Wall cracks and expansion joints


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. External factors like expansion and contraction caused by extreme or fluctuating temperature, rain, soil conditions, earth movement, and the sheer weight of the building will cause your foundation to settle or move, which in turn causes small cracks known as settlement cracks.

Your house is designed and built with expansion joints to make it more flexible and allow it to move. After some time, the foundation will settle, and fewer cracks will appear. As the owner, you are responsible for fixing these cracks as part of your home maintenance.

Our contractors will only repair cracks visible when they do your house’s formal three-month retention inspection. This is an extra service that we offer our clients. However, we do not assist further with crack repairs after this inspection.

If you have unsightly or concerning cracks, please report them to us urgently with pictures so that we can evaluate the cracks and make the necessary repairs, if applicable.

What are expansion joints?

Expansion joints are built into specific walls to ensure that sections of your home can move independently to accommodate these minor movements that happen as the house settles in the first few years without compromising its structural integrity.

What type of cracks are there?

Hairline cracks

Hairline cracks between one and five millimetres wide are not a cause for concern. They can be filled and painted over because they are only superficial cracks in the plaster, not the wall itself. Most houses will experience cracks in the walls at some point. For most homes, it’s a natural occurrence caused by settlement. Newly plastered walls can often get hairline cracks as they dry out.

Cornice cracks

These tiny cracks may appear on the cornices and are no cause for alarm. Due to daily temperature changes, they are caused by the contraction and expansion of hot and cold air in your ceiling or roof. These cracks are usually visible above the cornice (between your ceiling and the cornice), below the cornice (between the cornice and the wall), or where the cornice joints are. As the ceiling is attached to your roof trusses and your cornice is attached to your ceiling board and the wall, it is very common to see this. Cracks appearing below and above the cornice can be filled with clear silicone (to ease future movement) and painted if necessary. Where there are cracks in the cornice joints, you can use Polyfilla to fill it, sand it down slightly, and repaint it.

Structural cracks

Structural cracks fall within categories three to five in the NHBRC Home Building Manual. These cracks can be horizontal, vertical, diagonal, or look like steps. Cracks that are between five and 15 millimetres wide are considered moderate cracks. Cracks that are 15 to 20 millimetres wide are considered severe cracks. Cracks greater than 25 millimetres are considered very severe cracks.

Vertical cracks

Vertical cracks are acceptable and are generally not as severe as horizontal cracks. These cracks are a result of the concrete shrinking as it cures. Wide vertical cracks (exceeding three millimetres in width) may be caused by significant settlement issues that require detailed inspection and evaluation.

Horizontal cracks

Horizontal cracks can be the direct result of poor drainage or hydrostatic pressure. These cracks are generally more serious and require professional and immediate inspection and repair.

Staircase cracks

Staircase cracks occur due to the differential settling of the foundation. If they are only in the mortar joints between the bricks or blocks, the cracks are not serious and can be repaired by simply reapplying the mortar.

Precast wall cracks

Please do not be alarmed if you notice cracks in your precast wall. The wall is not breaking; this is typical of any prefabricated concrete item. Concrete is mixed with different building materials, including water. When concrete starts to dry, the water evaporates, creating what you see here. These cracks are classified as superficial cracks. There is no serious damage, so there is no need to worry.

Recurring cracks

Sometimes cracks will reappear in the same place after they have been repaired. While your new house settles on its foundation in the first few years, cracks will appear where the building is most affected by fluctuating temperatures causing expansion and contraction, soil conditions, etc.

While we repair cracks when we do the three-month retention work (three months after you moved into your house), if the cracks should reappear after this, it is your responsibility as the homeowner to repair them.

How to fix a crack in seven easy steps

What you need:

  • Putty knife or trowel
  • A soft brush
  • A sponge
  • Interior crack filler / ready mix
  • Fine sandpaper – 100 grit
  • A crack opener tool
  • A small bucket
  • Paintbrush, primer, and paint

When using a crack filler, please make sure that you use an “Interior” filler for internal walls and an “Exterior” filler for external walls.

Let’s get started:

  1. Identify the crack and open it with a crack opener tool.
  2. Clean the crack with a brush.
  3. Wipe the wall surface with a wet sponge.
  4. Mix the crack filler with water until you have a soft, putty-like paste. Always refer to the instructions of the product that you use. You can buy a ready-mix crack filler / Polyfilla to make it even easier.
  5. Use a putty knife or trowel to apply the crack filler to the wall’s surface. Fill it slightly above the level of the wall.
  6. Once the filler is dry, use fine sandpaper or a sponge to smooth the surface.
  7. Paint the surface with a plaster primer. After that, apply two coats of paint.
  8. Remember to paint the wall from corner to corner to ensure no colour differences.


The recommendations herein are given in good faith and are meant to guide the user. The recommendations imply no guarantee since the conditions of use and method of application are beyond our control.