The bunkers in Norway were originally slated for a second floor to be built over the submarine pens. This was to house accommodation, workshops and offices. The idea was abandoned at the end of 1941 due to the problems already mentioned. The choice of site did not help either. Accumulated mud, on top of clay and sand layers proved to be incompatible with existing designs and was unstable ground so that the bunker had to be built in parts and stabilized before continuing construction.