In July 1984, Leo Heijdenrijk, Hans Hermes, Wim de Lange and L.J. van der Stap established the Architekten Kollektief Heijdenrijk Foundation (AKH). Over the years, the name and legal form changed several times. From 1987 these architects, with the exception of Van der Stap who withdrew from the Kollektief soon after its establishment, have worked together under the name Architekten Kollektief Heijdenrijk B.V. Leo (in full Leonardus Justinus) Heijdenrijk was born in Den Helder on June 12, 1932. After attending the Hogere Burgerschool B at the Trinity Lyceum in Haarlem, Heijdenrijk studied to become a Construction Engineer at the TH in Delft. He graduated in 1961. Immediately after graduating, L.J. Heijdenrijk joined the Bureau van Architectuur, Industriële Vormgeving en Stedebouw ir. G.J. van der Grinten N.V. in Utrecht, later Amersfoort. Here he worked as an architect. In 1965 he becomes deputy director at the Maatschap voor Architectuur en Stedenbouw Van der Grinten and Heijdenrijk. In 1970 the management was expanded to include a third director, L. Manche, and the firm continued under the name Environmental Design B.V. The name of the firm and the composition of the management changed several times until it was dissolved in 1984 as E.D. Maatschap van Architecten en Ingenieurs Heijdenrijk Jansen Manche Raven en Stemerding. The co-founders of AKH Hans Hermes and Wim de Lange, as well as Van der Stap, were employed at E.D. at some point. Johan (Hans) Hermes, born April 21, 1940 in Surabaya, studies interior design at the Academy of Visual Arts in The Hague. He then attends the Academy of Architecture in Amsterdam. Incidentally, he does not complete that course. Based on his completed work, he is registered in the Register of Architects. Wim (full name Wilhelmus Gerardus Berhnardus) de Lange is born on June 11, 1938 in Diepenveen. He studies engineering at the HTS in Deventer and continues his education at the Academy of Architecture in Arnhem. He leaves the course prematurely and he too has obtained architect status based on his completed work. The trio forms a close-knit triumvirate that is responsible for both general organization and professional expertise, so that decision-making within Architekten Kollektief can take place quickly and deliberately. Wim de Lange, as project manager and executive architect, is responsible for construction engineering, construction organization and the preparation of schedules, budgets and specifications. Hans Hermes, in addition to his role as architect/designer, is also involved in construction engineering and internal office organization. Leo Heijdenrijk's primary duties consist of designing, maintaining office documentation and making acquisitions. The Kollektief did not specialize in designing one type of housing. By participating in competitions, they pushed the architectural boundaries. A competition always had a fertilizing effect on the development of architectural design, often adding something "new" to a later realized building. Acquisitions from one building type were transferred to others. Aspects such as routing, spatial hierarchy, incidence of light, architectural structure, thematic associations and application of art could always be highlighted from different angles. The social aspect always prevailed. Thus, the firm realizes many building types. Residential houses, stores, shopping centers, office buildings, schools, sports facilities, but especially through the state institutions for young people, AKH has become known. Most projects are built in and around Amersfoort. But also in other parts of the Netherlands. For Germany and England, plans have been made but not executed. Three aspects are central to each building task; efficiency, solidity and beauty. The Kollektief does not start from a fixed architectural concept but the architecture is mainly determined by the client, the program of requirements and the environment in which the building stands. The human aspect of a space is considered very important. So it is not only about the building, but also about the environment. Not only the exterior but also the interior is important. Major source of inspiration for Heijdenrijk was Piet Mondrian's use of color and tessellation. This is reflected in his architecture especially in his designs for the Rijksinrichting voor Jongeren Het nieuwe Lloyd in Amsterdam and the interior of the Mondrian House in Amersfoort. But you can also see subtle references to Mondrian's use of color in the administrative building for the Agricultural University in Wageningen and the projects in Kattenbroek. In addition to all the architectural and urban planning projects Heijdenrijk has brought about, he has been active in other areas as well. For example, in 1987 he co-founded the Kortegracht 9-11 Foundation. This foundation bought properties numbers 9 and 11 on Korte Gracht in Amersfoort with the intention of establishing the Mondrian House there. In 1989 Heijdenrijk co-founded Stichting De Nieuwe Beelding. This foundation takes on the management of the premises purchased by the Korte Gracht Foundation. In 1992 he and his wife founded the Friends of the Mondrian House Foundation. This foundation took charge of the running of the Mondrian House. His involvement in the establishment and operation of the Mondrian House once again revealed Heijdenrijk's fascination with Mondrian's ideas. Heijdenrijk was also a board member of the KIVI Section of Architectural Engineers, a member of the BNA Arbitration Committee, a government committee member at the HBO and a member of the jury for various competitions. Leo Heijdenrijk died in Amersfoort on February 19, 1999. The projects he had started are completed by Hermes and De Lange. They eventually do this from Aerdenhout where the office, after sixteen years in Amersfoort, has been located since 2000. Here it will operate for another two years to complete all ongoing projects. Hermes and De Lange will retire during 2002, after which Architekten Kollektief Heijdenrijk B.V. will be dissolved.