Hi Mike! Glad to hear your build is progressing. I bet that you went back to that hearth the next day and impressed yourself with how snazzy the herringbone looks.
So we’re looking at the same thing, here’s the section about stucco (OR mortar) from the general notes at the beginning of the manual:
STUCCO / MORTAR SHELL – The biggest misconception with the insulated oven occurs with the versatile stucco or mortar shell. This “shell” performs MANY duties and is required when insulating your oven with Ceramic Fiber Blanket.
- The shell is 2 rock-hard 1⁄2” thick layers of STUCCO or MORTAR MIX. While stucco is preferred, it can be regional and hard to find in some areas. If a dry stucco mix is not available, standard Mortar Mix can be used.
- Stucco is different from mortar mix as it contains synthetic fibers that increase its strength and durability.
- The stucco is used in conjunction with the metal lathe (chicken wire) to create a reinforced shell around the oven (think of the metal lathe in stucco like rebar in cement). This shell keeps the ceramic fiber blanket locked in place around the oven and also allows the end user to mortar ANY TYPE of veneer to the oven.
- The stucco or mortar shell can be painted, but it is preferred that you mortar a finish veneer to the shell.
- Once you paint the stucco, you cannot apply a veneer using mortar (unless you strip the paint).
- Only use dry stucco mix. Pre-mixed stucco is cost-prohibitive (you will need about 280lbs of wet / mixed stucco).
Looking at the three options you picked from Lowes, I’d say any of them would work fine, but you’d be wasting your money with Number 3 for sure. The “One Coat” option specifies it has fiberglass fibers, but I suspect the base coat has reinforcing fibers of some kind as well.
One random note I saw in the “Community Q&A” at the bottom of the page was from a QuiKrete tech rep who says that the base coat formula won’t work in this kind of application. He was presuming that it was being applied over soft insulation, not the mineral fiber that Brickwood specifies. He also was presuming that there would still be a lot of heat transmitted through to the stucco, which is not the case here.
I think you’d be fine using the Base Coat stucco. Just be sure to allow curing time between coats, because it will be tempting to judge by look and feel after the first coat. You don’t need the “finish coat” formula, except if you are considering stucco as your final outer shell. (Hint: don’t.)
And remember, you can use ordinary mortar as well. You’re not coating an exterior wall with this stuff—you’re ensuring the insulation stays mated to your firebrick oven liner and giving yourself a base for the “pretty finish” that is the last step in your project.
And, can’t wait to see those pictures!