18mm OSB T&G which way up?

[stevep98]

I'm going to be replacing the flat roof on my garage soon using18mm osb3 T&G 2.4x 600mm (norbord), for a nice flat even finish for the rubber. This might seem like a silly question, but does it matter which way up Iay it?

Also, I read that you should use 4 screws across the width of the board into every joist which works out at approximately 24 per board... Seems like a lot of screws.

 

[catlad]

On the boards I use its the writing face down if you look at the tongue it has a slight curve to help locate the next board.

 

[cotswoldbuilders]

Same as C/L, don't screw the edge down tight until you have next board slotted in.

 

[stevep98]

Yes i see what you mean about the curved tounge, thanks very much, that's very helpful, and thanks for the tip about not screwing the edge down tight.