A Failure Symptom Is Not a Diagnosis

When a coating lifts from concrete, moisture is often blamed immediately. Moisture may be involved, but the visible damage alone does not establish the cause.

A blister can form because of moisture, osmosis, trapped solvent, air entrapment, contamination, heat, chemical exposure, or improper application. Delamination can result from excessive slab moisture, weak concrete, laitance, dust, incompatible materials, insufficient surface profile, or application outside the manufacturer's requirements.

The investigator should document the symptoms, determine where the separation occurred, examine the pattern of damage, review the installation history, and perform appropriate testing before assigning responsibility or recommending repairs.

Common Moisture-Related Failure Symptoms

Blistering

Blisters are raised areas where a coating or flooring system has separated from the layer beneath it. They may be dry, gas-filled, or contain liquid.

The blister's location and contents provide useful evidence. Fluid-filled blisters can indicate moisture and osmotic activity, while dry blisters may suggest trapped air, vapor, solvent, heat, or another mechanism.

Questions to Ask About Blisters

• Are the blisters isolated, widespread, or concentrated near cracks and joints?
• Did they appear shortly after application or months later?
• Do they change with temperature, rainfall, cleaning, or facility operation?
• Are they filled with clear, cloudy, colored, or odorous liquid?
• Did the separation occur within the coating, at the coating-concrete interface, or within the concrete?
• Are salts, residue, softened material, or corrosion products present?
• Does the surrounding concrete show elevated moisture readings?

Osmotic Blistering

Osmosis involves water moving through a semi-permeable coating film toward a solution containing a higher concentration of dissolved material. Soluble salts, contamination, or water-soluble coating components at the interface can contribute to this condition.

As water accumulates beneath the coating, pressure develops and the film lifts to form a blister. The liquid inside may have a different pH, color, odor, or dissolved-solids concentration from moisture elsewhere on the slab.

Simply grinding away the blister and recoating the spot may not correct the underlying source of water or soluble contamination. Additional blisters can form nearby.

Delamination and Peeling

Delamination occurs when the bond between two layers fails. Determining the plane of failure is one of the most useful parts of an investigation.

Efflorescence and Salt Deposits

Efflorescence is a crystalline deposit produced when moisture dissolves salts within concrete or adjoining materials, carries them toward the surface, and then evaporates. The salts remain behind.

Efflorescence is evidence that moisture has moved through the material. It does not, by itself, reveal whether the source is ground moisture, a leak, rainwater, cleaning water, condensation, or another condition.

Removing the visible deposit without controlling the moisture source often results in its return. Salts remaining within the concrete can also interfere with coating adhesion or contribute to osmotic blistering.

Adhesive Deterioration

Flooring adhesives can soften, become sticky, lose holding strength, discolor, or ooze through seams when exposed to moisture and alkalinity beyond their limits.

Evidence may include curled flooring, shifting tiles, open seams, blackened joints, adhesive transfer, hollow areas, or wet residue beneath the flooring.

The investigator should identify the adhesive, flooring, substrate preparation, installation date, environmental conditions, moisture-test results, and manufacturer limits that applied when the floor was installed.

Whitening, Clouding, and Discoloration

Moisture can cause some clear coatings to develop a cloudy or milky appearance. Pigmented coatings may exhibit color changes, staining, or localized darkening.

Similar appearance changes can result from high humidity during cure, amine blush, chemical exposure, incompatible cleaners, improper mixing, contamination, or trapped solvent. The appearance alone is not enough to diagnose the cause.

Soft, Uncured, or Chemically Damaged Coatings

Moisture and high alkalinity at the interface can attack susceptible coating, adhesive, patching, and underlayment materials. The damaged material may feel soft, rubbery, sticky, or greasy.

However, incorrect mix ratio, incomplete mixing, expired material, low temperature, insufficient induction time, or chemical contamination can produce similar symptoms. Review batch information and installation records before reaching a conclusion.

Failure Patterns Provide Clues

The distribution of damage can be as important as the damage itself. Mapping the failure pattern may connect it with a particular moisture source or construction detail.

