Hi I have a large slab of soapstone that i want to use for the cooking surface.
Should I cut the slab so that it fits in the area that the herringbone bricks would go in or should I leave the slab big and then build the oven on top of the slab?
Hi, and welcome to the BrickWood forum!
Interesting. You already have the soapstone, and I presume you know where it came from and is appropriate for food use.
My advice would be to cut it about ⅛ inch smaller in both dimensions than the area, to allow for thermal expansion. This will give you a gap of 1/16 inch on all sides.
The oven as designed is built so that it overlaps the brick hearth frame (the area that encloses the hearth) and the hearth itself. When you place this slab you will be doing so permanently, so be very sure this is what you want.
You could choose to place firebrick “splits” inside the brick frame and have them come out from under where the oven will eventually rest. The idea will be to make your soapstone slab removable (with difficulty) if you ever have to do that. Should you choose to do this, lay out your frame according to the plans, place a couple of bricks on the leveled sand protruding into the space, rest the foam core on those bricks, then mark how far into the space you have to go to “shim” the oven wall with split firebrick.
From what I’ve researched, soapstone should make an excellent hearth surface once it’s placed properly, and your fires will stay well below the temperature where it starts to convert to lava.
Hope you’ll come back and post some photos when you have a chance, and thanks for stopping by!