Hey its your design, just take the advise from others into consideration as you create it. Here are some thoughts on ways of doing this. I was once in a machine shop near the Canadian border. As I was talking to the owner about knives I looked around at his mills and lathes. Then I seen this huge 100lb Little Giant. Talk about the *wow* effect. Anyways, he wouldnt sell it, it was the only thing that would draw out tines (or maybe shares?) for some local farmer, one time a year. Oh well... "how do you heat them?" I asked, not seeing a forge or oven. He points to the floor at a heap of welding fire bricks, with a weedburner wedged into them. He had rejetted for natural gas, but that was it. Another thought is to check with your local ceramic places, the ones where people make stuff, and then have it fired. They might have some pieces of broken "shelf". Thats high temp and should make a good floor to your forge. Just so you know though, the lite brick used in those ceramic furnaces disintegrate very fast in forge work using flux. Might be OK for the walls though. Good luck and if you can put some pics on your site of what the forge looks like now, in the early stages, you might get some other ideas here if we know what your working with.