support for bottom tray of form

[jimkramer]

Should the legs for the bottom tray of the form for the structural layer of hearth be screwed to the frame? Or does the frame just rest on the legs? This would make it easier to remove the form after it cures, but I suppose it could all fall down with the weight of concrete when it's poured which would be pretty bad.

[david s]

I would be just resting it on the supports, but use some thin wooden wedges that you can tap in under the supports to make micro adjustments for height.These also facilitate removal of the supports without stressing the cast slab when you take them out. The weight of the poured concrete holds everything in place. If you have any gaps more than 1/8" they can be sealed very effectively with some clay, if you have any at hand.

[NYC]

If you build a solid frame with cross beams you can just support the joint, center and corners with 4x4's on shims and then just knock them out and the plywood will drop down. Rub some diesel fuel or vegetable oil on the plywood and side forms to keep the concrete from bonding to them. It makes removing very easy.

[Mike D]

Diesel Fuel? Really? A little early to start the curing process.

Mike