Foundation Cracks – What’s Normal, When to Worry and How to Fix

If you’ve spotted a line in your walls or floor, your first thought is probably: ‘Is my house falling apart?’ The truth is, not every crack signals disaster. Most homes develop a few hairline cracks as they settle, especially after a new build. The key is to know which cracks are harmless and which need a professional’s eye.

Typical Causes of Foundation Cracks

There are three big reasons you’ll see cracks appear:

1. Settlement – When a new house is built, the soil underneath compacts over time. This shifting can pull the concrete or brick just enough to leave a thin line. These cracks are usually vertical and less than a millimetre wide. They often stop growing after a few months.

2. Moisture changes – Wet soil expands, dry soil shrinks. If the ground around your foundation gets too wet or too dry, the concrete can move and crack. Look for cracks that follow the mortar joints or appear near doors and windows.

3. Structural stress – Heavy loads, poor construction, or nearby excavation can put extra pressure on the foundation. Cracks from stress are typically wider, jagged, or step‑shaped. They may also appear horizontally, which is a red flag.

When to Call a Professional

Spotting a crack is easy, deciding what to do with it is trickier. Here’s a quick checklist:

• If the crack is wider than 3 mm (about a pencil line), call a surveyor.
• Horizontal or stair‑step cracks in brick walls often mean the wall is pushing out – get an engineer.
• Cracks that keep getting bigger, even after a few weeks, need a pro.
• Any new crack that appears after a heavy rain, earthquake, or construction nearby should be checked.
• If you see doors or windows sticking, it could be a sign the frame is moving.

When you contact a professional, be ready to share photos, the location of each crack, and when you first noticed them. This helps them focus on the right areas.

In many cases, a simple repair will stop the problem. Common fixes include:

• Injecting epoxy or polyurethane into the crack to seal it.
• Adding a “cavity wall tie” to pull loose bricks back together.
• Improving drainage around the house – like installing gutter extensions or a French drain.
• Using a pier or slab under‑pin to lift settling foundations.

Most of these jobs need a licensed tradesperson, especially when you’re dealing with load‑bearing walls.

Bottom line: a few tiny hairline cracks are normal, but bigger, spreading, or oddly shaped cracks are not. Keep an eye on them, take notes, and don’t wait too long to get a professional opinion. Early action can save you a lot of money and keep your home safe.