Wiss, Janney, Elstner Assoc. Inc


Many of the early American historic skyscrapers were demolished in the decades following World War II. Many of these unique facades fell into severe neglect and deferred maintenance at a critical point in the service life of these buildings.
Repairs performed in the 1960s typically either addressed the symptoms of the underlying distress mechanisms or focused on the overall appearance of the building. During the 1970s and 1980s, a greater understanding of the appropriate techniques emerged to maintain and repair these architectural treasures. The rise of appreciation for architectural and cultural heritage also drew attention to the significance of these buildings and greater focus on appropriate repair technologies, materials and techniques.
By the 1990s and into the 2000s lessons learned from previous repairs and materials have further refined the restoration techniques. One major issue which has emerged from assessing previous repairs is excessively ‘strong’ or ‘stiff repairs which cause distress from the redistribution of stresses within the facade system.
This paper will review the evolution of repair techniques and materials, focusing on understanding the structural stiffness of repairs, which will not introduce unanticipated redistribution of stress in the cladding systems. Case studies demonstrating inappropriate repairs will be presented.

Key words
Historic Skyscrapers, Repairs, Stabilization, Structural Stiffness