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The Seattle Aquarium Expansion is a transformative addition to the city’s iconic waterfront, connecting the vibrant Pike Place Market to the new Ocean Pavilion and the scenic waterfront.

Two local Washinton-based contractors, Snyder Roofing of Snohomish and Wayne’s Roofing of Sumner, were hired to waterproof the project’s elevated and winding walkways that extend over and around Seattle Aquarium’s newly constructed expansion.

Challenges on the 25,000-square-foot project included precision installation techniques for installing the waterproof membrane on the structure's sloped surfaces, installing complex expansion joints for a continuous waterproof barrier, and the need for constant coordination and communication with other trades for seamless integration.

Hydrotech® Monolithic Membrane 6125® (MM 6125®) was chosen because it is a tough, flexible, self-healing, hot fluid-applied asphalt membrane for waterproofing and roofing applications. The membrane conforms and bonds to all surface irregularities and has been successfully used worldwide on all types of horizontal and vertical structures for more than 60 years! It was the perfect option for this application.

The first step was to spray apply Hydrotech® Surface Conditioner, an asphaltic mastic designed to enhance the bond of MM 6125 on the new concrete. Once fully dried, the team applied a 90-mil coating of MM 6125 and embedded Hydrotech’s Flex-Flash F spunbonded polyester fabric. Over the top, they then installed another 125-mils of hot MM 6125 for a total thickness of 215 mils. To complete the installation, they installed Hydroflex® 30, a heavy-duty modified asphalt sheet, followed by Hydrodrain® 300, a crush-proof drainage geonet core with a non-woven filter fabric, Atlas Geofoam lightweight expanded polystyrene, and the top layer of concrete. The green areas also included a Hydrotech composite drainage system as well as growing media

Hydrotech’s Monolithic Membrane 6125 system was ideal because it is two to three times thicker than many other liquid-applied or single-ply waterproofing membranes, allowing for a wider variety of substrate conditions, and increased crack-bridging and self-healing properties.

All of which is critical for the long-term waterproofing performance of this project on the beautiful, yet often rainy, Seattle waterfront.