Fixing floor flex

Q: The living room floor in our 25-year-old home shakes whenever anyone over 100lbs. walks on it. How can we fix this problem?

A: Depending on how you feel about your basement space, there are a couple of ways to steady your floor. The easiest involves installing a secondary beam underneath the middle of the span of your springy floor joists, ideally across the middle of their span, held up by adjustable metal posts. This job could be completed in one afternoon at minimal expense, though it would also obstruct your basement somewhat. That’s the biggest drawback. Another option is to install additional floor joists in the space between the existing ones. This is a much more involved job, but does offer the advantage of not affecting the basement. The bottom line behind your problem is lack of wood in the floor frame. One way or another you’ll have to add more wood to get the flex out.