wood for the base?

[bgoeps]

to save time and money I was thinking of supporting the hearth slab with a framework of salttreated 6x6s. Think there would be any heat/combustion problem? the rebar coming out of the slab would rest of the 6x6s but could they transfer enough heat to matter if it was wood??? thanks, bruce

[dmun]

Wood bases are not recommended. Wood is flexible, and masonry is heavy and rigid. A rigid support will help you avoid cracks. It's not a heat transfer problem, as the bottom of the support slab barely gets warm if your insulation is working right.

[BackyardPermaculture]

I used a wood base for time, money, weight, reuse and sustainability reasons, but it was for a clay oven. Quite a few people build clay ovens over a wood base, but I wouldn't do so if I was building a brick oven. Like dmun says, there's potential movement which will cause cracks.

[Archena]

Clay/wood - no prob.
Brick/wood - er, I dunno... Dmun is right - masonry isn't very forgiving. But on the other hand, a floating base (no direct linkage between hearth and floor) shouldn't have that problem as long as it's contained (floating off the edge would be a bad thing... )

I'm not sure you'd actually be saving much in the way of time (money would depend on sourcing). Even a wood base needs a foundation and laying block on a foundation isn't likely to take that much more time - especially not if you're using carriage bolts. (You could cheat with block and only do two walls as long as you reinforce them.)