[gjbingham]

One of the small issues with the 5:1 ratio in the plans - it is not stated whether it is by weight or by volume. I used volume because the vermiculite is so light. I assume that was correct.

Eddie - need to know the size of the oven you're building. I used 3 large bags of vermiculite to pour the insulation layer (not really a support pad) directly under my oven. If you take that layer out to the edges of the hearth, probably somewhere around 6 - 8 bags. Check out the plans again. Make sure your terminology matches my description for the step you're trying to accomplish.