Plasterboard direction on pitched roof

[matlob]

Hi

Just about to plasterboard out a vaulted ceiling

Distance from wall plate to ridge is 2.1m. Would I be best having a vertical join every 1200mm (boards sitting vertically from wall plate) or have the boards join at 1200 half way up the roof.

Got 100mm in between the joists and 50mm over. Haven't put the 50mm on yet and looking to do the opposite direction to the 50mm/plasterboard

Thanks for any help

 

[^woody^]

Longways across the rafters

 

[matlob]

Thanks woody.

Is this just a stronger fixing rather than overlapping a join up the rafter, can the 50mm go in the same direction/joins?

Also, would you put a vapour barrier under the insulation or will foil tape across all joins be adequate

Thanks again, you've helped me out a bit on here!

 

[^woody^]

In principle, you fix a board across as many rafters or joists or studs whatever as possible as it makes the structure more rigid. And also half lap each row.

It won't matter with the insulation layer, but its best to. Otherwise, try and stagger them so that the joints are not aligned with the plasterboard joints.

Use foil tape if the insulation is foil faced, polythene if EPS or Styrofoam. Tape the bottom layer of insulation only, not both.

 

[mikeey84]

Tape the bottom layer of insulation only, not both.

Can I ask why this is advised? Is to prevent moisture getting trapped between the layers?

 

[matlob]

Thanks Woody

I'll crack on!

 

[HERTS P&D]

Just make sure you put it on the inside!

Andy