Most concrete driveways develop a few hairline cracks, and on their own that's normal shrinkage as the slab cures, not a defect.

Cracks that are wide, run at an angle across the slab, or show one side sitting higher than the other usually mean the ground underneath has moved, and that's far more common in Auckland because much of the region sits on reactive clay.

What causes cracking, at a glance

Slab Lab project site with new white buildings and a prepared gravel base

Reactive clay

Auckland's clay swells when wet and shrinks when dry. A slab sitting on top of that movement flexes with it, and enough cycles will eventually crack even a well-poured slab.

Normal vs a problem

Fine, hairline cracks along a control joint are cosmetic shrinkage. Wide, diagonal or stepped cracks point to settlement or movement in the base.

Control joints

Joints are cut every 3 to 4 metres so shrinkage cracking happens along a straight, deliberate line instead of at random.

Base prep matters most

Enough compacted hardfill, correct compaction and steel mesh reinforcing all reduce how much a slab moves with the clay underneath.

Drainage

Good falls keep water from pooling and saturating the clay directly under the slab edges, one of the most common causes of localised settlement.

Slab Lab project site with new white buildings and a prepared gravel base

What proper base prep prevents

The base underneath the concrete matters more than the concrete itself when it comes to clay-related cracking. That means enough compacted hardfill depth, correct compaction, and steel mesh reinforcing to hold the slab together if minor movement does occur.

Freshly poured concrete driveway at a modern two-storey Auckland home

Already have a cracked driveway?

Not every crack means a full replacement. We assess whether a crack is cosmetic shrinkage or a sign of base movement, and repair or resurface where that's the right fix.

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FAQ

Why does my concrete driveway have cracks?

Fine, straight hairline cracks are normal shrinkage from the concrete curing and aren't a defect on their own. Wider or stepped cracks usually mean the ground underneath has moved, which is common on Auckland's reactive clay soil.

Is cracking in a concrete driveway normal?

Some hairline cracking is normal and expected, especially near control joints. It only becomes a problem when cracks are wide, run diagonally, or show a visible step between the two sides, which points to base movement rather than simple shrinkage.

Why is clay soil a problem for driveways in Auckland?

Auckland's clay is reactive, meaning it swells when wet and shrinks when dry. A slab sitting on clay that hasn't been properly prepared with enough hardfill, compaction and drainage will flex with that movement over time, and repeated cycles eventually cause cracking.

How far apart should control joints be on a driveway?

Control joints are typically spaced every 3 to 4 metres on a residential driveway. They give shrinkage cracking a deliberate, straight line to follow instead of letting it appear randomly across the slab.

Can a cracked concrete driveway be repaired instead of replaced?

Often, yes. Cosmetic shrinkage cracks and many localised base issues can be repaired or resurfaced rather than requiring a full repour. We assess the cause of the cracking first, since the right fix depends on whether it's surface-level or ongoing ground movement.

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Customer reviews

“Zak and Shane were awesome. Everything was done professionally, on time and they stick to their quote. Easily one of the best experience I’ve had with tradespeople. I wouldn’t hesitate to call them for another job - and very happy to vouch for their work.”

Francis L

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“Used Slab Lab for a driveway at my business in Kumeu west Auckland. 5* service and fantastic finished job. Had this company referred by a friend and must say they lived up-to their promises. Great communication start to finish. Would 100% use them again.”

Elliot C.

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“Zak and Shane did amazing and expectional job on my driveway concrete. Highly recommended and high quality workmanship. On time and friendly team. Good job SlabLab. 5 stars.”

Jason T.

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“If you need a concrete driveway look no further!! I highly recommend. From my initial enquiry right through to completing our driveway, Zak and the team were very professional and proficient. Communication was on point, pricing was very competitive, and most importantly, they did a great job. A++”

Danny R.

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“We needed the concrete path of our rental dug up and replaced and we found the guys did a great job and at a great price. Will be recommending them to our friends and family.”

Kim M.

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