External crack

[cvdukes]

Originally Posted by Xabia Jim

FRC......but not the same issue with chickenwire? How about the steel reinforcing wire mesh?

I guess the chicken wire doesn't have enough mass to push anything around...each indiviual cell would expand slightly and might would crete just a slight internal pressure but not high enough to counteract the adhesive pressure of the cement...would also guess the stucco mesh is about the same but can't say from experience

[talisker63]

Well my first impression was that the flue (sheet metal) expanded on the first firing and caused the colored render shell to crack. The crack started at the flue and has worked it's way down to the arch. It is getting very slightly wider each time I fire the oven. It closes a little when the oven cools.

My plan is to keep firing the oven for another month or so (once per weekend) and then repair after that time. Repair will be;

1. cut a gap around the flue to allow for expansion. Suggestions on how to fill this gap so as to reduce heat loss??

2. re-render the entire oven with another 1" of sand/cement/oxide render.

I have quite a few hairline cracks on the sides so the re-coating will cover these also.

Any other suggestions?

cheers

[Frances]

Doesn't vemiculcrete have a bit of give in it? Maybe if you filled the gap with that, and it would insulate at the same time?