Beautiful Garden Roof for Transformed Post Office in Houston, Texas

by Marcus Dodson, editor & publisher

Once the hub of the Houston, Texas, United States mail system, the 1930’s-era Barbara Jordan Post Office was a shining example of modern, new formalist architecture.  In 2015, however, the historic post office was closed and fell into a state of abandonment and neglect.  Thankfully, that all changed when efforts surged to transform this 16-acre site into a mixed-use complex topped with a five-acre vegetated and amenity roof.  POST Houston (HTX) highlights how an adaptive reuse project can employ sustainable products and practices to transform a once unused space into a rooftop park with the largest urban farm in Texas. 

         This project features American Hydrotech’s MM6125® waterproofing membrane, formulated with a minimum 40% post-consumer recycled content.  Paired with DuPont™ Styrofoam Insulation and American Hydrotech’s Garden Roof® and Ultimate Assembly, the roofing system creates an unbeatable sustainable solution that keeps the owner and designer at ease with an assembly that is covered by a single-source warranty.

         The Garden Roof and Ultimate Assembly are playing a critical role in protecting this roof, while also providing environmental and economic benefits.  The green roof reduces stormwater runoff, combats the urban heat-island effect, and create acres of habitat for pollinators and other wildlife.  Not to mention the Skylawn, which is a one-acre urban farm that is accessible to the community and will supply ingredients to the restaurants within the building.  The amenity space will also serve as a hub for entertainment and leisure by hosting community events, concerts, and more.  POST HTX has seen a truly remarkable transformation and the team at American Hydrotech is proud to be a small part of it.  Other teams involved were: Powers Brown Architecture, Houston; Office for Metropolitan Architecture with Jason Long, New York City, New York; and Hoerr Schaudt, Chicago, Illinois. 

         American Hydrotech’s Monolithic Membrane 6125 was installed first to ensure a waterproof roof barrier.  It is a thick, tough, flexible, self-healing membrane that is a special formulation of refined asphalts and synthetic rubbers that has a minimum 40% recycled content.  The advantage of specifying the American Hydrotech waterproofing assembly on the Houston Post Office, as well as similar amenity decks, is that the membrane is a seamless hot rubber asphalt that is adhered directly to the structural concrete substrate in a protected membrane roof (PMR) application.  Unlike a traditional roofing or waterproofing assembly, where the membrane is installed atop the insulation board, a PMR is adhered directly to the substrate and utilizes the XPS insulation board that is above the membrane, thus protecting the waterproofing assembly and alleviating the potential for damage to the membrane throughout the life of the structure. 

         An additional advantage of specifying the American Hydrotech waterproofing and garden roof assembly is that the POST HTX was able to obtain a 20-year Single-Source Ultimate Warranty, which includes the removal and reinstallation of all of the garden roof components and insulation board if there were any deficiencies in the membrane that needed to be addressed, at no additional cost to the owner. 

         Aside from adding beautiful landscaping to the building’s roof, the rooftop garden also benefits POST HTX and its surrounding environment.  By utilizing a Garden Roof Assembly from American Hydrotech, the 217,800-sq.ft. garden helps to reduce stormwater run-off and heat absorption.  Stormwater affects a building’s surroundings in many ways, including contaminated drinking water, landscape degradation, and flooding. 

         POST HTX and Skylawn have quickly become one of Houston’s most dynamic and engaging outdoor venues.  The vegetative roof and urban farm serve the community in a variety of ways, and thanks to an American Hydrotech Garden Roof Assembly, it will continue to benefit the building and its surroundings for a very long time.

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