What Causes Cracks And Plaster Repairs

Tenant Rescue
Jul 30, 2021
What Causes Cracks And Plaster Repairs

Helping tenants understand the cause of cracks in a home and why it would need plaster repair is important. This is so a tenant can understand how and why it is the landlord's responsibility to repair the cracks.

Let's look at some of the causes of damage to walls and plaster.

Plastic shrinkage cracking

This refers to the cracking that occurs within the first few hours after plaster application. Plastic Shrinkage Cracks occur due to the excessive loss of water.

Dry shrinkage cracks

Plaster loses moisture then shrinks when they harden, which also causes cracks. The common culprit here is very high cement content and poor quality sand used in cement mortar. 

Sand with high water requirements causes dry shrinkage cracks. Fortunately, these types of cracks are usually stable and can be filled with fillers and painted over.

Lack of hardness

When a builder uses the wrong ratios of cement, sand and water to make cement mortar, they may experience a lack of firmness within the mixture. Using poor quality water or adding more water after first mixing, can also cause the problem. This lack of hardness can lead to cracks developing in the future.


Have you ever seen mortar joints visible through the plaster? This is grinning, which is primarily caused by the suction capacity differences between the brick wall and the cement mortar. With time grinning will cause cracks within the plaster.


During plastering, the outside layer of plaster is exposed to the air causing it to shrink, at a different rate from the plaster in contact with the wall. This problem, which is primarily caused by a thick layer of plaster, causes debonding.  An easy way to tell if the plaster has debonded, is listening for a hollow sound when tapping walls. This debonding process also causes cracks.


Contaminant particles in the mortar mix react with the moisture and cause cavities in the plaster. This causes popping which is visible when conical fragments break out of the surface of plaster. This problem leaves holes of different sizes within the mixture however they can be filled and painted over.

Structural cracks

As time goes by, various movements of a building foundation, dry shrinkage of a brick wall, moisture expansion, thermal movement of the roof slab due to temperature changes, can all cause structural cracks.

These cracks can be seen in plaster forming a straight vertical or horizontal line. Others are in steeped diagonal lines.


Expansion occurs when gypsum-based products are used in a mix. The problem is visible through swelling, softening, layer cracking, and spalling of the plaster.

Gypsum products, specifically sulphate, under moist conditions, react with certain cement paste and form compounds of increased volume, causing cracks in the plaster.

Construction practices and landlords should have experts who know how to treat plaster to build houses, in order to prevent cracks that can be caused by poor construction.

Other causes of cracks in plaster include:

• Seasonal change

• Over trowelling a rich mix causing nonstructural cracks

• Differential movement of foundations

• Moisture expansion

• Drying shrinkage on masonry units

• Thermal movement of the roof

• Hardness or strength of plaster

• Chemical reaction

• Dampness

• Crushed or decayed internal structural timber

• Growth of tree roots into a building

• Unstable adjacent walls

• Poor integrity foundation

• Fractured masonry

• Lowering of groundwater

• Vibrations from road traffic and other constructions

Cracks on walls are the responsibility of the landlord as per The Landlord and Tenant Act 1985. The act states that the landlord should provide suitable housing conditions.

You should inform your landlord of any cracks or damaged plaster, in order for them to provide repair services.

Should the landlord neglect these poor housing conditions, it becomes housing disrepair meaning you are eligible to make a claim.

Our solicitors at Tenant Rescue offer reliable legal advice to help you understand what you can do to improve your living conditions as a tenant. We can also help you claim compensation if you are living in poor conditions due to the landlord's negligence and disrepairs.