All firebrick would be great. They are very sharply cut so everything would fit together much tighter. The only downside is the cost. Where I bought them, they were $1.50 each. All the additional clay brick I bought for about 15 cents each. I used the fire brick for the floor because I wanted that tight fit for sliding the pizzas in. But, sure, firebrick would make a really great oven. Please send me pics if you do it. Dan
