Why concrete cracks
Concrete shrinks as it dries and moves with temperature, so some cracking is expected in nearly every slab and wall. Control joints are cut or formed to make that cracking happen in straight, planned lines. When joints are missing, too far apart, or cut too late, cracks find their own path.
Other cracks have different causes. Plastic shrinkage cracks form when the surface dries too fast during placement. Settlement, overloading, corroding reinforcing, and movement of the soil below produce patterns of their own, often with offset across the crack.
Reading the pattern is the starting point. Width, length, orientation, offset, and location relative to joints and reinforcing all matter, as does whether the crack is still moving. Together they help separate cosmetic conditions from ones that warrant further study.
Beyond cracking: surface and moisture problems
Not every concrete defect is a crack. Scaling and spalling can follow from finishing practices, inadequate curing, or freeze-thaw exposure, especially where deicing salts are used. Exposed or rusting reinforcing points to cover or corrosion issues that deserve prompt attention.
Slabs on grade also carry moisture. When a vapor retarder below the slab is missing or damaged, moisture rising through the concrete can break down flooring adhesives and lift finishes. Excess moisture from the original mix can do the same if flooring goes down too early.
Published test methods such as ASTM F1869 and ASTM F2170 measure moisture emission and internal relative humidity in slabs. Exterior flatwork raises its own questions: slope and drainage, displaced joints, and cracking at re-entrant corners.
How a concrete investigation proceeds
Investigators typically map cracks and surface conditions, measure widths and offsets, and compare locations with the plans, joint layout, and reinforcing details. Monitoring over time shows whether cracks are active or stable. Photographs with scale references make the record useful later.
Some questions need material evidence. Cores and samples can be examined for strength, composition, air content, and the depth and condition of reinforcing. If a material appears to have a manufacturing defect, we are aligned with several laboratories that test and analyze product failure. We also store field samples at our office in case they are needed at trial.
Where cracking suggests structural movement or soil behavior, the question may also call for review by a licensed design professional. A clear record of the construction conditions gives that review a sound starting point.
Codes, SB800, and repair scopes
Concrete work is measured against the plans, the specifications, and the code in force when it was built. For many newer California homes, SB800 also sets performance standards that address significant cracks in foundations, slabs, and other components. We are educated on past and current building codes and SB800.
Our reports include photo documentation, conceptual repair scopes, and cost estimates. For concrete, that may mean distinguishing between routing and sealing, epoxy injection, surface repair, and removal and replacement, each with its own cost and limits.
Common warning signs
- 01Cracks wider than a hairline, or cracks with vertical offset
- 02Cracks that grow, reopen, or keep appearing after the first year
- 03Spalling, scaling, or flaking at slab and step surfaces
- 04Rust staining or exposed reinforcing steel
- 05Flooring that lifts, bubbles, or debonds over a slab on grade
- 06Doors and windows that begin to bind as nearby cracks develop
- 07Water ponding on flatwork or flowing toward the building