It’s not a good idea to plaster over broken plaster (unless by broken you’re referring to cracked, in which case that’s perfectly fine). However, broken plaster can be a sign of a larger underlying issue like foundation damage or severe damage to the lath holding up the plaster, so it’s worth investigating before you simply plaster on top of the damage.

All plaster walls will crack over time due to normal house settling and expansion and contraction from temperature and moisture changes. Small, thin hairline cracks are generally not serious and are mostly a cosmetic issue. However, larger or more significant cracks can indicate structural problems.

Here's how to tell the difference:

• Cosmetic Cracks: Cracks that are 0.5 cm (0.2 inches) or thinner are typically cosmetic.

• Structural Cracks: Cracks wider than 0.5 cm, excessive or deep cracks, multiple cracks in the same area, or cracks that span around corners can signify a structural or foundation issue. Cracks along the joints where walls meet the ceiling also warrant attention.

For cracks wider than 0.5 cm, structural repair is needed. If a crack is 2.5 cm (1 inch) or wider, or if you notice any signs of a structural problem, it is best to contact a plaster repair professional to assess the damage.

Although they are used for similar tasks, spackle and joint compound are not the same. Joint compound, also known as drywall mud, consists of limestone and gypsum and is primarily used for large-scale projects like taping and finishing seams on new drywall. Spackle is composed of gypsum and binding agents, making it a thicker compound best suited for small wall repairs like filling nail holes or cracks, as it dries quickly and is easy to sand. For small repairs, either product can be suitable. However, you can use joint compound for small jobs in place of spackle, but you cannot use spackle for large-scale taping and mudding projects.

You should start looking for a drywall installer by choosing a local company with positive online reviews and ratings with the Better Business Bureau (BBB). Next, confirm that the professional is properly licensed using Angi’s contractor licensing tool, and ask the installer if they are fully insured. It’s a good idea to ask for recent customer references and call them to get their honest opinion about the contractor and their work. You can also ask the installer if they guarantee their work or provide a workmanship warranty.