I recently purchased a houe built around 1910-20. A small addition was built at the rear of the house, probably 10-20 years after original construction. In renovating the house, we discovered what appears to have been some kind of concrete/masonry room on the first floor at the back of the original house. The 2 side walls of this room have brick exterior finish over concrete or some kind of clay block. The front and back walls of this room were removed when the addition was built, I assume. When we opened up the ceiling, we found that 4-5 inches of concrete had been had been poured between the ceiling joists. The floor in this room is also concrete, while the rest of the house has a basment. My contractor and can't figure this out and are perplexed. Any thoughts?