Tommy Mac Discussions › Forums › Fix-it Forum: Home Improvement & Do It Yourself Repair Forum › 2×4 Floor Joists?! › alternate approaches
Joists can be supported on beams that reduce their span. If the space exists to install beams and appropriate foundation footers, and posts below the first floor, you can run beams perpendicular to the existing joists and cut the joist spans into 4 to 6 foot sections. This would be much less expensive than directly reinforcing the joists or jacking up the house. reducing span would eliminate excess deflections and increase floor load capability. It would reduce usable ceiling height in the basement and requires installation of properly sized footings to support any posts that carry the beams.
Check with your engineer and determine if you need permits.