Crack Size Guide: Measure It Right, Know What It Means, Fix It Fast

Found a crack in your garage wall or foundation? The first thing to ask yourself is: how big is it? A tiny hairline line might be harmless, but a wide gap can signal serious trouble. Knowing the exact size helps you decide whether a DIY patch will do or if you need a professional repair crew.

How to Measure a Crack Accurately

Grab a ruler or a flexible tape measure and place it directly over the crack. If the crack is uneven, measure the widest point. Write down the width in millimetres – most people forget that a 0.5 mm hairline is normal settlement, while anything above 3 mm usually needs attention. For length, stretch the tape from one end to the other; long horizontal cracks are a red flag for foundation movement.

What Different Sizes Tell You

0‑2 mm: These are typically surface cracks caused by minor shrinkage. They often seal themselves as the structure settles. 2‑5 mm: Watch these closely. They can be early signs of moisture intrusion or slight shifting. Seal them quickly to prevent water damage. 5 mm and above: This is where the alarm bells ring. Such cracks often mean serious structural stress, water pressure issues, or even soil movement. Ignoring them can lead to expensive foundation repairs.

If you spot a crack wider than 5 mm, take photos, note the date, and contact a specialist. Many garage door installers also offer foundation checks because a compromised base can affect door alignment and operation.

Repair costs vary with size. A simple epoxy seal for a 1‑mm crack might be under £100, while fixing a 10‑mm structural crack can run into the thousands, especially if underpinning is required. Getting multiple quotes helps you avoid overpaying.

In short, measuring crack size is the quickest way to gauge the seriousness of the problem. Use a ruler, note width and length, and match the size to the appropriate action – DIY seal, professional patch, or full structural repair. With the right info, you’ll keep your garage door working smoothly and protect your home’s stability.