Doubling up floor joists to cope with gym equipment.

[a long to do list]

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 doubling up the joists and may be even tripling under the weights rack. Or alternatively, I could take a course of bricks off the sleeper walls and replace the joists by 7" or 9".

Any advice would be welcome.

[ayjay]

I think I'd favour doubling up the 5 X 2s, they are already very slightly over specced for the span, and I don't think you'd gain anything by substituting them for 7 or 9 inch joists.

One area that I'd be looking at would be if the wall plates are fixed down, usually they are just bedded onto a sand and cement base and not fixed at all, this could lead to some unwanted bounce in the floor, (although only of an upward nature if weights are dropped, not a downward deflection due to weight).

[Grendel]

Is putting in additional sleeper walls a consideration. Would reduce the span to around 900mm , be quicker and cheaper , and not involve taking up the entire floor.