one or two screws on t+g joint

Hello All

Maybe this is a silly or obvious question to some but its not to me.

Fitting new t+g chipboard flooring with the 600mm edges finishing on a joist. If I'm say going to use 3 screws per joist, should I double that to 6 at the edge so that I screw down both boards? Or is it enough to put one screw into the centre of the join which would go through both boards (as t+g).

I hope that makes sense ?

if i understand you:
you dont attempt to screw two boards with one screw - ever.
screw down at each "corner" of the board then spread two or three screws spaced evenly between the two "corners".
where the next board butts up then match your screws.
as you cross the joists then use the same amount of screws set at the same centres. screws are enough.

Edit: i've just edited the above, i got distracted and thought i was dealing with t&g pine boards.

Thanks for that. Just to check I've got it right. You said to use 2 or 3 screws between the corners. So if I used 3 then that would be 5 in total along that joist. So for a 2400mmx600mm board with joists at 400mm centres, I'd be crossing 7 joists so I would be using 35 screws per full board. Have I got that right ?

Yes. Sounds a lot, but really it isn't. Don't skimp on screws or glue unless you like squeaky floors

Thanks J&K - I've read a lot of your posts and like them. I've already started and am about half way through now - did use 35 screws per board, D4 glue at the joinsts and pinkgrip on the joists.

Seems pretty solid so far but tends to be gaps of around up to 1mm (maybe 2mm worse case?) at the joints but pretty level and even. I did notice that even along the factory machined edges, you couldn't butt the boards up to closer than a 1 mm across the entire length even using a 14LB sledge hammer.

Next plan to add Vitrex 5mm underlay then laminate. So not the poshest floor ever but hopefully ok (laminate isn't the cheapest kind so has texture etc )

You can get slight gapping as a result of hydraulic pressure (when the glue in the joints is compressed). If the floor is being covered then slight gapping (1mm or so) isn't really an issue and may be preferable to no gap but insufficient glue