To Insulate or Not? To Fire Before Insulating?

Hey guys , I’m at a stopping point ,

budget wise , my question is ceramic insulation or substitute brick ?
Can I fire cure and use as is keep covered when not in use

You’ve come a long way on this journey! Congratulations on this milestone.

I would always go with mineral fiber insulation—for efficiency and relatively light weight. Brick will eventually do a similar job, but not as well and it will take more time to get your oven up to cooking temperature. It will also cost a lot less. Only you can decide which is more important to you.

The balance for me would be how much work, materials, and time I’ve put into the oven build up to this point. I want it to perform at its peak. We get enough frigid weather here that I applied a double layer of mineral fiber, and it works like a champ. To me, that justifies all the work I did on the site and all the materials I hauled in by hand. It almost justifies the day I rented a jackhammer to extract an absurdly well anchored clothesline pole from the site. :slight_smile:

As for firing: if you want to fire it in this state, stop just a minute! Make sure you water-seal the outer shell and chimney before you fire it for the first time. Do that even if you plan to cover it between uses. You’ll have to do that again once your final outer shell is in place (no matter what you decide about which kind), but you will be beholden to the weather and sudden storms unless you do this step now.

You still need to do all the steps of the initial firing as outlined in the manual, and do not skip a single day of that. You accomplish two things there:

  1. The wet brick (and they are still wet) have the moisture driven out of them slowly, rather than generating steam that can (and has been known to) break joints and explode individual firebrick.
  2. The high temp mortar requires several firings to cure. Once it does it will become and remain rock-hard.

Hope all this helps. You’ve got a beauty of an oven on your hands there, and you want it to perform well over a period of years. Let us know what you decide!

Thanks a lot for your input, I have siloxane sealer but I was afraid sealing it at this point might penetrate the bricks and leave a foulness to it , but your recommendation is to seal it , yes I’m going to be ordering the insulation and stucco mix

Whoops. If you’re planning to go ahead and insulate/stucco the shell, then my advice does not apply.

I’d like you to consider one of two possible ways to go here:

  1. Curing and firing the oven without insulating it first…a very temporary option because you have an immediate and urgent need to use the oven before you finish your build. In that case you should protect it with a non-toxic version of siloxane water-based sealant.
  2. Completing the steps to insulate and apply a hard stucco shell. In that case you should wait to seal it until after your stucco is applied. You apply the sealant to all exposed brick on the exterior, and not to your hearth brick. You also paint the stucco with a good exterior deck/driveway paint, which will seal the stucco.

I do not recommend mixing and matching from these—do one or the other.

Make sure that your siloxane sealant is water-based, not solvent-based. @BrickWood has an option when you purchase the oven kit for an organic sealant that is food safe; they do not sell it separately but other builders have found it online or in places like WalMart.

I’m hoping that this advice is very clear, because the choices you make at this point are going to affect your long-term use of your beautiful oven. If you have further questions, please ask them now rather than moving ahead—you’re at a point where undoing a misstep involves sledgehammers, and I don’t want to see you have to do that!

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Matt ,
Thanks for the swift response, constant needling from the peanut gallery was pressuring me , I’m holding off on insulating and a stucco finish for a later date , not going to fire it either. I’ll continue to air dry and cover when weather is t threatening. It’s a great thing to have you for advice, Thank you