APWA awards Milwaukee City Hall exterior restoration project

WALTHAM, MASS. — The American Public Works Association (APWA) has selected the exterior restoration project on the Milwaukee City Hall as its Public Works Projects of the Year for 2010. To date, the Milwaukee City Hall project has garnered 12 awards from national and regional competitions.

Milwaukee City Hall, constructed in 1896, was designed by H.C. Koch in the German Renaissance Revival style. A registered national landmark, the nine-story building is clad with granite, sandstone, brick, and architectural terra cotta with a slate mansard roof punctuated by gabled dormers.

At the south end of the building, the masonry and steel-framed clock tower rises an additional four stories to a height of 393 feet and is capped by a copper clad spire supported on steel trusses. A large skylight in the flat portion of the main roof floods the nine-story building atrium with natural light.

Moisture infiltration caused significant deterioration in the structure and envelope materials since its construction. The damage included stained interior finishes, corroded steel framing, and deteriorated masonry. Furthermore, large loads from the clock gables and the masonry self-weight caused stress cracks to open in the masonry walls of the South Tower.

Simpson Gumpertz & Heger Inc. (SGH) performed a comprehensive investigation identifying the causes of deterioration. SGH used industrial rope access techniques to inspect cracks and other deterioration; installed remote monitoring thermocouples and vibrating strain gages to identify causes of cracking on the South Tower; performed finite element analyses to identify and analyze structural load paths and stresses on the South Tower; and investigated the timber pile foundations to determine the cause of building settlement.

Following SGH’s investigation, SGH and Engberg Anderson, who is the lead architect on the team, formed a design team and prepared a stabilization and restoration program with multiple phases.

The project phases included controlled demolition and reconstructing the South Tower masonry above the 12th floor, repairing the corroded steel truss elements, rehabilitating the deteriorated brick and terra cotta elements; repairing and restoring the existing windows; installing the waterproofing at windows and band courses; and restoring the slate, copper, and membrane roofing. SGH also provided construction-phase engineering services for the project.

For more information about Simpson Gumpertz & Heger, please visit www.sgh.com.