The core activity of Keller Unternehmungen is the management and administration of various business fields, including engineering, ImRaum, facades, and real estate. The original core business, the production and distribution of bricks, is now handled by Kubrix AG, in which Keller Unternehmungen holds a significant stake.
The core activity of SIA-Haus AG is the ownership and management of the building of the same name at Selnaustrasse 16 in Zurich, which serves as the headquarters of the Swiss Engineers' and Architects' Association (SIA). The company does not operate any business and has no employees.