Loft conversion flooring question

[liamruairi]

Currently doing my own loft conversion and about to fit the 18mm m/r t+g chipboard flooring. I *think* I know the answer but a carpenter friend has got me questioning my own opinion and just wanted some clarification.
Am I right to glue the t+g joints and screw all boards down into floor joists as much as possible? Or loose fit and leave as a floating floor? This was his suggestion. If I did that of course there would be places it was screwed anyway where I’m going to put the walls etc. Thanks.

 

[Mottie]

I’d guess at T&G screwed but not glued.

 

[foxhole]

Screwed and glued to avoid squeaking .

 

[liamruairi]

Screwed and glued to avoid squeaking .

Thought so

 

[Deleted member 174758]

Make sure that you put enough glue (D4 - waterproof) on the tongues and that you close-up the gapping (hint: we tend to use a 5 to 6 ft long piece of 4 x 2in PAR or CLS softwood and a 14lb sledge hammer on the groove edges to achieve this in a commercial environment - no-use pussyfooting about when you want nice tight joints). Make sure that you support all the joints (ideally on a joist) and others have said, screw the stuff down well. If you don't use the glue, don't screw down and/or don't support the joints you'll end up with squeaking

 

[paulrockliffe]

Egger recommend you glue the boards to the joists with their gap filling adhesive too to take up any imperfections in the joist levels to minimise squeaks. But that might just be a ploy to get more money from you.

 

[liamruairi]

Egger recommend you glue the boards to the joists with their gap filling adhesive too to take up any imperfections in the joist levels to minimise squeaks. But that might just be a ploy to get more money from you.

Not a bad idea really

 

[liamruairi]

Egger recommend you glue the boards to the joists with their gap filling adhesive too to take up any imperfections in the joist levels to minimise squeaks. But that might just be a ploy to get more money from you.

Make sure that you put enough glue (D4 - waterproof) on the tongues and that you close-up the gapping (hint: we tend to use a 5 to 6 ft long piece of 4 x 2in PAR or CLS softwood and a 14lb sledge hammer on the groove edges to achieve this in a commercial environment - no-use pussyfooting about when you want nice tight joints). Make sure that you support all the joints (ideally on a joist) and others have said, screw the stuff down well. If you don't use the glue, don't screw down and/or don't support the joints you'll end up with squeaking

Thanks this was exactly my plan until I heard otherwise. Incidentally I thought the point of. T+g chipboard was that the joints didn’t have to be on the joists? 400mm centres joists but 600mm wide boards make this difficult

 

[Deleted member 174758]

Incidentally I thought the point of. T+g chipboard was that the joints didn’t have to be on the joists? 400mm centres joists but 600mm wide boards make this difficult

You actually need to lay the boards at right angles to the joists - that way a 2400 x 600 "plank" will start on a joist, span 5 joists and finish on another joist. Flooring is almost always laid perpendicular to the direction of the joists (or at least the first layer is). This is partly for strength, partly for ease (and speed) of installation. Should your joists not be quite on 400 centres then 2 x 2in softwood battens can be screwed onto the sides of the first/last joist to provide extra support. Supporting the joints increases the stiffness and strength of the floor

 

[foxhole]

And use screws which are fully threaded or the board can eventually travel up and down the screw head causing squeaking .

 

[Deleted member 174758]

And use screws which are fully threaded or the board can eventually travel up and down the screw head causing squeaking .

Purpose-made flooring screws for man-made boards are often fully threaded with a small reverse direction thread at the very top of the shaft, just below the head, like these Spax ones:

and these Reisser ones:

Closer to home, even Toolstation sell that sort of screw in smaller quantities.

Note that this type of screw generally requires a high torque drive bit (such as Robertson square drive or Torx) ratrher than the more usual Pozidriv/Supadriv or Phillips bit. Also note how small the head is on some of these - this is to permit sinking of the head into chipboard without the need to pre-pilot drill

 

[foxhole]

Purpose-made flooring screws for man-made boards are often fully threaded with a small reverse direction thread at the very top of the shaft, just below the head, like these Spax ones:
View attachment 170421
and these Reisser ones:
View attachment 170422

Closer to home, even Toolstation sell that sort of screw in smaller quantities.

Note that this type of screw generally requires a high torque drive bit (such as Robertson square drive or Torx) ratrher than the more usual Pozidriv/Supadriv or Phillips bit. Also note how small the head is on some of these - this is to permit sinking of the head into chipboard without the need to pre-pilot drill

I would never use those in chipboard .

 

[paulrockliffe]

Reissers's chipboard screws are really good, but they're not those ones. The Reisser Cutters are designed to cut their own pilot and their own countersink, you just bang them in with a driver, they're ace.

The reason for the smooth shank is so that if you don't hold the boards down when you screw them in the board will jack on the thread, the smooth bit takes the jack out again. The smooth bit will let the board rub and squeak. If you aren't being a lazy arse doing them as quick as you can, the fully threaded screws will leave you with a better floor.

 

[Deleted member 174758]

I would never use those in chipboard .

Your reasons?

 

[foxhole]

Your reasons?

See Paul’s post above .