Concrete is one of the most durable and widely used construction materials in commercial and residential buildings. However, even the strongest concrete is susceptible to damage over time, particularly in harsh environmental conditions. One of the most common forms of deterioration is concrete spalling. If left unaddressed, spalling can threaten the safety, performance, and appearance of your structure.
In this guide, you will learn how to identify concrete spalling, why it matters, what causes it, and how to respond effectively.
What Is Concrete Spalling?
Concrete spalling refers to the breaking, flaking, or chipping of the concrete surface. It occurs when sections of concrete begin to separate from the substrate, often resulting in pitted, cracked, or exposed areas. This degradation can occur on vertical surfaces such as walls and columns or on horizontal surfaces like balconies, decks, parking structures, and walkways.
Spalling is typically caused by internal pressure from corrosion of embedded steel reinforcement, freeze-thaw cycles, or moisture infiltration. It may start as surface-level damage but can eventually lead to more severe structural issues if ignored.
Spalling is not just an aesthetic issue. It is often a visible symptom of deeper material failure that requires professional evaluation and remediation.
Why Concrete Spalling Matters
Concrete spalling is a red flag for building health. When pieces of concrete begin to fall away from the structure, it compromises both safety and functionality. Here are the key reasons why spalling is a serious concern:
- Structural Integrity: Spalling can weaken load-bearing components, especially if it affects beams, columns, or slabs with embedded rebar. As steel reinforcement corrodes and expands, it exerts pressure on the concrete, accelerating cracking and separation.
- Safety Risks: Falling concrete fragments from facades, balconies, or ceilings present hazards to building occupants, pedestrians, and nearby property.
- Increased Repair Costs: Delaying repairs allows deterioration to worsen, often requiring full structural rehabilitation instead of localized patching.
- Water Intrusion and Mold: Spalled areas allow water to enter the building envelope, leading to interior damage, mold growth, and corrosion of adjacent building components.
- Code Violations: Spalling may cause a building to fall out of compliance with local safety codes, especially in areas with strict structural maintenance standards.
- Property Aesthetics and Value: Unsightly damage on concrete surfaces can reduce the curb appeal and perceived value of a building, making it less attractive to tenants or buyers.
Early detection and professional repair are the best strategies to avoid costly and disruptive damage.
Signs of Concrete Spalling
Spalling can appear in many different ways depending on the location and cause. Recognizing the signs early allows you to act before more serious damage occurs.
- Surface Flaking or Scaling: Pieces of concrete break off from the surface, often leaving rough patches or depressions.
- Pitting or Craters: Small holes or depressions develop on horizontal concrete, particularly in driveways, sidewalks, and balconies.
- Exposed Rebar or Wire Mesh: If you can see rusting steel inside the concrete, the protective layer has been compromised.
- Discoloration: Rust stains on the concrete surface may indicate corrosion of embedded steel reinforcement, which often precedes spalling.
- Cracking Around Damaged Areas: Cracks that radiate from a central point of damage can signal internal stress caused by corroded rebar.
- Delamination: Hollow sounds when tapping on the concrete surface may suggest that the material has separated from the substrate below.
- Loose or Falling Fragments: Pieces of concrete breaking off or lying below a wall or overhang may indicate active spalling.
These signs are often most visible after heavy rain, freeze-thaw cycles, or in coastal environments where salt exposure accelerates corrosion.
Causes of Concrete Spalling
Understanding what causes concrete spalling can help prevent it and guide effective repair strategies. The most common contributors include:
1. Corrosion of Reinforcing Steel
When water and oxygen penetrate concrete, they can reach the steel reinforcement inside. This causes the steel to corrode and expand, exerting pressure that cracks the surrounding concrete. Over time, this cracking leads to spalling and further exposure of the steel.
2. Freeze-Thaw Cycles
In cold climates, water inside concrete pores freezes and expands, creating internal pressure that breaks apart the surface. Repeated freeze-thaw cycles accelerate spalling, especially on exterior walls, balconies, and flatwork.
3. Poor Concrete Mix or Application
Concrete with low strength, poor curing, or insufficient cover over rebar is more susceptible to environmental damage and spalling.
4. Chloride or Salt Exposure
Salt used for de-icing roads and walkways or naturally present in coastal environments penetrates the concrete and accelerates rebar corrosion, leading to early spalling.
5. Water Intrusion
Improper drainage, roof leaks, or failed waterproofing can introduce excess moisture into the concrete, weakening the structure and promoting corrosion.
6. Mechanical Damage
Impact from vehicles, tools, or dropped equipment can chip or weaken the surface, leading to localized spalling over time.
7. Age and Weathering
Over decades, even high-quality concrete breaks down under UV exposure, traffic load, and weather conditions, especially if not maintained properly.
Identifying the specific cause of spalling is critical for applying the correct repair technique and preventing recurrence.
What to Do If You See Spalling
Once you notice concrete spalling on your building, it is important to act quickly to assess and repair the damage. Here are the steps to follow:
- Conduct a Visual Inspection: Determine the extent of the damage and document the location, size, and any exposed rebar or cracking.
- Avoid Temporary Patch Jobs: Superficial cosmetic fixes may not address the internal damage or stop further corrosion. Professional evaluation is essential.
- Check for Additional Moisture or Rust: Look for signs of water intrusion, rust stains, or nearby drainage issues that may be contributing to the problem.
- Mark Off the Area for Safety: If spalling is occurring in overhead or high-traffic zones, restrict access to prevent injury from falling debris.
- Contact a Structural or Waterproofing Expert: A professional can test the concrete, measure corrosion depth, and recommend a repair strategy tailored to your structure.
- Repair and Protect: Repairs may involve removing loose material, treating corroded rebar, applying bonding agents, and reapplying protective coatings or sealants.
- Schedule Follow-Up Inspections: After repairs, monitor the area periodically to ensure the problem does not return.
Prompt action not only prevents further structural decline but also helps avoid safety hazards and regulatory issues.
How Deluxe Waterproofing Can Help
Deluxe Waterproofing provides expert concrete repair and protection services tailored to the specific needs of commercial and industrial properties. Our
Frequently Asked Questions
What is concrete spalling?
Spalling is when concrete surfaces chip, flake, or break due to moisture, freeze-thaw cycles, or corrosion of internal steel.
What does spalling concrete look like?
You’ll notice cracked, flaking, or crumbling concrete, sometimes with rust stains from rebar.
Why is concrete spalling dangerous?
It weakens structural integrity and poses safety hazards to occupants and pedestrians.
How is spalling different from cracking?
Cracking involves splits in concrete, while spalling results in surface breakage and flaking.
Can Deluxe Waterproofing repair concrete spalling?
Yes, we offer expert spall repair services and preventive waterproofing solutions.