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Completing the Trinity Dome for the Basilica of the National Shrine of the Immaculate Conception

It was an honor to be entrusted with the completion of The Trinity Dome, the central and largest of seven domes that soar above the Basilica of the National Shrine of the Immaculate Conception. Affectionately known as “America’s Catholic Church,” The National Shrine is the largest Roman Catholic Church in the United States and among the world’s ten largest churches. Elevated 159 feet above the finished floor and adorned with Venetian glass mosaic and stone, the Trinity Dome’s ornamentation is the final step to completing this “Hymn in Stone,” according to the original architectural plans and iconographic scheme.

In addition to engineering a platform to support the scaffolding high above the public, another highly challenging aspect of this project was the development and execution of a steel erection and rigging procedure to hoist massive columns, beams, and trusses inside without the assistance of a crane. We created an innovative material transportation system to transport heavy loads with no impact to the floor or overhead lifting assistance. We also designed special steel sleds to accept the massive steel pieces outside and gently transport them through the narrow door opening and inside in position, ready for lifting.

One of our most extraordinary engineering achievements, our system allowed the church to remain open to the public during construction. Over two years, the project only closed the church for a single weekend, with Rugo’s skilled labor crews working around the clock for four weeks to minimize disruption of the church’s services.

Once the platform was complete, we built a custom-designed scaffold system along with two-manpower material hoists: one to access the platform and another to access the upper levels of the dome. This entire scaffold structure was enclosed to protect visitors from construction dust and debris.

Our team carefully removed 20,000 square feet of original gypsum plaster to expose the Guastavino tile substructure. The new Portland cement plaster installation tolerance was critical, because we needed to ensure that the new radial plaster surface matched the original curvature of the gypsum plaster, as the mosaic patterns and design were based on the original gypsum plaster surface curvature. Once the plaster had cured, it was ready to receive the mosaic, the installation of which took six months of continuous work. Our team in Italy was instrumental in fast-tracking the project, producing and assembling it in half the estimated time.

The basilica’s four massive brick arches were clad with a custom end-matched series of Roman travertine panels, mounted on a custom aluminum honeycomb substrate, and mounted to a secondary aluminum framing system. The dismantling of the scaffold and platform was completed six weeks ahead of schedule, and the mosaic work was completed and dedicated on schedule.

This totality of this project included structural steel, concrete, highly complex rigging, and engineering in an occupied space. The platform and scaffold systems were specially designed to allow access for the installation of 20,000 square feet of new Venetian glass mural mosaic and 8,000 square feet of new Roman travertine cladding.

For stone and mosaic craftspeople, a project of this magnitude and importance is a once-in-a-century opportunity. The project was awarded Grand Prize at the 2018 Coverings Convention, and the finished Trinity Dome has been applauded by the church and its visitors as the “crowning jewel” of the National Shrine.

Location: Washington, DC
Completion: 2018
Owner: Basilica of the National Shrine of the Immaculate Conception
Architect: Anthony J. Segreti, AIA
General Contractor: Rugo Stone LLC
20,000 sqft
Services: Rugo Stone served as the GC and self-performed steel erection, dismantling, fabrication, installation, mosaic, and stonework.

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We lend a sophisticated aesthetic and world-class expertise to large scale and special projects. Clients include religious, civic, cultural and educational institutions, public agencies, private developers, major corporations, and individuals.