Knackered oven floor

[sparty69]

Hello, I need some advice please. I built a vermiculite concrete pizza oven last year and after a few uses the floor has lifted making it impossible to use. Rather than dismantle the whole oven I was going to try and chisel out the floor , replacing it with fire bricks. Is this feasible? If so, I've found a local supplier of fire bricks but I would need to cut them to fit. Once cut is it acceptable to just lay them on a bed of sand or would they need to be cemented in place? Any advice welcome.

[oblertone]

Welcome to the site; floor bricks are usually laid on a bed of dry sand to allow you to level them, and to replace them should cracks occur. A cheap alternative to firebrick are storage heater blocks, usually found on eBay or Freecycle 👍🏾

ps - A few pics of your oven and progress would be welcome.

[downunderdave]

May 24, 2021 6:27:31 GMT sparty69 said:

Hello, I need some advice please. I built a vermiculite concrete pizza oven last year and after a few uses the floor has lifted making it impossible to use. Rather than dismantle the whole oven I was going to try and chisel out the floor , replacing it with fire bricks. Is this feasible? If so, I've found a local supplier of fire bricks but I would need to cut them to fit. Once cut is it acceptable to just lay them on a bed of sand or would they need to be cemented in place? Any advice welcome.

Vermiculite is an insulator and if you've made a dome using a fair proportion of it in the mix your dome will have very little thermal mass to store much heat. in addition it results in a concrete with low strength making it vulnerable to bumps and abrasions. If OPC (ordinary portland cement) is used rather than CAC (calcium aluminate cement) it is likely to break down under high heat (north of 300C) resulting in bits of vermiculite falling from the dome. This may become more of a problem than your floor bricks, so it could be a better solution to start again. Vermicrete is useful as an insulator for under the floor bricks and over the dome, but unsuitable in a castable mix for the inner dome facing the fire, especially if it is mixed with OPC.

Not sure what you have used for floor bricks, or what you mean by "lifting", but they should be laid loose to allow for individual brick expansion and have adequate insulation between then and the supporting slab.