Stucco over cement

[Vincent G]

Starting my oven exterior, lath over insulation blanket is complete. I’m a little hesitant to apply the stucco directly to the blanket...was considering applying a layer of cement or refractory cement first giving more of a structural base then apply stucco. Thoughts?

[randaloo]

I have exactly the same question.

[SableSprings]

Most people have chosen to use 10:1 perlcrete or vermicrete over the lath holding down the insulating blanket. We recommend completing your curing fires before doing the final outside stucco or even the insulating cement. You want to make it easier for the moisture to escape and it helps keep curing fire stress by reducing temp variations within the structure. Take a look at the build by Utahbeehiver (there are many others as well). You don't need much to help shape the outer lines and to give stucco an application base.

[Mongo]

Starting my oven exterior, lath over insulation blanket is complete. I’m a little hesitant to apply the stucco directly to the blanket...was considering applying a layer of cement or refractory cement first giving more of a structural base then apply stucco. Thoughts?

I've asked the same question and found that the pcrete over the dome is to provide extra insulation and help give shape to the dome before the stucco render. If you have sufficed insulation and the lathe has provided you with your shape the go with stucco over lathe.

I had 3 inches of blanket and had already applied lathe so went with stucco and skipped the pcrete.

[Vincent G]

Thanks for the info! You hit on my next question...should I complete my three step firing/curing process before I apply any of my final exterior stucco/cement finish?

[Vincent G]

Also...how long after your firing/curing process is complete do you have to complete the exterior finish?

[Mongo]

Question 1:

You should definitely complete your curing prior to covering your blanket. As Mike SableSprings mentioned above, you want to make it easy for the moisture to escape.

Question 2:

Short answer: Until you are confident you have driven out all the moisture you can. A good test is to cover your dome with clear plastic and look for condensation during/after a fire.

With my dome covered in blanket and lathe only, I completed my curing and used the oven a minimum of once a week for almost 2 months before applying the render.
Not sure how necessary that was but it was worth the piece of mind knowing it was dry. I did wake up one morning to a light mist over my uncovered oven. I was lucky and that dried out with one pizza fire.

About curing. You cannot go too slow. I recommend you start with a small pile of charcoal briquettes for your first fire. Day 2, larger pile of briquettes. Day 3, pile of briquettes and a small piece of kindling. You get the idea. Use an IR thermometer to monitor temps at the apex of the dome, 1/3 down from the apex and 1/3 up from the floor. As for "which reading do I use", I went by the reading at the apex above the fire.

Here is the curing thread: https://community.fornobravo.com/for...33-oven-curing

The 100 degree increments is great advice but I would replace 'newspaper' with 'small pile of briquettes'. Flames produce an incredible spike in temp.

You can't go too slow, but you can go too fast. And like cutting a board, it's easier to add to a fire than it is to take away.

[david s]

The outer shell’s function is to keep out the weather and also to provide a stronger exterior preventing damage to the softer insulation layers. You could use the oven in this state forever provided you kept out the rain. If any cracks appear in the outer shell they are of little concern apart from providing an entry for water and of course cosmetic appearance.