Biomedical Building Roof Replacement
Issue
Vital Structures was retained to perform evaluation and design services for the replacement of three (3) roof areas located above the third-floor of the building. The existing EPDM membrane roof systems had exceeded their service lives, and evidence of breaches in the existing roof system had been reported.
Diagnosis
The existing roof assembly of the three (3) roof areas consisted of an adhered 60 mil EPDM membrane, ½” thick gypsum coverboard, tapered polyisocyanurate insulation at 1/4” per foot slope with a 1” thick based layer of polyisocyanurate insulation, polyethylene vapor barrier, and a concrete roof deck. The existing roof decks were not to have not structural slope. Disintegration of the gypsum coverboard, as well as wet insulation were observed at test cut locations, indicated water infiltration. Previous patches to the EPDM roof membrane were also observed throughout the roof areas. Parapet walls extending approximately 1’-0” above the roof deck of The Northeast Roof and the Northwest Roof were noted to be capped with zinc parapet caps, which were damaged at several location due to thermal expansion and contraction, and inadequate expansion joint detailing. A granite capstone was installed atop the existing parapet wall of the Southeast Roof. There was no point of access from the interior of the building to both the Northwest Roof and Southeast Roof
Solution
Vital Structures design included the removal and replacement of the existing roof system with a new roof assembly consisting of an adhered 75 mil reinforced EPDM roof membrane, ½” thick high-density polyisocyanurate coverboard, ¼” per foot tapered polyisocyanurate insulation, a base layer of polyisocyanurate insulation, and a self-adhering rubberized asphaltic vapor barrier. New zinc copping caps were installed at the parapets of the Northeast Roof and Northwest Roof. New steel platforms and access ladders were installed to provide access through new operable casement windows at the Northwest roof and Southeast Roof.
Result
The new roof system prevents moisture from entering the laboratory spaces below, protecting the businesses from costly shutdowns. The new zinc copings provide an improved aesthetic appearance for the building, removing the existing faded copings that had become unsightly. With the addition of access platforms and ladders, the Northwest Roof and Southeast Roof can now be easily accessed by Facilities to perform routine maintenance of the roof areas.
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