Northshore Austin, a luxury high-rise in the Texas capitol, is a mixed-use building that includes 38 floors, 439 residential units and 40,000 square feet of retail and office space. As of 2019, the tower stands as the ninth tallest building in Austin. Northshore is positioned in the center of downtown’s most vibrant and exciting area with close proximity to Austin’s famed Lady Bird Lake, 2ND Street District and a multitude of upscale dining and entertainment hot spots.
Originally built in 2014, the apartments were in need of repairs come 2019. The post tension plugs were loose, protruding, incomplete and needed to be removed and replaced. Additionally, concrete was spalling and rebar was surfacing in certain locations, therefore needing remediation. Lastly, two roof davits were repaired.
Chamberlin was brought onto the project by Wiss, Janney, Elstner Associates (WJE) because of their long, trusting relationship with them and their vast knowledge of installations on high-rise buildings.
SKY HIGH SCHEDULING
In order to begin construction, Chamberlin, WJE and general contractor CAMP Construction created a detailed schedule as the building was in full operation during construction, including all residential units, retail and office space. The project was on a one-year schedule from September 2019 to August 2020. To accommodate the tenants and patrons, construction was performed only during the day, not to disturb anyone in the evening and night.
When planning a schedule, curing times and testing times on coatings and concrete repairs had to be taken into account. Time was allotted before construction began to lay sidewalk and pool deck protection and relocate or place protection over the plants. Even with a well-laid plan, unforeseen circumstances necessitated changes in schedule. A majority of the scope was performed on swing stages and on days where the weather was too windy, raining or too cold to be on the side of a building, the schedule had to be reworked. Crew members worked hard to make up for lost time and finish the project within the year time frame.
Grease caps were modified by crew to fit securely
Post-tension plugs were repaired and installed
TIGHTENING THE POCKETS
While Chamberlin crews worked on the post-tension pocket repairs, they were mindful of quality control. Post-tension plugs are used to strengthen the building structure, eliminate water intrusion and add longevity to the life of the building by mitigating post-tension corrosion. The existing post-tension plugs were loose, protruding and carried issues from partially improper original installation.
During the repair design phase, two approaches were assessed: trowel-applied and precast plug repairs. Performing mock-ups and petrographic studies helped determine the best repair approach for the Northshore building. Ultimately, precast plugs were the most successful approach for the project-specific conditions.
The crew had to first remove the existing slumped grout plugs. Protruding strand tails needed to be cut as they were not cut during original construction. Then the existing grease caps were removed. New grease caps were installed, and the crew modified them by trimming the caps to fit snugly in the crimped anchorage ring. The modified caps were epoxied into the anchorage pocket for a positive, watertight fit. In the end, the crew repaired a total of 451 pockets.
ANCHORING THE SLAB
The slab edge concrete was another area in need of repairs. The spalled concrete and exposed rebar was removed by the Chamberlin crew. The existing concrete was then prepped to receive new concrete by installing anchors and tie wire for support. Once the concrete was installed, it was protected and cured for 14 days before waterproof coatings were installed.
When the concrete had fully cured, it was time to reinforce the slab edge with elastomeric coating. The material installed on Northshore was an RD coating, one in a range of high-performance protective coatings. They are 100% waterborne, offering solutions for anti-corrosion, liquid waterproofing, anti-carbonation and wear resistance. The crew cleaned the substrate and then installed two layers of the coating along with embedded mesh.
All roof davits were tested prior to mobilization and two of them failed, requiring repair before swing stage use. The roofing material around the defective davits was removed, and the davits were sandblasted for surface prep. The crew then coated the davits and repaired the roofing material. WJE performed new testing after repairs were complete to ensure the system was safe to use.
Swing stages were used to repair over 400 post-tension pockets
SWINGING INTO SAFETY
In order for the crew to get to the construction zone, they needed to walk through the building to access the roof. With COVID-19 concerns, Chamberlin took precautions such as ensuring the crew was masked up and practicing social distancing. To accommodate the tenants and patrons, signage and barricades were used to keep everyone safely out of construction zones.
The post-tension pocket repairs, slab edge concrete repairs and coatings were all performed on swing stages. It was extremely important for the crew to inspect the equipment each day before beginning work to confirm proper functionality as well as keep safety as a primary focus while working. As Northshore Austin is a high-rise, crew members hung on the side of the building 30+ stories high. The team wore appropriate Personal Protective Equipment including harnesses, gloves, vests, safety glasses and hard hats.
Chamberlin’s attention to detail, internal and external communication and their ability to complete their scopes in a timely manner despite unexpected delays were critical in delivering a high-quality project on time with zero safety incidents.