Cracks in buildings cause more anxiety than almost any other structural condition, yet not all cracks are equal. Some are harmless consequences of normal material behavior. Others are early warnings of serious structural distress. The challenge for property owners in Nebraska is determining which category their cracks fall into and whether the appropriate response is continued observation or immediate professional intervention.
Why Buildings Crack
All buildings crack. Concrete shrinks as it cures, and this shrinkage produces cracks. Wood framing dries and shifts after construction, causing drywall and plaster cracks. Masonry expands and contracts with temperature changes. These material-driven cracks are a normal part of a building's life and do not indicate structural problems.
Structural cracks, by contrast, result from forces acting on the building that cause elements to move, deform, or break. Foundation settlement, lateral soil pressure, thermal expansion and contraction of the structural frame, overloading, and the effects of expansive soils can all produce cracks that reflect genuine structural concern. For more, see Expansive Soils in Nebraska.
The critical distinction is not whether a crack exists but whether it is static or active, and whether its characteristics indicate a structural cause.
Identifying Crack Types
Shrinkage Cracks
Concrete shrinkage cracks are typically thin, relatively straight, and appear within the first few years after construction. In poured concrete foundation walls, they are often vertical and located near the center of long wall spans or at points of geometric change such as window openings. These cracks are generally narrow, often less than one-sixteenth of an inch, and do not show evidence of differential movement across the crack. While they may allow water infiltration and should be sealed, they are rarely a structural concern.
Settlement Cracks
Settlement cracks form when different parts of a foundation move by different amounts. In poured concrete walls, they are often diagonal, wider at one end than the other, and may show measurable vertical offset across the crack face. In concrete masonry block walls, settlement cracks typically follow a stair-step pattern along the mortar joints. Settlement cracks indicate that the soil beneath part of the foundation has compressed or moved more than the soil beneath adjacent areas.
Structural Stress Cracks
Cracks caused by applied loads, such as lateral earth pressure on a basement wall, typically present as horizontal cracks, particularly in concrete block walls where the mortar joints are weaker than the blocks. A horizontal crack running along a mortar joint at or near the mid-height of a basement wall is a classic indicator of excessive lateral soil pressure and warrants prompt engineering evaluation.
Monitoring Methods
When a structural engineer determines that a crack should be monitored rather than immediately repaired, several methods are available to track whether the crack is active.
Crack Gauges
Crack gauges are simple devices installed across a crack that measure any change in width over time. The most common type consists of two overlapping plates, each mounted on one side of the crack, with a calibrated grid that shows relative movement. These gauges are inexpensive and can be read visually at regular intervals. More sophisticated versions include electronic displacement sensors that record movement continuously.
Photographic Documentation
Periodic photographs of cracks taken from the same position with a reference scale visible provide a qualitative record of changes over time. While less precise than crack gauges, photographic records capture changes in crack pattern, new branching, and changes in surface condition that gauges may not detect.
Survey Monitoring
For buildings with significant foundation movement concerns, periodic elevation and displacement surveys using precise leveling instruments or total stations can track building movement at a global scale. These surveys document how the entire structure is responding to soil conditions and loading over time.
When to Watch
Monitoring is appropriate when cracks are narrow, show no evidence of recent growth, and exhibit characteristics consistent with normal material behavior. Fine shrinkage cracks in a concrete foundation wall, hairline cracks at drywall joints, and minor stair-step cracks in masonry veneer that have not changed since the building was new are all conditions that can generally be watched over time without immediate intervention.
When to Act
Immediate professional evaluation is warranted when cracks are wide enough to insert a pencil tip, when they show evidence of recent or ongoing movement, when horizontal cracking appears in basement walls, when cracks are accompanied by wall displacement, bowing, or rotation, and when multiple new cracks appear suddenly. Cracks that admit water into the building also require attention, as the water itself can worsen the underlying condition through freeze-thaw damage and soil erosion. For more, see What Is Included in a Structural Engineering Report in.
Any crack that causes concern should be documented with photographs and measurements so that future changes can be objectively assessed. This baseline documentation is valuable whether the crack ultimately proves to be benign or develops into a condition requiring repair. In Nebraska's climate, where freeze-thaw cycling and expansive soils create ongoing demands on building foundations and structures, crack monitoring is a practical and cost-effective component of responsible building ownership.