Mixed-Use Residential
& Commercial Arcade – The Full Story
In the Year 2000, a mixed-use facility was constructed in the posh North Shore Chicago suburbs, near the shores of Lake Michigan. The property includes high-end stores, restaurants, offices, apartments, and a movie theater. Grade-level parking, supported by a conventionally reinforced concrete structural slab with a single level of parking located below the structural slab, both of which total 70,000 SQFT. The construction of the elevated slab includes a fluid-applied, rubberized asphalt membrane system and a variety of overburden that includes concrete topping slabs, pavers, and planters over a two-way, concrete structural slab. The parking lot is accessible from a congested road that serves the entire North Shore.
Completely Restored Parking Lot
The commercial arcade features a dozen storefronts, ranging from Starbucks and Chipotle to Williams-Sonoma, Restoration Hardware and L’Occitane en Provence. Because it is located in the downtown area, steps from the Metra commuter train line, this “lifestyle center” also features luxury residences located above the shops. The flagship department store anchoring the west end of the shopping center, Saks Fifth Avenue, is housed within a larger building separated from the arcade by a sidewalk, behind which is located the service court where trucks make daily deliveries and garbage is disposed of.
The Problem
Almost from day one, the site engineer noticed leaking into the underground parking garage. Ownership had tried to minimize water infiltration over the years via underside crack injection and other methods that all proved unsuccessful. Nine years later, the site engineer had to keep 55-gallon drums in the lower level of the parking garage to catch all the leaking from above, come rain or shine.
In addition to the subterranean leaking, the columns of the arcade and the base of the flagship Saks Fifth Venue building exhibited crumbling of the pre-cast stone façade. The concrete driveway to the service center also featured noticeable cracks leading to further leaking into the parking garage below.
The Cause
The main underground leaks appeared two feet past the arcade, leading the site engineer to believe they were coming from underneath the brick pavers that made up the walking surface. The restoration contractor was brought in to perform an initial investigation to determine how well the old buried waterproofing was bonded and, after opening up the topping slab in several places in the parking lot and arcade, it was discovered that the waterproofing was so loose that you could pick it up with your hands due to water being trapped between the waterproofing membrane and topping slab, combined with poor drainage – a nightmare waiting to happen in any facility. Later findings would reveal that the structural slab was never properly prepared or scarified, leading to the main reason that the waterproofing never performed or bonded properly. Water stains revealed that injections into the underside cracks had little effect. Additional investigation also found that the flashing in corners and surrounding the columns lining the arcade was missing or installed improperly. Water infiltration from the lack of proper flashings caused the metal studs and column enclosures to be in direct contact with the trapped water above the waterproofing membrane.
Because any leaking is a red flag, particularly so soon after the facility opened, the property owner was faced with the unenviable choice of resolving the source of leaking now to prevent a compromise of the structural slab or to institute a program of patch and defer, which would ultimately necessitate the replacement of the structural slab and would likely cost an additional $600K to $1M, not including any aesthetic upgrades necessitated by ongoing water damage, which were not needed at this time. Perhaps even more worryingly, further delay of repairs would have caused the closure of the entire parking lot and a possible debilitating loss of business to each storefront.
In addition to the parking lot, the topping slab in the service court entrance drive cracked because, in some locations, it was installed less than 2” thick. Water from the grade level parking lot in the northeast corner of the site drained across the expansion joint in the service drive and was retained at the membrane level, causing further leakage into the parking garage below.
Finally, the Saks Fifth Avenue wall cladding was wicking water out of the sand setting below the brick pavers and water tests indicated that leaks occurring in the parking garage 30 to 40 feet inside the Saks Fifth Avenue exterior walls were related to deficiencies in the waterproofing membrane flashing at the base of the exterior walls.
