Screw won't tighten (not stripped)

[mozar]

I am screwing 1/2 inch plywood to my 3/4 subflooring that is held up by joists. I have grk #10 general screws. I got 3 1/8" screws to go into the joists and 2 1/2" screws for screwing the plywood to the subfloor in locations where there is no joist.

I'm having a problem where I am putting the screw in and at the end when the screw is almost flush it pops up and starts spinning.  This happens with both screw sizes. And right next to screws that tightened fine. I thought it might be that my pilot hole isn't deep enough but that didn't seem to change anything.  Any suggestions?

[BECABECA]

Do your screws have threads all the way to the head? If so, you might need to drill the pilot hole in your plywood wider so that the threads don’t catch on it and it’s just held by the head. Or try a screw without threads for the last bit by the head.

[Wrenchturner]

Do your screws have threads all the way to the head? If so, you might need to drill the pilot hole in your plywood wider so that the threads don’t catch on it and it’s just held by the head. Or try a screw without threads for the last bit by the head.

This, also it's concerning that the 2"+ material is stripping before the 1/2" plywood.  Sounds like you're not getting good fastening.

[secondcor521]

Your pilot holes may be too deep or too wide.  Try drilling them with a smaller bit and/or less depth.

I'm no expert, but what I usually do that works well is use a drill bit that is approximately the diameter of the screw's body excluding the thread, and usually only about 1/2 or 2/3 of the depth of the screw's length.

[Papa bear]

You don’t need pilot holes.  About the only time I can’t get a screw to go in is if I’m hitting metal. Like another screw or a nail. 

But this should be easy peasy, drive the screw in, move to next one.  Keep at it.

Edited since people are talking pilot holes.  This isn’t finish hardwood.  It’s plywood. It’s soft. It takes the screws right in.  And it’s rough in subfloor.  Even if you’re at the edge and it splits, it doesn’t really matter.  And it definitely will not split in the center.  Plywood takes each wood ply and they run them perpendicular, glue, repeat, compress.   You could run 100 screws down a line and you’d have a hard time splitting it.


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[mozar]

Thanks for the fast responses. I know it should be easy. I've done so many complicated things for this renovation and everything is coming to a stop because of the screws.
I hadn't considered that my pilot holes might be too deep. I will try shallow ones and I will also try no pilot holes. The pilot holes are 1/16.
The screws do not have threads near the head.

[dragoncar]

Thanks for the fast responses. I know it should be easy. I've done so many complicated things for this renovation and everything is coming to a stop because of the screws.
I hadn't considered that my pilot holes might be too deep. I will try shallow ones and I will also try no pilot holes. The pilot holes are 1/16.
The screws do not have threads near the head.

Good luck!  Posting to find out if this fixes the problem

[J Boogie]

Thanks for the fast responses. I know it should be easy. I've done so many complicated things for this renovation and everything is coming to a stop because of the screws.
I hadn't considered that my pilot holes might be too deep. I will try shallow ones and I will also try no pilot holes. The pilot holes are 1/16.
The screws do not have threads near the head.

I buy GRKs mostly for their superior self tapping abilities. Cheaper off brand screws just spin and spin and then frustratingly disengage and fly away when you apply pressure. But GRKs grab and go.

Drilling pilot holes for GRKs is like using an unplugged sawzall to cut wood.  You already paid the premium, get the benefit of the performance!

[mozar]

I tried a short pilot hole and no pilot hole and the screw is still spinning. Could my screws be too long? Time for nails?

[Papa bear]

I tried a short pilot hole and no pilot hole and the screw is still spinning. Could my screws be too long? Time for nails?

Video this?  I’m having a hard time figuring out what is going on here.  I can’t say I’ve ever seen your problem as you describe it.  I’m stuck on this “screw pops up” when it’s flush.

If you’re running 3” screws and you’re not getting into the floor joists, it won’t pull down  through, but I wouldn’t say the screw pops up. It just doesn’t countersink itself and will spin freely. Pull the screw out and hit the joist.

