Lay a pizza oven floor

[Milo]

Good morning people ,
just started my pizza oven build ,using a 4inch vermiculite /cement insulation . My question is :
can i use outdoor fire cement to lay the floor briks instead than fire clay/sand ?
many thanks for your help

[fox]

Not the best idea as the bricks need to be able to move around a little as they expand and contract during the heat up and cool down periods.
You can use plain sand though.

[Pizzarotic]

My preference is to use a refractory mortar to bed the floor bricks much the same way as floor tiling. I find it is much easier to get a perfectly level floor than using bedding sand, especially if your bricks are of uneven thickness.
Some people worry about expansion and contraction but the bricks and mortar have similar properties so the variation is minimal. Yes some of the brick to mortar bonds will fail but the floor bricks will still hold there position and maintain a smooth floor.

If using a loose bedding material then some compaction is required to prevent any settling over time which can cause lipping. Either method should provide a satisfactory result.

[UtahBeehiver]

Plus one of Fox's suggestion. The material under the fire brick is only for taking our minor irregularities of the brick and not very thick, ie 1/4" to 3/8" and only really necessary if the surface that you are laying on is out of wack. Fire clay does help the sand bind better yet not set up like a mortar.

[NCMan]

I always use a 50/50 mix of fireclay and sand. Have built 15 or more ovens over the years and it never has been an issue. Wouldn't do it any other way.