Understanding Efflorescence and Spalling: Critical Assessment Points for Home Inspectors

by Nick Gromicko and Ben Gromicko

Introduction

According to the InterNACHI® Home Inspection Standards of Practice, Section 3.3, a home inspector is required to:

inspect the foundation, basement, crawlspace, and structural components, and
report as in need of correction observed indications of active water penetration.

The durability of the concrete and masonry foundation and structure of a home can be compromised by moisture-related conditions that manifest as efflorescence and spalling. You may have seen it countless times: that chalky white powder coating foundation walls or the cracked chunks of concrete flaking away from a brick wall. These symptoms are potentially serious indicators of underlying moisture problems.

This article describes the mechanisms that cause efflorescence and spalling and how to identify the underlying causes and preventive measures.

The 2024 International Residential Code (IRC) addresses several aspects pertinent to these moisture problems:

Section R405: Foundation Drainage
Section R406: Foundation Waterproofing and Dampproofing

Efflorescence and spalling often indicate that these moisture management systems are either missing, inadequate, or have failed over time. When these symptoms appear, it suggests that one or more of these building code requirements may not have been properly implemented or maintained.

Efflorescence: The Warning Sign

Efflorescence looks like a white, chalky residue on the surface of concrete or masonry structures. This crystalline deposit forms when water migrates through porous building materials, dissolving mineral salts within the substrate, and subsequently evaporates at the surface, leaving behind these salt deposits.

The term "efflorescence" derives from the French word meaning "to flower out," an apt description of how these crystalline blooms appear to grow from the surface. While primarily considered an aesthetic issue, efflorescence serves as a critical indicator of moisture penetration that may eventually lead to more serious structural degradation.

The Process of Efflorescence Formation

The formation of efflorescence relies on three essential elements:

Soluble salts present within the building material
Moisture to dissolve and transport these salts
Evaporation that concentrates the dissolved salts at the surface

Concrete, brick, stone, and mortar naturally contain mineral salts, as do the soils surrounding foundations. When these materials absorb water through capillary action—a process where moisture moves through the porous structure due to surface tension—the water draws salt with it. This capillary pressure, though relatively modest at 300-500 PSI, is sufficient to facilitate significant moisture movement through building materials.

Inspection Considerations for Efflorescence

When documenting efflorescence, inspectors should:

Note the pattern and extent of the white deposits
Identify potential moisture sources (groundwater, rainwater, plumbing leaks)
Assess whether the condition appears active or historical
Consider seasonal factors that might influence moisture levels
Evaluate the relationship between efflorescence and other moisture-related issues present

Spalling: The Structural Concern

While efflorescence serves as an early warning, spalling represents a more advanced deterioration process where the surface material actually breaks away from the main body of concrete or masonry.

This flaking or fragmenting occurs when hydrostatic pressure builds within the material to levels exceeding its tensile strength—typically between 3,000-5,000 PSI—causing portions of the surface to detach or "blow off."

Mechanisms of Spalling

Spalling frequently develops through two primary mechanisms:

Hydrostatic Pressure. As more salt accumulates beneath the surface, the osmosis process draws increasing amounts of water through the material. This osmotic action generates substantial hydrostatic pressure—potentially reaching 3,000-5,000 PSI. With concrete typically having a structural strength of 2,000-3,000 PSI, this pressure can overwhelm the material's capacity, resulting in surface failure.
Freeze/Thaw Cycles. In colder climates, moisture trapped within porous building materials expands upon freezing. Repeated freeze/thaw cycles progressively weaken the material's structural integrity. Materials with higher moisture content are particularly vulnerable to this cyclic damage.

You may be interested in learning more about soils that heave under foundations in “Frost Heave Caused by Ice Lenses” at nachi.org/frost-heave-ice-lens

Critical Assessment Parameters for Spalling

When evaluating spalling, inspectors should document:

Depth and extent of material loss
Whether reinforcing steel has been exposed
Presence of concurrent moisture issues
Location patterns that might indicate systemic problems
Structural implications based on the affected components

Prevention Strategies for Client Education

A critical function of the home inspection process involves educating clients about maintenance strategies to prevent moisture-related deterioration. Effective prevention typically focuses on interrupting the moisture pathway through:

Capillary Breaks: Installation of subslab polyethylene sheeting or liquid-applied elastomeric waterproofing creates a barrier to moisture migration.
Drainage Improvements: Proper grading, functional gutters, and effective downspout extensions direct water away from the foundation.
Masonry Maintenance: For existing masonry structures, repointing of mortar joints can help maintain the integrity of the assembly.
Sacrificial Mortar: In some masonry systems, mortar is intentionally formulated to be softer than the surrounding masonry, allowing it to degrade preferentially and protect the more valuable structural components.
Vapor Retarders: Proper installation of vapor retarders in crawlspaces and basement areas can reduce moisture movement through concrete. Learn how to inspect vapor diffusion retarders by visiting nachi.org/vapor-retarder-inspection.
Sealants: While sealants alone aren't a complete solution, hydrophobic impregnating sealers can help prevent water intrusion in some applications.
Dehumidification: In enclosed spaces with existing efflorescence, dehumidification can slow the process by reducing ambient moisture, though it won't address the underlying cause.

