Preventing chipboard creak

[lc155]

Hi,

In the middle of a job where a new stud wall is going up with PIR to replace the old lath and plaster one that did bugger all. Had to brick up a fireplace behind said wall as well as remove an old slate hearth in the floor, which left a great big gap as there were no floorboards around the area.

I've screwed in a 2x2 to the area of the joist they hacked out to fit the hearth in. I then put in a few noggins from that joist to the next one, then laid down 22mm chipboard I had lying around cut to size. I was just treating it like any other piece of wood, so I ended up drilling clearance holes and used wood screws I had on hand, which were the decking screw type that has a smooth shank at the top.

Further reading on this implies that this may not be enough to stop creaks from developing; the chipboard is too weak to be held down by just the force of the screw head, and may slide up and down over time. Seen some methods involving gluing down the boards to the joists before laying down, but would rather avoid taking the board back up and potentially weakening the screw holes already made.

I'm probably fussing too much, but would adding more screws in that are fully threaded to each side of the decking screws ensure that it'll stay down solid? My thinking is the decking screws will clamp the piece down and then the fully threaded screws will ensure it is never going anywhere.

 

[Deleted member 174758]

When installing new T&G chipboard it is now normal (i.e. recommended by the manufacturers) that you glue and screw all the boards. It is the only way to guarantee they won't creak, although it helps if the joists aren't undersized, are correctly spaced and level. A lot of people fret about how to lift the floor afterwards, but just how often do you need to do that in reality?

You say you've added "noggins" between the joists - the correct way to do this is to add solid strutting. Solid strutting is generally the same cross section as the original joists, or at the least the same thickness and at least 80% of the depth (so for a 7 x 2in joist the minimum would be 5.6 x 2in). This is because the function of strutting is to prevent joists from twisting under load (and this reduce bounciness by making the floor stiffer) - which is why a 3 x 2 "noggin" in a 7 x 2in joisted floor is not really going to be that effective. I'm just stating this for clarification as people often don't understand why you install these things and how they work (and in my experience that even includes builders)

I wouldn't have bothered with the decking screws and I wouldn't have pre-piloted - 4.5 x 50mm chipboard (i.e. fully threaded) flooring screws on 200mm centres (300mm for larger pieces, say 1/2 sheet size) would have done the job, providing you don't try driving them nearer than 50mm from the edges and that you hit the joists with the screws (a row of screws driven into the very edge of a joist won't hold well and can be a cause of squeakiness later on)

Is it creaking now? If it isn't and it is well fixed down you'll probably be OK. On repairs I generally don't glue the material back down, but I do support joints, etc with 2 x 2in cleats and I'm not stingy with screws

 

[blup]

If its a ground floor, then glue it down, I can understand a reluctance to do this if it is first floor with services underneath.

Blup

 

[lc155]

When installing new T&G chipboard it is now normal (i.e. recommended by the manufacturers) that you glue and screw all the boards. It is the only way to guarantee they won't creak, although it helps if the joists aren't undersized, are correctly spaced and level. A lot of people fret about how to lift the floor afterwards, but just how often do you need to do that in reality?

You say you've added "noggins" between the joists - the correct way to do this is to add solid strutting. Solid strutting is generally the same cross section as the original joists, or at the least the same thickness and at least 80% of the depth (so for a 7 x 2in joist the minimum would be 5.6 x 2in). This is because the function of strutting is to prevent joists from twisting under load (and this reduce bounciness by making the floor stiffer) - which is why a 3 x 2 "noggin" in a 7 x 2in joisted floor is not really going to be that effective. I'm just stating this for clarification as people often don't understand why you install these things and how they work (and in my experience that even includes builders)

I wouldn't have bothered with the decking screws and I wouldn't have pre-piloted - 4.5 x 50mm chipboard (i.e. fully threaded) flooring screws on 200mm centres (300mm for larger pieces, say 1/2 sheet size) would have done the job, providing you don't try driving them nearer than 50mm from the edges and that you hit the joists with the screws (a row of screws driven into the very edge of a joist won't hold well and can be a cause of squeakiness later on)

Is it creaking now? If it isn't and it is well fixed down you'll probably be OK. On repairs I generally don't glue the material back down, but I do support joints, etc with 2 x 2in cleats and I'm not stingy with screws

Thanks for the detailed post. The main reason I put in noggins tbh was because I do not trust chipboard flooring whatsoever! Would've used ply if I had it, but just had to make do. Additionally, there were floorboards put down under the hearth, just cleated in and sitting at the bottom of the joists. I elected to leave them in. There's an electrical cable running just over the top of them that supplies the ring circuit for that room, so would have complicated things if I put down huge noggins and had to drill through them, etc. It seems solid enough as it is.

