Unit 4: Field Defect Diagnosis and Remediation Guide
Updated: 16 min readBy the Azl technical team
Contents
Diagnostic method: four possibilities for every defect
Almost every defect in an insulation layer traces back to one of four sources: the substrate (moisture, dust, laitance, insufficient profile), the material (wrong mix ratio, contamination, expired, stored hot), the conditions (temperature, humidity, dew point, wind, sun), or the application (thickness, time between coats, technique). A good technician does not start with the repair but with evidence: photos, readings, a sample of the defective layer, and the daily records explained in Unit 3.
- 1
Describe the symptom precisely
What does it look like (blister, pinhole, peeling, crack, tackiness)? Where is it concentrated (near drains, on the sunny side, in a particular coat)? When did it appear (during spraying, after hours, after months)? Photograph it with a measuring scale.
- 2
Cut a sample
Cut a small X or square and inspect: is the separation between the material and the substrate, between two coats, or within the concrete itself? Each failure plane points to a different cause. Reseal the sample location per the data sheet.
- 3
Review the application-day records
Surface and air temperature, humidity, dew point, material batch numbers, machine settings (pressure and temperature), and coat times. Missing records are themselves a diagnostic finding.
- 4
Measure the current condition
Substrate moisture, dry film thickness, hardness or tackiness, and an adhesion test if the tool is available. Compare with the data sheet requirements.
- 5
Identify the root cause
Link the symptom to its cause using the tables below. If two causes are possible, test each; blisters, for example, may come from substrate moisture or from concrete outgassing, and prevention differs.
- 6
Decide the repair scope
Is the defect local or widespread? A widespread defect tied to mix ratio or an unprepared substrate usually means removing the system across the whole area. A local defect is cut back to sound edges and rebuilt with an overlap onto the sound layer.
- 7
Execute, document and retest
Carry out the repair with the same materials or compatible ones approved by the manufacturer, then repeat the water test or adhesion test for the area and document everything in the project file.
Defects in sprayed and liquid coatings (polyurea, polyurethane, epoxy)
| Defect | Symptoms | Scientific cause | Remedy | Prevention |
|---|---|---|---|---|
| Blistering and pinholes | Closed bubbles or pin-sized holes, most common on concrete exposed to sun | Air and water vapour inside concrete pores expand as temperature rises or barometric pressure changes and escape through the coating before it sets (outgassing), or surface moisture reacts with isocyanate to release carbon dioxide gas | Cut out and feather the blisters, fill the holes with a suitable primer or filler, then apply a fresh coat within the recoat window | Apply a low-viscosity penetrating primer to seal the pores, spray in the evening when air and concrete temperatures are falling, avoid air currents across the surface, and confirm the substrate is dry |
| Slow cure or tacky surface | Material stays soft or sticky beyond the data sheet time, in patches or across the whole area | Off-ratio A:B mix (excess of one component leaves unreacted groups), low temperature slowing the reaction, material contaminated by moisture or past shelf life, or inadequate hand mixing | Never coat over a tacky layer. Scrape off and remove the defective layer to the substrate or to a sound, hard layer, clean with the solvent the manufacturer specifies, and reapply the system | Test spray before work, monitor both component pressures and temperatures, check pump filters, store materials per the data sheet, and record batch numbers |
| Delamination or loss of adhesion | Coating peels in sheets, sounds hollow when tapped, or separates between coats | Inadequate surface preparation (weak profile, laitance or dust), omitted or incompatible primer, exceeding the recoat window so the lower coat has cured and no longer bonds chemically, or contamination between coats | Remove all detached areas back to well-bonded edges, abrade the edges and the sound old coating, then prime and reapply the system with an overlap onto the old | Surface profile per the data sheet (compared against ICRI CSP chips), respect the recoat window and sand beyond it as the data sheet requires, and run periodic adhesion tests |
| Cracking of the coating | Hairline or linear cracks in the coating, sometimes over concrete cracks or joints | Movement at an untreated crack or joint in the concrete, a rigid low-elongation coating over a moving substrate, excessive thickness of a rigid coating, or large differential thermal movement | Open the crack and determine whether it is moving, treat the joint with a flexible sealant or reinforcing strip, then recoat with a system suited to the movement | Treat cracks and joints before coating, choose a system with flexibility matching expected movement, and keep to the specified thickness |
| Amine blush on epoxy | Waxy, greasy or white hazy film, or dull patches, sometimes invisible to the eye | The amine in the curing agent reacts with moisture and carbon dioxide in cold, damp conditions or when the surface temperature approaches the dew point, or when fuel-burning heaters are used | Wash with warm water and detergent using a stiff brush, rinse and dry, then verify before the next coat. If left, it acts as a bond breaker for the next coat | Keep the surface at least about 3°C (5°F) above the dew point during application and cure, ventilate, and avoid fuel-burning heaters |
| UV yellowing and chalking | Colour shifts to yellow or brown with loss of gloss, and a powdery surface develops over time | Aromatic polyurea and polyurethane are not colour-stable under ultraviolet light, and epoxy in general is affected by UV | Clean and abrade the surface, then apply a UV-resistant aliphatic topcoat as the manufacturer recommends | Use an aliphatic or polyaspartic topcoat on exposed surfaces, or an aliphatic system from the start |
Concrete outgassing deserves attention because it is very common in Saudi Arabia. Euclid Chemical (external source via the Consumer Safety Center) explains that air and water vapour inside concrete pores expand as temperature rises and escape through the coating, and recommends applying in the evening when air temperature is decreasing and sealing the pores with a low-viscosity primer. In practice, spraying a concrete deck in the morning and then exposing it to the midday sun is a reliable recipe for pinholes.
