The proper method to repair these cracks in the plaster is not unlike finishing drywall seams. Some people recommend widening the crack and then filling it with compound.

Plaster is also prone to thinner spider-web cracks, which occur when the topcoat of the plaster degrades. It’s common to have both kinds of cracking — and both types can be repaired.

Patching up holes or cracks in plaster is one of those jobs that can often fall into a DIYers remit. But while it might seem ...