hearth slab

[tommy5]

thank you dmun for the suggetion, i laid out the blocks and have my foundation ready to pour if the rain ever stops here in jersey. i am looking for advice on the hearth slab, the instructions say it should be 58x66, when i lay the block out, closest i get to that withiut cutting 8x8x16 block is 64x72, do i need to cut block or use some other size, i quess i am wondering how crucial that number

thanks
Tommy

[Fio]

In MY humble opinion,

Bigger is better. You can always fill the gap between the wall and dome with vermiculite. Don't worry about cutting blocks. If you've got room for a slab that big, it will give you more room to play with.

The only thing I would add is that your foundation slab should be about 4" bigger on each side than the block base for your oven. If you've got that, then a bigger base should be no problem.