14 years later - and KÖSTER TPO is still good as new


KÖSTER has been manufacturing roofing membranes since the 1980’s. Many membranes from this time are still visible and intact on several roofs today including KÖSTER’s very own production facility.

Membrane type:

TPO 2.0 mm

Start of weathering exposure:


End of weathering exposure:


Outer Appearance

After such a long period the membrane shows signs of normal wear but otherwise is in perfect condition.

After cleaning the membrane with a high pressure cleaner and standard household cleaners, only minimal signs of wear are still visible. The surface is in excellent condition and does not show any deterioration through the weather exposure. The structure is still sharp and does not show any wear.

Tensile Strength Values

Tensile elongation chart: KÖSTER TPO after 14 years of weather exposure.

The tensile strength of the membrane remains excellent after nearly a decade and half in use. In July 2015 the following values were measured:

Tensile strength lengthwise:

9.39 N/mm²

Tensile strength across:

7.26 N/mm²

Elongation at break lengthwise:


Elongation at break across:


Remarkably, the weathered membrane still outperforms the values defined by our quality assurance according to the current declaration of performance for KÖSTER TPO 2.0. Based on these specifications, the membrane would still be able to be sold today.

Old meets new

Without further preparation other than cleaning the membrane, a KÖSTER TPO 2.0 roofing membrane from present production was welded to the 14-year-old KÖSTER TPO membrane with a welding machine at a temperature of 600° C and rate of 1.0 m / min.

The result is impressive: not only is the membrane still able to be welded like a new membrane but the seams are flawless. On average, a peel resistance of 470 N / 50 mm was achieved with no value recorded below 400 N / 50 mm.


The results of the examination have proved the exceptional durability of KÖSTER TPO Roofing Membranes. After 14 years in use, the membrane is still good as new. The membrane has not suffered any embrittlement and as a result has not experienced a decline in its mechanical properties. The membrane would still be able to pass today’s strict quality control guidelines without any problems.

A key advantage of the KÖSTER TPO Roofing Membrane is its ability to still be welded after long periods of weather exposure without any great preparation. This saves time and effort especially by large construction projects which can take several months or years to complete.

In this case, even after 14 years, the membrane maintained its weldability and did not require extensive preparation. Additionally, a connection to the membrane is possible so that additions can be subsequently connected without any difficulty.
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