Removal Techniques

When discussing efflorescence with clients, inspectors can mention these common removal methods:

Dry brushing: For light efflorescence, stiff brushing may be sufficient to remove the deposits.
Pressure washing: Water under pressure can sometimes remove efflorescence, though this may temporarily reintroduce moisture.
Mild acid solutions: Products containing diluted acids (like muriatic acid) can dissolve efflorescence but require careful handling and neutralization afterward.
Commercial cleaners: Several specialty cleaners are formulated specifically for efflorescence removal without the hazards of stronger acids.

Inspectors should note that removal without addressing the underlying moisture issue will only yield temporary results, as efflorescence will likely return until the moisture pathway is interrupted.

The Remarkable Capillary Effect

<span class="fr-mk" style="display: none;"> </span>
The capillary potential of concrete is extraordinary. According to the Building Science Corporation, while the theoretical limit of capillary rise in wood is approximately 400 feet, concrete's capillary action can theoretically extend nearly 6 miles. This remarkable characteristic underscores concrete's vulnerability to moisture transport and explains why seemingly minor groundwater issues can affect areas far from the apparent moisture source.

Applicable Building Codes and Standards

International Residential Code (IRC) References

Understanding the building code requirements related to foundations and moisture management provides inspectors with valuable context when evaluating efflorescence and spalling. The 2024 International Residential Code (IRC) addresses several aspects pertinent to these conditions:

Section R406: Foundation Waterproofing and Dampproofing establishes the requirements for preventing water infiltration in concrete and masonry foundation walls.
Section R405: Foundation Drainage specifies that "Drains shall be provided around concrete or masonry foundations that retain earth and enclose habitable or usable spaces located below grade." This is critical for managing moisture that could lead to efflorescence and spalling.
Section R404: Concrete Foundation Walls outlines structural requirements and proper construction methods for concrete foundations that affect their resistance to moisture-related deterioration.
Section R403: Requirements for Footings addresses the structural components of foundations, including specifications for rebar placement and other elements that impact structural integrity.

The presence of efflorescence and spalling often indicates that the moisture management systems required by these code sections may be compromised or inadequate.

InterNACHI® Home Inspection Standards of Practice

The InterNACHI® Home Inspection Standards of Practice (nachi.org/sop) provides specific guidance for foundation inspection that relates directly to efflorescence and spalling conditions:

The inspector shall inspect the surface drainage, retaining walls, and grading of the property, where they may adversely affect the structure due to moisture intrusion.
The inspector shall report as in need of correction observed indications of active water penetration and observed indications of possible foundation movement, such as sheetrock cracks, brick cracks, out-of-square door frames, and unlevel floors.

The Standards recognize that a home inspection is "based on observations made on the date of the inspection, and not a prediction of future conditions," which is particularly relevant when documenting early-stage efflorescence.

These standards help guide home inspectors when observing and reporting on conditions that may indicate moisture intrusion and structural problems.

Conclusion

Efflorescence and spalling represent more than mere surface phenomena; they serve as diagnostic indicators of moisture management within a building's envelope. By understanding the physical processes involved in moisture management, capillary action, osmosis, efflorescence, and spalling home inspectors can provide valuable information that goes beyond simple observations. Identifying observed indications of moisture intrusion early can help homeowners keep their homes in good shape and demonstrate the preventative maintenance value that home inspections provide.

The remarkable capacity of concrete and masonry to transport moisture through capillary action underscores why these conditions deserve particular attention during foundation inspections. By integrating an understanding of building science, code requirements, common building practices, and professional inspection standards, InterNACHI® Certified Professional Inspectors CPI® position themselves as invaluable resources in the preservation and maintenance of residential structures worldwide.

To find a local certified home inspector, visit nachi.org/certified-inspectors.

To become a certified home inspector, visit nachi.org/cpi-requirements

More Information

To learn more about homes, inspections, and building standards, visit www.nachi.org/education.

To become a certified home inspector, visit www.nachi.org/certifications.

Join the International Association of Professional Contractors.

Understanding Efflorescence and Spalling: Critical Assessment Points for Home Inspectors

Introduction

Efflorescence: The Warning Sign

The Process of Efflorescence Formation

Inspection Considerations for Efflorescence

Spalling: The Structural Concern

Mechanisms of Spalling

Critical Assessment Parameters for Spalling

Prevention Strategies for Client Education

Removal Techniques

The Remarkable Capillary Effect

Applicable Building Codes and Standards

Conclusion

Further Reading

More Information

Certification & Licensing

Education

Resources

Get Started

Grow Your Business

More…