On the upper floor of our house, there is a kind of fabric ceiling stretched between the walls. Now I am removing the stretch ceiling and replacing it with plasterboard (60 x 120). There is a rough wood panel under the stretch ceiling, so there is no problem screwing the plasterboard into it. In the staircase, the ceiling is lowered and there is no panel, so I don't have a good base to screw the plasterboard into there. Should I first nail down raw pine or some sheet material to get a good grip for the plasterboard in the staircase?
Yes 
The basic rule for plasterboard in the ceiling is CC30, so you should use something like 22X95 with cc30 so that the plasterboard is well secured. Then it's important to fasten the 22X95 so they don't warp, but it looks a bit sturdy like cc60 on the framework and it would be good for fastening against.
The basic rule for plasterboard in the ceiling is CC30, so you should use something like 22X95 with cc30 so that the plasterboard is well secured. Then it's important to fasten the 22X95 so they don't warp, but it looks a bit sturdy like cc60 on the framework and it would be good for fastening against.
Throwing in a sub-question:mats_o said:Yes
The basic rule for gypsum in the ceiling is CC30, so you should mount, for example, 22X95 with CC30 so that the gypsum gets a good grip. Then you also need to attach the 22X95 so that they don't warp, but it looks a bit rough like CC60 on the framework, and it will be nice to fasten against.
Does this mean you need a screw row every 30 cm? How close should the screws be positioned on 60/120 ceiling gypsum?