Foundation Crack Severity Guide: When to Worry and When to Wait
Learn to identify hairline cracks vs. structural cracks. Photo guide with severity levels and recommended actions for each type.
Not all foundation cracks are created equal. Some are cosmetic and harmless, while others signal serious structural problems. This guide helps you assess crack severity so you know when to monitor, when to repair, and when to call a professional immediately.
Level 1: Hairline Cracks (Low Concern)
Width: Less than 1/16 inch (1.5mm)
Hairline cracks are extremely common and usually result from normal concrete curing and minor settling. They appear in most homes within the first 2-3 years and rarely indicate structural problems.
Action:
Monitor every 6 months. Mark the ends with tape and date them. If they don't grow, no repair needed.
Level 2: Minor Cracks (Monitor Closely)
Width: 1/16 to 1/4 inch (1.5mm - 6mm)
These cracks may indicate early foundation movement. Vertical cracks in this range are less concerning than diagonal or horizontal ones. Pay attention to whether they're growing.
Action:
Measure and photograph monthly. If growing, schedule a professional inspection. Consider sealing to prevent water intrusion.
Level 3: Moderate Cracks (Professional Inspection Needed)
Width: 1/4 to 1/2 inch (6mm - 12mm)
Cracks in this range typically indicate significant foundation movement. Stair-step cracks in brick, diagonal cracks from window/door corners, and cracks that are wider at the top than bottom are especially concerning.
Action:
Schedule a professional inspection. Consider hiring an independent structural engineer ($300-$800) for an unbiased assessment before getting contractor quotes.
Level 4: Severe Cracks (Immediate Action Required)
Width: Greater than 1/2 inch (12mm+)
Large cracks, especially horizontal cracks in basement walls, indicate serious structural failure. Horizontal cracks suggest lateral pressure from soil and can lead to wall collapse if not addressed.
Action:
Contact a structural engineer immediately. Do not delay. Get multiple repair quotes but prioritize speed over cost savings.
Crack Direction Matters
Vertical ↕️
Usually from normal settling. Less concerning unless wide or growing.
Lower risk
Diagonal ↗️
Often indicates differential settling — one part of the foundation is moving more than another.
Medium risk
Horizontal →
Most serious. Indicates lateral soil pressure pushing against the wall. Common in basement walls.
High risk
💡 When in Doubt, Get a Professional Opinion
An independent structural engineer ($300-$800) can give you an unbiased assessment. This is especially valuable because contractors who diagnose and repair have a financial incentive to recommend more work than necessary.
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