Building codes governing framed floors include an allowance for sagging, which sounds bad. But the allowable limit is 1/360 of the span, which isn’t much. Spread over a 45-foot-long joist — if you ...

so how hard is it to fiz sagging floors? Assuming bad foundation or joists are not issues, is it possible to starighten the floors somewhat? Do you have to pull up old floors and place new, put floors ...