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.

Although they have similar applications, spackle and joint compound are not the same. Their primary differences lie in their composition, consistency, and ideal use cases.

Spackle is composed of gypsum and binding agents, making it thicker than joint compound. It dries quickly and is easy to sand, which makes it ideal for small wall repair projects like filling nail holes or patching minor damage.

Joint compound, also known as drywall mud, consists of limestone and gypsum. It is primarily used for large-scale projects, such as taping and finishing the seams on newly installed drywall. It tends to shrink more than spackle and can be more difficult to spread.

While both products can be used to fill small depressions and cracks, spackle cannot replace joint compound for taping and mudding new drywall. Conversely, you can often use joint compound for small patching jobs typically done with spackle.

If you only have tiny holes in your drywall (for example, dents or nail marks), you probably won’t need a patch kit. Instead, you can plug the hole with a small amount of spackle. Once the spackle dries, you can sand the area and paint over it—just like you would in the steps outlined above.

Yes, any parts of drywall that are wet or overly moist will need to be replaced. Drywall is intended to be dry (it’s in the name, after all.), as excess moisture can lead to mold and mildew and eventually corrode your home’s foundational building pieces. Do regular inspections in your home to make sure all your plumbing is intact and in good condition—this will go a long way toward preventing leaks.