Cob walls

[mauzi]

We are soon to start the cob walls for our power (come everything else) shed. I have done a little cob before but that was internal for a combined wood and cob bookcase. It is still standing after a year ha! so guess it was alright. The walls will be an entirely different project though - perhaps not quite so creative and certainly a lot bigger. Stay tuned to see how we go.

[bess]

Is a cob wall simular to mud brick with a then a mud render over the top?

[mauzi]

sorry for the delay in answering bess - haven't been on the internet for a bit - busy time of the year for me.

Cob is a mixture of damp soil with a little straw mixed through it. It is layed in sausages, shaped and allowed to dry. In the case of a wall - for a single story building - external wall - it is layed about 1 foot thick in sausages, smoothed off to whatever shape you desire, then allowed to almost dry before the next layer is done. In my experience you can lay about one foot high at a time before it will start to sag. The idea is that you go around and around the building so that by the time you get back to the beginning it should be ready (or almost) to start the next layer. It dosn't need a render over the top but it is best to seal it with something - we often use whitewash here but there are other commercial sealants available.

Cob is is load bearing but it has a lot of really interesting uses as it can be curved into various shapes and designs. I have done a corner bookcase out of it (in combination with wood for shelving). Internal walls - particularly those that are not load bearing, can have shapes, shelves, notches put into them. It can also be used for furniture i.e., bench seating, book cases, pretty much anything you have an interest in.

Kim, my DH, alias Ram was born in a 2 story cob house in Cornwall. I think from memory, it was built in the 14th century - so I guess we can say it is a lasting building technique.

I want to do a lot more in cob here - on my never ending list of jobs ha!

Cheers
Mauzi

[bess]

sounds very interesting and opens up the mind to wonderous ideas

[ram]

Hi Bess, The cob double story house that I was born in was built in 1470 and is still going strong. The walls were three feet thick on the base story and thinned down to about one foot at the top. It was load bearing (i.e., no wood structural supports) which in the long term picture gives it longetivity. Everywere you travel in the West Country (Cornwall, Summerset and Devon) you see these wonderful old cob houses.

[mauzi]

Bess - certainly does - I loved curved everything so cob is such fun - and if you don't like something you just take an axe/draw knife or any other sharp impliment to it and change it. (Mind you I did that with the rammed earth as well on the edges near the windows - I didn't like them square so decided to take a draw knife to them and made them curved My poor poor husband. luckily he is very patient with me ha! ha! but it does look good.

Cheers
Mauzi

[bess]

I was thinking I might start off with a dog house. Do you have to treat the walls with any thing to waterproof them? we used a silicon spray from "Grims" on the mud brick.

[mauzi]

A dog house sounds like a good idea - I think these earth building techniques are fantastic for animal houses as they are so warm in winter and cool in summer. One lucky dog

No need to waterproof cob (especially if you have thick walls) but you could white wash it if you want to. Like most earth walls I think it is better to have a bit of overhang on your roof though.

Interesting bit of info - their are earth walls in China that are around 6,000 years old and still standing. Says a lot for these modalities of building.

Cheers
Mauzi