Project Type: Waterproofing, Parking Garages and Balconies
Garage Plaza Deck and Parking Garage Repairs
Issue
The existing plaza deck system is a spacious, mixed-use facility which serves as the roof of a four (4) level underground parking garage. This plaza also facilitates pedestrian access to multiple storefronts and restaurants in Kendall Square, and includes several planters, trees, art podiums and landscape architecture features.
The owner reported that they have observed leaking from the garage roof slab, causing steel and concrete deterioration. Additionally, they identified concern for the condition of the plaza paving, as it was deteriorated and cracked along the balance of the structure. This appeared to be due to inconsistencies in construction and design, deferred maintenance, and years of exposure to the environment.
Within the garage, multiple drain covers, and components were observed to be deteriorated or broken with exfoliation from drain interior surfaces resulting in approximately 1/16” to 1/8” section loss. Various concrete surface spalls and wearing coating systems were observed throughout the garage with several areas of rusted/deteriorated galvanized metal deck. The garage traffic coating was also due for replacement in highly trafficked areas on Levels P1 through P3; specifically at drive lanes and turning areas.
Excavated plaza and exposed roof slab
Corroded Steel Deck in Garage Below
Cracked concrete paving
Epoxy & aluminum oxide binder/aggregate for heavy duty traffic coating system.
Completed area of drive lane traffic coating
Vital Structures design included a cast-in-place concrete repair with steel reinforcement around the drain bowls with new hydrophilic water stops and sealant joints.
Diagnosis
Vital Structures was contracted by the owner to provide an evaluation of the plaza deck waterproofing system, plaza deck concrete walking surface, existing traffic coating systems in drive lanes, and garage internal drains due to deterioration. Our evaluation included destructive test cuts, programmatic leak testing, excavation of planters, and a topographic survey performed by our sub-consultant.
Following completion of the evaluations, our recommendation to the owner was to remove the existing, deficient plaza waterproofing system and deteriorated concrete overburden. Then replace each with a new hot applied rubberized asphalt waterproofing system, drainage improvements and concrete paving, respectively. At garage parking levels, we recommended that the deteriorated drains be replaced and that new traffic coatings be installed in the drive lanes.
Our Solution
Vital Structures performing as the Prime Consultant developed design documents to replace drains with new cast iron traffic drains, new steel reinforced cast-in-place concrete encasements, heavy-duty traffic coating system for drive lanes, replace the failed plaza deck waterproofing system, new site retaining wall, light pole foundation design and replace the concrete paved walking surface in like kind to the pre-existing. Vital Structures provided the following services:
- Conducted visual evaluation with destructive test cuts to identify extents of drain deterioration/damage, plaza deck condition and waterproofing coating condition.
- Determine limited systems repair options with summary evaluation report.
- Hired the services of a landscape architect to perform design of new plaza deck aesthetic and pedestrian flow.
- Prepared design documents including bid forms, general and supplemental conditions, technical specifications, typical repair/replacement details and technical notes.
- Provided bid assistance to the client, based on a list of pre-qualified, licensed, and insured contractors.
- Reviewed submittals and shop drawings.
- Provided Controlled Construction administration services and a punch list review.
Result
The design for new cast iron drain bowl with sediment catcher eliminated debris buildup within the drain bowl. New cast-in-place concrete encasement with steel reinforcement and hydrophilic water stops around the drain bowl topped with heavy duty traffic coating system provided watertight system and eliminated water infiltration into concrete substrate. Drain repairs were completed in 2020 in the first year of a five-year phased plaza renovation and coating replacement project.
Traffic coatings have since been completed in a targeted approach and are expected to continue through 2024. Extensive concrete repairs, including full-depth repairs, were required in drive lane areas due to moisture infiltration and minimal concrete cover around reinforcing steel. Hydro-demolition was selected to ensure 100% removal of the existing traffic coatings.
Plaza deck renovation had been phased over a four (4) year schedule. Phase 1 was completed in 2021 and Phase 2 is currently ongoing. Phases 3 and 4 are scheduled to be performed in 2023 and 2024, respectively. At the plaza level, approximately ten (10’-0”) feet of excavation was required to transition the waterproofing at the foundation walls. Building façade panel removal was performed so that the new plaza waterproofing could be transitioned to the building waterproofing. Following removal of the existing failed waterproofing membrane, a new hot applied waterproofing system was installed, and new concrete paving placed.
These renovations resolved the client’s concerns of tenant/occupant complaints from repeated leaks, falling debris, trip hazards, and re-established protection of the unique garage structure.
