We have moved into a house built in the 1930's and the house as gorgeous old hardwood floors. The only negative is that they're extremely squeaky; particularly in the kitchen. I've seen many things online to try and remedy the situation, including shims under any distinct gaps under the floor joists (didn't work) and a bit of baby powder (also didn't work). The third option I researched was putting a screw at an angle up through the subfloor and into the bottom of the squeaky flooring. This seems scary. Is this something to leave to the pros? Anyone have any recommendations? Other ideas?
Squeaks are usually caused by the wood rubbing on a nail. They can be between the subfloor and the joists or the finished floor and the subfloor. If you have access from underneath, have a heavy helper duplicate the squeaks and determine where they are coming from. Determine how thick your overall floor is by measuring near heat ducts/pipes or other holes. If the are between the hardwood and the finished floor drive screws from underneath that are 1/2" shorter than the total thickness. I would advise drilling pilot holes into the old wood.
If the squeak is caused between the subfloor and the joists, I'd glue and screw a 2x2 along the joist and screw up through the 2x2 into the subfloor and the finished floor.