AirSprayTech Academy Certificate Program
Industrial Waterproofing and Fluid-Applied Membrane Systems
Article 21 of 24
Membrane Defects, Failure Investigation, and Repairs
A visible membrane defect is evidence—not necessarily the complete cause of the problem. Blistering may be associated with moisture, trapped air, contamination, curing conditions, excessive thickness, or incompatible materials. A crack may reflect substrate movement rather than inadequate membrane thickness. Effective repair begins by determining why the defect occurred and how far the condition extends. Covering the symptom without correcting the cause usually postpones the failure.
Defect, Damage, and Failure
These terms describe different conditions:
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Defect: A condition that does not meet the project specification, approved detail, manufacturer's instructions, or acceptance criteria.
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Damage: Physical harm caused after or during installation by traffic, tools, equipment, fasteners, impact, abrasion, backfilling, concrete placement, or another construction activity.
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Failure: Loss of the system's required function, such as leakage, loss of adhesion, inability to bridge movement, deterioration, or loss of continuity.
A membrane can contain a defect before leakage occurs. Finding and correcting that defect before concealment is one of the primary purposes of inspection and testing.
Do Not Repair Before Investigating
Premature repair can destroy evidence and make the actual cause more difficult to determine. Before cutting, removing, injecting, grinding, or coating the affected area:
- Stop work that could enlarge or conceal the condition.
- Mark and photograph the affected area.
- Record the location, dimensions, appearance, and surrounding conditions.
- Review material, weather, mixing, proportioning, application, thickness, and cure records.
- Determine whether the condition is isolated or repeated elsewhere.
- Obtain representative samples when required.
- Obtain an approved repair procedure before altering the area.
Pinholes and Holidays
Pinholes are small openings that pass through or substantially reduce the membrane film. Holidays are discontinuities where the waterproofing is absent or incomplete.
Possible causes include:
- Outgassing from porous concrete
- Air entrained during mixing
- Incorrect spray pressure or application technique
- Membrane applied too thinly
- Rough, porous, or incompletely filled substrate
- Missed spray, roller, brush, or squeegee coverage
- Bubbles that opened during cure
Repair normally requires cleaning and preparing the affected area, opening or removing unsound material where necessary, applying approved primer or detail material, restoring the specified membrane thickness, and retesting after cure.
Bubbles, Craters, and Outgassing
Air or vapor escaping from concrete can form bubbles in an uncured membrane. If the bubbles rupture, they may leave craters or pinholes. If they remain closed, they may create weak, hollow areas.
Contributing conditions may include:
- Rising substrate temperature
- Solar heating of concrete
- Porous or inadequately primed substrate
- Moisture or air within concrete voids
- Excessive wet-film thickness
- Air incorporated during high-speed mixing
If outgassing is widespread, repairing individual bubbles may not be sufficient. The application timing, primer, substrate porosity, temperature trend, and installation procedure should be reviewed before work continues.
Blistering
A blister is a raised area caused by separation or pressure within or beneath the membrane system. Blisters may be dry, water-filled, solvent-filled, or gas-filled.
Possible causes include:
- Moisture vapor or hydrostatic pressure
- Application over damp or contaminated concrete
- Trapped solvent, water, or air
- Application outside the permitted environmental range
- Loss of adhesion between coats
- Incompatible primer, membrane, or repair material
- Osmotic pressure created by soluble contamination
ASTM D714 provides photographic reference standards for describing blister size and density in paint systems. Its applicability to a particular membrane should be established by the specification or qualified project authority.
Opening one blister may reveal valuable information, but it should be done under an approved investigation plan. Record whether moisture, liquid, odor, contamination, uncured material, or a particular failure plane is present.
Delamination and Loss of Adhesion
Delamination may occur at several locations:
- Within weak or unsound concrete
- Between concrete and primer
- Between primer and membrane
- Between membrane coats
- Within the membrane itself
- Between the original membrane and a repair material
Potential causes include insufficient preparation, dust, laitance, moisture, surface contamination, expired recoat windows, improper primer, incomplete cure, or substrate deterioration.
ASTM D7234 provides a method for evaluating pull-off strength of coatings on concrete. Record the numerical result and the failure plane. A high test value in one isolated location does not establish acceptable adhesion across an entire affected area.
Thin Film and Incomplete Coverage
Thin membrane is often found on high points, edges, vertical surfaces, rough concrete, corners, transitions, and areas where application access is restricted.
Thin application can result from:
- Excessive spreading or insufficient material usage
- Incorrect spray-tip size, pressure, or travel speed
- Failure to account for substrate texture and porosity
- Inadequate wet-film measurement
- Material sagging away from high locations
- Incomplete application around details or obstructions
Repair should restore the specified total dry-film thickness and required continuity. Confirm whether the existing surface remains within its recoat window or requires cleaning, abrasion, and repriming.
Excessive Thickness
More membrane is not always better. Excessive thickness can contribute to:
- Solvent or water entrapment
- Extended cure
- Surface skinning over uncured material
- Sagging and displacement
- Cracking, wrinkling, bubbling, or foaming
- Loss of dimensional stability
Do not assume that an excessively thick area can simply be allowed additional time. Obtain the manufacturer's written disposition, which may require removal and replacement.
