# Forum More Stuff Owner Builders Forum  recommended screw torque to re-fix flooring

## peterlonz

Very recently, because I had access to the particle board flooring on the second story of our home, I finally had the opportunity to diagnose the reasons for the squeaky flooring.
The floor joists hardwood (Cypress pine ?) & are at 450 centres, the particle board appears to be the 900 wide tongue variety, probably 19 mm thick (I can not easily check this). It was originally fixed with 75 lng nails which are not evenly punched home.
It seemed prudent to re-punch the nails & the re-fix with decking screws.
I selected 304 stainless 10 G x 50 mm square drive screws, largely because they are readily available (used principally as decking screws).
I predrilled 3.5mm diam holes & set my Bosch pro drill/driver to max torque.
Mostly that setting was just too low to fully seat the c/snk heads so I ended up hand countersinking which is hard to do evenly.
Now I have a range of situations: some are too low, others are just right & still some are a bit high.
I decided that since no screws had broken I could apply further torque which seemed indicated since I had not properly eliminated the damned squeaks.
OK, so I used a 1/4 inch socket ratchet drive with the square drive bit & found I could easily get another half/threequarters turn before sensing that was "enough".
Squeak only a little better!
But I still don't know:
1) How much torque these screws can take?
2) If I get too close to the limit might they start popping heads with weather induced timer stress cycling?
3) Should I have selected a different screw (note that square drive is difficult to get in most screw ranges - at least in Queensland Australia).
4) Is there a better technique to solve this problem?
Any help appreciated.
Thanks

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## sol381

uhmm i think you are overthinking it...use an impact driver and just set the screw flush or just below the surface...you want the yellowtongue to pull towards the joist so the hole you predrill must be larger than the outer diameter of the screw so there is no contact when screwing.usually 5mm .the screw will then act like a vice.. 
yellow tongue is put down with liguid nails or similar and 75mm nails .. usually with a nail gun at about 200mm centres on each joist..a few screws will help with squeaks.

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## gpkennedy

Very good reply sol381. I had attempted such a repair on yellowtongue: without much success. Your hint about a larger predrill in the yellowtongue is very logical now that it has been pointed out. Never occurred to me before.

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## sol381

any hole you predrill whether a screw or bolt  or batten screw must be at least 1mm larger, never the diameter of the fixing you are using...learn something new everyday on this site mate..

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## Marc

> any hole you predrill whether a screw or bolt  or batten screw must be at least 1mm larger, never the diameter of the fixing you are using...learn something new everyday on this site mate..

   Why?

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## sol381

because you want the screw or bolt to move freely through the wood ,, especially bolts..if the hole is too small the screw will grip the first member and not pull in, leaving a gap between the two pieces..thats where you reverse the screw and go in again..not what you want.. drilling a larger diameter hole just works better.. bolts should be able to fall through the hole you drill with no force at all..

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## Marc

Mm ... If that happened and I understand it could, that means you chose the wrong screw. The screw must have a section of the shaft under the head free of thread for that precise reason.
On the other hand drilling a larger hole would allow the floor to move sideways. Squeaking comes from the floor rubbing against the joists. A flexing joist would flex under the weight of a person walking and pull the flooring down. Since the floor is not elastic, the floor would have to pull sideways and squeak by rubbing against the other joists. 
In ny experience to stop a particleboard floor from squeaking is a hit and miss job and needs a vast number of large screws to have a chance of working. A tight hole for the screw to work applying pressure vertically and fixing the floor horizontally is essential. Drilling a larger hole would defeat this in part.

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## sol381

fair point but with all the glue that is under the board i doubt it could moved sideways..for thoise screws tho id go exact outer diameter.. sqeaking would come form vertical movement i would assume.. anyway my point about holes was very general..if i had top put a few screws in particleboard i wouldnt even waste time predrilling id just drill straight through..goes against what i just said but its just for the few spots that move.. for particleboard the glue and nails do most of the work.. screws can help a bit as well.. 
apologies to the op for offshooting

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## Snipper

Better of using 65 - 75mm screws (stainless is expensive and overkill inside)  A pilot hole is a hole to prevent the thread receiving piece splitting, screws snapping or to make it easier in hard materials and a clearance hole is what sol is referring too. Slightly larger than the thread or if not a full thread, slightly larger than the shank. Only going through the top surface,  Example.  8 gauge screw I'd use a 2.5mm pilot hole and a 4mm clearance hole.  Obviously I would only do pilot holes in certain situations and materials but have and will always use clearance holes in everything taking a screw.  Batten screw, 6mm clearance hole.  A clearance hole prevents splitting and squeaking . In full thread screws it will pull one surface down harder to the other without unknowingly rising during screwing.

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## Marc

> Year 7 woodwork 101

  Uncalled for. 
And fixing squeaking particleboard is not the same as screwing decking material down.

