Advice on square set 2750mm wall height

Hi Guys,

I've got a DA, construction certificate and owner builders permit to do a renovation to our 3rd storey. We are removing all the internal walls and realigning which will mean we re-doing 4 bedrooms, 2 bathrooms, laundry and a sitting room. There are no changes the subfloor or roof.

I have a bit of a dilemma what to do with the plastering. The current walls are 2700mm studs with a 50mm gap to the truss roof, all rooms currently have a 90mm cove cornice. I would like to modernise and do square set to match the lower levels. The 2750 wall height is awkward as you can't use 1350 sheets.

I can think of two options:
- Use 3 x 1200 height sheets, which does add more cost for sheets and plastering the extra join
- Batten over the current roof sheets which would drop the roof about 45-55mm and I could then use 2 x 1350 height sheets. Save money on sheets, plastering and disposal costs of leaving the current roof inplace

Any advice anyone could give me what to do?

Thanks.

Given it's the top floor, the second option will also provide the opportunity to increase ceiling insulation. Even just leaving the current plaster ceiling and adding an air gap to the new ceiling will help. The batten system used for the new ceiling could adjust to help address any levelling issues that may be present. I'm not up with the latest, but worth exploring. Or keep it simple and just use regular battens

Typically plasterers lift the 1350 sheets to the correct height and the gap is at the base. This is filled a with plasterboard strip and the skirts cover the join so there's no need to plaster it. Alternatively, if you are rebuilding the internal walls you can set the spacing up to allow vertical installation of boards and if you offset the joins on opposite faces of the wall this will go towards bracing... look into that too.

I thought about vertical boards too, but as an amateur plasterer I find it harder to stop up smoothly from floor to ceiling. There is also a greater chance of seeing the vertical joins in glancing light conditions. All depends on the expertise of those doing the job