Ceramic fiber board

[Dgotch]

Can anyone tell me. I just received my "3 ceramic fiber board,. Does the fiber board have to be mortared to the slab ? And then do the fire brick also need to be mortared to the top of the fiber board

[timechanter]

Just a 50/50 of sand and fireclay as a dry bed for leveling is all. The sheer weight of the floor hold it down. So just thick enough (with a notched trowel) to level the board on the base and the same again on the board for the floor. I just did this yesterday and it worked a treat.

[dakzaag]

no and no. Gravity is pretty reliable. If you need to level up the slab, you can use clay under the insulation and or the brick as needed but hopefully that isn't necessary.