Mitigating Factors
The main underground leaks appeared two feet past the arcade, leading the site engineer to believe they were coming from underneath the brick pavers that made up the walking surface. The restoration contractor was brought in to perform an initial investigation to determine how well the old buried waterproofing was bonded and, after opening up the topping slab in several places in the parking lot and arcade, it was discovered that the waterproofing was so loose that you could pick it up with your hands due to water being trapped between the waterproofing membrane and topping slab, combined with poor drainage – a nightmare waiting to happen in any facility. Later findings would reveal that the structural slab was never properly prepared or scarified, leading to the main reason that the waterproofing never performed or bonded properly. Water stains revealed that injections into the underside cracks had little effect. Additional investigation also found that the flashing in corners and surrounding the columns lining the arcade was missing or installed improperly. Water infiltration from the lack of proper flashings caused the metal studs and column enclosures to be in direct contact with the trapped water above the waterproofing membrane.
Because any leaking is a red flag, particularly so soon after the facility opened, the property owner was faced with the unenviable choice of resolving the source of leaking now to prevent a compromise of the structural slab or to institute a program of patch and defer, which would ultimately necessitate the replacement of the structural slab and would likely cost an additional $600K to $1M, not including any aesthetic upgrades necessitated by ongoing water damage, which were not needed at this time. Perhaps even more worryingly, further delay of repairs would have caused the closure of the entire parking lot and a possible debilitating loss of business to each storefront.
In addition to the parking lot, the topping slab in the service court entrance drive cracked because, in some locations, it was installed less than 2” thick. Water from the grade level parking lot in the northeast corner of the site drained across the expansion joint in the service drive and was retained at the membrane level, causing further leakage into the parking garage below.
Finally, the Saks Fifth Avenue wall cladding was wicking water out of the sand setting below the brick pavers and water tests indicated that leaks occurring in the parking garage 30 to 40 feet inside the Saks Fifth Avenue exterior walls were related to deficiencies in the waterproofing membrane flashing at the base of the exterior walls.
The Solution
Restoration of the mixed-use facility was performed in three phases:
• Phase I – southern half of the parking lot & arcade overburden and columns
• Phase II – northern half of the parking lot & arcade overburden and columns
• Phase III – service court & façade restoration of the Saks Fifth Avenue building
Phases I and II
For the first two phases, the restoration contractor began by removing the existing arcade brick pavers, which were stored on pallets for reinstallation. This was followed by the disposal of the existing setting bed and demolition of the sloped concrete topping slab, concrete curbs, and waterproofing membrane down to the concrete structural slab.
Demolition of Parking Lot Concrete
Following removal of the compromised overburden and concrete, the restoration contractor then performed partial-depth repairs to the top surface of the structural slab. Additionally, an 85-foot watertight, split-slab, plaza deck expansion joint (the EMSEAL Migutan FP Series) was also installed down the center of the parking lot that extended all the way through the arcade area. The previous, inadequate joint had failed because it didn't enable proper expansion and waterproofing for a dual-tier parking structure.
Parking Lot Reinforcement, Concrete Pumping & Placement
Since the previous waterproofing membrane had thoroughly failed, surface preparation was very important. Prior to installation of the new membrane, the main field of the structural slab was shot-blasted and all edges were sandblasted with 1240 grit Black Diamond sand. An American Hydrotech 6125 reinforced hot rubber asphalt membrane system was then installed with a prefabricated drainage layer and all the related flashings, followed by a 48-hour water test to ensure an end to all leaks. New neoprene flashings were also embedded in the hot rubberized system at all perimeter curb locations and at the expansion joint.
Since the previous waterproofing membrane had thoroughly failed, surface preparation was very important. Prior to installation of the new membrane, the main field of the structural slab was shot-blasted and all edges were sandblasted with 1240 grit Black Diamond sand. An American Hydrotech 6125 reinforced hot rubber asphalt membrane system was then installed with a prefabricated drainage layer and all the related flashings, followed by a 48-hour water test to ensure an end to all leaks. New neoprene flashings were also embedded in the hot rubberized system at all perimeter curb locations and at the expansion joint.
