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.

Venetian plaster is a highly durable wall finish that becomes a rock-like substance once dried, making it last longer than most other wall finishes. Its lifespan can range from decades to centuries, potentially lasting a lifetime. Key factors influencing its longevity include the quality of the initial application, whether it's properly sealed against moisture, and how the wall is maintained and treated (e.g., how often it is touched or bumped). Due to its mineral content, it can also develop a patina over time.

If you already have plaster walls and ceilings, adding new plaster costs $2 to $10 per square foot. For an average-sized room, that would come out to $1,200 to $10,000. However, the cost to replace plaster with drywall is higher—running between $720 and $1,250 for a 10-by-8-foot wall or ceiling (not including drywall finishing).

Drywall can get wet and dry out without sustaining permanent damage, but only if the water damage is minor. If you have a small leak and are quick to correct the issue and set up blower fans and dehumidifiers, your drywall should dry out. If the leak is persistent, the drywall becomes totally waterlogged, or mold begins forming on the drywall, you should remove and replace it.