Cracks in Old House: What They Mean and How to Fix Them

If you’ve lived in a house that’s been around for a while, you’ve probably seen cracks appear in walls, ceilings or the foundation. Those lines can be harmless, but they can also point to bigger problems. Knowing the difference saves you money and protects your home.

Spotting the Common Types

First, look at where the crack shows up and how it looks. Hair‑line cracks (a millimetre or less) in plaster are usually just shrinkage – they’re cosmetic and easy to patch. Vertical cracks that run from floor to ceiling often mean the building is settling unevenly. They’re a sign to check the foundation and load‑bearing walls.

Horizontal cracks in the foundation wall are more serious. They usually happen when soil pushes against the wall, called lateral pressure. If you see a wide (over 5 mm) horizontal line, call a professional right away.

Stair‑step cracks in brickwork look like a set of steps. Those usually point to movement in the foundation or a shift in the soil underneath. They need a thorough inspection before you start any repair.

What Causes Cracks in an Old House?

Old houses settle over time. Soil types, moisture changes and even nearby construction can move the ground. Wood that supports the structure can warp when it gets wet or dry. Poor original construction or renovations that didn’t follow proper standards also add stress.

Seasonal changes play a big role. In winter, the ground can freeze and expand, pushing against foundation walls. In summer, drying soil pulls away, leaving gaps that turn into cracks. If your house sits on clay, expect more movement because clay expands and contracts a lot.

DIY Checks Before Calling a Pro

Grab a flashlight and a measuring tape. Measure the width of the crack at the top, middle and bottom. If it’s getting wider each month (even by a millimetre), note it – that’s a red flag.

Tap the area with a screwdriver. A hollow sound can mean the plaster has detached from the brick or block behind it. Also, look for water stains, mould or a musty smell nearby. Moisture often worsens cracks.

If the crack is narrow and static, you can fill it yourself. Clean the crack, apply a masonry filler or plaster, smooth it with a trowel and let it dry. Paint over it to match the rest of the wall.

When to Call a Professional

Any horizontal crack wider than 5 mm, stair‑step cracks, or cracks that keep growing need a structural engineer or experienced foundation contractor. They’ll check soil movement, load distribution and may recommend underpinning, wall anchors or a crack injection.

Also call a pro if you see cracks paired with doors or windows that stick, uneven floors, or sagging ceilings. Those symptoms suggest the whole frame is shifting, not just a surface blemish.

Preventing Future Cracks

Keep the soil around your house evenly moist. A garden hose with a timer can water the perimeter a few times a week during dry spells. Ensure gutters and downspouts direct water away from the foundation – a 6‑inch drop is a good rule of thumb.

Watch for tree roots growing close to the house. Roots can pull soil away and create voids. If a big tree is too close, prune the roots or consider professional removal.

Finally, schedule a home inspection every five years, especially after major weather events. Early detection keeps small cracks from turning into costly repairs.

Cracks in an old house are a normal part of aging, but not every crack is harmless. By learning to spot the warning signs, doing simple checks and knowing when to bring in an expert, you can protect your home’s structure and keep repair costs down.