Soft, Tacky, or Uncured Membrane
A membrane that remains soft or tacky beyond its expected cure period may indicate:
- Incorrect mixing ratio
- Incomplete mixing
- Off-ratio plural-component equipment
- Material applied below its minimum temperature
- Excessive thickness
- Inadequate ventilation or evaporation
- Contamination or incompatible material
- Expired, damaged, or improperly stored components
Applying another coat over uncured material usually conceals rather than corrects the problem. Isolate the area and obtain a written evaluation and repair procedure.
Cracking and Splitting
Membrane cracking may result from substrate movement, inadequate joint detailing, low temperature, excessive thickness, loss of flexibility, incomplete cure, or application of a material not suited to the expected movement.
Before repair, determine:
- Whether the substrate crack is active or dormant
- Whether the location is a designed movement joint
- The direction and estimated amount of movement
- Whether the existing detail matched the approved drawing
- Whether reinforcement or a transition assembly is required
- Whether structural review is needed
ASTM C1305/C1305M evaluates a liquid-applied membrane's ability to bridge a preexisting substrate crack under controlled laboratory conditions. Laboratory crack-bridging performance does not eliminate the need for correct field joint and movement detailing.
Mechanical Damage
Punctures, cuts, tears, gouges, and abrasion can occur during inspection, testing, protection-board installation, reinforcing-steel placement, concrete placement, landscaping, backfilling, or equipment installation.
Do not repair only the visible opening. Inspect the surrounding membrane for:
- Hidden separation from the substrate
- Stretching or distortion
- Crushed protection materials
- Contamination forced beneath the membrane
- Damage extending beyond the visible edge
Localized Defect or Systemic Problem?
A localized repair may be reasonable when the defect has a defined cause, limited boundaries, sound surrounding membrane, and an approved repair method.
Broader removal or replacement should be considered when investigation finds:
- Widespread adhesion loss
- Repeated blistering or outgassing
- Incorrect product or primer
- Off-ratio or incompletely mixed material
- Consistently insufficient thickness
- Application over unacceptable substrate or moisture conditions
- Movement exceeding the capability of the installed detail
Numerous small patches do not convert a fundamentally defective installation into an acceptable waterproofing system.
General Membrane-Repair Sequence
The exact repair procedure must come from the membrane manufacturer and project authority. A typical controlled repair sequence includes:
- Mark and document the repair boundary.
- Remove all loose, damaged, contaminated, or uncured membrane.
- Extend removal to sound, well-bonded material.
- Inspect and repair the exposed substrate.
- Clean, dry, and prepare the existing membrane edge.
- Apply approved cleaner, surface treatment, or primer.
- Install reinforcement or detail material where required.
- Apply repair membrane at the specified thickness and overlap.
- Allow the repair to cure under acceptable conditions.
- Inspect, test, photograph, and document the completed repair.
Chemical-Grout Injection
Chemical grout may be used to seal leaking cracks, joints, and voids within concrete. It is installed through drilled or surface-mounted ports and reacts within the leakage path.
ASTM D8109 addresses material selection, installation, and inspection for chemical-grout crack-injection waterproofing repairs. The work requires control of:
- Grout selection for the water and movement conditions
- Port location, spacing, and drilling angle
- Injection pressure and sequence
- Containment of grout and reaction products
- Confirmation that the leakage path has been filled
- Surface repair and compatibility with subsequent membrane work
Injection can stop an active leakage path, but it does not automatically restore structural capacity or replace an exterior membrane system.
Repair Verification
A repair is not complete when the new material has been applied. Verification may include:
- Visual inspection
- Wet-film or dry-film thickness measurement
- Cure verification
- Adhesion testing
- Holiday or electronic leak detection
- Controlled water testing
- Observation under the service condition that originally produced the leakage
Use the same acceptance standard applied to the original membrane unless a written repair specification establishes a different requirement.
Repair Documentation
Each repair record should include:
- Repair number and exact location
- Date the defect was discovered
- Description and dimensions of the condition
- Photographs before, during, and after repair
- Probable or confirmed cause
- Approved repair procedure
- Products, batch numbers, and materials used
- Environmental conditions
- Inspection and retesting results
- Name and authorization of the accepting party
Technical References
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ASTM D8109-25
— Standard Guide for Waterproofing Repair of Concrete by Chemical-Grout Crack Injection.
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ASTM C1305/C1305M-25
— Standard Test Method for Crack-Bridging Ability of Liquid-Applied Waterproofing Membrane.
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ASTM D7234-22
— Standard Test Method for Pull-Off Strength of Coatings on Concrete Using Portable Pull-Off Adhesion Testers.
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ASTM D714
— Standard Test Method for Evaluating Degree of Blistering of Paints.
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ASTM D7877-25
— Standard Guide for Electronic Methods for Detecting and Locating Leaks in Roofing and Waterproofing Membranes.
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The waterproofing manufacturer's current product data sheets, approved repair procedures, compatibility requirements, testing instructions, and written project-specific technical guidance.
Confirm the current edition and contractual applicability of every referenced standard. A repair procedure must be suitable for the specific membrane, substrate, exposure, defect, and cause of failure.
Professional responsibility: Do not cover a defect merely because the repair material will hide it. Determine the cause, establish the full extent of the condition, obtain an approved repair procedure, and verify the completed repair before the waterproofing system is concealed or returned to service.
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