What should be added if the floor joists can't handle a span by the size of the joist alone?

Adding columns and piers is an effective method to address situations where floor joists are unable to handle the specified span based solely on their size. When the joists are overloaded, their structural integrity can be compromised, which may lead to deflection, cracking, or even failure.

Introducing columns and piers redistributes the load more effectively by providing additional support beneath the joists. This helps reduce the load on each individual joist, allowing them to function within their design capacity. The added vertical support can significantly improve the overall stability and strength of the floor system, ensuring safety and longevity.

Strong band joists and pressure blocking are methods used in framing but do not directly provide the necessary load-bearing support for a full span issue. Simply adding nothing would not resolve the problem of inadequate structural performance either. Therefore, incorporating columns and piers is the most reliable solution in this context.