Damon54 wrote:K.A.M. ,
To be clear my volume is unchanged. My question: Is the area beneath the elevated coal base still relevant to the total volume calculation?? In my case the air inlets are close to fuel grate level.
If you want to get technical if you add solid matter to the inside of a cube it decreases the inside area. In my opinion adding grates to the inside does little to the numbers especially because I oversize my fireboxes slightly anyway. The air space below your grates is relevant to the air needed to pass through your coals to feed the fire. Some folks do not use grates and build their fire on the floor. This is okay if you are burning pretty hot but does not do well with small coal bases.