Wall cracks are normal in a newly built home. In Gauteng, soil conditions vary widely, so every house's foundation is designed differently (and built with expansion joints) to accommodate natural movement. Despite these precautions, settlement cracks commonly form in the first two to five years as your foundation settles under the weight of the building and responds to temperature changes, rain, and soil movement.
Most cracks are superficial and can be filled, sanded, and painted by the homeowner. Cosmopolitan Projects contractors repair visible cracks at your formal three-month retention inspection; after that, fixing cracks in walls becomes the homeowner's maintenance responsibility, with one exception for larger cracks reported early (see below). Report wide, horizontal, or concerning cracks to us urgently with photographs so we can evaluate them.
When you buy a newly built home, you can expect settlement cracks to form in the first two to five years. These cracks are entirely normal and typically result from external factors such as:
Your house is designed and built with expansion joints to make it more flexible and allow it to move. Over time, the foundation settles and fewer cracks appear.
As the homeowner, you are responsible for repairing cracked walls as part of your ongoing home maintenance.
Our contractors will repair cracks that are visible at your house's formal three-month retention inspection. This is an additional service we offer our clients. We do not assist with crack repairs after this inspection, with one exception:
Quality Control exception: if a large crack (wider than the edge of a R5 coin) appears within three years of key handover, our developer will inspect it and may repair it under our Quality Control process, provided it's reported to us with photographs.
Please get in touch with our client care team urgently and include photographs if you have unsightly or concerning cracks, so that we can evaluate them and carry out the necessary repairs, if applicable.
Have an urgent plumbing, electrical, or roof fault? You may be interested in our Home Repair and Emergencies Guide.
Expansion joints are built into specific walls to allow sections of your home to move independently. This accommodates the minor movement that happens as the house settles in its first few years, without compromising the structural integrity of the building. We also use sound construction techniques during the build to minimise the likelihood of hairline cracks forming in the plaster.
The National Home Builders Registration Council (NHBRC) grades crack severity using the following categories, based on crack width:
| Width | NHBRC Category | Classification | Typical outcome |
| Less than 1mm | 1 | Very slight | Normal decoration |
| 1–5mm | 2 | Minor | Normal decoration |
| 5–15mm | 3 | Moderate | Repair by replacing damaged masonry; may be serviceable damage covered by the NHBRC warranty |
| 15–25mm | 4 | Severe | Extensive repairs; may include distorted window/door frames, leaning walls, or gaps at cornices; may be serviceable damage covered by the NHBRC warranty |
| Over 25mm | 5 | Very severe | Significant rebuilding; stability damage, may be covered by the NHBRC warranty |
Categories 1 and 2 are cosmetic. Categories 3 and 4 are serviceable damage. Category 5 is stability damage. Categories 3 to 5 may be covered under your NHBRC warranty; see our NHBRC Warranty guide for full terms.
Non-structural cracks are typically not serious and can be easily repaired by following the seven steps at the end of this article.
Hairline cracks under one millimetre wide are classified by the NHBRC as "very slight" and require normal decoration only. Cracks between one and five millimetres are classified as "minor," also requiring normal decoration. Both are superficial cracks in the plaster rather than in the wall itself and can be filled and painted over. Most houses experience cracks in the walls at some point; it's a natural result of settlement. Newly plastered walls commonly develop hairline cracks as they dry out.
Because expansion joints are built into certain walls to allow movement between sections, cracks often form along them. This is expected and not a cause for concern.
Cornices are non-structural features that hide the junction where the ceiling meets the wall; they serve no purpose beyond aesthetic appeal, so cracks here are no cause for alarm. They're caused by the contraction and expansion of hot and cold air in your ceiling or roof as daily temperatures change. Because your ceiling is attached to your roof trusses, and your cornice is attached to both the ceiling board and the wall, cornice cracks are very common. They usually appear:
How to fix them: Cracks above and below the cornice can be filled with acrylic sealant, which eases future movement and (unlike silicone) can be painted over. Note that Polyfilla joints allow less movement than acrylic sealant for cracks at the cornice joints, fill with Polyfilla, sand lightly, and repaint.
Structural cracks are uncommon but more severe, and may require professional attention.
Vertical cracks are generally acceptable and less serious than horizontal cracks. They result from concrete shrinking as it cures. Wide vertical cracks (those exceeding three millimetres) may indicate significant settlement issues that require detailed inspection and evaluation.
