This weekend I started an install of 5/8 inch wood floor. There are a couple of spots where the floor sags up and down when I step on it. The flooring was laid over the cement slab and an underlay material.
What is the best way to fix this problem?
Thanks for the help.
Sounds like the concrete surface has dips in it that are deep enough that even the underlayment cannot fill adequately. The flooring boards are acting as a "bridge" over the gaps and will continue to flex up and down until the voids in the concrete are leveled out. Good luck.
If you have never made a mistake, you haven't done much.
In other words you are out of luck w/o removing the floor from that area and leveling out the concrete. This is precisely why I hate 'floating' floors. I am considering a glue down approach over my concrete in case I missed some small dips. Hopefully the glue approach will minimize the effects of the bridging if I encounter any.