Oven floor insulator materials and process…

[mnagy]

I’m trying to decide how to insulate the floor of my oven. I’m planning to use 1.5” of 5:1 vermiculite concrete rather than ceramic fiberboard (because I’m worried about it getting ruined if it ever gets wet).

But I can’t decide whether the vermiculite should be only under the dome floor (less weight) or under the dome walls also (much heavier). Is vermiculite concrete strong enough to support the entire dome? I know that would be better from an insulation perspective.

the whole thing is on top of a 4” concrete counter top.

[Gulf]

5 to 1 vermicrete is strong enough to hold up the dome walls. It is critical that the dome walls rest on the insulation. However, 1.5" of vermicrete is not enough. 4" is the recommended minimum for vermicrete. I suggest that you follow a few build threads on this forum that are similar to yours. I'm sure that you will find much more critical information included in them.

[mnagy]

Thanks! I was thinking 1.5” just because that’s the thickness of the landscape edging I happened to have in the garage. I suppose I should be a bit more deliberate! I’ll go by some 4” stuff and use that.

[Gulf]

Ceramic fiber nor Calcium silicate board are "ruined" by simply getting wet. No insulation needs needs to get soaked. Drying a water soaked oven can be a real pain. However, simple steps can be taken to keep insulation dry during the build and after completion. Vermicrete is installed wet. Many gallons of water need to be eliminated before it is an efficient insulation. Regardless the material used, I'm guessing that you haven't looked into "weep holes" and "elevating" the insulation layer. A proper chimney cap and "storm door" and "steam vent" should also be considered for an oven standing alone out in the elements.

Again,

.....I suggest that you follow a few build threads on this forum that are similar to yours. I'm sure that you will find much more critical information included in them.....

I also suggest that you use some of the key words that I highlighted on a search of the forum. You may also do a google search of the forum which sometimes gives more results.

[mnagy]

Thanks Gulf. I’ve got all winter to look through these build threads, and will certainly take your advice.

my oven will have a custom cover for when it’s not in use; and I’ll certainly make sure the chimney is sufficiently housed to avoid water getting in.

I’ve heard that scrap mosaic tiles can be used on the slab (grid facing up) to separate the insulation from the slab, but I didn’t think I would need that if I used vermicrete.

I have other questions that relate to spacing and weep holes for the brick I plan to mortar to the outside of the stand, and other questions related to the colored/polished concrete I intend to pour for the counter top (I want the oven floor to be flush with the top).

I designed everything in Sketchup. But my practical masonry knowledge is lacking. I’ll be sure to research and brush that up.

[mnagy]

[mnagy]

A few more pictures

[UtahBeehiver]

I did notice that in one of your sketch-up drwgs you show a full soldier brick. You may want to rethink this since a full header base is prone to outward pressure from the dome and may require buttressing of the full soldier. Consider a half soldier or a half header.

[mnagy]

Thanks! Yes, that’s an older drawing. I’ll probably use half soldiers. But there will also be a second poured countertop that will be at least 2” up the side of that brick. That first ring is gonna be rock solid. If anything, I’m worried about any brick damage cause by the concrete having less movement than the brick dome.

[UtahBeehiver]

By pouring the counter top up against the half soldier you will create a heat sink in the dome which will draw off heat making the oven less effective. The dome/floor must be isolated and insulated from the concrete hearth or concrete counter.

[mnagy]

Ah. Shoot. I need to rethink this.

[Gulf]

I'm glad that you found us before you got any further along. You may even find out that it would have been best before you built the stand. Regardless, please take the time to download the Free Brick Oven Plans. That will be a good start. Take the time to look at all the links on the start page that I provided. We all really need to a firm grasp on the subject before jumping in. Note that the plans are a little dated. They would keep you from making those critical errors that you were about to make. There have been some great improvements added by members of the forum who learned by trial and error. Take the time to read the plans, follow some build threads from start to finish, and you will end up with the perfect oven for you. After you've done your research, start a build thread. We will be here to give advice.

I'm looking forward to your build thread

[mnagy]

Ha. Me too.

I’m confident I wouldn’t have started pouring without talking to someone.

I feel pretty good about the stand. Filled and reinforced concrete block walls (probably overkill) and 4” reinforced concrete hearth.

I’ll be sure to share.

Thanks!

[mnagy]

I did a redesign last night. This method adds 4” of vermicrete on top of the entire structural hearth. Oven floor and sailors next. I’ll use blankets, wire, and vermicrete around the dome, and will scratch the poured top idea. I’ll maybe do a decorative granite piece in front.

[UtahBeehiver]

The pic is not really viewable to see detail. Did you mean soldiers and not sailers? Sailers do not give you enough dome depth, ie 2.25" to 2.5". The brick dome should be 4" to 4.5" (1/2 brick). Min. 4" 5 to 1 v or pcrete under floor. 8 to 10 to 1 on dome,