Originally Posted by nealtw
. . . . You are not adding a lot of weight by adding a basement.
That all depends on one's definition of "not adding a lot of weight."
The approximate weight of just concrete walls, floor and footings for an average-size (1600 S.F.) basement will be approximately 274,000 pounds (137 tons). And that's not counting any interior support structure (girders, columns, pier footings, etc.).