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Cosmetic or Critical? When to Worry About Wall Cracks

Cracks creeping up the walls of South African homes are becoming a common sight – and just as commonly, they’re being ignored. At first, many homeowners assume wall cracks are harmless, but what seems like a small surface flaw could be the first sign of something much more serious.

Wall cracks

It used to be routine: homeowners would splash out on a coat of paint for their homes every few years, often as a DIY job or with the help of a local handyman. The world has changed, and this kind of maintenance has become more difficult to keep up with.

  • Paint is more expensive, so people are stretching their surfaces as far and as long as possible.
  • To get the job done between busier-than-ever schedules, homeowners are forced to hire labour or DIY the project very slowly, in stages.
  • For paint guarantees to remain in effect, homeowners must hire skilled labour who are certified to apply the selected paint.

Over and above these issues of growing costs and lack of time, long-lasting guarantees on paint – 10 to 15 years in some cases – have lulled homeowners into a false sense of security. As a result, minor structural changes and surface issues, like wall cracks and bubbling, often go unnoticed until they escalate into far more costly repairs.

The danger lies in how insignificant a wall crack appears. They might not look like much, but even a hairline crack behaves like a thirsty sponge in a glass of water! In fact, studies show that cracks as narrow as 0.3 mm can increase water penetration by up to 1.7 times compared to uncracked masonry. Even small wall cracks act like capillaries, actively drawing water into plaster and brickwork. This moisture weakens the plaster, leaches cement, and can eventually cause entire sections of the wall to crumble.

4 types of wall cracks in South African homes

Whether you’ve just moved into your newly-built house, or you’ve long grown roots in the family home you love, spotting a new crack in the wall can be unsettling. Naturally, the first questions that come to mind are: what caused the crack, and is it critical or just cosmetic?

  • Settlement Cracks and Soil Movement

    You might not feel it happening, or want to think about it, but the ground beneath your home is always on the move. The soil constantly responds to changes in moisture, swelling when it’s wet and shrinking when it’s dry. With climate change, erratic weather patterns, and fluctuating water tables, a more unpredictable ground places pressure on building foundations. Although these underground shifts are minuscule, they’re enough to create fine settlement cracks.

  • Structural Cracks from Material Expansion

    South African homes often combine materials like brick, concrete, steel, and aluminium. These materials all react to temperature changes, but not in the same way. For example, bricks and concrete expand and contract slowly and predictably, while steel and aluminium react quickly – just think of the loud cracking sounds a metal carport makes when the sun comes out on a cool, cloudy day. Now imagine you have a metal beam connected to a brick wall, or aluminium window frames set into a plastered wall. On a sunny summer’s day, heat will cause the metal elements to expand faster than the surrounding brick and concrete. When the temperatures drop at night, the metals will contract far quicker, too. Over time, this repeated cycle of expanding and contracting weakens the slower-responding materials, like brick and plaster, causing visible cracks to appear.

  • Foundation-level Moisture and Rising Damp

    Your walls are more vulnerable to moisture at ground level, where your home rests on the earth. That’s why builders install a damp-proof course (DPC) on every home, which is a type of waterproofing. This thin water-resistant barrier lies horizontally between the foundation and the brickwork. Its sole purpose? To stop water in the ground from seeping upward through capillary action. (Remember the sponge we spoke about earlier? Same-same.) If the DPC installation fails or degrades over time, moisture will find its way into the walls. The water, which is rich in salt and minerals, ends up damaging the plaster and paint from the inside, and the results can be far more devastating than mere wall cracks. Here’s how to tell if your DPC might be compromised:

●  Blistering or peeling paint near the floor
●  Damp or discolouration along the lower parts of interior and exterior walls
●  Salty, powdery residue on the wall surface
●   A musty smell near the base of the wall
●  Visible cracks and deterioration when the plaster meets the ground
●   Facebrick appearing patchy or darker at ground level after rain
 
When these problems arise, it’s wise to call a professional waterproofing company to assess the scope of damage and recommend action as quickly as possible.

  • Top-down Water Ingress

    Rising damp gets a lot of attention, but water ingress from above is just as common. Flat surfaces like parapet walls, boundary walls, and windowsills are frequently affected because they’re more exposed to the elements. UV radiation from the sun degrades paint and waterproofing membranes faster on these surfaces. When rain arrives, water pools and starts to seep into vulnerable plaster, cracks or joints. Over time, this repeated cycle results in moisture ingress, where water is easily drawn into the structure, causing even deeper wall cracks and damage.

Make Home Maintenance A Habit Again

The lifecycle of an untreated wall crack follows a predictable path: water seeps in, plaster and cement are weakened, damp spreads, and structural materials begin to fail. Ironically, many homeowners jump to the conclusion that “the builder skimped on cement”, when in fact, the original construction was sound. It’s an uncomfortable truth that a lack of upkeep is the usual cause of structural deterioration.

South Africa’s National Building Regulations (SANS 10400) outline the standards for construction and moisture protection. Part K (Walls) and Part H (Foundations) address structural detailing, moisture ingress, and foundational movement. The NHBRC also requires a minimum five-year structural warranty on homes built by registered builders.

So, if your home was built by a professional construction company that followed all the right building protocols, what can you do to ensure wall cracks never become a critical issue?

> Inspect your home annually, especially after the rainy season.

> Pay special attention to joints, parapets, the base of walls, and previously patched areas

> Don’t delay wall crack repairs! Early patching and painting are far cheaper than future structural fixes.

For recurring cracks or damp issues, consult a professional – not everything can (or should) be solved with Polyfilla.

Wall Cracks? Prevention Is Better Than Cure

So, to answer our original question: many wall cracks are indeed cosmetic, but left unchecked, they’re almost guaranteed to become more critical over time. They’re often early warning signs that your home may be under stress from external elements. A little time spent on inspection and prevention today can save you a fortune in remedial work tomorrow.

If a wall crack is causing you concern, or you’ve spotted other structural anomalies in your house, get in touch with Jukka. We understand that your home doesn’t just need to look beautiful and feel comfortable – it needs to be structurally sound and built to last.

Related Articles: What are the Different Types of Waterproofing | When does Insurance Cover Water Damage?

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