I am looking at using a ground floor room as a gym but would like to ensure the floor is strong enough to cope. It is a 1930s semi. The floor is a suspended timber floor with 2" x 5" joists at 380mm centres. The room is 3.6m wide but there is a sleeper wall around the perimeter and down the middle, so the max span is 1.8m. One area will hold my son's weight rack. This weighs 80kg + weights 170kg + him 80kg = 300kg in an area about 1.35m x 0.85m. The floor seems pretty sound and the joists have no signes of rot or infestation. I was considering the following options: doubling up the joists and may be even tripling under the weights rack. take a course of bricks off the sleeper walls and replace the joists by 7" or 9". adding steels under the rack using a flitch plate between the doubled up joists under the rack. Any advice would be welcome.