Outdoor plazas are ubiquitous on the urban landscape, providing access to otherwise limited outdoor space. Due to tight urban space demands, plazas are often located above occupied spaces, which complicates their design and maintenance. In addition, as plaza systems age, plantings and trees can become overgrown, hardscapes worn and deteriorated, and failing waterproofing can result in interior leakage and damage. Maintenance and repairs are generally difficult because of the overburden and multi-layer systems, and so frequently the systems are either partially or completely replaced. Replacement is often complicated given perimeter constraints, changed code requirements, and constructability issues. In addition, the plaza system selection must consider life expectancy, durability, maintenance, and cost.

This presentation will provide strategies to evaluate plaza system replacement options within project-specific restrictions through a series of case studies. It reviews investigation strategies to evaluate existing plaza conditions and the field information critical for making design decisions. A range of replacement plaza waterproofing options and their advantages and disadvantages, including durability, constructability, and cost implications will be discussed. Key design considerations, such as drainage, overburden selection and setting, and building code requirements that can impact the material selection and overall system detailing will be presented.