[The following is an internal incident report filed on August 20, 2026, by James Robertson, Project Manager, to the General Contractor's head office in Singapore. The report was shared with us by a source who works on the project. Names and specific project details have been removed to protect identities. The report itself is unedited.]

INTERNAL INCIDENT REPORT – CONFIDENTIAL

Project: [Redacted] Mixed-Use Development, Ho Chi Minh City
Date of Report: August 20, 2026
Reported By: James Robertson, Project Manager
Incident: Roof waterproofing failure – liquid membrane system
Financial Impact: Estimated $45,000 for remediation + $22,000 for internal damage repairs
Status: Remediation in progress

1. Incident Summary

On August 15, 2026, during routine inspection following a heavy rain event (72mm in 4 hours), water penetration was detected in the penthouse level of Tower B. Upon investigation, leaks were found across an estimated 85 square meters of roof area. The waterproofing membrane had failed at multiple locations.

The waterproofing system was applied in April 2026. The product was specified by the design consultant. The application was carried out by the approved subcontractor. The system was signed off by the independent inspector in May 2026.

Six months later, it failed.

2. Investigation Findings

I have conducted a visual inspection of the failed areas, reviewed the application records, and interviewed the subcontractor's site supervisor. I have also contacted the product manufacturer for a technical review.

Finding A: Product Specification

The specified product is a two-component liquid-applied polyurethane membrane. It is a mid-range product from a mid-tier Chinese manufacturer. The product holds ISO certification and has been used on similar projects in the region.

However, the specification called for a dry film thickness of 1.5 millimeters. The manufacturer's data sheet recommends 2.0 millimeters for tropical climates with high rainfall. The specification did not account for the local climate.

The design consultant has stated: "We used the standard specification from the product data sheet." The product data sheet lists 1.5mm as the minimum for all applications. The data sheet has a footnote saying "2.0mm recommended for high-rainfall regions." The designer missed the footnote.

Finding B: Application Conditions

The application was carried out in April 2026. According to the subcontractor's records, the ambient temperature was 34°C. Relative humidity was 82%.

The product data sheet specifies application between 10°C and 35°C, with relative humidity below 80%.

The application was at the edge of the acceptable range.

The subcontractor's records also show that the roof was power-washed the morning before application. The surface was dry at the time of application. But the substrate temperature was measured at 38°C. The product data sheet does not specify a maximum substrate temperature. The manufacturer's technical representative later told me that application on a substrate above 35°C can cause the solvent to evaporate too quickly, leading to pinholes and reduced adhesion.

The subcontractor did not know this.

Finding C: Inconsistent Coverage

I removed six core samples from failed areas. The dry film thickness varied between 0.8 millimeters and 2.2 millimeters. The specified thickness was 1.5mm.

In the thinnest areas (0.8mm), the membrane was not continuous. There were pinholes that could be seen with a magnifying glass. The pinholes were the leak paths.

In the thickest areas (2.2mm), the membrane had blistered. The blistering was caused by solvent trapped during curing. The thick layer cured on the surface but trapped solvent underneath. The trapped solvent expanded, created blisters, and the blisters eventually ruptured.

The subcontractor used a roller to apply the coating. The roller application was specified in the method statement. But the subcontractor used the wrong roller nap length. The nap was too short. The coating was applied inconsistently.

Finding D: The Inspector's Role

The independent inspector signed off on the application in May 2026. The inspector took three core samples at the time of sign-off. All three samples measured 1.4mm to 1.6mm. The inspector did not check for pinholes or blistering.

The inspector's report stated: "Satisfactory."

The inspector did not witness the application. He only saw the final product. He did not test for adhesion. He did not test for continuous film integrity.

He signed off anyway.

3. Root Cause Analysis

Three contributing factors caused the failure:

1. Specification error. The specified thickness was too low for the climate. The design consultant used a standard specification without adjusting for local conditions.

2. Application error. The subcontractor applied the product outside the recommended conditions (temperature and humidity) and used the wrong roller nap, resulting in inconsistent thickness.

3. Inspection gap. The independent inspector performed a superficial inspection. He did not test for film integrity or adhesion. He assumed the subcontractor had followed the specification.

4. Lessons Identified

From this incident, I have identified four lessons for future projects:

1. Match the spec to the climate, not the data sheet. The product data sheet is a starting point, not a conclusion. The designer should have adjusted the thickness for tropical conditions.

2. Monitor application conditions. The subcontractor should have checked temperature and humidity against the product spec. They didn't. The PM team should have checked that the subcontractor checked.

3. Test the application, not just the product. The product is certified. The application is not. The inspection should focus on the application quality, not just the material quality.

4. The inspector's sign-off is not the end of the process. The inspector signed off. The roof still failed. The PM team should have performed a second inspection after the first rain.

5. Remediation Plan

The failed areas will be stripped and reapplied. The new application will be 2.0mm, using a different product with a proven track record in tropical climates.

The subcontractor will be replaced. The new subcontractor will be one with experience on similar projects.

The new application will be supervised by a technical representative from the product manufacturer.

The new application will be tested with a flood test: the roof will be flooded with water for 48 hours before sign-off.

6. Cost Summary

These costs will be shared between the subcontractor (50%) and the general contractor (50%). The general contractor's share will be $37,500.

7. Final Note

I am filing this report to document what happened and to prevent it from happening again.

The waterproofing spec is a starting point, not an ending point.

The application conditions matter as much as the product.

The inspector's sign-off is not a guarantee.

I will be changing our future waterproofing specifications for all projects in tropical climates. I will be adding a mandatory flood test to the sign-off process. I will be checking the subcontractor's equipment and materials before they start.

[This report was filed on August 20, 2026. The remediation work is scheduled to begin September 1. The project is now delayed by 10 weeks.]

The product was certified. The application was certified. The inspector signed off. Six months later, the roof leaked. H

Certified product. Certified application. Inspector sign-off. Six months later, the roof leaked. Here's the incident report I had to file.

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