I have an addition of the house built about 30 years ago and I would like to create a bit more headroom in this basement portion. The past owner used this room as a clean room to make portions of airplanes. Without the HVAC the exposed floor joists are about 6'3" of clearance, I would like to finish the room and a put in a ceiling. I know that there is no electrical or plumbing in the concrete and at one end where the room slopes towards there is a hole lined with a metal bucket laid in the poured concrete. It would seem to me that there us a good 8-10 inches of poured concrete based on the sounds I get from hitting the inside of the bucket. How deep can I go down - I would like to get another 6 inches of headroom. I guess it is more important to know can I do this? What could I do to properly check the depth of the crete and also How do I check for the footing on the exterior wall and thier depth. I figure that once I am down to the height that I want then I would pour new concrete to level off.