On December 15, 1993, the parliament of North-Rhine-Westphalia (NRW) decided along with the adoption of the budget for 1994 to reserve an item for the planning of a "replacement- and extension-building for the ZFMK. The first scheme of rooms comprised 1800 m². On the 25th of May, 1994, the Regional Commission of Cologne granted the permission to abandon the so-called montage-building (a provisional building erected in 1950 and housing three sections of the Department of Arthropoda and parts of our molecular laboratory).
In spring 1994, Prof. Dr. C.M. Naumann declined the offer from Munich.
The Ministry for Science and Research of NRW approved the final floor plan on August 30, 1995. It comprised 1486 m² of effective area (383 m² for the library, two collection magazines of 232 m² each, numerous studios), the external dimensions were 30 x 27 m, 13 m in height.
In the course of repair work on the electric supply of showcases in the exhibition in the summer of 1995, massive and seriously dangerous damages were detected. As a consequence, the Ministries of Science, of Construction and of Finances agreed on immediate measures to fundamentally renovate the main building.
In the summer of 1996, another assessment by a specialist assigned by the Regional Commission of Cologne revealed that the "montage-building" was still overstrained and should be checked every year from then on.
The fundamental renovations of the main building began in 1997. The continuation of planning the new building was postponed for "3-4" years (until the renovations had been paid fully).
Planning the new building was restarted in January 2002. However, the parliament of NRW had again to decide on the approval.
Construction work began on September 8, 2003, with an archaeological screening of the excavation pit conducted first. Prof. Dr. C.M. Naumann passed away on February 15, one day before the construction site was definitively used. The construction work proper started on the 1st of March, 2004. On the 5th of March, the Board of Directors of the ZFMK decided to act on a suggestion from staff members and name the new building the 'Clas M. Naumann-Bau' (Clas M. Naumann-building').
The foundation stone was laid on April 15, 2004 and the topping-out ceremony was celebrated on October 8, 2004, in the presence of Dr. Michael Vesper, then Minister of Urban Development, Dwelling, Culture and Sports, and the Lord (Lady) Mayor of Bonn, Bärbel Dieckmann. In August 2006, staff and collections of the Department of Arthropoda, the molecular laboratory, and the library moved into their new accommodations.