Waterproofing Membrane & Water Test
The arcade columns consisted of structural steel with metal studs clad in decorative stone and tile cladding. Because of the lack of sufficient waterproofing, water and winter road salt had come into contact with the metal studs, causing them to corrode, expand and break apart the cladding at the base of each column. The restoration contractor removed the stone and tile cladding for later reinstallation, cut out the metal stud corrosion two feet above the finished grade, shored the remaining metal studs off of the ground, cast a new concrete curb to take the metal “out of the bathtub,” installed two-piece, 4” metal counter-flashing to add an additional level of waterproofing, and then re-clad with the original stone and tile. All brick pavers were then reinstalled.
Column Prep & Shoring
Phase III
Beginning with the service court, the restoration contractor performed an elevation survey of the existing construction, then removed all overburden, cracked topping slab concrete and the failed waterproofing membrane. A 30-foot expansion joint was then installed and new waterproofing membrane added. New dual-tier plaza drains and piping were installed, followed by a new topping slab (up to 4” thick) and new curbs being poured.
At the Saks Fifth Avenue building, all overburden was removed for reinstallation, along with two feet of wall cladding. Neoprene flashing embedded in hot rubberized asphalt and a new concrete fill slab were installed, followed by reinstallation of all brick pavers.
All demolition consisted of saw cutting the existing topping slab into large squares (like a grid), which was removed with Bobcats with forks, loaded and hauled away to a crushing plant for recycling. Saw cutting replaced jack-hammering in order to minimize noise pollution and dust infiltration, and also helped to expedite the schedule. All demolition, waterproofing, concrete pouring, and façade restoration was performed by the restoration contractor.
The Biggest Challenge
Site logistics and tenant interaction was the biggest challenge of the project for the restoration contractor. In order to begin working on the parking lot, ramps had to be built and fencing erected to accommodate a new entrance and exit to each half of the parking lot so that traffic could be accommodated while work commenced without disruption to the restoration process. For loading and removal of broken concrete and rebar for subsequent recycling, traffic along the congested downtown street needed to be re-routed and coordinated with city officials. Additionally, in order for the stores to remain open, wooden ramps had to be constructed over the area where new concrete was being poured with fencing also installed to keep anyone from falling, all of which was compliant with the Americans with Disabilities Act. A wooden ramp was also installed in the service court to handle all delivery and garbage disposal traffic.
Temporary Walkways After Demolition, Reinforcement & Concrete Pour
Fortunately for the facility owner, business owners and shoppers alike, the restoration contractor has much experience in this area as many of its clients are high-rise structures located in downtown Chicago and other Midwestern cities, as well as at other high-end properties. As such, customer service for all impacted by the restoration being done is always viewed as a top priority, second only to the high quality of investigation, restoration work and follow-up offered by the restoration contractor. As such, the restoration contractor project manager communicated daily with site engineer, and the restoration contractor's superintendent also worked very closely with shop owners and employees in order to avoid doing work that would interfere with their busy times, to inform them when sandblasting would be performed, and to let them know that odors emanating from the site were related to the waterproofing material. In particular, the staff at Starbucks loved him. Everyone on the restoration contractor team knew what had to be done, and by when, at each store location, many of whom presented challenges to deal with because of their high expectations.
Completion
Restoration to the mixed-use facility commenced on May 20, 2008 and was substantially complete before the Thanksgiving shopping deadline, when the entire parking lot and arcade were fully reopened and functioning as before – even after many change orders from the structural engineer. The full scope of restoration utilized 300 yards of topping and 2,000 linear feet of curbs, covered up to 30,000 SQFT of repairs: 28,000 SQFT of repair to the parking lot, arcade, pedestrian walkways; 1,200 SQFT to the service court; and the remainder to the Saks Fifth Avenue building.