I'm preparing my subfloor for 3/4" hardwood plank installation. I am using screw-type flooring nails for securing subfloor prior to install. After several hundred square feet of hardwood flooring installation, my securing has been successful, so far: no squeaks over the last year or so.

Now, I have a joist that refuses to shut up! I nailed it...no fix. I pulled all old nails and replaced with 2-inch galvanized screws...no fix. I added a few extra screws...no fix. Aaack!

The ceiling under the joist is finished. There is a finished duct race right by the squeak. I believe the squeak is caused by the duct carrying warm air that has dried out the joist in the area, causing it to warp upward rather than downward. The upward rise does not appear to bring the floor out of flat beyond what basic 30# shimming can fix.

In fact, I am wondering if there is not a slight twist to the joist such that any pressure on the floor "unwinds" the joist slightly. The "squeak" is more like a massive cracking and popping as you enter the room, not duct-related and certainly not nail-related (not any more!).

I am going to try to angle 3" screws into the joist in parallel rows to see if this helps. Any other ideas? Thanks!

I just so happen to have your answer

Go to ebay and search "wood floor squeek" .( Yes, that's one of my auctions)

Thanks for the idea. I am certainly considering the Squeak-Ender if required that I tear into the ceiling below, but I am not convinced that the break-off screws will do anything that galvanized screws can't do at this point. I'm not even sure that the Squeak-Ender is the best solution in that my floor will become even less flat!

Note that I am working on a clean subfloor right now--3/4" plywood sheathing over floor joists. House is about thirty years old.

I misread your post. I thought the hardwood was in.

Just an idea...Sounds like the screws aren't pulling everything tight. How about some countersunk lag bolts ?

Ofcoarse it would be nice to identify the problem, just hate to see you tearing out ceiling. Your theory on the warm air from the duct makes sense. As long as there's no plumbing in there , I would give lag bolts and washers a shot.

I have found that often, stubborn squeaks that refused to go away by screwing the plywood subfloor down are not cause by the subfloor at all. Usually, it is in the framing or something attached to the framing. And usually, it's sloppy workmanship. If you do not want to tear into the ceiling below ( I wouldn't ) then the way we deal with it is to cut out the subflooring where the offending noise is coming from. You can use the cut out plywood to patch your hole later, after you locate and fix the noise. This will be the most effective way at determing why you're getting noises. Just driving fasteners into the floor ain't the answer.

This really sounds like an issue caused by the duct work, but I dont think its the excessive dryness. I think the normal flexing of the structure is in some way causing the noise by crimping a duct panel or movement of a strap attached to the joist.
To avoid damage to the ceiling, open up the subfloor by cutting along the edge of the two adjoining joists to expose the offending squeak. It may even be that the strap mentioned earlier is attached to the bottom of the subfloor.
When reinstalling the plywood, you will need to add sister joists to the two adjoining joists, and you should add one to the centre joist as well.

This really sounds like an issue caused by the duct work, but I dont think its the excessive dryness. I think the normal flexing of the structure is in some way causing the noise by crimping a duct panel or movement of a strap attached to the joist.

There is no way to know for sure without removing the subfloor. You're assuming it's the ducting.

To avoid damage to the ceiling, open up the subfloor by cutting along the edge of the two adjoining joists to expose the offending squeak.

Yeah, just what I said one post earlier.

It may even be that the strap mentioned earlier is attached to the bottom of the subfloor.

You're assuming again and speculating. Of course that's a possibility, but so are a dozen other things as well

When reinstalling the plywood, you will need to add sister joists to the two adjoining joists, and you should add one to the centre joist as well.

If the subfloor panel is cut out along the panel's seams, and just to the thickness of the subfloor itself, additional blocking may not be needed as the panel can be re-installed exactly in the same way it was installed the first place, including having a fully intact T&G. I do this ALL THE TIME without issue. And it's easier to carefully remove a panel and not have to add blocking than it is trying to sister on additional lumber in those tight places where hammers don't fit and even screw guns barely work.

Of course I am just speculating. Unless you have some magic way to let me see through the subfloor from here, thats ALL I can do, or anyone else for that matter.
And ya, maybe cutting the subfloor out the full width if a sheet may be easier, but if the seam falls along the joist in question, then you would have to remove an 8 ft (two sheet) section of subflooring, wouldn't you?

This squeeking..... is there a wall fairly close to where the problem is?

Thanks gentlemen, for the great ideas!

Jerry, the problem is located about one to two feet in the room, in from the center of a doorway leading into the hall. The wall is only a partition upstairs, but the nearby wall underneath (running under the middle of the upstairs hall) is oddly load bearing. I know this because I have already torn into the hall flooring to fix a height problem and noticed then that the joists ended and overlapped on the top plate of the wall below. One joist was twisted up, raising the hall subfloor well out of tolerance. This is, I believe, the same joist that is causing the squeaking problems. By the way, I shaved off the offending wood and let the overlapping joist carry the load; this fixed the problem here, at least.

This is also why I am fairly certain that it is twisted. The fact that the subfloor is slightly raised is more evidence.

The joist is in the middle of a full sheet, so my plan is to cut 4'x4' up to the adjacent joists. I will use sister joists to secure the panel back in.

I also am planning to plane the joist even, insert some cross bracing, apply strong adhesive along the joints, and then both cross screw and straight screw the panel back in. I pray that this works!

Well, the reason I asked was because a few years ago I had almost the same problem as you've described. On this job there wall about 2 feet or so from the problem area. Taking a chance I removed the baseboard and used long screws, drove in at angle, thru the bottom 2x4 plate of that stud wall into the subfloor. That fixed my problem, the subfloor and nearby joist must have been bowing slightly directly underneath that bottom plate from weight as one walked next to it. To be clear I'm talking about a stud wall on the same floor level as the squeek.

That certainly seems worth a try, Jerry! The noise seems centered in the subfloor panel, but it can be transmitted from the nearby wall too, I would suspect. It would certainly save a lot of work!

Worth a shot , good luck

Not at all. One simply cuts that panel in half directly over the joist. That's why you only cut to the plywood's depth, so as not to cut up the floor joists. We do these types of subfloor repairs all the time, especially on remodels where plumbers and electricians need access to the space below. In fact, most remodels will have these types of subfloor repairs. It's true, occasionally, one may need to add additional blocking. My point is to plan it out in advance to avoid as much blocking as possible. All I'm saying is most of the time, with a little for thought, these types of repairs can be made easier rather than harder. Oddly enough, many general contractors hand this task off to the apprentice just hired last week, who promptly FUBAR's it.

While I agree in principle that you should minimize the amount of blocking required, the rough carpenters (very rough indeed) that we find here do not align their subfloor fasterers in such a fashion as to allow a straight cut down the centre of a joist if needed. (and really, why would they) I find it easier, faster, and cheaper to just cut out the subfloor along the edge of the joist on the side I want to open up, thus avoiding the nails, but making it necessary to add sister joists.