It can cost as little as $20 per square foot to repair small cracks in plaster. For more extensive cracks and those over 1/4-inch wide, expect to pay around $120 per square foot.
Yes, crumbling plaster on a ceiling or high up on a wall is potentially dangerous as large chunks of heavy material can fall and cause serious injury if they hit a person or animal. Plus, if the plaster contains asbestos, which was a common plaster additive until the mid-1980s, or lead from old layers of paint, it carries a significant health risk. “Asbestos in plaster becomes a health risk once airborne, such as when crumbling plaster is agitated,” says Ezra Laniado, Expert Home Building and Remodeling Contributor.
If you don't know the age or content of your plaster, it's always worth getting a home inspection. A lead-based paint inspection typically costs $600 while an asbestos inspection costs around $500. For peace of mind and the safety of your family, these inspections are well worth the cost, as they highlight problems like the presence of lead and asbestos before the plaster crumbles and causes health issues so that you can take early action.
With proper maintenance, plaster can last over 100 years if not exposed to high humidity or water damage.