I've seen the opinion of some just saying stand on the boards and drive fully threaded screws in, but I didn't want to risk the board rising up when trying to do that and not noticing. If I did it on the regular and had the experience, I'd probably sing a different tune.

I didn't notice creaking, but it has only been down for a couple of days. The edges are all supported by being screwed into cleats made from the old pine skirting that was taken out that are screwed into the adjacent floorboards. There are a decent amount of screws in but like in the initial post if I'd be safer to then put down some fully threaded screws I could do that as well?

To make it clear, the majority of the board will have a wardrobe sat on top of it. Just want to avoid the door opening of the wardrobe (they are very heavy) potentially causing slight shifting of the weight of it that may transfer to the board and creak. That'd be annoying.

If its a ground floor, then glue it down, I can understand a reluctance to do this if it is first floor with services underneath.

Blup

Yeah, it is a first floor that has an electrical cable underneath, although my main trepidation is avoiding unnecessarily unscrewing things whenever possible as I always think it weakens the screw hole. That's probably just my perfectionism kicking in. I also did throw a few 1mm and 2mm packers underneath to get it level with the adjacent 25mm floorboards. I said the chipboard was 22mm but when I measured the thickness it was actually more like 24mm!

 

[Deleted member 174758]

I've seen the opinion of some just saying stand on the boards and drive fully threaded screws in, but I didn't want to risk the board rising up when trying to do that and not noticing. If I did it on the regular and had the experience, I'd probably sing a different tune.

That's how I do it, although TBH for a lot of full floors I use a collated screw gun which runs at 4000rpm (life is too short for hand screwing) - so a lot faster than a standard drill, however you can generally feel if the board is jacking up, stop, reverse out a bit then re screw. A sort of cure is to use screws like Floor-Tites (or for that matter the Reisser R2 screws I often use) which have a small unthreaded section at the top of the shank thus:

or alternatively a screw with a short section of reverse thread just below the screw head like these Screw-Tite screws:

(Please note - there are other brands available, these are just used for illustration purposes)

I didn't notice creaking, but it has only been down for a couple of days. The edges are all supported by being screwed into cleats made from the old pine skirting that was taken out that are screwed into the adjacent floorboards. There are a decent amount of screws in but like in the initial post if I'd be safer to then put down some fully threaded screws I could do that as well?

Go ahead, but TBH sounds as though you have it covered

Yeah, it is a first floor that has an electrical cable underneath, although my main trepidation is avoiding unnecessarily unscrewing things whenever possible as I always think it weakens the screw hole.

I'm constantly amazed at how often this comes up from DIYers. It is a relatively simple task to cut out an access piece in an existing floor and make good afterwards (think about it, you really already know how to do the make good part - so learning to do a neat cut out and a snug infill shouldn't be that much extra effort), or alternatively cut out an access through the plasterboard or lath and plaster ceiling below and make good afterwards using 2 x 1 laths, plasterboard, screws, scrim tape and a bit of filler. This only become a problem if you need to cut out through cornices, etc

 

[lc155]

That's how I do it, although TBH for a lot of floors I use a collated screw gun which runs at 4000rpm - so a lot faster than a standard drill, however you can generally feel if the board is jacking up, stop, reverse out a bit then re screw. A cure is to use screws like Floor-Tites (or for that matter the Reisser R2 screws I ofyen use) which have a small unthreaded section at the top of the shank:

View attachment 295817

or alternatively a screw with a short section of reverse thread just below the screw head like these Screw-Tite screws:

View attachment 295818

(Please note - there are other brands available, these are just used for illustration purposes)


Go ahead, but TBH sounds as though you have it covered


I'm constantly amazed at how often this comes up from DIYers. It is a relatively simple task to cut out an access piece in an existing floor and make good afterwards (think about it, you really already know how to do the make good part), or alternatively cut out an access through the ceiling below and make good afterwards using 2 x 1 laths, plasterboard, screws, scrim tape and a bit of filler

I've seen those kinds of SPAX screws before, would have definitely used them, but 20 quid for a box when I'd use a handful of them is probably stupid. Maybe if I was doing a whole room.

