Repair questions

[maineoven]

Hi everyone,

I had some questions about my oven which I built 11 years ago. It is certainly not perfect as I made several mistakes, but it has stood the test of time, mostly because I baby it. During the summer it is covered with a canopy when not in use, and wrapped up tight in the winter.

I really had two questions. The first are the cracks in the mortar of the outer chimney. This was made of a 3:1:1:1 mix. To repair these cracks, can I just chip out the cracked mortar and force fresh mortar in the joints?

The second are the cracks on the outer dome, which have been there for many years. I want to improve the look of the dome. After the firebrick dome, there is a thick layer of vermicrete with an outer layer of surface cement. I mistakingly did not use any chicken wire and/or insulation blanket between the layers. I was considering wrapping the whole dome with a few layers of chicken wire so there is a gap in between, then do another outer layer of fresh surface cement.

Thanks for any help. I've included pictures.
Stew

[david s]

I thought some of the more experienced brick builders may have offered some advice here, but as they haven't here's my two bobs worth. In many cracks in the outer arch that I've seen, it is caused by the inner oven parts expanding against the cooler outer decorative arch. With no expansion joint between them the outer arch is taking a lot of stress. Even if you repair the joints they may reappear again. One of the benefits of ceramic fibre blanket is that it acts as an expansion joint far better than a vermicrete layer. I cracked the outer stucco shell of an oven many years ago that only had vermicrete insulation, no blanket. Firing the oven before the vermicrete was properly dry deep in meant that the inner layer of vermicrete still had considerable moisture in it. When the hot dome suddenly heated that inner vermicrete layer it turned to steam expanded rapidly and cracked the outer shell. I fired it more gently to expel the moisture , did another rendered layer over the top and it's never been a problem since. Cracks in the outer shell are only cosmetic, but they do provide an entry for water, which can cause more problems, so filling them is prudent. Repointing cracks or joints is a common job, but even more important where thermal expansion takes place. Attached is the usual procedure for repointing walls and the same applies for cracks or joint repairs on ovens.

https://www.bobvila.com/articles/how-to-repoint-brick/

[maineoven]

david s, thank you for taking the time to answer my questions. Much appreciated!