Instructables

How to mix cob in a wheelbarrow

video How to mix cob in a wheelbarrow
Mix a batch of cob in 10 minutes or less in a wheelbarrow!
 Faster than the traditional tarp method.
nicofrog3 years ago

So if you have bad knees,or no one around,this might be the way to go
otherwise its 10 times less work using the tarp method,I have children mix it!
music is good,and a clear work space,you have built a
beautiful cob building!! if you look up
propotions of fiber used in cement, you get clue as to how little straw you need
plastic fibers are available,as is human hair for interior plasters!!
(10 oz per yard)


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gaiatechnician (author)  nicofrog3 years ago
Cob isn't concrete. It is a composite material. I have been told by long term cobbers that the more straw you put in the better. The straw binds it and will allow it to settle over hundreds of years without cracking.
And I beg to differ about the tarp method.
It is a lot more work than mixing in the barrow and at the end of the job, you have to pick the stuff up off the ground to get it to where you want it.
I have done cob by tarp and by wheelbarrow so I have the benefit of experience.
Tarp mixing is a lot more work and it takes longer too.
It is great if you can get a bunch of volunteers to do the mixing. But if you cannot, then you need to use the least effort possible. And the wheelbarrow comes close to that. If your clay is well soaked before it goes into the wheelbarrow, or if the clay is mixed with a heavy drill and mixer attachment, it is even quicker.
About 2.5 cubic ft per mix, 6 mixes per hour, comes to about half a cubic yard per hour. Thats a lot of cob.
Brian

Agree 100%! Tarp was mind-dumbingly slow and I don't know how I forced myself to do it for an entire day. The next day I used this exact method shown here in a wheelbarrow and it was much faster and more fun.
Or maybe I should get myself some more child workers, eh?

gaiatechnician (author)  antioch29 days ago

Glad you tried it. If you break up the clay and let the clay soak in buckets or on a tarp! overnight, it is probably easiest. But one time I left it on a tarp for 2 or 3 days and the clay got hard again. Really annoying. If you have a cement mixer, you could definitely mix the sand water and clay in it and it is really quick but don't dare add the straw into the mixer, It will bind around the blades and take forever to remove! Brian

mick5023 years ago
hey gaiatechnician, are you from ireland? im going to attempt to build my own straw shed to start of with but my end goal is a cob house. what adive can you give me? i am from Antrim in Ulster
gaiatechnician (author)  mick5023 years ago
I am from Co. Carlow. Now I live in Canada
There are still clay houses in Wexford and my mum used to live in one when she was younger. My uncle also had a clay house.
It is not a job for this time of year! I think the main thing now is to find good clay.
You need to start cobbing in decent weather and probably in Ireland it needs to be finished before the start of September because it has to dry out before the first heavy frost.
I only have barley straw available here. You will have wheat straw available and maybe rye straw. I think rye straw might be best.
I think some people have built Cob houses in Ireland too but I have not been back in ages. You could make contact and see what they are doing.
I am also interested in light clay construction. Basically they mix straw and wet clay (with only a little sand) and then use it as "infill" in the walls.
AND, as far as I know, it is in the building code in parts of Germany!
I have a link in the video introduction on utube.
This probably uses a lot less material than cob and has more insulation value. In Ireland I think the more insulation, the better.
I hope you go ahead with your project. I imagine that simple cob sheep houses would be super useful in winter in Ireland.
But I doubt that farmers will make them unless they see that it can be done.
nevar3 years ago
http://www.youtube.com/watch?v=pph25P0qVH8