Overview

Quality control on a TPO roofing system means verifying every weld before the project is signed off. A seam that looks good from a distance can have cold spots, thin areas, or unbonded sections that will fail in rain or wind. The probe test is the only way to know. At Trust Roofing, probing every seam is a non-negotiable step on every TPO project. This training covers the Trust Roofing standard for quality control and probing on a TPO flat roofing system.

Our Field Standards

TPO quality control and probing follows Trust Roofing field standards.

Field standards include:
* Every field seam and hand-welded detail is probed before the project is signed off
* Probing is completed after the weld has cooled — minimum 15 minutes after welding
* The probe tool is inserted along the full length of every seam — not just spot-checked
* Any area where the probe penetrates more than 0.25 inches from the edge is marked for re-weld
* Re-welded areas are probed again before sign-off
* The QC process is documented — problem areas and re-welds are noted in the project record

Our Process

How to Probe a TPO Seam

1. Allow the weld to cool — minimum 15 to 20 minutes
2. Hold the probe tool at a low angle — almost parallel to the membrane surface
3. Insert the probe tip into the seam edge with consistent, moderate pressure
4. Move the probe continuously along the full length of the seam
5. A properly welded seam: the probe cannot penetrate more than a few millimeters
6. A failed seam: the probe slides in easily — you will feel the difference immediately

What to Look For During Probing

Beyond the probe test, visually inspect for:
* Burn marks or areas of membrane damage from excessive heat
* Wrinkles at seam edges — indicates tension or improper installation
* Areas where membrane has pulled away from the edge — indicates under-welding
* T-joint areas — insert the probe carefully at the three-way intersection

What to Do When a Problem Is Found

1. Mark the problem area
2. Re-weld with the hand welder
3. Apply pressure with the silicone roller immediately after welding
4. Allow to cool
5. Probe again before moving on

Final Inspection Walkthrough

* Walk every seam in order — do not skip any section
* Document all re-welded areas
* Photograph the completed QC walkthrough

Roofing Terms

Probe Test

The standard quality control method for TPO roofing, a blunt probe tool is inserted along the seam edge to test whether the weld has achieved full molecular fusion. A properly welded seam resists the probe; a failed seam allows easy penetration.

Cold Seam

A TPO weld that appears visually complete but has not fully bonded due to insufficient heat, speed setting, or roller pressure, only detectable through probing and a leading cause of flat roof leaks in Florida’s rainfall conditions.

Re-Weld

The process of applying additional heat and roller pressure to a failed or incomplete TPO seam to achieve a complete, watertight bond, required whenever probing identifies a failure, before any adjacent seams are started.

Florida Roofing Inspection QC

Florida building inspectors may probe TPO seams on permitted flat roofing projects to verify weld quality, Trust Roofing’s internal probing standard ensures every seam meets or exceeds what an inspector would require.

Florida Product Approval Compliance

The requirement that TPO roofing systems be installed strictly per their Florida Building Commission product approval, including minimum weld widths, fastener patterns, and QC procedures, to maintain the system’s legal installation status in Florida.

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