On delamination, a KTA case study (external source via the Consumer Safety Center) describes a polyurea coating whose coats separated because the recoat window (16 hours for that product) was exceeded without the sanding the data sheet required, and because the surface had been water-cleaned without any profile. The remedy was removing the whole system. The lesson: a recoat window is not a suggestion but a condition of adhesion.
Spray polyurethane foam defects
| Defect | Symptoms | Scientific cause | Remedy | Prevention |
|---|---|---|---|---|
| A-rich foam (isocyanate) | Hard, brittle, friable foam, sometimes darker in colour | Excess isocyanate due to a cold B component, a pump fault, or a restriction on the B side | Cut out defective foam back to sound foam and respray after correcting the cause | Monitor both pressures, heat both components per the data sheet, and test spray |
| B-rich foam (resin) | Soft, rubbery, tacky foam with a strong odour | Excess resin due to an A-side fault, storage outside the recommended temperature, or contamination | Remove the affected area completely, ventilate the space, then respray | Check A-side filters and pumps, and store materials within the specified temperature |
| Shrinkage, cracks and voids | Foam pulling away from edges, internal cracks, voids visible when cut | Over-thick passes trapping heat, insufficient cooling time between passes, thermal shock from rapid cooling, or poor mixing | Cut defective sections at an angle back to sound foam, clean the substrate and respray in passes | Keep to the maximum pass thickness in the data sheet and the cooling time between passes |
| Poor cell structure and friable surface | Large irregular cells, a crumbly surface or a hard glossy skin, poor adhesion | Low substrate or material temperature slowing the reaction, inadequate resin mixing in the drum, or wrong ratio | Remove the affected layer and respray after correcting temperature and mixing | Mix resin in the drum per the data sheet before and during spraying, and measure substrate temperature |
| Internal scorching (fire risk) | Dark or burnt foam core, smoke or burning smell, and possible self-ignition | Reaction heat (exotherm) builds up in thick passes because foam insulates and traps the heat; SPFA recommends keeping internal temperature at or below about 82°C | Stop spraying immediately, do not touch hot foam by hand, move hot masses to a safe area outside the building, and remove the damaged foam | Never exceed the maximum pass thickness, and allow 15–30 minutes between passes per SPFA or as the data sheet sets |
| Blistering in roof foam | Bubbles or blisters in the foam or its topcoat after sun exposure | Moisture or dew on the substrate at the time of spraying, or a first pass thinner than the minimum | Cut out the blister, dry the substrate, respray, then topcoat | Spray the first pass at no less than about 13 mm on roofs per SPFA, and check substrate dryness and dew point |
The BASF application guidelines (external source via the Consumer Safety Center) note that the risk of scorching and fire increases with pass thickness, and warn against removing foam build-up by hand. The JLC article (external source via the Consumer Safety Center) explains that A-rich foam is hard and brittle, while B-rich foam is soft, rubbery and odorous. For machine setup see the equipment unit, and for fire procedures the safety unit.