If the problem is just that you are having the screw spin and not countersink with the 1/2” to the 3/4”, go get some 1 1/4 or 1 1/2 and have at it.





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[mozar]

I'll see if I can capture the moment it pops on video. It just pops up a little bit when I get to the end of the screw. Sometimes it doesn't pop. I get to the bottom (screwed in almost all the way) and it starts spinning, it does sound like it popped out of something.
It's possible that I'm not hitting the joists but that's confusing because I mapped out where the joists are after seeing them. It seems like 3" would be enough to get down to the joists?

[Papa bear]

3” is plenty to get through 1 1/4 and then into joists. 

Even if you marked your joists, they can be off slightly, bowed, you could be screwing it at an angle, etc.  or, if you just measured them out, you could have joists that changed directions or where one was cut out and a plumbers box was built, etc.

So, if you have wood the entire way, that screw should keep going through that plywood and not stop until you do.  If you don’t hit wood. it will start spinning and not pull tight. 





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[lutorm]

Is it possible you're twisting the screw clean off? That's happened to me with 3" hardware store wood screws if your pilot hole isn't large enough, the resistance to turning towards the end got so large that the screw just twisted off somewhere between the head and the threads. That usually manifests as it suddenly turning easier and it popping back out a bit since it's no longer held in by the thread.

[dragoncar]

Is it possible you're twisting the screw clean off? That's happened to me with 3" hardware store wood screws if your pilot hole isn't large enough, the resistance to turning towards the end got so large that the screw just twisted off somewhere between the head and the threads. That usually manifests as it suddenly turning easier and it popping back out a bit since it's no longer held in by the thread.

Presumably OP is backing out these screws and examining them but it’s worth checking

Another vote for missing the joists.  I’m also having trouble picturing this

[Papa bear]

Is it possible you're twisting the screw clean off? That's happened to me with 3" hardware store wood screws if your pilot hole isn't large enough, the resistance to turning towards the end got so large that the screw just twisted off somewhere between the head and the threads. That usually manifests as it suddenly turning easier and it popping back out a bit since it's no longer held in by the thread.

With the screws that OP is using and that it’s going into plywood, it would be pretty damn hard to break a screw off.  I would have to try very hard to do that. These aren’t drywall screws going into hickory. 


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[rab-bit]

I had exactly the same thing happen recently. For me it only happened with about 10% or so of the screws, the rest of them secured well.

I'm not completely sure why this happened but in my case the sub-floor was OSB so I assumed that I was just hitting a spot in the OSB between strands, so if I moved the screw to another location a 1/2" or so away, it usually secured itself there.

As a side note, is the 1/2" plywood an underlayment for the finish floor (hardwood, laminate, etc.)? If so, I had read at the link below that you should not secure it to the joists, only to the sub-floor, so in that case you should use screws that are 1/2" + 3/4" = 1-1/4" so you do not secure to the joist in those locations.

https://thefloorpro.com/community/topics/how-to-install-5-8-plywood-over-osb-sub-floor.6959/

[mozar]

I'm thinking that the joists aren't flush to the subfloor. It sounds to me like I'm going through the subfloor, going through air for a split second then hitting the joist, but I can't get purchase in the joist so it pops up (a little bit) and starts spinning.
I have been backing screws out and looking at them. I have to use a tool to hold it while I bring it up so it doesn't slip.
If 1 1/2 or 1 1/4 screws are fine (yes it is underlayment) I'll just do that with the rest.

[Jon Bon]

I'm thinking that the joists aren't flush to the subfloor. It sounds to me like I'm going through the subfloor, going through air for a split second then hitting the joist, but I can't get purchase in the joist so it pops up (a little bit) and starts spinning.
I have been backing screws out and looking at them. I have to use a tool to hold it while I bring it up so it doesn't slip.
If 1 1/2 or 1 1/4 screws are fine (yes it is underlayment) I'll just do that with the rest.

Well your standing on the subfloor right? You should not have much of an airgap between the joist and the subfloor. If you do the screw will rapidly pull that down. Kind of the whole point of using a screw.

