Unsupported edges/joins on plasterboard

[Crofter]

I've got a vaulted ceiling, where the buildup will be, from outside to in: rafters, 100mm PIR, vapour barrier, 25mm battens, and then plasterboard.

The battens will follow the rafters, then the plasterboard will be fixed to the battens along the long edges. The total length from eaves to ridge is 3.17m so there will have to be a join along the short edge of the plasterboard.

What sort of support do I need to give along this edge? Can scrim tape do the job? I am toying with filling the service void in this area with 25mm PIR which could perhaps be another form of support. Or I could run a batten perpendicular to the rafters but obviously it would only be supported by one screw every 600mm. I guess I will need to do that at the ridge and eaves anyway?

 

[jamiehamy]

I can't offer a definitive answer, but we have the same issue coming up (I was going to post about this later) - our walls are 2.7m and 3m going up to 3.3m, so have to have a join. 

 

My plan is to put a 45x45 dwang across the join to catch the screws (in your case 25x45?), but not quite sure how to smooth the join as I don't think that edge will be tapered? If I scrim then it will not be flush with the rest of the board...

 

We had though about buying 2.7m gyproc and 3m, but couldn't buy partial pallets so everything is 2.4. 

 

 

[Stones]

We had 50mm PIR underside of our rafters.  Same issue.  Vertical battens on rafters and horizontal battens between rafter battens to catch plasterboard edge.  

[ProDave]

Simple.

 

the joint does not have to fix TO anything, it must just fix the two ends of plasterboard together. We had this in several places.

 

simple solution. Fix one sheet. Cut an offcut of 4 by 1 or 6 by 1 that just fills the gap. Hold it in place and screw through the board that is already there. This then leaves the overhanging edge for the next board to screw into.

 

It might not be what the professionals do, but it worked for me.
 

[Crofter]

@ProDave That sounds very practical, spot on!

Now a question that I *should* know the answer to, because I've done plenty plasterboarding before: how do you tape/fill the joints between boards which are end to end, without a feather? As @jamiehamy pointed out above.

[ProDave]

The tapers just tape over them. To the purist, if you lay a straight edge on afterwards there is a very slight "bump" but that's all you can do without a taper edge.

 

If the budget runs to it, our new house will be skimmed with plaster rather than just taped and filled, for the much better finish (providing the plasterer is good)
 

[Nickfromwales]

4 hours ago, ProDave said:

Simple.

 

the joint does not have to fix TO anything, it must just fix the two ends of plasterboard together. We had this in several places.

 

simple solution. Fix one sheet. Cut an offcut of 4 by 1 or 6 by 1 that just fills the gap. Hold it in place and screw through the board that is already there. This then leaves the overhanging edge for the next board to screw into.

 

It might not be what the professionals do, but it worked for me.
 

I consider myself proffesional'ish, and that's EXACTLY what I've done for years. . The off-cut cut to fill at least 80% of the 'stitch', say 350mm off-cut for a 400mm gap, and then stick the two boards together accordingly.