OSB3 board options and direction for flat garage roof

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I'm about to board my garage roof
Length is 7.3m x ~2.4m and the garage is link detached joining me and my neighbor

Can anyone confirm the following for me please :

  1. are the tongue and groove or flat edge panels best ?
  2. screw down or nail down ?
  3. should i lay the OSB3 boards length ways down the length of the roof and then stagger, or across the width ?
  4. if using the t&g boards, must they join on a joist ?
  5. i assume flat edge boards MUST join on a joist for strength ?
  6. as its a link detached roof between 2 walls, how tight should the boards be to the brickwork, considering there will need to be an arris rail around the edge (tight or 5mm all around ?
Thanks in advance (y) and sorry if any of these are dumb questions :confused:
 
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Sorry for the bump

Would anyone be able to advise please as I'm hoping to purchase and board this week ? (Between rain showers that is)
 
What are you finishing the roof off with (weatherproofing) and what are the joist gaps, centre to centre.
 
Either ivor for T&G or not.

The boards should go longest length ways across the joists and stagger the joints 1/2 bond like brickwork.

Yes the boards should butt over a joist, but you don't need noggins under joints between joists if the joist space is 450mm or less, or if T&G.

Use screws (best) or ring shank nails

Leave a 5-10mm gap off any wall to avoid any damp transfer
 
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What are you finishing the roof off with (weatherproofing) and what are the joist gaps, centre to centre.

Still deliberating between EPDM and felt

Joist gaps are 400mm centres
 
Either ivor for T&G or not.

The boards should go longest length ways across the joists and stagger the joints 1/2 bond like brickwork.

Yes the boards should butt over a joist, but you don't need noggins under joints between joists if the joist space is 450mm or less, or if T&G.

Use screws (best) or ring shank nails

Leave a 5-10mm gap off any wall to avoid any damp transfer


Thanks Woody

The new joists that i have installed to extend my flat roof forward are at 400mm centres so they are likely good and i can butt them over a joist, but i can't vouch for the old joists and where the joints will land

As i see it, this is more of an issue where the boards are flat edges, but where it is T&G and they join between joists, how much of an issue do you think it will be, or just beef up underneath with a noggin to help ?

Thanks again for your valuable input as always
 
So i've just been on to B&Q's site and can see that they have 4 x 18mm options :

https://www.diy.com/departments/bui...erials/sheet-materials/osb/18/_/N-8tuZ1z0niir

Description :

Smooth OSB3 board (2440 x 1220)
Smooth OSB3 board (1690 x 645) - TGV4
Smooth OSB3 board (1220 x 610) - "Softwood"
Smooth OSB3 board (810 x 410) - "Softwood"

I'm thinking of the TGV but am puzzled by the "softwood" options


Can anyone confirm please and whether they are all suitable for construction/a garage roof also ?

Are they all equal, except for size (obviously) and whether flat or T&G ?
 
Looks like B&Q crap descriptions.

But those are some random sizes for boards. You really need 2440x1220 or x610 for roofing
 

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