Crack arch of oven

Hey! I re-did my chimney this summer- because the harsh winter destroyed the chimney. I noticed a hairline crack that developed over the summer- maybe I didn’t dry it out slow enough? How do I fix this? This is a picture of the top of the oven and the front

It’s getting cold here into the 30s at night- is it ok to try to fix this now or wait until next summer? If it’s warm enough I was hoping to get a sealer on the oven before it gets too cold.

Hi Steve and welcome back!

I’m glad you got some good service from your oven after your rebuild.

I only see one photo, which looks like your chimney crown. I wouldn’t wait for spring. If you apply a high-temp silicone sealant now (don’t wait until your overnight temps are consistently below freezing), you have the advantage of the crack being at its widest due to contraction. Do a small bead and wipe off the excess. The high-temp silicone is a solid orange color, so you don’t want any of it obviously above the crack.

Best time to do it is in the morning, before the mortar expands. That will allow daytime temperatures to give it an initial cure.

In the afternoon I’d lay a moderate fire in the oven, and put on the door once the flames die down. That will give the high temp silicone the heat it needs to cure properly without putting your oven under too much stress.

I recommend this rather than waiting until spring because you don’t want a freeze/thaw cycle to get ice into that crack, which would set you up for the problems you had before your rebuild.

Good luck and let me know how it turns out.

Thanks of the advice! I also included the crack on the front arch- I’ll assume I use the same product all the way down through that crack. Thanks!!

Also- I assume this product will work- is this food safe?

Yes, that’s the stuff!

I can’t say whether it’s food safe, but you’re not using it where that would be an issue. I’ve used it inside my oven, and unlike mortar once it’s there, it will stay there.

I would dab a little into the mortar, and not worry about the cracked brick. Even better, I would leave that area entirely alone for now.

There was some stress introduced when you laid that section, and the crack represents the area where that stress was relieved. It’s unlikely to spread. The beauty of laying brick in offset rows is that the rows above and below are not in line with cracks. That hairline crack is stopped definitively by solid brick rather than finding a vertical mortar line, or several, to keep on going.

For that one, I’d just pay a little extra attention to waterproofing it.

Thanks so much!!

Sorry I had one more question….should I clean the soot off the firebrick before I seal it for the winter? I bought the organic sealer stuff- but wasn’t sure if I needed to clean the spot off first?

No worries, Steve. Yes, for sure clean off the soot first. A little Dawn detergent and a bristle brush will do the trick. Rinse and allow to dry before you apply the sealant.