Below Grade: A Solution in a Complicated Situation
Waterproofing systems can be one of the most complex components of building design — especially below-grade protective applications. These are often required to be multipurpose systems, and must be strategically applied to the foundation in order to mitigate conditions.
These systems are also the unsung heroes of construction; without effective, below-grade envelope protection, a building might be worthless the second that water, harmful gas, and contaminated vapor infiltrated the foundations. Below grade building envelope protection is always a challenge and site-conditions can arise that exponentially increase complexity; in this situation, a team must make an extra collaborative effort to ensure the best possible solution is employed to keep the building and its occupants dry and safe.
The 1840 N. Highland Ave apartments project in Los Angeles is an excellent example of how a sophisticated, well-designed waterproofing system can make the seemingly impossible entirely possible. The facility is extremely high-profile and well situated, just steps from the Hollywood Bowl and Hollywood Boulevard. The lot was zoned for a multi-housing project, yet the Alquist-Priolo Earthquake Fault Zone runs through the property boundary. This created some interesting challenges for the team. It was decided that to further protect the structure against the potential for seismic activity, the team had to install a 2’ thick layer of Geofoam between the shoring system and below-grade shotcrete walls. These were put in place to reduce and eliminate seismic movement impact on the building’s structure.
Three stories of the structure sit below grade, meaning that groundwater infiltration was a major concern. Add to that the fact that the foundation was in the water table, and this meant some major problem-solving had to take place.
“There were some real twists to the project, including two fault lines under the cantilever of the building and the water table, which sat at different levels,” said Josh Heidt, CP, with Terra-Petra, who was contracted to provide waterproofing consulting services. “The building owner and general contractor were not thrilled – they didn’t want one drop of water entering the building, as there was the issue of bulk water entering,” he added.
The team chose protective products by EPRO, Inc, a leading manufacturer of waterproofing and contaminant barrier systems. The company provides effective, long-term, cost-efficient, and warranted protection for buildings and their occupants against the hazards of water and contaminant intrusion into buildings. EPRO offers below-grade systems for underslab, wall, and shoring wall applications, as well as deck applications – including podium decks, planters, and green roofs – allowing its products to be a single-source provider for the entire building.
EPRO is the pioneer of the proven system methodology called redundant field-installed composite design, a method requiring that systems be fabricated in the field – not in the factory – using multiple and redundant protective materials. This redundancy is achieved by combining different types of waterproofing materials to leverage the positive attributes of each and eliminate a continuous seam. Within each application category, EPRO offers a good (E.Proformance) , better (E.Protect), and best (E.Protect+) system, allowing for cost-efficient system/site condition matching.
For the 1840 N. Highland Ave. project, the team determined that E.Protect+ Underslab was the best solution to protect the building foundation and blindside vertical walls for water intrusion considerations. In addition, E.Protect+ transitioned to E.Proformance Shoring system above the design water table. Complexity increased as EPRO’s negative side waterproofing systems were applied directly to the Geofoam layers for below-grade waterproofing purposes. The transition between E.Protect+ (hydrostatic) and E.Proformance (non-hydrostatic) was at 2'-0 above the high historical water table level and extended to grade.
“EPRO helped us and the geotechnical consultant work through the issue regarding the north face of the building where the fault line divided the water table across the north and south sides,” says architect Ronald Rosell, AIA, with the project architect, Arquitectonica. “The fault acted like a subterranean waterfall, and EPRO gave us recommendations for how best to prevent that hydrostatic pressure and constant flow of water from impacting the structure.”
The waterproofing system was also carefully detailed around many pipe penetrations and several pits for both elevators and utilities.
Finally, EPRO’s E.Proformance Shoring blindside waterproofing system was used for the non-hydrostatic waterproofing system. E.Proformance was also selected as a solution at grade level where it was transitioned to a hot rubber horizontal waterproofing system, a landscaping area for planters, and a stucco wall system.
Thanks to the selection of such a dynamic waterproofing solution, this high-profile multifamily residence will be able to eventually welcome residents. It is currently expected that the 1840 N. Highland Ave. apartments will be completed in 2019. In addition to EPRO, the project team included general contractor Frymer Construction, architect Arquitectonica, waterproofing consultant Terra-Petra, and certified EPRO applicator BMG. All parties shared their expertise and insight, and were successfully able to collaborate to determine an effective solution to a unique problem.