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We have built an oven from scratch - really looks good, used fire brick and refractory mortar. We would now like to put something over the top, such as stucco. Any suggestions of what type to use? Appreciate any information we can get!
The process that I would take to get to a stucco finish is as follows...
Step 1: Cover dome with insulating blanket and Cure oven out to 400 to 500 degrees.
Step 2: Cover insulating blanket with 3 to 4 inches pearlcrete or vermicrete. This will give the stucco a good backer material. This could be skipped and wire lath could be used in place but stucco is much more likely to crack then. Cure this layer out to full oven operational temps.
Step 3: Scratch coat: Use Type S mortar (Almost identical to conventional cement stucco) and install a 1/4" to 3/8" layer of material and scratch with a notched trowel creating horizontal lines.
Step 4: Brown Coat: again use Type S mortar (apply brown coat 24 hours after scratch coat) Apply coat this time about 1/2" thick over scratch coat, trowel smooth with a steel trowel. Allow to cure for at least 2 weeks, Fire oven to operational temps at around 2 week point. It is very likely that this layer will crack and that is fine.
Step 4: Finish: The best finish IMO for these ovens is an elastomeric synthetic stucco, namely, Dryvit, STO, Stucco Flex and there are a couple others I cant remember. Trowel this on with a steel trowel about 1/8" to 1/4" thick and depending on finish style chosen, float out accordingly to desired finish. Most finishes use a plastic float but some of the smoother finishes use a pool trowel.
This week I started applying the final coats of stucco on my oven. I'm using Quikcrete Quikwall (surface bonding concrete/stucco) with acrylic fortifier. We don't get much rain here in SoCal so hopefully this will be enough protection from water penetration.
The quickcrete will work just fine. Just expect to see cracks. The Acrylic based stuff I talked about can expand and contract a lot more than cement based products without cracking, that is why I think it is better suited.
I dont know how well stucco performs in Wisconsin. I only know how it performs in the north west and California. The synthetic stucco or Acrylic based finishes do a very good job of keeping water out, but they also do a better job of holding water in if water finds a way behind it.
If I lived in an area where there is a lot of freeze thaw I would cover my oven with a roof or tarp it in the winter.