Question 1

Are cracks in plaster walls serious?

Accepted Answer

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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.

Question 2

How do I know if I have plaster walls?

Accepted Answer

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If your home was built before the 1940s and was not remodeled in the past 50 or so years, you probably have plaster walls. Aside from assuming, there are some practical ways to tell if you have plaster walls, including the following: If you knock on the wall and it feels solid, not hollow, if you can’t insert a thumbtack easily, if there are cracks that look like spiderwebs, or if your home has curved, arched, or swirled walls, doorways, or window openings.

If you have an unfinished basement or attic, you could examine the backs of any finished walls to check, too.

Question 3

Can I use drywall primer on plasters?

Accepted Answer

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Technically speaking, you can use drywall primer over plasters. However, oil-based primers work the most effectively on wall plasters. Meanwhile, water-based primers work just as well with drywalls. Nowadays, there are also universal primers suitable for drywall and plaster. Overall, you will be fine as long as you are using a trustworthy brand.

Question 4

What are the disadvantages of using plaster?

Accepted Answer

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Plaster is a beautiful finish but is labor-intensive to install and remove. It’s vulnerable to cracking and more sensitive to moisture variance than drywall. Installing plaster on a new wall is an expensive process that can take days to weeks, depending on the scope. Removing a plaster wall can also be quite expensive and time-consuming.

Question 5

Can you install drywall over plaster?

Accepted Answer

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Yes, you can install drywall over plaster, but there are important factors to consider. While it can create a smooth, flat surface, it is often not the best approach. Installing drywall over plaster will increase the wall's thickness, which can cause issues with existing window and door frames that may no longer fit. You might also need to adjust power outlets to keep them accessible. A better, though more expensive, option is to remove the old plaster and lath entirely before installing new drywall. Drywalling directly over plaster seals in the old material, and if any problems arise later, you will need to remove both layers down to the structural beams for repairs. Given the potential complications, this job is best handled by professionals.