Can humidity cause plaster to crack?

Author: Prof. Roberto Bartoletti  |  Last update: Tuesday, April 1, 2025

Cracks in plaster can be caused by many factors, and these scenarios are specific to the conditions of your home and your location. Temperatures, relative humidity, soil conditions, structural components, and even the attention to detail when the house was being built or remodeled can contribute to cracks in plaster.

Can moisture cause plaster to crack?

If your home has walls that are plastered, then straight vertical cracks typically form when the plaster expands in humidity and shrinks as it dries.

Does humidity affect plaster?

These elements can speed up or slow down the process, affecting your home renovation timeline. Humidity: High moisture in the air slows evaporation. This makes plaster take longer to dry. Temperature: Warmer air helps plaster dry faster.

Can high humidity cause cracks in walls?

Drywall's sensitivity to moisture can also lead to joint cracking. During periods of high humidity, drywall absorbs vapor from the surrounding air and expands. Once the humidity decreases, the drywall dries and shrinks.

Why does my plaster wall keep cracking?

There are several reasons why this happens. Cracks can be the result of thermal movement, the settling of a foundation or sill work, or even exposure to moisture for an extended period of time. The extent of the crack can also vary across different plastering types.

Say Goodbye to Rising Damp - A Simple Solution!

Why are my walls suddenly cracking?

Temperature Fluctuations – Changes in temperature and humidity levels can cause materials like drywall to expand and contract. Over time, this repeated movement can result in cracks, especially in areas with extreme temperature variations or homes left vacant for multiple months without temperature regulation.

How do you permanently repair cracks in plaster?

In nine simple steps, you can repair plaster cracks.
  1. Score the Crack. It's best to start by scoring the crack with a Stanley knife. ...
  2. Prepare the Drywall Tape. ...
  3. Mix the Joint Compound. ...
  4. Spread the Joint Compound on the Crack. ...
  5. Position the Drywall Tape. ...
  6. Sand the Area. ...
  7. Vacuum the Area. ...
  8. Repairing the Corners of Plaster Walls.

Does plaster crack more than drywall?

More likely to crack: Plaster cracks faster than drywall after settling due to its brittle nature.

Can humidity damage walls?

Dampness causes multiple problems in the house like leakages, paint peeling, cracks, etc. If it is not dealt with properly, the moulds and fungus that form it can result in a negative impact on your health. Dampness can also cause damage to the structure of your house. This is why it's important to prevent it.

Does crack in wall mean mold?

If your wall cracks have water trails or moisture around them, then it likely means that you have some leaks in your home. These will most often show up in your basement or crawl space. Not only will those cracks get bigger over time, but they can lead to other issues, such as mold or decreased energy efficiency.

Can mold grow behind plaster?

Yes, mold can grow on plaster. Just like other types of building materials, plaster that has been painted, is dirty, or has been damaged is prime for mold growth. If you find mold growth on your plaster walls, what can you do about it? Read on to learn about mold remediation and prevention for plaster walls.

Will a dehumidifier help dry plaster?

You have to be really careful before introducing a dehumidifier to your newly plastered home. Take out too much humidity, and the plaster will dry too quickly, causing hairline cracks and brittleness over time. Plaster needs a humidity of around 60-70% to dry properly, while still staying hydrated enough to dry evenly.

How do you protect plaster from moisture?

Once the surface is prepared, a damp-proofing agent or primer is applied. This agent acts as a sealant and improves the bond between the wall and the plaster or render. It helps to prevent moisture from seeping through the walls and ensures the longevity of the damp proofing system.

Should I be worried about hairline cracks in plaster?

Hairline cracks are usually not a major concern and can be fixed with simple solutions like patching and repainting. However, if the cracks are large, deep, or widespread, it might indicate more significant issues that require professional assessment and repair.

How to tell if plaster needs replacing?

The first step in determining if your plaster needs replacing is to look for signs of deterioration. Some common indicators include cracks, bulging or sagging walls, and water damage. These issues can stem from a variety of factors, such as moisture, settling foundations, or simply old age.

How to fix cracked walls permanently?

How to fix cracks in walls ?
  1. Buy a joint compound that can either be premixed or 'setting-type'
  2. Cut a V-notch along the cracks you want to fix.
  3. Clean the area around the crack to remove debris or dust.
  4. Apply a thin layer of joint compound to the crack and spread it evenly.

Does humidity cause cracks in walls?

Settling: As a house settles into its foundation, slight shifts can lead to minor cracks in the drywall or plaster. Temperature changes: Seasonal temperature variations cause building materials to expand and contract. Humidity changes: Changes in humidity levels can cause drywall or plaster to contract or expand.

How to fix humidity on walls?

II. Removing Moisture from Walls: Effective Solutions
  1. Fix Any Leaks: Start by inspecting your home for any leaks in plumbing fixtures, roofs, windows, or doors. ...
  2. Improve Ventilation: ...
  3. Use a Dehumidifier: ...
  4. Remove Mold and Mildew: ...
  5. Replace Damaged Materials:

At what humidity does mold grow on walls?

Relative humidity greater than 60 percent is likely to result in condensation in the building, which can lead to mold growth.

Why do my plaster walls keep cracking?

Cracks in plaster can occur as the plaster dries and shrinks and can grow over time due to fluctuations in conditions. Plaster cracks can be caused by non-structural, structural, debonding, chemical reactions, thickness, and damage due to dampness, plastic shrinkage, and dry shrinkage.

Can you drywall over cracked plaster?

Yes, because as long as you can screw the drywall sheets securely to wall studs, you can hang drywall over almost anything.

How much does plaster repair cost?

Plaster is one of the most beautiful ways to finish a wall, but plaster wall repair costs can be high if there is any damage. Most repairs are priced per square foot, with an average plaster repair cost of $48 per square foot. Total costs average at $3,840 but range between $1,500 and $9,000.

Can you just paint over cracks in plaster?

Yes, But Take These Steps First. You can paint over plaster as long as it is in good condition. Prep plaster walls before painting by removing old paint, repairing damage, sanding, and priming. Identify and address the root cause of damaged plaster before you repair and paint it.

What is the best filler for cracked plaster?

However, a plaster filler like Polyfilla or a powder filler are probably the best options for filling plaster cracks, as alternatives such as caulk are best used for other purposes, like sealing gaps around pipes or tiles.

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