Subfloor variance causing creaking noises?

Q imported from our old site, Face Lift Floors: To clarify: the floor only makes noises when we walk across it. It didn’t creak initially when installing it, but within a couple of days, it started. The more I research it, the more I’m convinced it’s likely due to the subfloor being uneven.

Some websites mention a standard rule that subfloors must not deviate more than +/- 3/16″ over 10 ft spans, or hardwood would creak.

Our floors were slightly worse than that. My husband thought it would be okay if we just nailed the hardwood down extra good.  I’ve heard that proper preparation of a subfloor is THE crucial factor in successful hardwood installation.

Going forward, I doubt we’ll go to the extremes of pulling off the subfloor to fix the evenness of the joists; but we’ll probably try other methods as we go along. For example, I’ve read that we can “shim” the high/low spots with felt underpad (0-1-or 2 layers depending on dips). Or we could look into a self-leveling compound to spread across the subfloors. One website even suggested drilling a hole where it creaks and squirting glue in to fill the gap, but to me, this method could create more problems than solutions. And I guess we’ll have to live with creaking in the bedroom and hallway.  

A: I don’t necessarily agree with the stipulation of not more than 3/16 variance over 10 ft. span for 3/4 thick. Take a board 16 inches long, which is the usual joist center. Try to bend it! You can’t. It is too rigid. Nail well, and nail close to the ends. You can use felt paper where needed. There is a company called Vermiester that makes a squeeze in expandable adhesive to fill hollows between the finished floor and subfloor.

One of my customers also bought a device to use with a drill, from Home Depot. You drill a tiny pilot hole and use special 2″ screws that break off below the floor surface at a certain point. This would work if you have a squeak over a joist. The hole is insignificant, and after filling with a color match wood putty, would not even be seen.

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