Why are Köster TPO membranes the most suitable for waterproofing?



Waterproofing membranes are an essential part of any construction project, whether it is a new build or a rehabilitation.


In order to see a remarkable performance from waterproofing systems, it is necessary to have a deeper knowledge of their products and their application techniques.


Therefore, in this article we will discuss waterproofing membranes and more specifically the advantages of Köster TPO membranes over PVC and bituminous membranes.


Continue reading the article and clarify all your doubts regarding these solutions.



Prudêncio's work at Nave in Marvila
Prudêncio’s work at Nave in Marvila


Köster TPO membranes

Ideal for use in various applications, Köster TPO membranes are Prudêncio’s commitment to excellence in waterproofing. Composed of thermoplastic polyolefin (hence the term TPO), they are applied through thermal welding, with robotic systems.


Unlike most TPO membranes that are made of polypropylene (PP), Köster’s TPO is based on polyethylene (PE), which gives greater resistance to abrasion and tensile strength, to thermal amplitudes, among many other advantages.


Köster’s TPO membranes have a 10 to 25 years warranty, with a useful life of more than 40 years. In addition to this major advantage, others can be highlighted:


  • High resistance to UV’s and ozone;
  • Resistant to root perforation, with FLL certification for garden coverings;
  • Resistant to all weather conditions (certified for hail);
  • Resistant to acids, solvents, oils, alcohol and bitumen;
  • Allow direct application on any type of thermal insulation;
  • Reflect sunlight;
  • Reduced maintenance.


Köster TPO is also highly environmentally responsible, as it doesn’t contain or release toxic or environmentally hazardous compounds, doesn’t include plasticizers and non-molecular binders like PVC membranes and is fully recyclable.


For its general characteristics, it has been certified for sustainable construction and awarded the Gold rating, the highest awarded by the german organization: Institut Bauen und Umwelt e.V. (IBU).



Prudêncio's work at Amélia Madaíl Parish Home, in Aveiro
Prudêncio’s work at Amélia Madaíl Parish Home, in Aveiro


PVC Membranes

We have often been called to rehabilitate roofs with PVC membranes that have shown poor results in terms of integrity, stability and durability, sometimes presenting problems well before the expected lifetime (15 to 20 years).


One of the features that contributes to the weakness of these membranes is the fact that they have plasticizers in their composition, which ensure flexibility to PVC, which is naturally a very rigid and not very ductile material.


Under adverse conditions – the PVC membranes are chemically sensitive to contact with various products, such as bitumen, oils, some thermal insulations, among others, and aren’t resistant to dripping, due to the microorganisms that develop on them – the plasticizers migrate easily, leading to their loss, causing the membranes to shrink and become rigid and brittle, leading to ruptures that occur more quickly in areas of greater stress, such as fastening points and peripheral trim.


The plasticizers used in the production of PVC membranes are generally toxic chemicals that generate negative impacts during their production, use and application (noticeable, for example, in the smoke released when welding the joints of PVC waterproofing systems, which affects the applicators). As they are released in the aging process of the membranes, they enter the soil through the drainage of contaminated rainwater from the roofs, causing risks to the environment and public health. Consequently, there is a growing trend to seek alternatives to PVC, and Prudêncio stopped applying this solution several years ago.


PVC membranes also have limited resistance to the sun’s rays, when compared to Köster’s TPO.


Being included in the family of thermoplastic membranes, their application is similar to that of TPO: they are single-layer systems, which are joined together by thermal welding and gluing profiles.


Still, there are important differences in the procedures, as in the case of the temperature of the welds. PVC is welded at an air temperature of around 400°C, while Köster’s TPO membranes are welded at 620°C.



PVC membrane with about 10 years of use that presents shrinkage, ruptures and loss of components, with visible reinforcement
PVC membrane with about 10 years of use that presents shrinkage, ruptures and loss of components, with visible reinforcement



Bituminous Membranes

In modified bituminous membranes, their properties are altered during the manufacturing process by the use of one or more chemical agents, which include synthetic polymers that, in turn, confer better characteristics when compared to non-polymer-modified bituminous membranes.


Bituminous membranes, also popularly known as asphalt membranes, are usually applied as a double layer. These systems have a high weight, which imply great physical efforts in the unloading and its application, and which need more attention to possible structural risks for the roofs.


As an example, in the rehabilitation of the Pingo Doce roof in Aveiro, performed by Prudêncio, with 21,500 m², a waterproofing solution with a two-layer bituminous system (minimum 3+4 kg) would weigh 150,500 kg. But, for the Köster TPO system applied, we obtained the value of 32,250 kg, i.e. 1.5 kg/m², saving the building structure and the application team from an overload of 118,250 kg / 118.25 tons.


These are systems with more overlapping and welding joints, because of the smaller width of the rolls that are 1 meter (1.5 to 2 meters wide for Köster’s TPO rolls) and dirty application, not only because of the very characteristic of the membranes, but also because of the use of bituminous emulsions to ensure the adhesion of these systems to the supports. Moreover, it is necessary to use gas to fuel the powerful torch flames that allow the gluing of the membranes, causing danger of fire and risk of damaging finishing materials such as paint, frames, broken glass or air conditioning equipment, among others.


The limited UV resistance of bitumen implies the use of a mineral finish on the apparent layer of the system which, over time, tends to come loose and deposit itself in the gutters, requiring more frequent maintenance to remove residues and small plants that grow, thus preventing clogging of the stormwater outlets or damage of the membranes.



Prudêncio's work at IPMA (Matosinhos) with bituminous membranes
Prudêncio’s work at IPMA (Matosinhos) with bituminous membranes



For the reasons explained in this article, Prudencio currently applies Köster TPO membranes in over 90% of its works.


Concerns with sustainability and the health of the environment and our teams led us to stop responding to requests for PVC systems.


On smaller jobsites and for special customers, we sometimes still apply bituminous systems.



Prudêncio is a specialist in waterproofing services

Prudêncio is available to collaborate in the development of your project. We are here to help you waterproof it in the most correct and safe way possible.


Contact us for more detailed information.


We offer professional advice and specialized technical support.

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