Membrane and crystalline system defects, and leaks after testing
| Defect | Symptoms | Scientific cause | Remedy | Prevention |
|---|---|---|---|---|
| Bituminous membrane lap failure | Raised lap edge, trowel tip slides under the lap, leakage along the lap line | Under-torching that does not melt the underside bitumen, lap narrower than specified, wet primer, mineral granules not embedded at end laps, or dust and moisture | Open the lap, dry it and re-torch, or cut out the damaged section and apply a patch with full overlap per the data sheet | Probe every lap with a cold trowel tip, watch for the bitumen bead at the edge, and keep to the lap width in the data sheet |
| Blistering under the membrane | Large bubbles under the membrane that grow in the heat | Moisture trapped in the slab or primer vaporising in the sun, or air trapped by uneven torching | Cut the blister in an X, dry it, re-bond it, then apply a patch over it | Install only on a dry substrate, and let the primer dry fully |
| White efflorescence on a crystalline system | White deposits on the surface or at cracks | Soluble salts (mainly calcium hydroxide) carried to the surface by water react with carbon dioxide and deposit as the water evaporates | Brush off the deposits with water and monitor; if they persist, water is still passing through and the crack may need injection | Surface preparation that opens the pores, adequate moist curing, and treating cracks wider than hairline before coating |
| Dusting or cracking of the crystalline coat | Powdery surface that rubs off by hand, or hairline cracks in the coat | Rapid drying before reaction due to sun and wind, an unsaturated substrate, or a coat thicker than allowed | Remove the weak coat with a wire brush and reapply on a saturated substrate with correct moist curing | Apply in cooler hours, mist-cure several times a day per the data sheet, and keep to the specified thickness |
| Leak after the water test | Seepage on the soffit, at drains or walls during or after the test | Usually details, not the field: around drains and pipes, a low or unsecured upstand, an unbonded lap, or a mechanical puncture from equipment | Trace the water path by dividing the roof and flooding each zone separately, then repair the detail and retest | Reinforcement details around drains and penetrations, protect the membrane before trades walk on it, and check laps before testing |
Why do we suspect details first when a leak appears after testing? Because the flat field is easy to install and inspect, while drains, pipes and corners gather every difficulty: a change in membrane direction, hard access for the torch or spray gun, and the meeting of different materials. Water takes the shortest path and often appears far from where it entered, so dividing the test into zones is the fastest way to locate it.
Plural-component proportioner and spray gun faults
Many foam and polyurea defects start in the machine, not on the substrate. The Reactor troubleshooting guide published by Huntsman (external source via the Consumer Safety Center) summarises the common faults below. The actions are general; the actual repair is per the manufacturer's manual for your machine model and carried out by a qualified technician.
| Fault | Symptoms | Likely causes | Action (per the manufacturer's manual) |
|---|---|---|---|
| Pressure imbalance between components | Clear difference between A and B gauges, pressure imbalance alarm, foam with abnormal colour or texture | Restriction in the mix chamber, gun screen or hose, starved supply from the drum pump, clogged filter, viscosity difference from inadequate heating, or a faulty pressure transducer | Stop spraying, clean the mix chamber and screens, check feed pumps, drum levels and venting, and check the transducer by swapping connections as the manual describes |
| Cavitation | Low, fluctuating pressure on one side, reduced flow from one side at the gun | Feed pump stopped or weak, drum nearly empty, blocked drum desiccant breather, debris or a dented drum bottom, or faulty pump check valves | Confirm the feed pumps work and material is sufficient, clear the breather, inspect pump check valves and the pressure relief valve |
| Temperature not reaching setpoint | Slow-reacting foam or poor cell structure, low temperature reading | Failed heater element, disconnected or damaged thermocouple, a module not energising, or inadequate circulation from the feed pump | Check sensor connections and heater element resistance against the values in the manual, and check the breakers |
| High fluid temperature | Over-temperature alarm, very fast-reacting material | Faulty thermocouple or a heater module not switching off at setpoint | Shut off heat and check the sensor and module per the manual before restarting |
| Hose heat faults | Material cools in the hose, or a no-current alarm on the hose zone | Tripped breaker, broken hose connections, or a fault in the hose transformer | Reset the breaker, and check connection continuity and transformer output as the manual describes |
| Motor over-temperature or high current | Machine stops with a temperature or current alarm | Pressure or mix chamber too large for the machine, cooling fan stopped, or binding in the pump | Reduce pressure or mix chamber size, check the fan and clear obstructions, and inspect the pump |
| Irregular spray pattern | Intermittent spray or tails at the edges of the fan | Partial blockage of the mix chamber ports, low pressure or temperature, or pressure imbalance | Clean the mix chamber with the tools in the manual, reset pressure and temperature, then test spray |
Before calling the machine technician
- Material level in both drums is sufficient and the feed pumps are working
- Drum vents and desiccant breathers are not blocked
- Gun screens and pump inlets are clean
- Set temperatures for both components and the hose match the material data sheet
- Static and spraying pressures are recorded for both sides
- The mix chamber suits the application and is clean
- Generator or supply voltage matches the machine's requirements
Printable checklist — use your browser's print command.