Moisture Damage Versus Preparation Failure

Moisture and poor surface preparation can exist together. A contaminated or weak surface may fail at a lower moisture exposure than properly prepared sound concrete.

Examine the concrete for laitance, curing compounds, sealers, oil, grease, dust, weak surface paste, incompatible repairs, and insufficient profile. Determine whether the preparation method opened the concrete and removed all bond-inhibiting material.

When concrete remains attached to the removed coating, moisture may still be involved, but the immediate failure may have occurred within weakened concrete rather than at the coating interface.

A Practical Failure-Investigation Process

1. Protect the area. Address slip hazards, loose flooring, sharp edges, chemical exposure, and unsafe conditions.
2. Document before disturbing. Take overview and close-up photographs and mark the affected areas on a floor plan.
3. Record the pattern. Note relationships to cracks, joints, walls, drains, equipment, doors, and previous repairs.
4. Determine the failure plane. Identify which layer separated and what remains attached to each surface.
5. Review project records. Examine specifications, product data, moisture tests, preparation records, batch numbers, environmental logs, and daily reports.
6. Investigate water sources. Consider the slab, ground, plumbing, exterior drainage, cleaning, condensation, and process operations.
7. Perform appropriate tests. Testing may include moisture, adhesion, surface strength, pH, soluble salts, contamination, and coating-film evaluation.
8. Compare evidence. Do not rely on one observation or test result.
9. Obtain qualified assistance. Significant failures may require an independent consultant, laboratory, engineer, or manufacturer representative.
10. Develop a written repair plan. Correct the cause before replacing the failed system.

Information to Collect

• Installation and failure-discovery dates
• Product names, batch numbers, colors, and expiration information
• Concrete age, thickness, mixture, and construction history when available
• Surface-preparation method and resulting profile
• Moisture, surface-temperature, humidity, and dew-point records
• Mixing, induction, application, recoat, and curing records
• Film-thickness and coverage information
• Previous coatings, adhesives, repair materials, and contaminants
• Cleaning, washdown, chemical exposure, and process conditions
• History of rainfall, flooding, plumbing leaks, or HVAC interruptions
• Location and condition of cracks, joints, drains, and penetrations
• Photographs, samples, test results, and written communications

Repairing the Cause, Not Just the Symptom

Localized patching can be appropriate when the cause is isolated and corrected. However, spot repairs frequently fail when they are applied over a continuing moisture source or when the surrounding system has the same underlying condition.

A sound repair plan may require removal of failed materials, correction of leaks or drainage, concrete repair, contaminant removal, moisture testing, surface preparation, installation of an approved mitigation membrane, and replacement of the coating or flooring system.

The repair system should be approved for the documented moisture condition, substrate, exposure, cleaning procedures, traffic, chemicals, temperature, and intended service.

Knowledge Check

Technical References

Use the current edition required by the project and the current instructions issued by the specified product manufacturer.

• ASTM D714 - Standard Test Method for Evaluating Degree of Blistering of Paints.
• ASTM D7234 - Standard Test Method for Pull-Off Adhesion Strength of Coatings on Concrete Using Portable Pull-Off Adhesion Testers.
• ASTM F2170 - Standard Test Method for Determining Relative Humidity in Concrete Floor Slabs Using In Situ Probes.
• ASTM F1869 - Standard Test Method for Measuring Moisture Vapor Emission Rate of Concrete Subfloor Using Anhydrous Calcium Chloride.
• ASTM F710 - Standard Practice for Preparing Concrete Floors to Receive Resilient Flooring.
• ICRI Guideline No. 710.3 - Guide for the Mitigation of Moisture in Concrete Floor Slabs.
• Current technical data sheets, installation instructions, and safety data sheets issued by the specified coating, flooring, adhesive, repair, and moisture-mitigation system manufacturers.

These references provide technical guidance but do not replace the project specification, governing regulations, manufacturer requirements, laboratory evaluation, or assessment by a qualified professional. Final failure conclusions and repair selections must be based on the complete body of available evidence.