TPO membrane welding: the key to long-lasting waterproofing

 

Waterproofing is one of the fundamental pillars of any building’s durability. Among the most advanced solutions in the European market, TPO membranes stand out as a technology that combines technical performance, sustainability, and versatility. One of the most critical aspects of this system’s effectiveness is the welding process, which ensures the watertightness of membrane overlap joints.

 

In this article, we explore the evolution of TPO membranes in Europe and the critical importance of hot-air welding in waterproofing system performance.

 

 

 

Origin and evolution of TPO membranes in Europe

 

TPO membranes began to be produced in Europe in the 1980s by Köster, the first company to manufacture these membranes, as a modern alternative to conventional PVC or bitumen-based solutions.

Their plasticizer-free and halogen-free composition made them an eco-friendly and efficient response to increasingly stringent environmental demands.

 

Since then, their application has grown significantly, driven by:

• Superior resistance to UV rays and thermal variations
• Stable chemical behavior and low maintenance
• Easy installation and homogeneous welding

 

Today, TPO membranes are widely used in industrial, commercial, and residential buildings across Europe, valued for their durability and contribution to energy efficiency.

 

 

The European Standard EN 13956

 

In the European context, standard EN 13956 defines the requirements for waterproofing systems using plastic and elastomeric membranes for roofs. For TPO membranes, this standard sets strict performance criteria, including:

• Resistance to artificial aging by UV exposure

• Tensile strength and elongation

• Impact and puncture resistance

• And, most importantly, the strength of welded joints

 

These requirements place welding at the heart of the installation process, making it a critical factor for the reliability and durability of the system.

 

 

 

 

Hot-air welding: a meticulous process

 

Unlike other systems that use chemical bonding, TPO membranes are welded exclusively by heat, using hot air. This method ensures a homogeneous fusion between the TPO membranes, creating a permanent, watertight bond.

 

The welding process essentially involves three steps:

• Definition of welding parameters
• Execution of the weld
• Testing and verification of the weld

 

 

Welding parameters

 

Defining the welding parameters involves four fundamental variables:

• Welding temperature: Must be precisely set and controlled to ensure fusion without degrading the material. The temperature must be high enough to fuse the membranes but stay within the manufacturer’s recommended range to avoid degradation.

• Airflow volume: Adequate and precisely controlled airflow is essential to evenly and effectively transfer heat across the membrane surface.

• Machine travel speed: A consistent and appropriate speed is crucial for joint uniformity.

• Applied pressure: Correct pressure ensures both surfaces come into full contact during fusion.

 

The TPO membrane welding process is considered complex and meticulous because the parameter settings are interdependent. For a given temperature, specific speed, airflow volume, and pressure are required.

Additionally, external factors such as ambient temperature and surface moisture must also be considered.

 

 

Executing the weld

 

The precision required for TPO welding has led to the development of highly specialized equipment. Most welds are carried out using automatic welding robots that ensure a perfect bond between membranes, provided the parameters are correctly defined. Edges and details, which cannot be handled by automatic machines, are done using manually operated equipment by experienced professionals.

 

One of the current highlights is the Leister VARIMAT 700 – a state-of-the-art automatic welding machine offering excellent performance in larger areas.

 

 

 

This equipment offers:

• Digital control of temperature and speed, adaptable to different membrane thicknesses and external factors

• Real-time monitoring to ensure uniform welding quality

• Ergonomic and robust design, ideal for large roof areas

 

The VARIMAT 700 technology allows faster, more efficient, and more consistent installation, reducing the risk of human error during the process.

For specific applications in smaller areas and details such as skylights and parapets, the Leister UNIDRIVE 500, which combines manual and automatic welding, is a suitable option.

 

 

 

The Leister TRIAC ST, a manual welding tool, also delivers excellent performance for detail welds.

 

 

 

Weld testing and verification

 

Optimal values for welding temperature, travel speed, airflow, and pressure are validated through preliminary welding tests, which must be carried out on-site to consider actual conditions.

After completing the waterproofing, manual verification of the welds should be performed using a Weld Seam Tester, with the aim of identifying and correcting any non-conformities.

 

 

The complexity of the welding process is justified by the superior bond quality it provides—one of the most reliable among all flexible waterproofing materials.

 

 

Joint quality defines system quality

 

Waterproofing with TPO membranes is only as good as the quality of its welds. In this context, technical expertise, installer experience, and the use of appropriate equipment are essential.

 

In an increasingly sustainability-focused European landscape, TPO membranes offer an outstanding solution—provided they are installed with precision. Hot-air welding, using equipment such as the VARIMAT 700, ensures a perfect union between membranes, resulting in decades of effective protection against infiltration.

 

At Prudêncio, we trust in tested and proven technical solutions. Our team specializes in TPO waterproofing, delivering high-performance and long-lasting results.