Could anyone tell me the best way to repair an interior cob wall. I have used tetrion filler for small holes but this is rather a large (2ftX1ft) slice that has come away from the wall. It was also quite damp underneath.
You will have to be guided by what has been put on the wall already, chances are that it is lime plaster. You should try to minimise the damp coming through the wall before covering up.
commonly cob walls suck water up by osmosis. if lime render is used the water evaporates off no worries and it is not an issue. in the 70's loads of cob walls got cement rendered so the walls can't 'breath'. the render then blows off the wall at 1m high or there abouts. (often indoors) so you need to work out why the damage has occured, especially seeing as it is damp.
i would hazard a guess at the above but without more info it is hard to help.
as stoneyboy says lime render is the way forward, but do research as it is a dangerous chemical.
i'm a conservtion architect so can help more with further info. what finish is inside and out?
has anyone ever tried to inject a dpc? (never do this!)
what level is the ground to the outside of the wall in relation to inside? a french drain may be needed.
also is this on going or has it just happened for the first time in 10 years?