Oven floor insulation radius

[Mara]

We are building a small Pompeii oven. We were thinking that instead of cutting the ceramic FB insulation radius to be the outer radius of the brick dome, we would cut it to a radius 2" bigger than this. Then the insulating blanket, instead of going all the way down to the concrete platform, would rest on this 2" lip.

One advantage would be that it would give us a perfect, solid circle to begin the outer shell.

Has anyone tried this? Does anyone see any potential downsides of doing it this way?

[MarkJerling]

I see no problem with that thinking.

[Kvanbael]

Many, including yours truly, did it that way. It Makes perfect sense and allows you to put screws in the side of the board for (chicken) wire to hold the blanket in place.

[david s]

It makes little difference so long as the whole oven is encapsulated in insulation. As the blanket layer is somewhat lumpy and springy it does not provide a good substrate to apply a render against. The normal method is to cover it with a layer of 10:1 vermicrete which is a pretty good insulator and firm enough to render against. There should not be any exposed insulation or it will pick up moisture. The outer rendered layer needs to cover the insulation and make a good bond with the supporting slab.

[hngten]

I have done exactly that on a previous build. It worked well.

[mongota]

We are building a small Pompeii oven. We were thinking that instead of cutting the ceramic FB insulation radius to be the outer radius of the brick dome, we would cut it to a radius 2" bigger than this. Then the insulating blanket, instead of going all the way down to the concrete platform, would rest on this 2" lip.

One advantage would be that it would give us a perfect, solid circle to begin the outer shell.

Has anyone tried this? Does anyone see any potential downsides of doing it this way?

I actually think that's a smarter way. This way the footprint of the firebricks that form the dome are not bearing down on the very edge of the board insulation, they are 2" away from the outside edge of the insulation. It can help minimize potential compression at the very edge of the insulation board.