Overall view of building.
Damaged terra cotta from corrosion of steel supports.
Removal of Portland Cement Mortar Joint above the terra cotta modillions.
Discreet anode connected to power supply and ready for placement into mortar joint.
Placement of lime-based mortar after anode and reference electrode installation.
Monitoring equipment installed inside the building allows for remote monitoring and system adjustment.

Cathodic Protection of Historic Terra Cotta Cornice

Project Description 

Constructed in 1904, this building houses the administrative functions of a major historic museum in Washington, D.C. Located along the Mall, the facility is a National Historic Landmark and an important destination for many.

In 2005, a condition survey revealed the need for an entire exterior envelope repair, re-pointing of the brick, patching and repair of the terra cotta elements, cleaning of the exterior brick façade, removal of old scaffolding pins and cleaning of the decorative metal elements on the windows. The report also indicated that the building’s terra cotta modillions were deteriorating due to corrosion of the supporting steel elements and that the main joint above the modillions, which was cracked and open in areas, had been previously improperly repaired.

Because the owners required repair options that would protect the historic integrity of the building as well as prevent further damage, the project team developed a solution to install an Impressed Current Cathodic Protection (ICCP) system. The method had been used on hundreds of projects in the United Kingdom, but this project represented only the fourth large scale installation in the United States and one of the first systems installed in the United States to protect terra cotta masonry.

The project team contracted Structural Group because of its experience in historic masonry preservation using cathodic protection systems. Contractor selection and training was a crucial because of the limited ICCP installations on historic buildings in the United States. The installation crew also was trained on project-specific procedures and quality assurance for this structure.

The use of ICCP provided a better end-result, while saving money and materials for other required repairs.