Hi @glennh,
Thank you for your question and welcome to the Bunnings Workshop community, it is fantastic to have you with us.
I'd suggest that when the plasterboard was installed, the screws were overdriven causing them to pull through the paper face of the gyprock which will have compromised their ability to hold the gyprock.
This is definitely something that needs to be fixed in a timely fashion and luckily it is a very simple repair.
To prop the plasterboard in place, you could hire some Acrow Props and place them in the problem areas. Please note that these acrow props are available in conjunction with Coates Hire, so it is best to call ahead to your local store to discuss availability.
To resecure the plasterboard, you'll need a drill, some 18 x 30mm Plasterboard Screws, Multi-Purpose Joint Compound, a 50mm Plastic Scraper and a 120 Grit Sanding Sponge.
Start by locating the ceiling battens above where the plasterboard has dropped. This can be done by following any visible screw lines or with the use of a stud finder. You might like to check out How to use a stud finder for some guidance.
Once the ceiling batten has been located, push the plasterboard sheet upwards until you feel it hit the timber above and then drive your screws through the plasterboard and into the ceiling batten. You should install a number of screws to ensure the plasterboard is solidly secured in place.
Be careful not to over drive the screws or they will pull through the paper face of the gyprock. The screwhead should sit just below the face of the plasterboard, dimpling the paper but not tearing it.
Once the screws have been installed, apply the joint compound over the screws using the plastic scraper. Allow the joint compound to fully dry and then sand smooth with the sanding sponge.
You can then use some matching paint to paint over the patch for a fully finished repair.
If you have some concerns with your ability to carry out this repair, I'd suggest contacting a handyman to assist. You might like to use a service such as HiPages or True Local to find someone in your area.
Let me know if you have any further questions.
Jacob
