Grand St. Commons

commercial | multi-family

Grand Street Commons is a mixed-use commercial and residential development in Seattle, Washington, and holds the record as one of the largest construction jobs in Washington for 2022.


WG Clark general contractor chose Seattle commercial roofer Axiom D7 to handle roof installation and waterproofing for two buildings: Grand St. Commons East and West.

This massive 85,100-square-foot waterproofing job required Axiom to add a below-grade membrane called Bentonite in the excavation. Rolled sheets of Bentonite clay are 33’ x 4’ and can be mounted vertically against the blindside of a lagging wall or horizontally over the rat slab. A significant portion of this happens below the water table—a logistical feat even for Axiom’s experienced technicians.

A technical challenge was that two buildings were going up at the same time. This required the Axiom team to carefully coordinate cranes and deliveries to ensure the safety and efficiency of both projects.


The most obvious solution to this waterproofing challenge would have involved doubling up the Bentonite sheets, but that wouldn’t have been very cost-effective for the owner. Axiom’s engineers were ultimately able to propose an alternative solution that saved the owner from having to buy an additional 50,000 squares of material. The Axiom team secured their waterproofing goals by painting the seams with mastic to prevent water incursion.

General Contractor: WG Clark
System Type: Bentonite


Despite facing multiple challenges, and doing groundbreaking engineering work, Axiom met every deadline and milestone, ensuring the owner and the GC continued success on this massive project.


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