Cracks in your brick walls: when to worry and who to call

If you own a brick home in the Sutherland Shire, Wollongong or Kiama, chances are you have seen a crack or two over the years. Some are harmless. Others are a sign that your house needs structural help. So how do you know the difference?

In this guide we walk through common types of cracks in brick walls, when to worry, and what a remedial builder like MJ Reilly can do to fix them.

Hairline vs serious cracks

Small hairline cracks in plaster or mortar can be quite normal as your home settles. These are often easy to fill and paint.

You should pay closer attention when you see:

  • Cracks wider than 5 mm

  • Cracks that run through bricks, not just the mortar

  • Stepped cracks that follow the brick pattern

  • Cracks above windows and doors

  • Cracks that appear quickly after heavy rain or movement

These can point to structural movement, failing lintels, or issues with footing and drainage.

Why do brick walls crack?

In our work across South Sydney and the Illawarra, we see a few common causes:

  • Rusted steel lintels above windows and doors

  • Ground movement or poor soil conditions

  • Long term water entry into brickwork and cavities

  • Ageing materials in older homes

  • Extra loads added over time, like new openings or extensions

A proper inspection is important so you are not just patching over a deeper problem.

How we repair cracked brick walls

At MJ Reilly Constructions we focus on long term repair, not quick cover ups. Depending on the cause, we may recommend:

  • Crack stitching and repointing for localised cracks

  • Lintel replacement where the steel above openings has rusted and expanded

  • Brick replacement where bricks are damaged or spalled

  • Cavity flashing and drainage improvements to keep water away from the structure