Horizontal cracks can be a direct result of poor drainage or hydrostatic pressure. These are generally more serious and require professional inspection and repair immediately. If you notice a horizontal crack in any wall, contact Cosmopolitan Projects with photographs as soon as possible.
Staircase cracks occur due to differential settling of the foundation. If they appear only in the mortar joints between bricks or blocks, they are not serious and can be repaired by reapplying mortar or sealant.
Cracks in precast walls and staircases are common in prefabricated concrete, caused by drying and material shrinkage as the concrete cures. Do not be alarmed because the wall is not breaking. These are classified as superficial cracks, with no serious damage and no need to worry.
Conclusion: while some cracks may seem serious, many are cosmetic or easily repairable. Only wide or horizontal cracks typically signal structural concerns needing expert evaluation.
Cracks sometimes reappear in the same place after being repaired. While your new house settles on its foundation over the first few years, cracks will form where the building is most affected by fluctuating temperatures, soil conditions, and similar factors.
We repair cracks during the three-month retention work. If cracks reappear after this, outside of the Quality Control exception above, repairing them is your responsibility as the homeowner.
Watch:
What you need:
Use an interior filler for internal walls and an exterior filler for external walls.
Let's get started:
See House Alteration and Additions: Protecting Your NHBRC Warranty before making any home modifications.
Tip: Paint the wall from corner to corner to avoid visible colour differences.
Disclaimer: The recommendations given here are provided in good faith as a guide to the user. They imply no guarantee, as conditions of use and methods of application are beyond our control.
Send us photographs and we will evaluate it if you are unsure whether a crack is superficial or structural. Contact the Cosmo client care team to report a crack or ask a question about your new home.
Yes. Settlement cracks are entirely normal in a newly built home and typically appear within the first two to five years. They are caused by the foundation settling under the weight of the building and by expansion and contraction from temperature changes, rain, soil conditions, and earth movement.
The NHBRC grades cracks by width: less than 1mm is "very slight" (Category 1), 1–5mm is "minor" (Category 2), both requiring only normal decoration. 5–15mm is "moderate" (Category 3), 15–25mm is "severe" (Category 4), and over 25mm is "very severe" (Category 5). Categories 3 to 5 may be covered under your NHBRC warranty.
Cracks usually form during the first two to five years after your house is built. As the foundation settles over this period, fewer new cracks appear.
An expansion joint is a deliberate gap built into specific walls so that sections of the house can move independently. This accommodates minor movement during settlement without compromising the building's structural integrity.
Horizontal cracks, wide vertical cracks over three millimetres, and any crack over five millimetres wide should be inspected by a professional. Horizontal cracks in particular may indicate poor drainage or hydrostatic pressure and require immediate attention. If you are concerned about a crack in your Cosmopolitan Projects home, contact our client care team with photographs so we can evaluate it.
Hairline cracks in plaster (under 5mm), cracks along expansion joints, cornice cracks, precast wall cracks, and staircase cracks confined to mortar joints are all superficial. They can be filled, sanded, and painted without structural concern.
Contact our client care team through the contact page on our website and include clear photographs of the crack. We will evaluate the images and arrange the necessary repairs if applicable. Crack repairs are carried out as part of the three-month retention inspection; after that inspection, repairs are the homeowner's responsibility, except under the Quality Control exception for large cracks reported within three years of handover.
Our contractors repair cracks that are visible at your formal three-month retention inspection, as an additional service to our clients. After that inspection, crack repairs are generally the homeowner's responsibility, unless a large crack (wider than the edge of a R5 coin) appears within three years of handover, in which case it may be repaired under our Quality Control process.
Recurring cracks appear where the building is most affected by temperature fluctuation, soil conditions, and ongoing settlement. This is normal while the house settles, and repairing recurring cracks after the three-month retention work is the homeowner's responsibility.
Use an interior crack filler for internal walls and an exterior filler for external walls. Ready-mix filler or Polyfilla is the easiest option for most homeowners. Use acrylic sealant instead for cracks above or below a cornice; it allows movement and, unlike silicone, can be painted over.
Yes. Once the filler is dry and sanded smooth, apply a plaster primer followed by two coats of paint. Paint from corner to corner so there is no visible colour difference on the wall.
Looking for more guidance on what you can expect after buying your first house? See A Practical Cosmopolitan Projects Guide to Owning a Home.