Building regs requirements joist sizes

[nelliedee]

Hi

We are currently adding a shower room to the rear of our garage and are about to put the new floor joists in. We have approx 195mm total from existing concrete garage floor to existing floor level inside our house and would like to keep it all level. What is the smallest joist permitted? the room is small, measuring 1.5m x 1.5m.
Also is there a required gap that needs to be maintained between the underside of joists and concrete floor?

 

[stephenf8542]

Think your air gap needs to be about 100mm-150mm

 

[nelliedee]

thanks
have now decided to do a concrete floor