Concrete Cracks: Which Ones Are Normal and Which Ones Need Repair?

Concrete has a reputation for strength, but even well-built concrete can develop cracks over time. For homeowners and commercial property owners, spotting a new crack in a driveway, sidewalk, patio, floor, or foundation can understandably be a cause for concern.

However, a crack alone doesn’t always indicate a serious problem. Concrete naturally shrinks as it cures, responds to temperature changes, and rests on soil that can move over time, so minor cracking is to be expected. Larger cracks, on the other hand, can point to drainage problems, excessive loads, or movement beneath the slab.

Knowing what to look for can help you decide whether a crack simply needs to be monitored or deserves professional attention.

Why Does Concrete Crack?

Concrete begins changing as soon as it is placed. During the curing process, moisture leaves the mix and the concrete shrinks slightly. Temperature changes can also cause concrete to expand and contract.

At the same time, conditions beneath the slab can change. Soil may settle, dry out, absorb water, or erode. All of these factors can place stress on the concrete.

Because concrete handles compression extremely well but has less ability to flex when pulled apart, cracking can occur as those stresses build.

Proper construction helps manage that movement. Good base preparation, appropriate slab thickness, reinforcement, drainage, proper curing, and correctly placed control joints can all reduce unwanted cracking.

Even with careful installation, however, some minor cracks may develop during the life of a concrete surface.

Concrete Cracks That Are Often Normal

Not every crack requires a major repair. Several common types of cracking are often cosmetic or relatively minor.

Hairline Shrinkage Cracks

Very thin cracks sometimes appear as concrete cures and loses moisture. These are commonly known as shrinkage cracks.

A hairline crack that stays narrow, does not continue spreading, and has no difference in height from one side to the other is generally less concerning than a crack that continues changing.

Outdoor cracks should still be monitored. Even small openings can eventually allow moisture into the concrete, especially if they begin to widen.

Cracks Around Control Joints

Control joints are intentionally created to help manage where concrete cracks as it shrinks and moves.

If cracking occurs within or close to a control joint, the joint may be functioning as intended. The surrounding concrete should still remain stable and relatively level.

Surface Crazing

Crazing appears as a network of very fine cracks across the surface of the concrete. The pattern can sometimes resemble a spider web or cracked glass.

These cracks generally affect the surface rather than extending through the entire slab. Crazing is often more of an appearance issue, although it is worth watching for additional symptoms such as scaling, flaking, or deterioration.

Small Cracks That Remain Stable

Time can tell you a great deal about a crack.

A narrow crack that has remained unchanged for several years is usually less concerning than one that noticeably expands over a few months. If both sides remain level and the surrounding concrete feels solid, monitoring the area may be sufficient.

Signs a Concrete Crack May Need Repair

Width is important when evaluating a crack, but it shouldn’t be the only factor you consider. Movement, location, depth, drainage, and surrounding damage can also provide valuable clues about a crack’s severity.

Here are several signs that a crack deserves closer attention.

The Crack Keeps Getting Wider

A crack that continues opening can indicate ongoing movement.

If you are uncertain whether a crack is changing, take a clear photo and record the date. You can also note its approximate width. Comparing the area over time makes it easier to identify gradual movement that may otherwise go unnoticed.

One Side Is Higher Than the Other

A difference in elevation between the two sides of a crack can signal settlement, heaving, or movement beneath the slab.

This type of damage can also create a safety concern. Uneven sidewalks, patios, warehouse floors, and other walking surfaces may become trip hazards. Uneven driveways or commercial concrete can also interfere with drainage and vehicle traffic.

Water or Debris Collects in the Crack

Open cracks can create a pathway for water beneath a concrete surface.

Over time, repeated moisture intrusion may contribute to erosion, additional movement, or deterioration around the damaged area. In climates where temperatures fall below freezing, moisture inside vulnerable concrete can also contribute to freeze-thaw damage.

Cracks that regularly collect water, dirt, weeds, or debris are worth addressing before the opening becomes larger.

Cracking Appears Along With Settlement

Pay attention to the surrounding slab.

A sunken corner, low spot, tilted section, or separation between adjoining pieces of concrete may indicate that something beneath the slab has changed. Soil settlement, erosion, drainage problems, or insufficient support can all contribute to movement.

Simply filling the visible crack may not provide a lasting solution when the slab itself is still moving.

The Crack Is in Structural Concrete

Cracks in load-bearing concrete deserve more careful evaluation than minor surface cracks in a patio or walkway.

Foundation walls, footings, retaining walls, columns, structural slabs, and other load-bearing components have different performance requirements. Cracks accompanied by displacement, water intrusion, or other signs of movement should be inspected by a qualified professional.

The Concrete Is Spalling or Crumbling

Look beyond the crack itself. Broken edges, flaking concrete, rust staining, crumbling areas, or exposed reinforcing steel can indicate more extensive deterioration. Once water reaches embedded reinforcement, corrosion can contribute to additional pressure and damage within the surrounding concrete.

Repairing these areas early may help keep localized deterioration from spreading.

What Causes More Serious Concrete Cracking?

Significant cracking is often connected to conditions beyond the surface.

Possible causes include:

• Poorly compacted soil or base material
• Soil settlement or movement
• Drainage and erosion problems
• Repeated freeze-thaw cycles
• Heavy loads
• Inadequate slab thickness
• Water infiltration
• Changes in the soil beneath the concrete
  

Identifying the underlying cause is an important part of planning an effective repair.

Filling a crack may improve its appearance, but the opening can return when movement underneath the concrete continues. A thorough evaluation looks at the crack pattern, age of the concrete, surrounding drainage, condition of the slab, and how the concrete is being used.

Does Every Concrete Crack Need to Be Repaired?

Some narrow, stable cracks can simply be monitored. Others may benefit from sealing to reduce moisture intrusion.

More significant conditions could call for crack repair, joint repair, slab stabilization, lifting, partial replacement, or complete replacement.

The appropriate solution depends on the reason the concrete cracked.

For example, sealing may work well for a stable, nonstructural crack. A sunken slab may require a solution that addresses the support underneath it. Concrete with widespread deterioration or continuing movement may require more extensive work.

Choosing a repair based on the cause gives you a better chance of achieving a lasting result.

Protecting Your Concrete for the Long Term

Routine maintenance plays an important role in keeping concrete in good condition.

Keep water from pooling around slabs, maintain proper drainage, clean damaging chemicals and spills from exposed surfaces, and address vulnerable cracks before significant moisture intrusion occurs.

Periodic sealing may also help protect exposed driveways, patios, and other concrete surfaces from moisture and everyday wear.

Most importantly, pay attention to changes. A small crack that stays unchanged may never become a major concern. A crack that continues moving provides useful information that something else may be happening.

Have Questions About Cracked Concrete?

Cracking is part of the reality of concrete, and many small cracks are manageable. Hairline shrinkage cracks, cracking near control joints, and narrow cracks that remain stable are often less concerning.

Widening cracks, vertical movement, settlement, water intrusion, spalling, and damage in structural areas deserve closer attention.

Meyer Construction understands that determining the difference is not always easy from appearance alone. If you have concerns about cracked concrete or are planning a new concrete project, contact us today to discuss your concrete needs and determine the appropriate next steps.