OSB3 board options and direction for flat garage roof

[shd1970]

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 and sorry if any of these are dumb questions

 

[shd1970]

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)

 

[denso13]

What are you finishing the roof off with (weatherproofing) and what are the joist gaps, centre to centre.

 

[^woody^]

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

 

[shd1970]

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

 

[shd1970]

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

 

[^woody^]

Pick your boards, lay them and if you are concerned you add noggins afterwards.

 

[shd1970]

I saw elsewhere that to decide upon the screw length, to multiply the board depth that you are fastening (OSB3 x 18mm), by 2.5
Also, to choose a screw WITHOUT a complete thread as the boards pull down onto the joist better

Can anyone confirm that the above guidance is correct please as i have purchased these :

https://www.screwfix.com/p/goldscre...ews-5-x-50mm-200-pack/6686f?_requestid=592055

 

[denso13]

Can anyone confirm that the above guidance is correct please as i have purchased these :

Looks good, I've followed that advice for flooring and should be fine.

 

[shd1970]

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 ?

 

[^woody^]

Looks like B&Q crap descriptions.

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