The exterior was originally conceived in concrete, but due to construction difficulties with the complex design and shortages from the war, much of the building was actually realized in brick, covered with stucco. Because the material was changed during construction of the building, the designs were not updated to accommodate them. This caused many problems, such as cracking and dampness. Extensive repair work had to be done only five years after the initial construction, overseen by Mendelsohn himself. Since then numerous renovations have been done periodically.