What's interesting is this problem started getting worse over the summer. If the issue was dependent on it being winter, this would have also occurred last winter. Is it typical for wood/fasteners to deteriorate so quickly and at the same time?

The carpet does not have much, if any, pad. Could this be a contributing issue? There are also areas where there is a clear ridge from the sub floor present when looking at the carpet. Is it typical for a sub floor to be not level?

The surest solution is to take up all the floor coverings, pull the nails one by one and replace with screws.
Casey

Very rare indeed for relatively new construction to be level and flat.

It still baffles me, and no one here has made mention of it, why a subfloor would suddenly get squeaky in just a year or so. You'd think it would be a slow progression over 20 years, but going from a few squeaks to sounding like I'll fall through the floor in just 1-1.5 years is crazy to me. There must be something that causes this ... especially now that the subfloor under title is squeaking (can't really get to this).

its quite possible that as glennsfc mentioned that you joists are not level, or flat. they install the plywood very early on in the construction process. and if they didn't have the entire house buttoned up and it rained, or received high moisture until the house was buttoned up then that's one thing than can cause the nails to come loose a bit, the moisture will swell the plywood causing the nails to loosen. also they don't pepper the plywood with nails, or rarely do they glue the plywood and use nails.

Thanks for the post. I have a carpet guy coming next week. Figure they've seen their fair share of subflooring issues. Thought it was good they admitted they would not do more than screw down existing boards or replace a handful of bad boards. Guess I'll need a GC for that.

It's simply strange to me the issue would suddenly become pervasive within the last two years (e.g., 20+ years after the home was built). If the joists were not level/flat, this would have reared its ugly head earlier. I can't help but think the owner did something when they staged the house. The carpet, although junk, looks new. It is lacking much of any kind of pad, which probably doesn't help with squeaks. I did look under the first floor and the joists look good and there's only a handful of nails that missed the joist.

I won't be surprised, when we pull up the carpet, we'll find the previous owners put some caulk/glue or other element to alleviate the squeaks temporarily.

I'm getting mentally prepared for the cost of the repair (we just replaced the roof and HVAC). It's a shame because, while the carpet is junk, it's clean and we've got small children and (well-behaved) pets. This is no time to replace the carpet, but the squeaks are so pervasive and if the carpet is up then might as well replace it.

I bet those posting here would be amazing how bad they are. Maybe I should post a video :-)?

I know this is an old post but did you end up fixing this issue? We have a very similar situation and considering replacing all carpet (even tho not bad condition) to remedy all of the squeaking.