Strasbourg Factory Visit: Bitumen Roofing membrane

By The Helpful Engineer / On / In Technical & Discussion


Soprema HQ

I was delighted to be invited by Soprema to tour one of their factories last week in Strasbourg, France. I had a lovely time with my generous hosts and as a bonus the weather was wonderful, it reached 28 degrees Celsius and there wasn’t a cloud visible in the sky for the whole trip.

Soprema is one of the largest roof membrane manufacturers in the world. It was set up by Charles Geiser in 1908 in Strasbourg and now has 4,500 employees world wide with 16 manufacturing plants. It is an independent privately owned company and its current CEO is Pierre Etienne Blindschedler, a great grandson of the founder. As a result it can concentrate on long term growth and development.

Approximately 60% of Soprema’s turnover is supplied by the EU and greater European market while North America supplies most of of the remaining 40%. The manufacturing site I visited in Strasbourg is excellently located for importing raw materials and exporting the finished product. One side of the site is parallel to a dock on the river Rhine, railways run alongside two sides, while a national motorway (N83) is less than 5km away.

Soprema sell a large range of roofing products. I was given a tour of the bitumen membrane manufacturing line, along with the testing and the R&D sections of the plant. Modified bitumen water proofing membranes were originally invented in Europe by the founder of Soprema, Charles Geiser, and if installed correctly provide good protection against water ingress.

Modified Bitumen is composed of oxidised bitumen, (bitumen is oxidised to help it resist high temperatures), which is then processed with plastic or rubber additives to give it different properties. The two most common types produced by this method are known as APP (Atactic PolyPropylene) and SBS (Styrene Butadiene Styrene). Both types are manufactured by Soprema.

The APP membrane is modified with a plastic. It is stiffer during hot weather and has weaker joints compared with SBS. The SBS membrane is superior in my opinion and is modified with a type of synthetic rubber and as a result is much more flexible. As with rubber, if it is stretched it will return to its original length once the force has been removed. It is also more flexible at low temperatures.

The finished membrane is supplied on rolls. It is rolled out on site and seamed together with heat from a blowtorch. Self adhesive membranes are also available. Usually the roof membrane is made up of two or three layers overlaying each other, with the top layer (cap sheet) being impregnated with aggregate to prevent damage by sunlight, i.e. UV rays.

See photographs below of the production line. I have added some sightseeing photographs that I took while in Strasbourg City center. Among those are the European Parliament building and  Strasbourg cathedral. Strasbourg Cathedral is a remarkable building and at 144m high this is the 11th highest church in the world. It was the tallest building in the world for 227 years between 1647 and ending in 1874.

1. Bitumen oxidation
2. Start of membrane production line, fleece rolls
3. First accumulator, to allow line to continue when new fleece rolls are added
4. Coating fleece with treated bitumen
5. Coating membrane with 'non-stick' layer
6. Cooling membrane with water filled drums
7. Final accumulator to allow line to continue while membrane is cut and spun on to rolls for delivery
8. Membrane roll collector
9. Finished roll of membrane being checked and weighed
10. Pallet of rolls of membrane being shrink rapped
EU parliment building, Strasbourg
Courtyard of European Parliment, Strasbourg
Strasbourg sights. The Cathedral
Looking down from Cathedral roof, not spire
Cathedral doorway

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