The monumental Legislative Building, completed in 1928 and listed on the National Register of Historic Places, was leaking. SHKS completed the third phase of its repairs: restoring four historic skylights, and cleaning and repointing the masonry. Earlier phases focused on the dome of the Legislative Building.
Forensic investigation to determine the cause of sandstone deterioration and water intrusion requires hands – on inspection and testing – inside and out. Exfoliation of the Wilkeson Sandstone veneer appeared to be caused by a combination of moss growth and water penetration of the stone. In addition to visual and tactile observation of exposed surfaces, investigative video imaging using a boroscope provided visual access to concealed, interstitial spaces at the mini-domes.
The treatment solutions included considerable experimentation with cleaning pressures, techniques, and solutions. Cleaning pressures below 400 psi were found to clean organic growth from the very soft sandstone, conserving the material for future generations.
Careful examination of the underside of the domes reduced the need for selective demolition to map the pathways of water infiltration. To minimize damage to the building, additional non-invasive testing – drill resistance testing and ground penetrating radar – were conducted.
The building’s ornate plaster finishes are vulnerable to water damage. A small amount of plaster repair was included in the repair project.
“…instead of constructing a single building to reflect suitably the needs and aspirations of state government, a plan was chosen for a group of buildings. In its time, this century barely a decade old, it was an unprecedented idea in our national experience, especially audacious for a state with scarcely over 800,000 inhabitants.” — Norman J. Johnston
