Why Do Cracks Appear in House Walls and Can They Be Repaired?

Why Do Cracks Appear in House Walls and Can They Be Repaired?

Finding cracks in the walls of a home you’re looking to purchase can be concerning. However, most wall cracks are harmless and can be easily repaired. This article from Inner West Property Inspections in Sydney will examine the common causes of cracks in house walls and explain how they can be fixed.

What Causes Cracks in Walls?

There are several typical reasons why cracks form in walls:

Settling – All houses experience minor settling and shifting over time as the soil underneath naturally compacts. This can cause small cracks along wall joints, ceilings, and around door and window frames. Settlement cracks are usually diagonal or stair-step shaped.

Drying and Curing – Concrete, stucco, plaster, and mortar need time to fully dry and cure when first applied. As they shrink during this process, they can crack. These types of cracks are often small and horizontal.

Temperature Changes – As seasons and temperatures fluctuate, materials like wood and masonry expand and contract. This puts stress on walls and can cause cracks at seams or corners. Heat also accelerates drying and curing, leading to more shrinkage cracks.

Poor Construction – Unsatisfactory wall framing, inadequate expansion joints, poor drainage, and weak or missing foundations can all trigger cracks in walls. These types of cracks tend to reappear even after repairs.

Vibration – Ground vibrations from heavy traffic, nearby construction, earthquakes, and even loud music can jostle walls and make them crack. The cracks are often jagged and centered around windows or doors.

Leaks and Moisture – Plumbing leaks, rainwater infiltration, and high humidity can cause swelling, erosion, and deterioration of wall materials. Cracks form as the sodden walls shift or crumble. Discolored staining around cracks is a telltale sign of moisture issues.

Not all wall cracks indicate serious problems. Many are simple cosmetic flaws related to normal shrinkage and settling. However, large, rapidly spreading, or recurring cracks do warrant further evaluation. Contacting a professional building inspector is advisable if you have any doubts about crack severity.

How to Repair Common House Wall Cracks

Here are some general guidelines for fixing typical minor wall cracks:

  1. Prepare the crack – Use a utility knife to open or widen hairline cracks. Clean away old paint and debris with a wire brush. Vacuum out any dust.
  2. Apply patching compound – For narrow cracks, use lightweight spackle. For wider cracks, apply joint compound. Press firmly into the crack with a putty knife.
  3. Smooth the surface – Once dry, sand the area smooth and wipe clean. Apply a second coat if needed to feather the edges.
  4. Prime and paint – When smooth, prime repaired cracks before painting over them with finish paint. This helps blend patched areas.
  5. Monitor – Keep an eye on repaired cracks to make sure they don’t reopen. If so, the underlying cause needs to be determined.

Here are some tips for specific crack locations:

  • Ceiling cracks – Apply painter’s tape along each side to keep patching material off sound surfaces.
  • Corner cracks – Use a thin flexible patch to prevent re-cracking when walls shift. Avoid rigid dried compound.
  • Masonry cracks – Seal with caulk or hydraulic cement. Wider cracks may need brick repointing or stucco patching.
  • Timber cracks – Epoxy wood fillers work well for minor surface cracks. Larger cracks may require carpentry repairs.

When to Call a Professional

Contact a qualified contractor or a structural engineer if you encounter any of the following:

  • Cracks wider than 5-6mm
  • Deep cracks exposing the wall or ceiling substrate
  • Cracks accompanied by bulges, sags, or wall leaning
  • Signs of serious structural issues like foundation cracking
  • Major moisture damage or leaks related to cracking
  • Recurring cracks that reopen rapidly after patching
  • Any cracks you are unsure how to properly repair

While most common wall cracks are cosmetic, cracks can also indicate more serious problems in some cases. Having an experienced home inspector evaluate concerning cracks is wise. They can assess the origin and severity and recommend appropriate repairs. This ensures your peace of mind about the structural integrity of your property.

Inner West Property Inspections has over 7 years of experience inspecting Sydney homes. Our experts can quickly diagnose cracks and explain the necessary fixes to protect your investment. Don’t risk buying a property with underlying defects – contact us today to book an inspection.