Light surface scaling with sound concrete below
- Likely next step
- Evaluate surface repair
- Why it matters
- A shallow defect may be suitable for localized repair or resurfacing after diagnosis.
Concrete Spalling: Causes and Repair
Updated August 2026
Concrete spalling is the breaking, flaking, or loss of surface concrete, often leaving a rough depression or exposing aggregate and reinforcement. A durable repair removes unsound concrete, addresses contributing moisture, freeze-thaw, salt, corrosion, or material problems, prepares sound edges and substrate, and replaces the lost section with a compatible repair system.
Start with the condition, not the product
The depth, extent, soundness of the remaining concrete, moisture exposure, and reinforcement condition determine whether localized repair, resurfacing, or replacement deserves evaluation.
Hollow-sounding or delaminated areas
- Likely next step
- Map and remove unsound concrete
- Why it matters
- The visible opening may be smaller than the detached area below the surface.
Exposed rusty reinforcement
- Likely next step
- Obtain a defined repair scope
- Why it matters
- Corrosion products expand and can continue breaking surrounding concrete.
Widespread deep deterioration
- Likely next step
- Compare repair with replacement
- Why it matters
- Many adjacent repairs can be less predictable than rebuilding a failed section.
What is the difference between spalling, scaling, and delamination?
Spalling involves concrete breaking away and leaving a depression or exposed material. Scaling is usually shallower surface flaking, while delamination is a separation below the surface that may sound hollow before it opens. The distinction matters because a coating cannot restore detached or unsound concrete.
Shallow scaling with sound concrete below may lead to a different scope. Review the concrete resurfacing decision guide before treating resurfacing as a repair for deep or detached concrete.
- Mark loose, hollow, cracked, and previously repaired areas
- Record whether aggregate or steel is exposed
- Look for water, salts, leaking joints, and poor drainage
- Note whether the affected area grows after winter or wet periods
How do you repair spalling concrete?
To repair spalling concrete, remove loose and unsound material to a defined boundary, evaluate and treat exposed reinforcement, prepare sound edges and substrate, place a compatible repair material, finish the surface, and cure the repair under the product and project requirements. The method and repair depth depend on the diagnosed condition rather than the visible opening alone.
What causes concrete spalling?
Concrete spalling can develop when reinforcement corrosion, freeze-thaw exposure, saturation, deicing salts, chemical attack, joint failure, impact, or material and construction deficiencies damage the surface or concrete below it. Drainage and exposure can matter as much as the patch material because an active contributing condition can damage the repair or nearby concrete.
- Redirect ponding and runoff where water contributes
- Repair failed joints when they are part of the diagnosed condition
- Select a compatible repair system for the actual exposure
- Do not coat over active moisture or unsound concrete
What should a concrete spalling repair quote include?
A concrete spalling repair quote should define the damaged area, removal limits, preparation, reinforcement treatment, repair material, exposure conditions, and expected finished result.
- Mapped repair locations, dimensions, depth, hollow or delaminated areas, cracks, and exposed reinforcement
- The method for reaching sound concrete and preparing edges and the repair substrate
- How exposed, corroded, loose, or section-loss reinforcement will be cleaned, evaluated, treated, supplemented, or replaced
- The repair material, bond requirements, placement depth, finish, and expected color or texture difference
- Drainage, joints, deicing exposure, leaks, or other contributing moisture and durability conditions included in the scope
- Weather protection, curing, return-to-service timing, cleanup, warranty, exclusions, and responsibility if additional unsound concrete is discovered
Technical references and limitations
These references support the general repair and planning guidance on this page, but they do not establish requirements for an individual residential project.
ACI RAP 7 addresses horizontal concrete-surface repairs. Its preparation and repair-planning principles provide useful context, but the bulletin does not establish a repair design for every residential slab, wall, foundation, or reinforced member.
Residential conditions, local codes, product requirements, and structural significance vary. Use a qualified local professional for diagnosis and design where safety or structural performance is involved.