Commercial Roofing Case Study: Diagnostic Core Sampling & TPO Roof Replacement

At Green Valley Roofing & Construction, our commercial roofing team specializes in identifying hidden roof failures, navigating code requirements, and delivering high-performance systems backed by industry-leading warranties. This case study highlights how we assess complex flat roofs, determine the correct installation method through core sampling, and complete a fully warrantied TPO roofing system built for long-term performance.

Project Overview

• Type: Commercial Flat Roof Assessment & Replacement

• Scope: Core sampling, tear-off, insulation, TPO installation, metal edge securement, manufacturer warranty

• Objective: Provide a code-compliant, durable roofing system designed to reduce long-term risk and withstand weather exposure

1. Comprehensive Roof Evaluation

Green Valley Roofing & Construction was contacted by a commercial property management group seeking expert guidance on a failing flat roofing system. The building owner was interested in determining whether a repair, partial replacement, or full replacement was the best long-term solution.

After reviewing preliminary concerns shared by the management team, our commercial roofing experts scheduled an on-site evaluation to assess the roof’s condition, identify hidden issues, and provide a clear, code-compliant path forward.

Our commercial team began with a full rooftop assessment, documenting existing conditions and identifying potential points of failure. Because visual inspections alone cannot reveal what lies beneath the membrane, we recommended performing a core sample, a critical diagnostic step in commercial roofing.

Core sampling enables us to:

• Determine the number of existing roof layers

• Identify whether underlying materials are dry or saturated

• Confirm the roof deck type

• Ensure compliance with state roofing codes

• Select the correct installation method for long-term performance

This upfront discovery ensures our recommendations are accurate, code-compliant, and aligned with manufacturer warranty requirements.

Internal Resource: Learn how we approach roof inspections on our Commercial Roofing Services page. For additional reference, building owners can learn more about core sampling from the International Institute of Building Enclosure Consultants here.

2. Core Sample Findings & Code Compliance

The core sample revealed two existing roofing layers, which is the maximum allowed by code. A new system cannot be installed over two layers, so a full evaluation of the roof’s condition was essential.

Through testing, we confirmed:

• Both layers were dry and structurally sound

• The bottom layer could remain in place

• The top layer required removal before installing the new system

This allowed us to design a compliant, cost-efficient solution that maintained structural integrity.For readers wanting deeper code insights, the International Building Code (IBC) outlines these requirements.

3. Customized Roof Installation Plan

Based on our findings and warranty requirements, Green Valley Roofing & Construction implemented the following commercial roof system:

Removal of the top roofing layer

Ensured compliance with roofing code and proper adhesion for the new membrane.

Installation of ½-inch fanfold insulation

Provided a smooth substrate and improved thermal performance.

Installation of a 60-mil TPO membrane

A durable, energy-efficient single-ply system designed to withstand heat, UV exposure, and long-term weather conditions.

Installation of metal edge securement

This is one of the most important components of a commercial roofing system.
Edge failure is the #1 cause of roof blow-off during storms. By installing a reinforced metal edge, we significantly increased the roof’s wind resistance and met key insurance and manufacturer requirements.

Flashing all penetrations to warranty specifications

Ensured long-term watertight protection and eligibility for a full system warranty.

4. Manufacturer Inspections & Warranty Approval

Once installation was complete, the roofing manufacturer conducted an inspection to verify that every detail met their strict warranty criteria.

Key results:

• No welding failures were identified

• Only minor punch-list items were noted and corrected promptly

• The roof qualified for a 20-year No-Dollar-Limit (NDL) Warranty covering both labor and materials

This warranty guarantees that the manufacturer will repair or replace any warranted issue at no cost to the building owner—providing unmatched long-term security.

5. Results & Professional Impact

The completed roofing system provided the building owner with:

• A code-compliant installation meeting all industry and warranty standards

• A high-performance TPO system engineered for durability and energy savings

• Reinforced edge securement for better wind protection

• Full manufacturer-backed warranty coverage for 20 years

• A long-term roofing solution with reduced risk of leaks, uplift, or premature failure

This project reflects Green Valley Roofing & Construction’s expertise in diagnosing complex commercial roofing conditions and delivering precision installations that stand the test of time.

Frequently Asked Questions

1. Why is core sampling important for commercial roofs?

Core sampling uncovers the number of roof layers, moisture levels, deck type, and structural condition—information that cannot be obtained from a visual inspection. It ensures the new roof system complies with code and manufacturer standards.

2. Can a new roof be installed over old roofing?

Only when building code allows it, and only if the layers are dry and structurally sound. Code prohibits roofing over more than two existing layers. Our diagnostic process determines the safest and most cost-effective path.

3. Why is TPO a popular choice for commercial buildings?

TPO offers strong UV resistance, heat reflection, energy savings, flexibility, and long-term durability. It also pairs well with reinforced edges and insulation upgrades.

4. What causes commercial roofs to fail during storms?

Edge uplift is the most common failure point. That’s why we install reinforced metal edge securement to protect against wind, pressure changes, and storm damage.

5. What is a No-Dollar-Limit (NDL) warranty?

An NDL warranty means the manufacturer will repair or replace eligible roofing issues at no cost, regardless of the price of the repair. It is the highest level of coverage available in commercial roofing.

6. Does Green Valley Roofing handle warranty service?

Yes. If an issue arises, our team works directly with the manufacturer to assess, document, and complete covered repairs.

References: CertainTeed TPO & Single-Ply Roofing Overview