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

Noticed a hairline line spreading across a wall or a stair‑step in a floor? Those cracks are more than just a cosmetic mishap – they can tell you a lot about the health of an older home. In this guide we’ll break down the common reasons cracks show up, what to look for, and the most practical ways to stop them getting worse.

Why Cracks Appear in Older Homes

Older houses settle over time. As the soil beneath the foundation dries out or shifts, the structure moves with it. This natural settling often creates settlement cracks that are thin, straight, and usually found near windows, doors, or corners. If the crack is wider than 1/8 inch or follows a stair‑step pattern, it could signal foundation problems like soil pressure or moisture intrusion.

Another big cause is moisture. When water gets into the ground around the foundation, it expands the soil, pushing against the walls. When it dries, the soil contracts and can pull the walls inward, creating horizontal cracks that are a red flag. Leaky roofs, poor drainage, or blocked gutters all feed this cycle.

Temperature changes also play a role. Metal fasteners and timber expand and contract with heat and cold, sometimes causing tiny cracks in plaster or drywall. These are usually harmless, but they can become a problem if they hide water leaks.

Spotting Serious Cracks vs. Cosmetic Ones

Here’s a quick cheat‑sheet to help you decide if you need a professional:

• Width: Under 1/8 inch – often cosmetic. Over 1/8 inch – investigate further.
• Pattern: Straight, hairline lines – likely settling. Stair‑step or diagonal – could be structural.
• Location: Cracks near doors/windows, corners, or foundations need attention.
• Movement: If a crack keeps widening over weeks, call an expert.
• Moisture: Dark, damp spots around a crack suggest water damage.

When in doubt, grab a pencil and mark the ends of the crack. Check back after a few days – if the marks have moved, you’ve got an active issue.

Do‑It‑Yourself Fixes for Minor Cracks

For small, non‑structural cracks you can often repair them yourself. Here’s a step‑by‑step:

1. Clean the area: Use a brush to remove dust and loose plaster.
2. Apply a filler: Choose a flexible, paint‑able crack filler for drywall or a cement‑based patch for brick.
3. Smooth it out: Spread the filler with a putty knife, feathering the edges.
4. Prime and paint: Once dry, prime the patch and match the wall colour.

These steps work well for hairline cracks in interior walls. They won’t stop a shifting foundation, but they’ll keep the look tidy.

When to Call a Professional

If you see any of the following, call a structural engineer or a reputable contractor:

• Cracks wider than 1/8 inch that keep getting bigger.
• Horizontal cracks in basement walls.
• Stair‑step cracks that run across multiple bricks or blocks.
• Signs of water pooling near the foundation.
• Doors or windows that no longer close properly.

Professionals can perform a foundation inspection, recommend underpinning, pier installation, or waterproofing solutions. While these repairs cost more, they protect your home’s value and prevent expensive damage down the line.

Remember, older homes have charm, but they also need regular check‑ups. Spotting cracks early, understanding what they mean, and taking the right action can keep your house safe, comfortable, and looking great for years to come.