My clay oven is now almost one year old and, to be honest, it was starting to look it!
The last time I fired her up I noticed that the cracks in the outer layer had grown substantially and, disaster upon disasters, the following day I noticed what I thought was steam streaming out of a crack at the back. In fact it turns out that the oven was on fire!! It seems the cracks in the outer layer had penetrated deep into the insulation layer which, happy with its new source of oxygen, subsequently caught fire. After dousing the smoldering mass with water I decided it was time to do something about it.
This week I repaired the broken chimney (see photo) and filled all the cracks with a new load of sand/clay mixture. There is nothing difficult about this. Just make up the mixture as per the usual method. Remove any damaged/friable bits of your oven. Wet the area you are working on so that the new mixture can bind to the structure more easily. Mould and fill cracks as required. Simplicity itself!
I have fired the oven since repairs and of course cracks re-appear (part of the normal expansion of the oven) but hopefully it should extend the lifetime of the oven a while longer. We’ll see!