EXTERIOR SANDSTONE AND DOME RESTORATION

In 2014, the Michigan State Capitol Commission launched a study to determine the condition of the Capitol building’s envelope—that is, the exterior surfaces of the building, including the stonework and the dome. The study showed that the Capitol’s exterior sandstone needed to be repointed (remortared), and the Capitol’s tall, slender iron dome required painting. These findings inspired the Commission to launch a major exterior restoration and renewal project in 2015.

THE DOME
decorative flourish used to seperate sections

The Capitol’s dome is made of sheet and cast iron produced by the S.J. Creswell Ironworks Company of Philadelphia, Pennsylvania. Heralded by architects for its strength, the ease with which it could be cast into ornamental shapes and forms, and its resistance to fire, iron was a very popular building material in America from the 1830s until well into the 20th century. Yet it also requires consistent maintenance, as it expands and contracts in response to temperature fluctuations. As a result, iron must be regularly sealed and painted to prevent rust and decay.

The 2015 restoration and renewal of the dome began with a focus on repainting the dome and resealing open joints in the metalwork. As workers began to spend more and more time on the scaffolding around the dome, it became apparent that a significant number of original metal decorative elements were gone. Missing elements included acanthus leaves on the dome’s Corinthian columns, scrollwork found around the dome’s octagonal windows, and decorative balls flanked by molding that appear to spiral around the dome’s ribs. Also missing were a significant number of decorative balls that ornamented the ribs located at the dome’s lantern level. The Capitol Commission made the commitment to restore all of these elements, using cast iron and sheet metal as appropriate, with the goal of restoring the dome, for the first time, to its full original Victorian splendor.

Click and drag the center bar left or right to reveal the entire images of the dome restoration.

  • images/beforeafter/1after1b.jpg
    BEFORE
    AFTER
    Dozens of missing decorative balls were crafted and attached to the Capitol’s dome at the lantern level.
  • images/beforeafter/2after2b.jpg
    BEFORE
    AFTER
    Dozens of missing decorative balls were crafted and attached to the Capitol’s dome at the lantern level.
  • images/beforeafter/3after3b.jpg
    BEFORE
    AFTER
    Hundreds of decorative balls flanked by moldings that appear to spiral around the dome’s ribs were replaced during the Capitol’s 2015 renewal.
  • images/beforeafter/4after4b.jpg
    BEFORE
    AFTER
    Custom decorative acanthus leaves were cast for the dome.
  • images/beforeafter/5after5b.jpg
    BEFORE
    AFTER
    Cast iron acanthus leaves were made to complete the Corinthian columns at the dome’s drum level.

Photos Courtesy of Michigan State Capitol Archive




THE STONEWORK
decorative flourish used to seperate sections

Capitol architect Elijah E. Myers called for the use of “the very best quality of Number One Amherst sandstone” for the building’s exterior. Quarried from the Berea sandstone formation in northeastern Ohio, the Capitol’s stone has stood the test of time remarkably well. Nevertheless, it too requires regular maintenance to address the intermittent movement of the stone caused by temperature fluctuations. Over time such movement breaks the mortar bonds between the stone blocks, opening joints and allowing moisture in. This moisture can then freeze in the stone, causing the stone to spall, or fracture.

The 2015 restoration of the stonework began with a focus of grinding out, cleaning, and repointing (remortaring) any failed or failing joints. The stonework was then cleaned in the attempt to reduce the dark stains penetrating into the pores of the sandstone. Also, an aluminum sheet metal covering, or flashing, was installed to protect the weathered and worn surfaces of the stone located at the top of selected cornice bands near the Capitol’s roofline.

Early work on the stone revealed that many of the Capitol’s original sandstone modillions (ornamental brackets consisting of an acanthus leaf topped by an s-scroll), found under the roofline, were badly decayed. The Michigan State Capitol Commission made the decision to remove the damaged modillions and replace them with newly carved replicas, crafted from stone quarried from the same formation as the original sandstone. While the initial plan was to remove 147 modillions, eventually this number grew to more than 200.

Another dramatic moment in the sandstone restoration was the installation of large “Dutchmen repairs” on the massive sandstone columns on the east and south porticos. (A Dutchman repair is when damaged or faulty sections of stone are removed and replaced with stone that matches the surrounding area as closely as possible.) The columns were in fair to poor condition due to damage from graffiti, weathering, the improper use of salts and snow melting agents, and poor patch jobs. The new Dutchmen, measuring between four and six feet, were hewn offsite by skilled stone carvers and carefully installed by expert masons.

  • images/beforeafter/Poor Dutchmanb.jpg
    A poorly executed Dutchman, or section of replacement stone, on the large columns on the Capitol’s east portico, or porch. New pieces of replacement stone were used to properly patch the columns in 2015.
  • images/beforeafter/Dutchmanb.jpg
    Stonemasons work to install a new Dutchman, or section of replacement stone, to the Capitol’s east, or front, columns
  • images/beforeafter/Modillionsb.jpg
    A series of decaying modillions (architectural decorations composed of s-scrolls and acanthus leaves) under the Capitol’s roofline. Over 200 modillions were replaced during the Capitol’s renewal.
  • images/beforeafter/Open Mortar Jointsb.jpg
    Hundreds of open mortar joints in the sandstone, like those seen here on the Capitol’s east façade, were repointed, or remortared, in 2015
    Hundreds of open mortar joints in the sandstone, like those seen here on the Capitol’s east façade, were repointed, or remortared, in 2015.
  • images/beforeafter/Stonework Cleaningb.jpg
    Water and an appropriate cleaning solution was used to remove stains and debris from the Capitol’s light buff colored sandstone.


Pictures of the sandstone before restoration.
Photos Courtesy of Michigan State Capitol Archive