not really that bad. Not wanting to put anyone off here
It's keeping up with all my other activities I need to keep on top of at the same time which is the difficult bit. I'm almost tempted to send the kids to school for a term
 
#25 ·
Quote:

Originally Posted by maplesugar View Post
Oceanmomma-thank you for the pictures. I have been flirting with the idea of cob building for a long time. Is the rest of your house just a regular frame built, then? Was is easy to connect the two? Why did you choose to only do one wall cob?

I really like the accesablity of cob. Neither dh nor I have much construction experience so when we decide to build this will be a major factor.

We will probably (hopefully) be building in Northern Michigan, however, so climate may be a major downfall for building with cob. Does anyone have experience with cob in a cold cliamate?
We too plan on DIY low cost building (straw bale, cob or cordwood perhaps using timberframing) We now live near Toledo, but I am working on MDiv to be a pastor when I grow up. When I do, we will be moving into a parsonage and plan on taking the proceeds of our house sale to buy land in Northern MI to build something debt-free on. My dad is near Gaylord and dh's gma is in between Petoskey and Charlevoix on Lake MI. So we hope to be somewhere in that area (although away from the beaten fudgie path
) LMK if you get to build something, or what you find in regards to cob in MI, maybe we can come help!

PS Do you make syrup? My dad makes some of the best!
 
#26 ·
Hey the waggonerfamily! Believe it or not, that is exactly the part of Michigan we are moving to! Our land is north of Petoskey, not on the lake, but really close to Burt Lake. I just love that area! How cool to see another cob wannabe in Northern Michigan.


Sadly, we are not in Michigan yet, but in Alaska. This is a bit off topic, but I was born in Petoskey and my family is in that area. I just get so dang exited when I think of going back. We have to sell this house before we get started...

With regards to cob in the area, I have done a lot of research, and have found a method called light straw clay which I think might be a tad more prudent for the cliamate of the area.

With light straw clay, you build a wooden frame and infill with a mixture of straw and clay. There is quite a bit of info on the web and I found the sight of some folks out of Traverse city who build using this method. It can then be plastered with a cob mix, thus taking advantage of the thermal mass properties of cob, with the insulative properties of straw. Since the straw is coated with clay, it is not so vulnerable to water damag as with strawbales.

I hope to be there by this summer, and we will definately be doing some green building one way or another, will keep you updated.
 
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