Recommended span for joists?

[marev]

What is the max recommended unsupported span for joists (220mm X 50mm).

Originally below our bedroom there was a separate kitchen and dining room, however the previous residents removed the stud wall and made it into one kitchen/diner.

Currently there is no support where the stud wall used to be and when you walk around the bedroom floor there is a noticeable bounce to the extreme where the wardrobes, chest of draws,etc move. The light units downstairs in the kitchen/diner also vibrate when you walk around the bedroom.

The joists are currently spanning exactly 15ft

 

[splinter]

For joists@220mmx50mm:- Centres 400mm 450mm 600mm
4.64m. 4.47m 3.91m

 

[rangersman]

Full depth bracing at third points between each joist will help reduce the deflection, but (as posted above) I would suggest that your joists are maxed out

 

[Static]

Yep your maxed on span, you could try screwing down all your floor boards to the joists.