Flat roof - cutting OSB T&G

[Peter500]

My extension flat roof is L-shaped ('wrap around extension'). I have T&G OSB for the roof, but I can't think of a way to use the T&G for every joint as some of the joist spacings aren't 600mm. I think I will need to cut some and just leave an expansion gap (3mm IIRC). Is this what people do in these scenarios?

I can't see there being any problems with the lower deck (for the vapour barrier and insulation), but I'm slightly more concerned about the top deck where the EPDM membrane will go, although I think the EPDM will be fine.

 

[robinbanks]

(For the part of the deck that is attached to joists)

Just cross brace between joists, if you have short edges that dont land and need support. You dont need to support the full length of a short edge, (after all, you dont support the full length of a long edge) just one or two perpendicular members would be fine


(For the part of the deck that is sitting atop the insulation)

Presumably you're not regularly walking on this roof; I wouldn't even bother bracing this part of the deck, just stagger all joints so adjacent shorts don't align. If the joints are well butted up and glued with the manufacturer recommended substance they won't be a problem.

 

[Peter500]

(For the part of the deck that is attached to joists)

Just cross brace between joists, if you have short edges that dont land and need support. You dont need to support the full length of a short edge, (after all, you dont support the full length of a long edge) just one or two perpendicular members would be fine


(For the part of the deck that is sitting atop the insulation)

Presumably you're not regularly walking on this roof; I wouldn't even bother bracing this part of the deck, just stagger all joints so adjacent shorts don't align. If the joints are well butted up and glued with the manufacturer recommended substance they won't be a problem.

I wasn't going to glue the joints. Some people have said that it makes it hard to get up in future, but if I ever remove the EPDM then the OSB is likely to be ruined anyway as it will be stuck to the OSB. I think i'll glue them to reduce the chance of noises etc.

I'll see how it goes without bracing. Once the insulation is on there, there will be no point loads, so it probably wouldn't be necessary. It's a good idea though. If I position the joists correctly, then I can probably sister some timber to the joists rather than doing cross bracing. The joints will hopefully only miss by a couple of inches.

I think I will just screw where the joists are on the top deck (not at the joints in some cases). The top deck is supported by insulation, so I think the screws are only there to prevent uplift.

 

[SpecialK]

You could cut a new T&G?