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Private pool house “Graz”

Sub base compensation

Project name Private pool house "Graz" Volume 800 m³ expanded clay crushed 1-16 mm Location Graz, Austria Year 2014
Contractor Pongratz Bau- Graz Designer Kamper ZT KG Owner/Builder Private


Because of the hillside the project consists of three parts. 1st) to build a horizontal foundation for the pool, 2nd) to fill the space between slope and foundation and 3rd) to backfill the the pool itself. After finishing the big construction of the foundation it was necessary to fill up the cavities inside the foundation with a stable and durable material. Originally it should be done with common earth, but compacting seemed too difficult, especially in comparison with the stiffness of the concrete foundation. So, it was necessary and helpful to use a material with a low necessity for compacting- like expanded clay. The ability to inject the material offered the chance to reduce time and increase the comfort for the workers. Side effect was a plus in time because of the rapid method and it meant also a minus in costs for the owner.

Why Expanded Clay:

With expanded clay it was possible to reduce weight load on the underground as well as on the pool. A massive weight and load reduction could be reached; the application was possible in a short time.


Directly on the surface a geotextile was put on. The material was blown out to backfill the space between foundation and slope. By blowing the material into the cavities inside the foundation, a stable underground for the pool could be achieved than to build the level for the swimming pool. After this the pool made of concrete was backfilled with expanded clay.

Key Issues:

Blowing, Load reduction, Settlement, and Stability

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