[stanbalder]

Thanks for both of those comments

In your case Acoma it seems as if you did everything pretty much by the book and still you got cracking so there must be plenty of others out there who had this too. Very nice job on the oven too I checked out the pics.

I don't know whether refractory cement and firebricks would have cracked just as much. Does this still need the 7 step firing?

I think the initial casing with no crack cement should indeed have had a slip layer as suggested by Dutchoven, but I've ordered the blanket as suggested.

I installed a small oven kit recently that had needles set in to the cement, I wondered if anyone has tried this instead of fibres to prevent cracking?

Cheers

stan