18mm hardwood ply thickness variation? Do I need to countersink? (Floor job)

[Deleted member 174758]

so you glue the plywood down to the joists and screw?

The standard way to lay chipboard or spruce ply sub-floors these days is to glue the sheet material to the joists - intended to reduce creaking. I don't see why ply should be any different

and you put in a loose tongue as well?

I don't think the OP will, but the last plywood restaurant floor I did, about 10 years ago now was done that way. That one was three layers of 18mm plywood, no less, but then we were cutting an 18 foot diameter hole out of the building's floors from the basement to the first floor to form a feature circular stair well through the middle of the building. So maybe a bit belt and braces, but it's a proven approach for high load floors. The tongue and groove approach stops movement at the sheet joints so should reduce creaking

 

[JohnD]

The standard way to lay chipboard or spruce ply sub-floors these days is to glue the sheet material to the joists - intended to reduce creaking. I don't see why ply should be any different

Surely a source of great sadness and expense when you need to run a new cable or repair a leaking pipe.

 

[Deleted member 174758]

Surely a source of great sadness and expense when you need to run a new cable or repair a leaking pipe.

Which is why you need to group your services properly and put in accesses if you really need access, but how often is that? (BTW ever seen a Routabout?). It's a case of the the 6Ps - Proper Planning Prevents P1ss Poor Performance! TBH lifting and relaying laminate, vinyl plank, tile, solid oak or parquet floor is often going to cost far more than breaking into the sub-floor. Once you have the sub-floor exposed a good tradesman should open the floor up by making a neat rectangular cut-out with a plunging rail saw and rail, then battening the opening and screwing the piece back in once they are done, making sure it's all level then caulking the joints neatly with silicone. I've seen lots of bodged cut-outs done by monkeys who don't give a damn about whether or not the floor is screwed, nailed or glued - they just hack bits out, cobbld an infill together and leave a right royal mess for someone else to sort out in the future (even seen it on new builds). But worst of all is trying to deal with underfloor heating if the services run beneath that...

As I said, remember your 6Ps!

Edit: That said there have been times when I've found it necessary to cut a track across a floor (where an extra service had to be run across the line of the joists). The solution was to do two parallel rips using the Festool and rails, clean-up the tops of the joists where the glued down flooring ran across joists. The flooring had to be replaced, but the replacement was neat, tight and properly supported. That's what a professional should always do - if you make it you should be able to repair it. In the days before Festools I used to screw two battens to the floor and use them to guide the saw - it's what I was taught to do. You just keep an old blade (and an old guide rail) to deal with floors full of iron!

 

[JohnD]

a good tradesman should open the floor up by making a neat rectangular cut-out with a plunging rail saw and rail, then battening the opening and screwing the piece back in once they are done, making sure it's all level then caulking the joints neatly with silicone.

hahahahahahahaha!

 

[Draughtsman]

No gap. Everything needs to be tightly screwed down and all joints fully supported. Still best to use a bit of something like PU glue on the edges. Why aren't you using glue to secure the plywood to the joists?

All joints/edges are fully supported. I was just going to fire in loads of screws, plus a few extra supporting noggins between the outer CLS and the next one in.

 

[Deleted member 174758]

hahahahahahahaha!

I can see that you are used to working with the moron brigade (especially electricians - plumbers seem to ask a bit more often)...

Oh well, you get what you pay for, I suppose

Even if you don't glue to the joists, where you are using any form of man-made material T&G flooring (and spruce plywood, for example, is T&G in 8 x 4ft sheets) the tongues still get glued together, so there is no chance at all of being able to lift a single board to access beneath the floor without first cutting it, and wouldn't be even if you didn't glue the tongues. Double and triple skin floors are even worse to deal with.

 

[Draughtsman]

There are no tongues. Or grooves.

Any tips on edge distance for (5x60) screws in 18mm ply? (can I butt 2 sheets of 18mm together on a 38x63 CLS laid flat/is 63mm wide enough)

Tnx,

 

[Notch7]

The standard way to lay chipboard or spruce ply sub-floors these days is to glue the sheet material to the joists - intended to reduce creaking. I don't see why ply should be any different


I don't think the OP will, but the last plywood restaurant floor I did, about 10 years ago now was done that way. That one was three layers of 18mm plywood, no less, but then we were cutting an 18 foot diameter hole out of the building's floors from the basement to the first floor to form a feature circular stair well through the middle of the building. So maybe a bit belt and braces, but it's a proven approach for high load floors. The tongue and groove approach stops movement at the sheet joints so should reduce creaking

many thanks for that advice, I shall bear that in mind

Ive been working on a townhouse in Tonbridge -probably built in last 5 years, goodness me the stairs is unbelievably creaky, its really bad and its fully carpeted. My guess is its made of mdf treads and risers or wasnt glued properly

whereas my 1959 built house stairs makes almost no noise, if at all.

 

[Deleted member 174758]

Any tips on edge distance for (5x50) screws in 18mm ply? (can I butt 2 sheets of 18mm together on a 38x63 CLS laid flat/is 63mm wide enough)

Ideally a minimum of 25mm in from the edges, slightly less if you pre-drill and countersink. You can certainly butt-up two sheets on 63mm wide stuff, especially if you angle your screws slightly

 

[Draughtsman]

Ideally a minimum of 25mm in from the edges, slightly less if you pre-drill and countersink. You can certainly butt-up two sheets on 63mm wide stuff, especially if you angle your screws slightly

The 63mm is an existing frame, I might just add a brother to get the width. And stick with 89mm landings after that.

I got some Goldscrew Plus 5x60mm, partial thread. But they're cutters, which I didn't start out with. Are they Ok for fixing the 18mm ply down?

 

[Deleted member 174758]

Should be fine - I find that 5.0mm screws sometimes need a drill/countersink to ensure that they drive in flush. The flooring screws we used are 4.0mm (sometimes 4.5mm) and will flush into plywood using just an 18 volt impact driver most of the time

 

[Draughtsman]

Skirting to sit on ply boards, then insulation/underlay, then click vinyl, then trim? Or vinyl, then skirting - no trim?

How much insulation beneath the click vinyl? I really want a minimum, I'd like minimal 'give' when walked across or under furniture?

Thank you
D

 

[Deleted member 174758]

Skirting to sit on ply boards, then insulation/underlay, then click vinyl, then trim? Or vinyl, then skirting - no trim?

If you want the vinyl to floor joint to look slicker then skirtings after vinyl, Personal taste, but I don't like to see quadrant trims, etc

As to the underlay, I think you'll need to talk to a flooring bod (what does the manufacturer say?) - as a wood butcher I really haven't a scooby because they normally take over when I finish the mucky stuff

 

[crazydaze]

Skirting to sit on ply boards, then insulation/underlay, then click vinyl, then trim? Or vinyl, then skirting - no trim?

How much insulation beneath the click vinyl? I really want a minimum, I'd like minimal 'give' when walked across or under furniture?

Thank you
D

Whatever the Click Vinyl manufacturer recommends, go with it, click vinyl failures are notorious on the joints, if you don't use their recommended underlay, they have an easy get out clause. Click vinyl needs to be laid on thin, heavy and very dense specialist underlay, regular floating floor underlays for laminate/engineered floors are to thick and too soft, even premium underlays like Timbermate XL or Multitex arent suitable for click vinyl.