Question about plywood underneath hearth

[Frances]

This may be a dumb question, but is there any reason against leaving the plywood board in place after pouring the hearth?

I've got a board which sits just on the edges of the stand walls, and it strikes me that it would be a lot less work to leave it as it is, rather than sawing it into shape and then having to suport it from below. (Well, obviously I'd still have to support it, but to a lesser extent.)

The walls are somewhat irregular, so in some places there would be like a cement "step" as wide as the walls up to the hearth proper. Would this reduce the strength of the hearth at all?

It would be great if some of you could give me your thoughts on this!

[DrakeRemoray]

No huge issue with that. Is it damp where you are? I guess it could mold, but even if it rotted out, it would not effect the oven stability. I think if I was going to leave up there, I would use durrock or other concrete board instead, and then it would take a lot more to support it during the pour as the concrete board is not as rigid as plywood.

Drake

[Ken524]

Originally Posted by Frances

This may be a dumb question, but is there any reason against leaving the plywood board in place after pouring the hearth?

If you are going to leave the plywood, I suggest using treated plywood (more expensive) so it won't rot, mold, etc. I really like the concrete board idea that has been mentioned. I believe they are considering adding this to the official plans.