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Case Studies

Below-Grade Waterproofing – San Jose City Hall Water Feature (CA)

Case History GacoFlex LM60 San Jose Water Feature CA Photo1


Cutting-edge buildings should have cutting-edge art. This is the basis for “Waterscape,” the interactive water feature built above the parking structure of San Jose’s new city hall building. Located in the heart of Silicon Valley, it seems appropriate that everything about city hall should be high tech – even the parts hidden from view. The finished water feature includes slabs of granite with recycled water flowing and trickling down towards the plaza in front of the building. The sculpture was designed to mimic the landscape of the San Jose region with amounts of water varying by both time of day and season. Hidden beneath the granite slabs is a concrete basin to catch the water, and concrete pylons to support the structure, both of which needed to be waterproof.


GacoFlex LM60 Liquid Applied Polyurethane Elastomeric Membrane proved to be the perfect solution for the project as it has demonstrated proven reliability in below-grade applications since the 1970s. Gaco Western-approved applicator Alliance Roofing was selected to apply the materials.


First, GacoFlex E5320 2-Part Epoxy Primer/Filler was spray-applied to all surfaces to be waterproofed. With the primer/sealer system applied, the next step was to apply GacoFlex LM60, the waterproofing membrane, also spray applied to save time. In order to provide the most effective waterproofing membrane, GacoFlex LM60 was installed to a thickness of 90 mils on horizontal surfaces and 60 mils on vertical surfaces. Once the GacoFlex LM60 cured, the granite slabs and other decorative

features were installed to complete the project. Dedicated in October 2005, the water feature lends a natural and relaxing air to the city hall courtyard. Beneath the surface, the tough GacoFlex LM60 membrane will continue to provide reliable waterproofing for years to come.

Location: San Jose, CA
Specification: GacoFlex LM60 Polyurethane
Product Type: Outdoor Art Waterproofing
Contractor: Alliance Roofing
Problem Solved: The basin and supporting structures of water sculpture needed to be waterproof.
Customer: San Jose City Hall