Why Does Concrete Flooring Crack When It Dries?

If you’ve just had new concrete flooring installed in your factory, warehouse or retail unit, you may have noticed a few cracks forming across the surface. Why does this happen? Is your concrete floor compromised? And can it be prevented? Our concrete flooring experts go the extra mile to reduce cracking risks from the start — using the right materials, mixes and methods for your specific site conditions.

Why does concrete crack when drying?

Concrete (and cement) tends to shrink slightly as it cures and hardens. This shrinkage creates tension in the slab, and if the tension exceeds the concrete's strength, it cracks.

Often, this leads to hairline cracks, especially in the first few days after installation. While certain mixes include shrinkage-reducing additives, it’s not possible to eliminate all cracking completely. These cracks are usually superficial and do not affect the structural integrity of the floor.

What causes concrete flooring to crack?

Aside from natural shrinkage, other factors can lead to increased risk of cracking:

• High temperatures or wind: These speed up moisture evaporation, which interrupts the chemical curing process and weakens the surface.
• Incorrect mix ratios: If the concrete is too wet or dry, it may dry unevenly or too quickly.
• Overworking during finishing: Disturbing the surface too much can weaken the top layer, making it more vulnerable to cracks.
• Poor sub-base preparation: If the base shifts or settles, it can cause flexing or cracking in the slab.

If you're wondering why is my concrete cracking, these are the most likely reasons — especially early on in the drying phase.

Are cracks in concrete floors always a problem?

In most cases, small cracks caused by shrinkage or drying are cosmetic and not structural. However, deeper or wider cracks, or cracks that appear later under traffic, could point to poor installation, an inadequate mix, or sub-base movement. If left unaddressed, cracks can worsen over time, allowing moisture in or weakening the slab.

How do we stop concrete cracking when drying?

With over 40 years of experience in the concrete flooring industry, we use a range of techniques to minimise cracking risk from the start:

• We work with trusted concrete suppliers to ensure the right mix for your specific needs and environment.
• We follow best practices for curing — using curing agents or covers to prevent rapid moisture loss in hot conditions.
• We install control joints in the slab, which help manage where cracks appear and relieve tension safely.
• We ensure sub-bases are compacted and stable to avoid slab movement post-installation.

Cracks from shrinkage may never be completely avoidable, but with expert planning and execution, they can be significantly reduced. Our team combines high-quality materials, professional installers, and advanced machinery to ensure your concrete flooring is strong, stable, and built to last.

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We are the leading concrete flooring contractors in the UK, offering outstanding concrete finishing results with every project. For more information about our services, contact our team today on 01590 676 585.