The 'decking screws' I mentioned are basically like the first ones you linked, unthreaded shank at the top, so clamped the wood down good nice and tight. Just hoping the compressibility of chipboard over time doesn't work itself loose from that, if you know what I mean? I saw a few people when looking through threads mention that. I don't know if that's just a theory or if it happens in reality.

As for the DIYers thing, LOL yes. I'm a perfectionist and tend to want to make things bombproof (I always assume sods law), even though the reality is the people who build your houses will tend to just cut corners wherever they can.

 

[Deleted member 174758]

I've seen those kinds of SPAX screws before, would have definitely used them, but 20 quid for a box when I'd use a handful of them is probably stupid. Maybe if I was doing a whole room.

£20? Try more like £11 - and that's Toolstation (OK, those are Reisser R2s, but they are a similar quality and price to Spaxes and they are the right size, 4.5 x 50mm). If you want a solution and you can't work with chipboard screws, that's how you do it. Lamming in girt great decking screw or the like makes no difference once you've got the first 20mm or so of thread into the joist. I have come across people selling those screws on a local market at 10p a screw as well (or £10/100 - about twice the price of the boxed screws I buy - Toolfix aren't the cheapest source by any means). Better to learn how to work with cheap screws IMHO

Just hoping the compressibility of chipboard over time doesn't work itself loose from that, if you know what I mean? I saw a few people when looking through threads mention that. I don't know if that's just a theory or if it happens in reality.

It's a theory. If the screws are properly tightened down (and not too deeply countersunk), there are enough of them and the joists aren't bouncy it'll never happen. Better if the chipboard is glued, though. I bet none of those theorists do this for a living. And yes, I have had to revisit some of the sites I've floored to do adjustments to fire doors, etc - but never yet needed to deal with a sub-floor problem, any problems we get are generally down to the finished flooring (e.g. laminate, engineered flooring, etc)

...even though the reality is the people who build your houses will tend to just cut corners wherever they can.

Well, I'm trade, mostly commercial, or where it is housing it's generally a listed building conversion or a bespoke build, not "cookie cutter" houses, On the rare occasions I work on those the poor quality (often unnecessarily so IMHO) encourages me to move on, sharpish

 

[lc155]

£20? Try more like £11 - and that's Toolstation (OK, those are Reisser R2s, but they are a similar quality and price to Spaxes and they are the right size, 4.5 x 50mm). If you want a solution and you can't work with chipboard screws, that's how you do it. Lamming in girt great decking screw or the like makes no difference once you've got the first 20mm or so of thread into the joist. I have come across people selling those screws on a local market at 10p a screw as well (or £10/100 - about twice the price of the boxed screws I buy - Toolfix aren't the cheapest source n
by any means). Better to learn how to work with cheap screws IMHO


It's a theory. If the screws are properly tightened down (and not too deeply countersunk), there are enough of them and the joists aren't bouncy it'll never happen. Better if the cgipboard is glued, though. I bet none of those theorists do this for a living. And yes, I have had to revisit some of the sites I've floored to do adjustments to fire doors, etc - but never yet needed to deal with a sub-floor problem, any problems we get are generally down to the finished flooring (e.g. laminate, engineered flooring, etc)


Well, I'm trade, mostly commercial, or where it is housing it's generally a listed building conversion or a bespoke build, not "cookie cutter" houses, On the rare occasions I work on those the poor quality (often unnecessasilly so) encourages me to move on, sharpish

Thanks for the info. One or two of the screws did end up countersinking fairly deep (what would you consider too deep?), so I guess I should probably put a few more screws around where that happened at the very least.

 

[Deleted member 174758]

The heads should end up flush or just under the surface - sink too deeply on thin stuff and the screw heads will just end up pulling through. Back them out and add another screw alongside (don't re-use the hole)

 

[lc155]

The heads should end up flush or just under the surface - sink too deeply on thin ply and the screw heads will just end up pulling through. Back them out and add another screw alongside (don't re-use the hole)

Fair enough. The screws are in there tight as hell as I went over with a manual just to make sure, just that one or two did end up penetrating a bit deep for whatever reason, but they weren't going to go any deeper.

