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.

You’ll get better results if you soundproof the whole wall. A hole through which light can pass can also let sound waves in. Acoustical or silicone sealant applied to holes and cracks can block enough sound to make a difference. However, the more layers absorb vibrations and slow or stop sound waves, the less noise you’ll have. 

According to the EPA, mold grows within 24 to 48 hours if left untreated after a water leak. So unless you notice the leak and stop it right away, you only have a day or so before mold is a real concern. If you don’t notice the leak, it can take about three weeks for the mold spores to become visible. That means you’ve likely had an active mold infection for a few weeks by the time you notice discoloration.

Drywall insulation costs around $1,800, on average, but prices can range from $500 to $4,500, depending on a few different factors. The following things are important considerations to make when pricing out your insulation project:

• Square footage of insulation

• Type of insulation 

• Climate in your area and the insulation R-value required

• Whether or not your walls are already finished

• Accessibility of the area 

• Whether or not you need old insulation removed first