You also you be able to fell your drill/impact working harder as it hits the joist. They are hard tought wood so listen and feel your drill.

I really think you are just missing the stud. No screw is gonna spin iunless its got nothing to bite into. Also dont do pilot holes either, your over thinking this. Maybe drive a nail in, you should easily be able to tell if your hitting the stud.

If the screw is "spinning" as you say into a stud the screw head would rapidly be pulled below the plywood. Also you would have a ton of torque and tension that you could feel in your drill.

[dragoncar]

I'm thinking that the joists aren't flush to the subfloor. It sounds to me like I'm going through the subfloor, going through air for a split second then hitting the joist, but I can't get purchase in the joist so it pops up (a little bit) and starts spinning.
I have been backing screws out and looking at them. I have to use a tool to hold it while I bring it up so it doesn't slip.
If 1 1/2 or 1 1/4 screws are fine (yes it is underlayment) I'll just do that with the rest.

Well your standing on the subfloor right? You should not have much of an airgap between the joist and the subfloor. If you do the screw will rapidly pull that down. Kind of the whole point of using a screw.

You also you be able to fell your drill/impact working harder as it hits the joist. They are hard tought wood so listen and feel your drill.

I really think you are just missing the stud. No screw is gonna spin iunless its got nothing to bite into. Also dont do pilot holes either, your over thinking this. Maybe drive a nail in, you should easily be able to tell if your hitting the stud.

If the screw is "spinning" as you say into a stud the screw head would rapidly be pulled below the plywood. Also you would have a ton of torque and tension that you could feel in your drill.

You should also be feeling the stud when doing the pilot hole.  When other methods fail me, I usually just try to find studs with a bunch of little pilot holes

[J Boogie]

Can we finally solve this damn mystery???

Why are those screws spinning???

But seriously, I am perplexed. Are there existing fasteners that the screws are hitting? If it's an old house, it's possible there was a rotted subfloor that was removed and the nails were folded and/or pounded rather than pulled.

[mozar]

Well I think it's the quality of the subfloor itself. It was milled in 1937. All the size screws I have tried have spinned. So I think when I screw down it hits a week spot and spins in the wood. So now I'm just randomly putting in screws hoping that it will tighten, and backing them out when they don't which is about 70% of the time. It's a very laborious process.
I did go through and pull out every old nail and screw I could find in the subfloor. And I'm glad I did that.

[dragoncar]

Well I think it's the quality of the subfloor itself. It was milled in 1937. All the size screws I have tried have spinned. So I think when I screw down it hits a week spot and spins in the wood. So now I'm just randomly putting in screws hoping that it will tighten, and backing them out when they don't which is about 70% of the time. It's a very laborious process.
I did go through and pull out every old nail and screw I could find in the subfloor. And I'm glad I did that.

Granted I know nothing, but if my subfloor wouldn’t hold screws I’d be worried about the integrity and would probably replace it.  Then I could get a good look at the joists which apparently are also somehow soft

[mozar]

I agree! My HOA won't let me replace it because its "antique" they did agree to put put a 4by8 3/4 ply around the section where my roommate fell through the floor(!). The rest I have to live with, unless i move.

[dragoncar]

I agree! My HOA won't let me replace it because its "antique" they did agree to put put a 4by8 3/4 ply around the section where my roommate fell through the floor(!). The rest I have to live with, unless i move.

*cough* would they know/ *cough*

[J Boogie]

Well I think it's the quality of the subfloor itself. It was milled in 1937. All the size screws I have tried have spinned. So I think when I screw down it hits a week spot and spins in the wood. So now I'm just randomly putting in screws hoping that it will tighten, and backing them out when they don't which is about 70% of the time. It's a very laborious process.
I did go through and pull out every old nail and screw I could find in the subfloor. And I'm glad I did that.

Ahhhhhhhh thank you.