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## peterlonz

Thanks for the contribution by everyone.
I think it may be worth restating (and maybe adding) a few of the facts observed on this particular job:
The joists are hardwood & by trial I soon discovered that without the pilot hole (3.5 mm) undue torque was needed just to drive the screws home.
The screws I used were smooth & free of thread for 16 mm under the head & diam here is 3.75mm.
I can't tell whether good practice & good liquid nails was used on my home aged about 28 years. But my own experience of liquid nails has proved it frequently fails. The irregular setting of fixing nails indicates some lack of care in construction.
Since i found it possible to exert sufficient torque (not with my drill/driver) to pull any screw head well down I think it's reasonable to suggest the mating joist & P Brd are not being held apart.
The whole of my upper story is best described as lively, just walking around you can feel the floor flexing but I cannot determine the exact cause of the squeaking.
Do I:
1) just keep screwing down regardless of the number of screws, or
2) accept I have a lively floor & the squeaks will remain a fact of life? 
I am surprised that the code has allowed joists capable of such load induced movement, can anyone comment on this? 
Again thanks.

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## Snipper

Apologies to those who took offence to my not to subtle joke.  Deleted and awaiting the consequences. Thanks to those who have helped me during my time here. My mannerisms and sarcasm don't portray me very well on an internet forum.  Ciao.

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## Farmer Geoff

A mate once had the same problem as  you peterlonz and he drilled clearance holes in the flooring then filled an old grease gun with liquid nails and with a modified nozzle, injected some in to each hole so it was forced into any space between flooring and joist. Then a screw through each hole into the joist. 
Snipper if your worst crime is the 101 quip then I think and hope you'll be staying with us. Your contributions always seem relevant and useful. We are a diverse lot, and that's a strength of this forum.  
.

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## Marc

> The whole of my upper story is best described as lively, just walking around you can feel the floor flexing but I cannot determine the exact cause of the squeaking.

  Well as a matter of fact you just did. Joist spanning more than they can, will flex and the flooring will rub against the joist producing noise. 
It will probably prove to be difficult to eliminate short of adding a cross beam under the joist. Plenty of large screws should help, but if the flex is as significant as you describe I am afraid we are talking structural problems not installation problems. 
You could measure the amount of flex in the joist to have an idea where you stand, by measuring the distance between floor and ceiling from below without extra load with a laser, then place a load of say 100 kilos or two people in the centre of the room above and measure again. 
If you know the size span and wood type of the joist, that would be a start. 
Snipper, a simple delete and sorry would have sufficed, no need to go to theatricals. I have made way more booboos than that.  :Rolleyes:

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## METRIX

> My mannerisms and sarcasm don't portray me very well on an internet forum.  Ciao.

  I thought you had already departed a few weeks ago, after offending other people on here ?? 
BTW, Square drive screws are ok, but most of them have been manufactured with shallow recess or have coatings on them that interfere with the square bit staying in under pressure, which ends up destroying the square recess. 
The only square non stainless screws I would use are the ones below, these have a deep recess, which is slightly bigger then most others, this allows the bit to sit in deeper, and wont jump out, I am yet to round out one of these.

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## peterlonz

Regarding Metrix's recommendation for Buildex (treated) decking screws:
I bought some of these (well a close cousin anyway), they were for fixing treated fence palings.
The result was badly rusted screws allowing the palings to pull away within a period of about 3 years.
I'd suggest to stay away from screws with this kind of protective coating.

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## Marc

I believe the situation here is particleboard on hardwood joist and of course indoors, so no worries about rust. The issue is driving screws home and eliminate flooring rubbing against joist or each other. With old and dry hardwood joist pre drilling is essential. The debate is/was if the flooring needs to be drilled out larger to allow for the screw to go in without engaging the flooring, something that I see as counterproductive. I say the tighter the better. If it was pine or oregon joist I wouldn't predrill at all. 
But then I would also use 14G screws. Stopping floor from squeaking is not easy most of the time.

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## METRIX

> Regarding Metrix's recommendation for Buildex (treated) decking screws:
> I bought some of these (well a close cousin anyway), they were for fixing treated fence palings.
> The result was badly rusted screws allowing the palings to pull away within a period of about 3 years.
> I'd suggest to stay away from screws with this kind of protective coating.

  I agree, any exterior product I use is Stainless or HDG, I don't like any bolts / screws which have a painted type finish, but I still stand by these screws as the benchmark for how square drives should be manufactured,  
I did not recommend them for the purpose the package says, as anyone on here will know I only use Stainless Steel screws for decks, and if asked to do a TP deck I nail it down, 
These screws are used primarily inside for fixing skirting to masonry walls, and countless other jobs where a strong hold is required and I am using square drive screws. 
I wonder how the new square drive specifications are against the original ones developed in 1908 and are technically called Robertson screws. 
BTW, Do you have a photo of the rusted screws, I am curious as to why this coating gave out ?

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## sol381

Those screws you mentioned are brilliant.. never have a problem with them.. as you say, never burred one yet..they state decking on them and i have used them for kwila decking..they blend in well.. it was on a roofed deck and gets minimal rain and after  a few years they still look like new..

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## METRIX

> Those screws you mentioned are brilliant.. never have a problem with them.. as you say, never burred one yet..they state decking on them and i have used them for kwila decking..they blend in well.. it was on a roofed deck and gets minimal rain and after  a few years they still look like new..

  I don't know why they can't manufacture all square drive with insertions like these ones, the majority of the others available are rubbish, and bur to easily.

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## sol381

indeed.. i find most buildex screws are very good tho. even the batten screws which are easy to burr up..

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