Plaster ceilings can sag for several reasons. In some cases, the plaster and other building materials shift and come apart over time, which is why you’ll commonly find drooping plaster ceilings in older homes. Improper installation, foot traffic, and water damage—often from a leaky roof or a broken pipe—can also cause plaster ceilings to sag.

Applying plaster to a wall will usually cost between $2 and $10 per square foot for both the material and labor. The cost will vary based on the quality of the plaster you’re using and whether or not prep work is required before the work begins. Wall prep can add up to about 10% to your total costs. Plastering exterior walls can be more expensive in many cases because they are taller and require scaffolding and safety equipment.

While not always necessary, you can glue a drywall ceiling in addition to using screws or nails. Drywall is typically secured to ceiling joists with fasteners, which is often sufficient. However, adding construction adhesive can offer benefits like preventing sagging, bridging gaps, and reducing air leaks for better energy efficiency. It may also be used for specific acoustic or insulation needs. On the other hand, many professionals advise against it because properly placed screws make the drywall structural, glue doesn't add strength, and it makes future repairs or replacements significantly more difficult. Ultimately, it's best to follow local building codes and project-specific requirements to decide if adhesive is right for your ceiling.

If you don’t have studs in the area where you want to install your TV mount, you may still be able to install a TV mount on drywall. The easiest way to install a mount on drywall is by using drywall anchors—but not just any plastic anchors. Choose molly bolts or toggle anchors, which have a weight capacity of around 50 pounds. For added support, consider pairing drywall anchors with a wall mounting plate. Extra heavy TVs may need to be mounted via the ceiling joists or beams.