Vermiculite Compressive Strength

[pappap]

Does anyone know if the hearth four inch vermiculite-cement insulation layer is stable enough to support a six foot brick flue? Vermiculite seems to be too soft and is causing concern. If any of you have or know of any ovens with longer flues, please advise.

[Faith In Virginia]

Yes it is stable. My oven has over 7 inches of thermal mass for the floor and dome. So it's almost twice in weight of a standard oven and my vermiculite has not settled at all. You are good to go.

I though the same thing when I built mine. I made a test piece and was truly surprised how strong it is.

[sonomacast]

How about a half ton oven sat on 1" of vermiculite?

[mrchipster]

Originally Posted by sonomacast

How about a half ton oven sat on 1" of vermiculite?

You may need to put some sort of support ring around the outside of the vermcrete to contain and protect the outer edge.

Chip

[rodeair]

I built my oven on a 4.5 inch layer of 5:1 vermicrete. As I was mortaring the oven, I used the excess mortar on the outer edges. I finally mixed a big batch and finished covering the ends of the vermicrete layer, worked fine.
Leigh

[pappap]

Thanks for the comments. I feel better about the vermicrete supporting the heavier than usual flue.