When to patch and when to remove the whole system
The practical rule: if the defect results from a local condition (a damp spot, a mechanical puncture, a single lap), a local repair with an overlap onto sound material is enough. If the cause is systemic (an unprepared substrate across the whole area, a wrong mix ratio through a full spray day, an exceeded recoat window on every coat), patching only postpones the problem, and the solution is removing the system in the affected area and reinstalling. That is what we call insulation restoration, and our insulation renewal service may be the more economical option in the long run. For the properties of each material, see the materials guide.
If you want an opinion on a specific case, send photos and application records through the form below or request an inspection. Repairs carried out by Azl are covered by a written warranty whose duration depends on the insulation type and surface condition, according to the warranty policy.
Frequently asked questions
Why do bubbles appear in a coating on concrete an hour after spraying?
The most common cause is air and water vapour escaping from the concrete pores as the concrete warms, passing through the coating before it sets. That is why manufacturers recommend applying when temperature is falling (late in the day) and sealing the pores first with a low-viscosity primer. The second cause is substrate moisture, especially with materials that react with water, so check substrate dryness and dew point.
Can I coat over a polyurea or epoxy layer that stayed tacky?
No. A tacky layer usually means an off-ratio mix, low temperature or contaminated material, and it will not finish curing under a new coat; it will become a failure plane instead. The solution is to scrape and remove the defective layer down to a sound surface, clean with the solvent the manufacturer specifies, and find the cause in the machine or the material before reapplying.
What is a recoat window and why does it cause delamination?
It is the period during which the next coat can be applied and bond chemically to the previous one. Once it passes, the lower coat has cured and adhesion becomes purely mechanical, so data sheets require sanding or a tie primer. In one documented case a contractor exceeded a 16-hour window on a polyurea coating without sanding, the coats separated and the owner had to remove the entire system.
How can I tell that spray foam came out off-ratio?
Isocyanate-rich (A-rich) foam is hard, brittle and crumbly, while resin-rich (B-rich) foam is soft, rubbery and has a strong odour. The simplest check is spraying a sample before work and comparing, and watching that both pressures stay balanced during spraying. Any off-ratio foam is cut out back to sound foam and never covered with a new pass.
White deposits appeared on a wall treated with crystalline waterproofing. Has it failed?
Not necessarily. The white deposits are salts carried by water from inside the concrete and left behind as it evaporates, and they can appear in the first weeks while the crystalline reaction develops. Brush them off with water and monitor: if they stop, it is normal; if they persist or concentrate at a crack, water is still passing through and the crack may need injection or further treatment.
What should I check first when a proportioner shows pressure imbalance?
Start with the simplest: material level in both drums, feed pump operation, blocked drum vents, and clean gun screens and mix chamber. Then check both component temperatures, because cold material is more viscous. If the imbalance persists, the problem may be a pressure transducer or the pump itself, which should be checked per the manufacturer's manual by a qualified technician.
Technical or training enquiry
For technicians and engineers: ask about an application, a machine or a step in this unit.
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References and sources
- How to Prevent Coating Defects Caused by Concrete Outgassing — Euclid Chemical · euclidchemical.com
- Causes, Detection, and Removal of Amine Blush — KTA-Tator · kta.com
- How to Identify, Prevent & Remove Amine Blush in Epoxy — Sherwin-Williams · industrial.sherwin-williams.com
- Amine blushing: identification, prevention and remediation — Carboline · carboline.com
- When a Good Idea Goes Bad: Delamination — KTA-Tator · kta.com
- The Ultimate Guide to Aliphatic and Aromatic Polyurea — Ultimate Linings · ultimatelinings.com
- Troubleshooting Spray-Foam Insulation — JLC · jlconline.com
- TechTip I2: Exothermic Temperatures in SPF — Spray Polyurethane Foam Alliance · upcfoam.com
- ENERTITE Max Application Guidelines — BASF · download.basf.com
- Reactor Error Code Troubleshooting Guide — Huntsman Building Solutions · huntsmanbuildingsolutions.com
- Concrete Coating Installation and Procedures — Xypex Chemical Corporation · xypex.com
- 5.2.2 Application of Membrane — Canadian Roofing Contractors Association · roofingcanada.com
External links pass through Azl's Consumer Safety Center for checking before leading to other organisations' websites. Citing them does not imply they endorse Azl. Technical values are typical and vary by product; the final reference is the approved product's datasheet and the project design. Editorial policy