Solving subfloor squeaks

Question

I am planning to remove carpet in a living room and dining room area of my house and replace it with floating laminate flooring. There are some spots in my current floor that squeak so I was planning on using an impact driver to drive down some screws from above the subfloor to the joists below.

I currently did not remove my carpet or tack strips yet but I was wondering is there a trick to find the joists underneath the subfloor? Also, what screws would be best for this job? I was currently looking at Senco 08F200Y Duraspin Number 8 by 2-Inch Subfloor Collated Screws. I didn't know what length of screw would be best for the job.

Also, underneath my living room and dining room subfloor is my basement which is unfinished so I could look up to see where the joists are. For the most part they are 24 inches apart on center however there are some joists which are slightly less than 24 inches apart and in some areas its about 16 inches apart.

Answer 1

When you remove your carpet you should be able to see little impressions where the floor has been nailed or screwed into the joists. It should be a simple matter to line up your screws and put them in. If you somehow miss the joists you can merrily move a little bit to the side and try again. You might also consider pulling any nails at the squeaky spot as the problem may be a loose nail. Sometimes the squeak is an underlying problem (no pun intended). If the screws don't do the trick you could have someone move around on the floor while you go downstairs and try to locate the problem.

Answer 2

is there a trick to find the joists underneath the subfloor?

You don't need a "trick"because you have access to the joists from the basement. Just drill a tiny hole upwards from below at one end of the span, on one side of each suspect joist. Then drill another, on the other side of each suspect joist, at the other end of the span. Knowing the thickness of each joist, this will allow you to draw lines from above showing exactly where each joist is.

The screws suggested in your question should be fine, with 2" being fine depending on the thickness of your subfloor.

There are some other tricks for squeaky floors that you could try, since you are lucky enough to have access to the joists from below. Try tapping glue-coated wood shims between joist and bottom side of subfloor, wherever a gap is large enough to allow it. Check for any rubbing or movement between joists and any pipes or conduit that run through them. Any subfloor seams that might be rubbing/squeaking can be stabilized from below with mending plates. You might also consider working some wax into the subfloor seams from above and below.