A recent letter from a remodeler describes a common problem: a springy great room floor, framed with 2x10s 16 inches on-center spanning 15 feet on both sides of a center girder. The existing condition poses no real safety issue; it's just plain too bouncy. What's the best way to stiffen this floor, the reader asks, with minimal disturbance to existing finishes? Upstairs there is tile in the great room kitchen area and carpet in the living and dining area; downstairs, in the basement, there is a dropped ceiling. The usual methods would be to either double the joists or add a second girder in the middle of the 15-foot span. Adding joists becomes less attractive because of
