Originally Posted by sixeightten
The span of the joists is what is important. You may be able to double up every third joist, but sometimes electric, plumbing, hvac makes this tough.
You should also check the existing floor with a string and see how much deflection is there already. This will probably be a real eye opener for you.
I definitely hear you on that. The house was built in the 40's I believe, if not earlier than that. There are many places where things aren't square, plumb, or level. Now to find some string...