Fireclay and sand below the floor

[andrewe]

Hi, I'm about to finish up the oven floor. Do I need to put sand and fireclay under the bricks or is this just a measure to create a level surface? Below the floor I have a layer of vermiculite concrete and then below that is the slab of concrete.

Thanks!

[Les]

It's used to get the floor even. If your surface is level and the bricks uniform thickness - it can be omitted. I used it but ended up using a belt sander to get the surface flush.

[Chach]

That Fireclay sand mix is some sticky stuff. Works very well if you need to use it