Wall Cracks Explained: What Causes Them and How to Fix Them
Understanding the causes of wall cracks and how to fix them can help homeowners protect their property and maintain its value.
05/06/2025
Wall cracks are a common issue in homes and buildings, often triggering concerns about structural stability and long-term damage.
While some cracks are harmless and cosmetic, others may indicate deeper problems that require professional attention. Understanding the causes of wall cracks and how to fix them can help homeowners protect their property and maintain its value.
Common Causes of Wall Cracks
Wall cracks can result from a variety of factors, ranging from natural settlement to environmental conditions. One of the most frequent causes is foundation movement.
As a building settles over time, slight shifts in the foundation can lead to hairline cracks in walls, especially around doors and windows. While minor settlement is normal, major or uneven settling may point to a structural issue that might need to be addressed alongside wall crack repairs.
Another major contributor is moisture. Water damage from leaking pipes, poor drainage or rising damp can weaken plaster, drywall or brickwork, leading to visible cracks. Moisture can also cause expansion and contraction of building materials, exacerbating existing fissures.
Temperature changes also play a role. As materials like concrete and plaster expand and contract with heat and cold, stress can build up and result in cracking. This is especially common in exterior walls or areas exposed to direct sunlight.
Poor construction practices, such as using inferior materials, skipping control joints, or applying finishes too quickly can also cause cracks to develop over time. In multi-story homes or older buildings, natural aging and wear and tear are additional causes.
Types of Cracks and What They Mean
Not all wall cracks are created equal. Hairline cracks that appear in paint or plaster are usually cosmetic and can be easily repaired with filler and a fresh coat of paint.
Vertical cracks, especially those that are narrow and run straight, often result from foundation settling and are usually not serious if they don’t widen.
However, horizontal or stair-step cracks in brick or concrete block walls can be a sign of significant structural movement. These types of cracks often require professional assessment.
Wide or growing cracks, especially those wider than 5mm, may indicate serious foundation or structural issues.
How to Fix Wall Cracks
Wall crack repairs start with identifying the underlying cause. Cosmetic cracks can often be handled as a DIY project. Clean the crack, apply filler or patching compound, sand it down once dry, and repaint the surface.
For cracks caused by moisture, it’s essential to first resolve the water issue. This might involve fixing leaking pipes, improving drainage, or installing a damp-proof course. Only after addressing the source should you repair the affected wall.
Structural cracks require a more cautious approach. If you're unsure about the severity of a crack, consult a professional. In some cases, appointing a structural engineer and/or geotechnical engineer may become necessary, depending on the severity of the damage.
Prevention is Vital
Preventing wall cracks involves maintaining good drainage around the home, keeping gutters clean, ensuring the soil around the foundation is stable and inspecting the property regularly for signs of movement or moisture.
By understanding what causes wall cracks and how to address them, homeowners can prevent minor issues from becoming major repairs, safeguarding both the aesthetics and the integrity of their property.