Rainwater has been seeping into the Old Capitol Building, the castle-like building facing Sylvester Park in downtown Olympia, damaging interior plaster, windows and the sandstone exterior.

Work begins the week of March 2 on an $860,000 project that will address some but not all of the water intrusion problems in the Romanesque Revival-style building, which is the headquarters for the Office of the Superintendent of Public Instruction.

The leaks are caused by inadequate flashing between the walls and roof. Water has also penetrated deteriorated mortar joints between the sandstone blocks that form the exterior walls. And there are problems with the drainage around the building's foundation.

In 2014, the Department of Enterprise Services, which manages the Old Capitol Building, hired Peter Meijer Architect, a Portland firm that specializes in historic building work, to do an exterior survey of the structure to identify the most immediately needed repairs.

Now the state has hired Jones and Roberts, a general contractor based in Olympia, to:

• Repair the gutters and roof flashing.
• Replace the garage and mechanical room roof.
• Improve drainage at the site by repairing collapsed drain lines and install new storm-drain cleanouts.
• Repair water-damaged plaster at various interior locations, and more.

Like any construction project, there will be noise: from trucks, backhoes, workers jackhammering concrete, removing roofing material, sheet metal work, saw cutting around the dormers and other activities.

Two sections of the sidewalk on the north side of the building, along Legion Way, will be replaced. The sidewalk work will impact the entrance on the north side of the building that complies with the Americans With Disabilities Act. Enterprise Services is working with the Office of the Superintendent of Public Instruction to mitigate this issue.

Some parking stalls around the site may be closed to accommodate the construction. Most of the lawn next to the building will be fenced off. The project is scheduled to be finished around July 1, 2015.

The building opened in 1892 as the Thurston County courthouse, and is on the National Register of Historic Places, the U.S. Department of the Interior's list of sites, buildings, and structures regarded as worthy of preservation. The state purchased it in 1902 for use as the state capitol building. The Legislature met there until the completion of the current Capitol Building, officially known as the Legislative Building, in 1928.

Although the Old Capitol Building and Sylvester Park are in downtown Olympia, both are owned and managed by the state as part of the Capitol Campus.

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