Brick Arch entryway problem

[lwood]

The arched entryway to my oven is being pushed off the oven dome by the expanding metal of the flue. I only used half bricks to form the archway and no reinforcement around the flue. I am ready to tear off the archway and re-do it but not sure how to fix it. Should I leave a space btw the archway and the flue to accommodate the expansion, also thinking about adding perlcrete to the outside of the archway. Any thoughts? Will get pics.

[Les]

I need a picture. It's hard to believe that the flue is the cause. The flue should not be attached to the dome - it's sitting on top of the entry. Anyway, pictures help us all to understand what is going on, I'm sure we can solve this.

Les...

[david s]

I had this problem when I built my second oven. I used a stainless steel flue pipe that was about 0.9mm thick. It gets hot first and expands. It cracked the castable refractory surrounding it. I now use thinner material which is 0.55 mm thick and I surround it with the slightly flexible vermicrete. No more problems at the join of the flue to the inner oven or to the outside shell. Take a look at the drawings page on my website.
davespizzaovens.com.au

[lwood]

Here are a couple of pics

[lwood]

I'm certain it's flue expansion, because when the oven is really hot, that gap widens to maybe 1/4" and I can't push it in to close the gap.

[dmun]

If you rebuild that, i would expand the space where the metal flue interacts with the masonry and stuff it with some refractory blanket, for expansion. A quarter of an inch expansion seems like a lot to me, but I don't have time to do the calculation now.

[lwood]

I didn't measure, 1/4" may be an exaggeration, but that's the flue bowing out, not the metal expanding 1/4". That's exactly my thought, leave more space and stuff it with flexible insulation. Thanks, I guess that's a heads up for everyone to use .55 mm stainless for their flue matl.

[Tscarborough]

For the correct construction detail, Google "chimney cap construction detail".

That is certainly your problem, and it is pretty easy to fix without tearing apart the oven.

[david s]

This is my solution. Seems to work pretty well.

[lwood]

david s...so you would put perlcrete extending onto the OD of the arch also? Is that correct?