St. Mark's Cathedral in Seattle was dedicated in 1931 but the exterior wasn't finished. When Western Waterproofing began work on the Thomsen Chapel at St. Mark's, stopping moisture intrusion through the unfinished exterior was a key part of the project. The exterior work included cleaning, patching and repairing the concrete, limestone and brick trim. Western applied stone consolidation to the surrounds on windows and doors, cut out and caulked exterior window perimeters, and applied clear water repellent to the exterior.

In the chapel's interior the crew removed stains and efflorescence left by years of water infiltration and made modifications to accommodate the installation of a new organ. Infills that comprised a significant portion of the interior posed a particular challenge. The acoustical engineer was concerned the infills, which were made of a porous material similar to stuccocrete, would negatively affect the sound quality of the new organ. Several mock-ups were made to test the appearance and acoustic characteristics of different materials for church officials and the acoustical engineer.