Short answer: Thin vertical or hairline cracks, especially above door and window corners, are usually cosmetic and come from normal movement. Bob Vila says cracks under 1/8 inch are likely cosmetic, 1/4 inch is worth watching, and cracks 1/4 inch or wider, or groups of cracks, deserve a professional assessment. Horizontal cracks, 45-degree cracks with sticking doors, and cracks that keep coming back are the ones to take seriously.
Quick diagnosis
| What you notice | Most likely cause | What to check | Call a pro? |
|---|---|---|---|
| Hairline crack above a door or window corner | Normal movement and drywall stress | Watch it | No |
| Diagonal crack at about 45 degrees near a door | Uneven settling | Check if doors stick | If it grows |
| Horizontal crack | Soil pressure or structural load | Measure and photograph | Yes |
| Stairstep crack in brick or block | Settling of masonry | Check width and growth | Yes |
| Crack with yellow or brown stain | Moisture behind the wall | Look for a leak | Often |
| Crack that returns after repair | Ongoing movement | Mark and date it | Yes |
Read the crack
- Width: under 1/8 inch is likely cosmetic; 1/4 inch and up deserves a closer look (Bob Vila).
- Direction: vertical cracks are usually the least worrying; diagonal cracks near doors suggest uneven settling; horizontal cracks need an expert.
- Company: cracks together with sticking doors, sloping floors or gaps at trim point to foundation movement.
Monitor before you patch
This Old House recommends marking the ends of a crack with a pencil line and the date so you can see if it grows. Photograph it with a ruler beside it. Check every few weeks through a change of seasons.
Patching cosmetic cracks
Once you know the crack is stable, open it slightly, apply mesh tape and joint compound, sand and paint. If the crack returns quickly, the movement is ongoing and patching will not fix it.
When to call a professional
- The crack is 1/4 inch or wider, or there are several.
- It is horizontal, stairstepped in masonry, or keeps growing.
- Doors and windows stick, or floors slope.
- There are water stains or mold along the crack.
What it usually costs
Cosmetic drywall crack repair is usually a small job (HomeGuide lists ceiling crack repair at about $150 to $400). If a structural cause is found, This Old House reports foundation repair averaging about $5,179, with a typical range of $2,224 to $8,134.
Frequently asked questions
Are wall cracks normal in an old house?
Fine cracks are common in older homes, especially in plaster. Watch for new, wide or growing cracks.
Who do I call for cracks in walls?
For cosmetic cracks, a drywall or painting contractor. For wide, horizontal or growing cracks, a structural engineer gives an independent opinion before you hire a repair company.
Related problems
Sources
- Bob Vila: When should you worry about cracks in your walls?
- This Old House: Foundation settling vs. foundation problems
- This Old House: Foundation cracks, what is normal and when to worry
This guide is general information, not a substitute for an inspection by a licensed professional. See our disclaimer.