By the by, is driving screws in fairly deep on construction likely to lead to something going wrong later on as well, or is it just whatever when it isn't for finishing/being seen?

 

[Deleted member 174758]

By the by, is driving screws in fairly deep on construction likely to lead to something going wrong later on as well, or is it just whatever when it isn't for finishing/being seen?

It's partly to do with the structure of the material.

Unlike plywood, which is fairly consistent all the way through (other than voids in poorer quality material), most flooring grade chipboard seems to have a millimetre or two of "skin" on either face which is somewhat finer grained and denser than the core. If your screw head is within this "skin" you are going to get the best fixing within the toughest part of the board and with 16mm or so of board beneath the head. it will have the best pull-out resistance as well. If, on the other hand, your head is 8 to 10mm down inside the board, in the core, it is in the weakest part of the board and with only 8 to 10mm of chipboard to hold down will just give you a less firm fixing. A couple of times I have seen boards pop (granted, there were other issues to csuse this, but the screw being deeply sunk in the board didn't help).

The other thing is that if you are ever using an SLC over the top (as you might for fitted carpet), the floorers won't thank you for giving them loads of mini potholes to deal with (they either get lumps or hollows in the SLC which can need additional smoothing)

 

[lc155]

It's partly to do with the structure of the material.

Unlike plywood, which is fairly consistent all the way through (other than voids in poorer quality material), most flooring grade chipboard seems to have a millimetre or two of "skin" on either face which is somewhat finer grained and denser than the core. If your screw head is within this "skin" you are going to get the best fixing within the toughest part of the board and with 16mm or so of board beneath the head. it will have the best pull-out resistance as well. If, on the other hand, your head is 8 to 10mm down inside the board, in the core, it is in the weakest part of the board and with only 8 to 10mm of chipboard to hold down will just give you a less firm fixing. A couple of times I have seen boards pop (granted, there were other issues to csuse this, but the screw being deeply sunk in the board didn't help).

The other thing is that if you are ever using an SLC over the top (as you might for fitted carpet), the floorers won't thank you for giving them loads of mini potholes to deal with (they either get lumps or hollows in the SLC which can need additional smoothing)

Ah, sorry, I meant when dealing with standard framing lumber like 2x2's and whatnot, although this is handy to know as well.

I'll add some additional screws where a couple went astray in that case. Although from what you are describing even if it does cause issues it seems to be quite rare, which is good.

Not sure what SLC standard for as Google is giving me random results.

 

[Deleted member 174758]

SLC = seld levelling compound (aka flooring latex). Sorry.

In your softwood laths, etc it is a lot less critical whether or not the screw heads are flush.

 

[lc155]

SLC = seld levelling compound (aka flooring latex). Sorry.

In your softwood laths, etc it is a lot less critical whether or not the screw heads are flush.

Perfect, good to know… because as I'm building the 2x2 framing some screw heads also just drove in fairly deep, I presume because the wood is still fairly wet and probably pretty malleable. I just wondered, as nobody seems to be asking that question either on Google. It was all just about not driving the screw through the bottom piece of wood for 'too deep', nothing about the head going in deep.

Checked today and despite the few screws that went in too deep, the chipboard doesn't seem to be creaking with my dancing and jumping on top of it. Will just belt and braces it with some additional screws and hope once it is set it doesn't move in the future. It's looking like the framing is actually going to sit on the wall facing edge of the chipboard so that will drive some extra downwards pressure I imagine with the extra screws going through the 2x2, chipboard, and then into the joist.

 

[lc155]

SLC = seld levelling compound (aka flooring latex). Sorry.

In your softwood laths, etc it is a lot less critical whether or not the screw heads are flush.

Okay, so I drove through a bunch of fully threaded screws on either side of where I'd driven in the decking screws; with the decking screws keeping it clamped down so it didn't separate from the joists when screwing the fully threaded ones through. Made sure the heads were flush or just slightly driven inside the chipboard instead of going in fairly deep.

Think it's going absolutely nowhere now.