Plywood or chipboard subfloor

[Craig89]

I need a substantial amount of subflooring for the entirety of my property, approximately 150m2. I am looking at either 18mm hardwood ply or 22mm t+g chipboard.

My main requirements are solidity and no squeeks. Im leaning towards plywood as i believe it to be a better material, it is about 30% more expensive.

If using ply I will fit noggins along the long edge joins. Screws in either case will be these: https://www.screwfix.com/p/spax-tx-countersunk-wirox-flooring-screw-4-5-x-60mm-300-pack/88716

First and second floor will be mostly carpeted, unsure about the bathroom yet. Ground floor will be a subfloor for parquet, floorboards and quarry tiles. I will be putting 2 overlapping layers down for underneath the quarry tiles.

Any opinions or advice welcomed.

Thanks, Craig

 

[Cynan]

I had this same decision in a previous, modern house and in my experience with the two, ply will give a bouncy feel whilst chipboard will be rock solid. I opted for treated chipboard.

 

[Craig89]

Thanks for the reply. That does surprise me. I assumed plywood would be a stiffer material.

The first floor I will be boarding is the second floor which for the immediate future will just be a storage space so maybe I will do that in chipboard and see how it feels.

Anybody else have anything to add? I understand its not technically a period property question but with the vast knowledge on this board some people must have experiances of this.

 

[Feltwell]

Chipboard does the job fine for this, I'd be tempted to use that inside. I've used 18mm ply for the first floor in my garage and it doesn't feel particularly bouncy, but then again I have put noggins down the long edges and only jointed over joists. Plus of course it's only storage up there and only ever me up there.

Squeaks seem to be down to movement in joints, chipboard floors can be squeaky. If you can face the hassle maybe don't use T&G, but use square edge jointed over joists / noggins, with a small deliberate gap at the joints to stop any rubbing between boards? Plus of course screwed down rather than nailed.

Bear in mind access needs for the future for plumbing / electrics.

 

[Flyfisher]

Surely the ‘bounce’ in a floor is largely determined by the supporting structure. Yes, the boarding material will also have an effect but if the underlying structure is rock solid then almost any boarding material (within reason!) will not bounce.

I know there are standards regarding joist sizes, spans and spacing but if rock-solidness is an important desired goal then the standards could be enhanced in some way. Deeper joists, closer spacing, shorter spans or a combination of all three, depending on which is easiest.

 

[Craig89]

My joists are 7 x 3s spaced at 450mm centres (a continuation of what was there originally, which is just big enough for the span from a building regs point of view). So potentially not as stiff as it could be but also does pose a bit of a problem with 8 x 4 or 8 x 2 sheets as I will have to cut them to make them finish in the centre of the joists. Yes the size and spacing does dictate the strength of a floor but the flooring sort of ties it all together and adds a good deal of strength, thats my take on it anyway.

Im leaning towards trying T + G chipboard at the moment mainly due to the copious amount of noggins I would have to use with straight edge boards to keep the waste down on the amount cut off the sheets. I dont know why but it just strickes me as a lesser quality material, maybe I will just have to get over that

 

[Toby Newell]

Plywood 1000%

Chip board is a very poor sub floor material only used for cost purposes, plywood is superior in every engineering metric.

Not only is it more dimensionally stable it is far more water proof if you go for quality WBP.

The problem is chip board can expand and warp if it absorbs moisture, I see dozens of floors ruined by chip board sub floors.

Finally plywood has much better holding power for fixings, chip board is ok for dry lofts under carpet or similar, I never lay floors onto chip board.

Make sure you buy a high quality board like WISA from a proper timber merchant as Wickes, Homebase etc do not always stock high quality boards and there is a massive difference in quality.

Skimping on your sub floor is really quite foolish as the cost of removing already laid tiles / boards can be several multiples of the entire job, it's one of the areas where it's really not worth cutting corners, make savings elsewhere.

Correct preparation is perhaps the most important advice for any building or craft work.

PS WISA ply also comes in a T & G version, yes it is more expensive but you may not have to fit extra noggins.

 

[fernicarry]

Bear in mind access needs for the future for plumbing / electrics.

The Trend Routabout is a very good bit of kit for gaining access through sheet floors.

 

[Craig89]

Thanks all for the comments. I believe I am going to use chipboard for the first and second floors (apart from the bathroom, I will use ply there) and use ply for all of the groundfloor.

I havent installed the downstairs joists yet so I will put them at 400mm centres so I will work out better with the sheets of ply.

I am wiring and plumbing from scratch in the next phase. Ideally I will have as little as possible under the downstairs floor as once the tiles and wood floors are down I never want to lift them again. I will try to keep all my runs together so if I ever need access it causes minimum disturbance.

 

[MikeG]

....I believe I am going to use chipboard for the first and second floors (apart from the bathroom, I will use ply there).......

Chipboard these days is almost always moisture resistant, and therefore fine for use in bathrooms etc. If this was the reason for your comment, then you are maybe thinking back to the previous generation of chipboard flooring, where the wrong type would turn to pulp in damp conditions.

If you choose ply, then T&G flooring ply is great. Don't even think about using square-edged ply. However, both ply and chipboard require the joints to be fully glued, otherwise you will get squeaks.

 

[Craig89]

Chipboard these days is almost always moisture resistant, and therefore fine for use in bathrooms etc. If this was the reason for your comment, then you are maybe thinking back to the previous generation of chipboard flooring, where the wrong type would turn to pulp in damp

I said plywood for bathroom for a couple of reasons, firstly I assumed it was stronger to support, lets say worst case scenario, a cast iron bath full of water with 2 people in. Secondly I dont know what floor finish to use in the bathroom so 18mm ply would give me a few mm head start so to keep height gain as low as possible

 

[Toby Newell]

Watches have designated water resistance and depth ratings.

Water resistant watches 30 metre rating can let water in in a steamy environment, showers kill them. Watches with a depth rating of 50 metres are only certified for static pressure, surface swimming and can let water in below 2 metres.

No one really dives with a watch without a certified dive rating of 200 metres even though most recreational diving is done above 40 metres.

The point is green chipboard may be moisture 'resistant' but I have seen several rotten chipboard floors and probably a few dozen of totally ruined floors where the green chipboard has bowed and pushed the floating floor up, not as bad as OSB but still pretty naff.

Chipboard is weetabix. Green chipboard is that sugar coated weetabix. Still weetabix. Also have you tried screwing fixings in and out of weetabix? You may get half a dozen goes with plywood, you may only get the one or two with chipboard and it has very little holding power, which is fine if nothing moves...

Chipboard is a material with only one usp, cost. WBP plywood has many.