Hi everyone , just after some advise on the pizza oven base and potential water capillary action as i am based in rainy manchester.

i was planning and have already made a sturdy base with sleepers and 50mm of concrete , i was then planning a 100mm insulation layer of bottles and vermiculite. On top of this was 25mm silica board capped off with 64mm fire bricks.

1) can the board be laid over the entire base , or is it better just under the oven footprint .
2) same with the firebricks , over the full base or cut to size under the oven only

if the recommended is just under oven, what is used to fill around the void of the oven after raising it up on silica board and firebrick