Virginia State Capitol Moisture Intrusion and Skylight Leakage Repair Design

Virginia State Capitol Moisture Intrusion and Skylight Leakage Repair Design

Designed by Thomas Jefferson and built in 1788, the Virginia State Capitol is a National Historic Landmark, which accommodates the Virginia General Assembly, the oldest legislative body in the Western Hemisphere. An underground addition to the Virginia Capitol building was completed in 2007 to add a visitors’ center and additional meeting space. After completion, the underground addition began experiencing leaks through the south terrace skylight and failed waterproofing on the plaza.

WDP was retained to evaluate the water infiltration, conduct a condition survey, and perform diagnostic testing to determine the underlying chronic structural issues and the cause of acute failures of previously attempted exterior surface repairs. Based upon the findings, WDP also provided repair alternatives consisting of temporary repairs, a repair-in-place option to address the waterproofing issues only, structural repairs to the skylight, and an option for the complete rebuild of the skylight.

After considering WDP’s findings and recommendations, the Virginia Department of General Services decided to remove the skylight, infill the opening with a new structural slab, install new waterproofing over the plaza, install new plaza pavers to match the existing skylight pattern, and install a new simulated skylight luminaire beneath the slab. WDP was engaged to design the new structural concrete infill slab, waterproofing and insulation assembly, structural topping slab, and paver assembly. The design was complicated by requirements to support heavy, concentrated wheel loads from firefighting vehicles on the plaza.

During construction to repair the waterproofing at the terrace, WDP performed periodic site visits and meetings to coordinate directly with the project team. During construction of renovation projects, very often, unexpected conditions are discovered. During demolition, the cheek wall weeps located at the south side of the terrace were discovered to be partially infilled, and the fluted insulation which was intended to provide some drainage was fused to the waterproofing membrane. These unexpected discoveries provided unique challenges, which WDP worked through with the project team.

WDP is currently performing design-phase services for removing the remaining plaza pavers and stone stair treads from the monumental stair leading up to the portico and historic entrance to the capitol, replacing the waterproofing membrane, installing additional drainage provisions to eliminate standing water on the terrace, and reinstalling the pavers and treads. The repair design is being carefully developed to maintain the historic nature of the building and historic materials.