Project Type: Evaluation, Design, and Construction Administration
The Vital Structure:
Balcony Terrace Waterproofing Replacement
Issue
Vital Structures was retained to perform waterproofing and roofing system engineering services for a Cambridge MA pharmaceutical space. The balconies serve as an accessible terrace space with an Inverted Roof Membrane Assembly (IRMA) system installed during the original construction of the building in 2001.
Diagnosis
The existing coating system had been a source of several leaks and subsequent repairs over the 20 years. In addition to the general age of the roof system, the following conditions were noted during the evaluation.
- Poor slope-to-drain conditions, including negative slope of the concrete deck (sloped away from drains).
- Interior flush floor drain covers used in exterior drainage applications, resulting in corrosion, failed drain covers and drain blockages.
- Architectural details necessitate perimeter flashings from the concrete deck to low-profile curtain wall metal components, necessitating a high-performance fluid-applied waterproofing system.
- Masonry and terracotta rainscreen through-wall flashing deficiencies.
Our Solution
Vital Structures prepared an evaluation report and developed complete building envelope repair design documents, including the following:
- New sloped topping slabs to provide a minimum of ¼” per linear foot positive slope towards drains.
- Full roof replacement for the balcony terrace roof systems, including fully reinforced polymethyl methacrylate (PMMA) cold fluid-applied waterproofing, with drainage composite, insulation, and high-density concrete architectural pavers and pedestals.
- New PMMA roof membranes were tested with low-voltage Electronic Leak Detection.
- New through-wall flashings at terracotta and CMU walls.
- New transitional copings and edge-metal.
- Drain restoration, including removal of blockages and new drain accessories with gravel screens.
