Thomas Jefferson Memorial Roof and Portico Restoration

Washington, D.C.

Award of Merit

Submitted By: Submitted by Grunley Construction Co.

Owner U.S. National Park Service

Lead Design Firm GWWO Architects

General Contractor Grunley Construction Co.

Stone Restoration (Laser ablation): Evergreen Architectural Arts

Subcontractors Atlantic Refinishing & Restoration Inc.; Welch and Rushe; Worch Electric; Scaffold Resource; The James Myers Co.

In 2006, the 79-year-old memorial’s white dome started getting covered in dark splotches and water began to infiltrate the portico roof. Years of research determined the building’s marble had an overgrowth of biofilm—a microbial community of cyanobacteria, fungi and algae.

The project’s primary intent was to remove this film and reduce water infiltration. The team replaced roofing, waterproofing and flashing systems above the colonnade and at the upper roof as well as performed the associated repairs to the stone along the architrave.

Work also included laser cleaning of the dome, portico roof and cornices—the first time laser ablation had been used against biofilm. Lasers were also deployed to remove gypsum crust. Low-pressure, high-temperature steam cleaning technology was also a first in the U.S. in terms of large-scale memorial projects, the team says.

Complex, massive scaffolding was required to achieve the restoration’s entire scope, which involved work at elevated areas— including the entablature, portico roof, multiple levels spanning from the dome down to two marble drum walls and column capitals—without anchoring into or damaging the stone.

Before putting up the scaffolding, the team conducted in-depth existing conditions surveys and installed extensive temporary protection to all marble surfaces to prevent potential damage. The $14.8-million project was completed on time and on budget.