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Foundation Settlement Cracks
in Wilmington, NC
Foundation settlement cracks are different from small shrinkage cracks. They happen when the soil under part of the foundation compresses or shifts, causing that corner or section to drop. Wilmington's mix of sandy soil and pockets of soft organic material, particularly in older areas near downtown and the riverfront, makes uneven settlement more likely. If one part of the foundation drops and the rest does not, the house tries to bend and the foundation cracks.
Quick Answer
Foundation settlement cracks happen when the soil under the foundation moves or compresses unevenly. In Wilmington, this is common in older homes near the Cape Fear River and in areas with mixed sandy and clay soils that shift when they get wet. Steel or helical piers driven to stable soil below can stop the movement and stabilize the foundation. Any crack wider than a credit card or any crack that is growing needs to be inspected. Call (910) 408-5690 to have someone take a look.
Telltale Signs
Warning Signs to Watch For
- Diagonal cracks running from the corners of windows or doors toward the foundation
- Cracks in the foundation that are wider at the top than the bottom
- Doors or windows on one side of the house that no longer open or close properly
- Visible gap where the foundation pulls away from the sill on top of it
- Cracks in interior drywall that line up with foundation cracks outside
- Floors that slope noticeably toward one end of the house
Root Causes
What Causes Foundation Settlement Cracks?
Soft Organic Soil Compression
Parts of Wilmington, especially near downtown and the older neighborhoods along the Cape Fear River, were built on soil that contains organic material like old root systems and decomposed fill. This soft material compresses slowly under the weight of a house and never fully stops. When it compresses unevenly, the foundation drops in one spot more than another and cracks.
The Fix
Helical Pier Underpinning
Helical piers are screwed deep into the ground past the soft soil until they reach stable material. They are then connected to the foundation to transfer the load to solid ground and stop the settlement.
Plumbing Leak Under Foundation
A slow leak from a water supply line or sewer line under the slab keeps the soil saturated, which causes it to compress and wash away under the foundation. Homes built before 1978 in Wilmington often have original galvanized or clay pipe that corrodes and cracks with age.
The Fix
Pipe Repair and Foundation Stabilization
The pipe must be repaired first, then the soil needs time to dry before stabilization work can begin. Depending on how much the foundation has moved, piers or grout injection may be needed to stop further settlement.
Drought-Related Soil Shrinkage
Wilmington usually gets plenty of rain, but dry spells do happen, and when clay-rich soil dries out it shrinks. If the soil under part of a foundation shrinks and pulls away, that section of the foundation loses support and can crack or drop. This often shows up after a summer with below-normal rainfall.
The Fix
Foundation Crack Repair and Soil Moisture Management
The cracks are filled and sealed to keep water out. Maintaining consistent soil moisture around the foundation with proper grading and even watering during dry periods can slow or stop this type of movement.
Self-Diagnosis
Which Cause Applies to You?
Check the signs you're observing to narrow down the likely root cause before your inspection.
| What You're Seeing | Soft Organic Soil Compression | Plumbing Leak Under Foundation | Drought-Related Soil Shrinkage |
|---|---|---|---|
| Diagonal crack running from a window corner toward the ground | |||
| Crack wider at the top than at the bottom | |||
| Settlement concentrated near one bathroom or kitchen wall | |||
| Cracks appeared or grew noticeably worse after a dry summer | |||
| Floors slope toward one corner and doors on that side stick | |||
| Wet soil under crawl space with no visible water source |
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