There are several techniques that can be used to repair cracks in a plasterboard ceiling, which can generally be completed in 24 hours. You can use a basic water-based latex injector to fill the cracks with adhesives. This entails some preparation, including drilling small injection holes.
Size up the ceiling
Observe the cracked area. Look for structural changes or a leaky roof. After that, determine how far the ceiling has pulled away, and assess the amount of movement between the plaster and lath by gently pushing on the surface. Slight separation requires reattachment.
Vacuum all debris between the plaster and lath
If the plaster sags 1/2 inch to 1 inch from the lath, there can be excessive debris between the plaster and lath. Vacuum all of the debris to apply reattachment. Remove the section of the ceiling with too much debris, reattach the edges, and inject the missing parts with new plaster.
Bore injection holes
Bore through the injection surface, initially. When reattaching from the plaster side, bore thoroughly through the plaster, but stop before reaching the wooden lath. Vacuum the debris and drilling dust after boring the injection holes.
Inject an adhesive
Use a water-based, latex product to inject adhesive until the plaster moves a little. Push the plaster back into place afterward, and secure it with flexible plywood squares covered with a layer of sheet polyethylene. Secure these with screws, and let the adhesive set up for 24 hours.