60 Wall Street, New York, NY
60 Wall Street is a 47 story high office building constructed in 1987. Diaz Architects was asked to prepare a roof condition survey of the all 44 roof setbacks. After careful study of the roof system and adjacent walls and parapets, which included probing each roof assembly, we were able to assess the condition of the original unreinforced, rubberized asphalt membrane as being in advanced state of deterioration. The membrane was exhibiting mass blistering and removal of the insulation and gravel overburden would cause further damage to waterproofing system. The existing detail at the parapet consisted of a curtain wall panel that was hung off the steel structure, leaving a gap between the slab edge and backside of the parapet which was covered with a stainless steel bent metal that extended under the parapet aluminum panel to create the desired flashing height. The detail at the building wall was equally as challenging because the panels were part of a curtain wall system which were installed in the factory originally and not designed to be removed for future roof replacement projects. The building wall panel also contained a recessed portion for the window washing track between the various curtain wall sections that extended to the bottom of the base flashing with a vulnerable connection.
Diaz Architects designed different roof systems for the various roof setbacks and addressing the building’s requirement for sustainable roofs. All the roof were covered with highly reflective precast concrete pavers, high R-Value rigid roof insulation, and drainage mat to encourage positive drainage on the flat roofs. Because of the restrictive nature of the existing low flashing heights and tight worker environment, we selected a reinforced liquid membrane system that could be warranted by the manufacturer with no slope. Where base flashing could be raised or altered to accommodate the higher base flashing heights, roofs were designed with modified bitumen vapor barrier, tapered insulation and two modified bitumen membrane with liquid membrane base flashing.
Aluminum and granite panels and copings were removed on the inboard face of the parapet walls, and sheet metal panels were installed to cover the curtain wall structure and provide a substrate for the rubberized asphalt waterproofing sheet membrane. Aluminum metal clips were installed at the base of the recessed window washing track to function as division point between the new base flashing and the existing waterproofed window washing track.