Cracked Foundation? Quick Guide to Spotting, Measuring and Acting
If you notice a line cutting through your slab or wall, your first thought might be "just a hairline crack". But a crack can be a warning sign that the house is moving. Knowing what to look for, how to measure it, and when to get help can save you time, money, and stress.
What Crack Sizes Mean
Start by measuring the width. Grab a ruler or a simple feeler gauge – you don’t need fancy tools. A crack under 1 mm (about the thickness of a credit card) usually isn’t a structural problem. Anything thicker than 3 mm (the width of a pencil) deserves a closer look. Cracks that keep getting wider over weeks or months are a red flag.
Where the crack appears matters too. Horizontal cracks on walls, stair‑step patterns in brick, or cracks that run from the foundation up through multiple floors often point to movement. Vertical cracks are more common and can be caused by normal shrinkage, but if they’re wide and deep they still need attention.
When to Call a Structural Engineer
Don’t wait for the crack to double in size. If you see any of these signs, call a professional straight away: the crack is wider than 5 mm, it’s spreading quickly, there’s water seepage, doors and windows start sticking, or you hear loud creaking noises.
A structural engineer will assess the foundation, check for subsidence, and recommend repair methods. Their report is useful if you plan to sell the house, as buyers will ask for proof that the issue is under control.
While you wait for an expert, you can take simple steps to stop the problem getting worse. Keep the ground around the foundation dry, fix any gutter leaks, and avoid heavy loads near the footings. A dry, stable soil reduces pressure on the base of the house.
If the crack is small and stable, you might be able to fill it yourself with a suitable mortar or epoxy. Clean the crack, apply the product according to the instructions, and let it cure. This is a temporary fix – it doesn’t replace a proper structural repair but can keep moisture out.
For larger cracks, common UK repair methods include underpinning, pier installation, or using hydraulic cement that expands as it sets. Each method has a cost range, so getting a few quotes helps you budget correctly.
Remember, not every crack means disaster. Many homes develop minor cracks as they settle, especially after new builds or extensions. The key is to track the crack over time. Mark the ends with a pencil and note the date. If the marks stay the same after a few months, you probably have a harmless settlement crack.
Bottom line: measure, observe, and act early. A quick check can tell you if the crack is harmless or if it needs a professional’s eye. Keep an eye on moisture, protect the soil, and don’t ignore signs like stuck doors or growing cracks. With these steps, you’ll know exactly when to DIY and when to call a structural engineer, keeping your home safe and sound.