I can now sleep at night knowing the problem is rotted wood, either from fungus or moisture or both. That would make perfect sense why the screw would sometimes pop up, as it would be initially getting purchase into the rotted section before the rotted section gives out and releases any spring that your top board would have from initially being screwed down for a few moments.

[Jon Bon]

BUT but, but.....

I still dont know what is going on, and I need to know!

If you have rotted sub-floor your HOA can take a hike and you should do this right. Rotted wood serves no purposes. If the sub-floor cant bear the weight due to rot it should be replaced. Like this is basic safety stuff. Your gonna wreck your finished floor if you put it on top of crappy sub-floor.

Also the screw should not spin unless its missing the stud. THe ONLY way I can think a screw hitting a stud and spinning is basically a rotted/cracked stud that the screw cannot bite too.

Just attach a picture of your subfloor already and we can tell you! If you have old plank sub-floors (not 4*8 sheets) the studs should be clearly visible and you should really never miss it. If you have rotted floor joists you are in for a world of hurt.

I feel like we are doing car talk on NPR but for houses!

[mozar]

The joists seem fine. The rest of the floor seems like it can bear weight but I don't know that much about floors. Pics of the work done are attached.

[J Boogie]

BUT but, but.....

I still dont know what is going on, and I need to know!

If you have rotted sub-floor your HOA can take a hike and you should do this right. Rotted wood serves no purposes. If the sub-floor cant bear the weight due to rot it should be replaced. Like this is basic safety stuff. Your gonna wreck your finished floor if you put it on top of crappy sub-floor.

Also the screw should not spin unless its missing the stud. THe ONLY way I can think a screw hitting a stud and spinning is basically a rotted/cracked stud that the screw cannot bite too.

Just attach a picture of your subfloor already and we can tell you! If you have old plank sub-floors (not 4*8 sheets) the studs should be clearly visible and you should really never miss it. If you have rotted floor joists you are in for a world of hurt.

I feel like we are doing car talk on NPR but for houses!

Based on the pics and how many screws get purchase vs pop out, it seems the rot is sporadic and probably dried out long ago. Sometimes you can't tell what's rotted and what's not until you try to chisel it with a screwdriver.

Not sure what you're installing on top, but if it's anything but tile, I'd remove the subfloor so you can apply liquid nails or some other type of adhesive/sealant between the joists and the subfloor. That's a good way to prevent squeaks. If you are going with tile, make sure to use a decoupling membrane like ditra to prevent any cracking tile/mortar from house movement.

[Wrenchturner]

That is all rotten.  You should inspect the joists.  Looks dangerous to me.

[kenner]

Yeah, maybe it's just me, but while there are certain kinds of antiques that I'd absolutely save even if I didn't personally have a use for, a rotted 'antique' subfloor is nowhere on that list.  I'm surprised your HOA wouldn't require it's removal for safety reasons given that someone apparently already fell through (and also: what the hell???)

[Jon Bon]

Are the screws spinning only in the plywood, old plank subfloor or both?

Hard to say from the picture, id recommend getting underneath the joists and give them a solid poke with a flat head screwdriver. You should not be able to indent them at all if they are in good shape. If they crumble on you that is trouble. However I never seen rotted interior floor joists, that takes YEARS of water to do.

Maybe look under and see if you are hitting the joists with your screws?

As other have said a 2 inch wood/decking screw  is what you want. 3 inches will work but is overkill and much harder to drive that big of a screw in.

As for the subfloor itself: You should just be able to tell by standing on it for the most part. Does it feel firm? Does it bounce or give? Was this house like open to the elements at some time? I mean falling through the subfloor is again nearly impossible. Roof yes due to moisture and rot. But an interior floor should never be rotted accept for the long term presence of water.

[mozar]

Yes there was a decades old leak. The maintenance man went around bouncing on the wood and he is twice my size, and I went around with a hammer and knocked out any thing rotted.

[fixie]

In my experience, GRKs do not need a pilot hole.  They have a flute at the tip that is self-drilling, and the threads to not go all the way to the head, so that the screw doesn't lift up the material you are fastening...
-fixie