T&G Chipboard Flooring - Do end joints need to be staggered?

[Prior69]

Hi All,

I am currently re-boarding my loft after lifting old chipboard to put down insulation.

I am using 22mm P5 T&G Caberfloor boards. 2400mm x 600mm.

The floor was previously strengthened and levelled by running 3x2 joists at right angles across the top of the existing 4x2 joists.

The room is 3.9 metres wide and I am laying the boards at right angles to the 3x2 joists

The centres of the of new 3x2 joists are slightly erratic and range between 400mm and 500mm. I think that some have not been laid dead straight and are slightly on the tilt, or the room is wonky or both.....its a Victorian semi.

Because of this I have a bit of a problem where at the start of the room I have been able to stagger the ends of the boards so that the board end joins have landed on a joist for maximum strength. However, I am now at a point where I cant get the boards to land on a joist at their end unless I have them all landing on the middle joist. So I would effectively have 2 boards spanning the room (cut at either end of the room) with the join landing on a joist but the boards would no longer be staggered.

So my questions are:

1. Do the boards really need to be staggered?
2. If so, why?
3. Do the end of board T&G joints HAVE to end on a joist? Or can some be left with no support?
4. Am I better to stagger the boards and have some ends with no support underneath or (as described above) not have staggered boards but have all joins supported with a joist underneath.

As a bit or extra information: I am using "Floor tite" screws and glueing the T&G with D4 adhesive.

Any answers gratefully received as I am now in a state of "DIY FREEZE"!

 

[EFLImpudence]

1. Yes.
2. So the joint is supported by an adjacent continuous board.
3. That shouldn't arise, see 4
4. The ends should be at right angles to the joists so they are supported.

 

[Prior69]

The boards are being laid at right angles to the joists but there is no way to align the boards so that the end of the board always lands on a joist.

Even if I use an off-cut of board to start the row, there is no way lay the next two boards so that the end of each board can butt together over the top of a joist.

The only way I could get that to happen is if I cut some of the boards so that the ends are just butt joints and not T&G. I don't really want to do that.

 

[EFLImpudence]

The boards are being laid at right angles to the joists but there is no way to align the boards so that the end of the board always lands on a joist.

They will be supported by the adjacent boards.
Are you sure the joists are not in the right place? Very old?

Even if I use an off-cut of board to start the row,

You have to do that at least every other row.

there is no way lay the next two boards so that the end of each board can butt together over the top of a joist.

The only way I could get that to happen is if I cut some of the boards so that the ends are just butt joints and not T&G. I don't really want to do that.

No. Don't do that.

There are plenty of videos and articles to help you. Do a search.