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Preserving Decorative Plaster in Your Historic Building | Wisconsin Historical Society

General Information

Preserving Decorative Plaster in Your Historic Building

Preserving Decorative Plaster in Your Historic Building | Wisconsin Historical Society
EnlargeDecorative painting

Second Ward Savings Bank, 1913

Milwaukee, Wisconsin. Often times the decorative plaster ceilings, medallions and cornices were painted to further enhance the detail. Source: Phil Thomason. View the property record: AHI 16299

If the walls or ceilings of your historic house or commercial building have any decorative plaster features, these features contribute to the historic character of your building and should be preserved. Plaster has been widely used as a building material for centuries because this material is fire-resistant, durable and easily worked. However, your decorative plaster features can deteriorate over time. If you need to repair your decorative plaster features, you should use plaster to match the original in texture and chemical composition.

Learn the History of Decorative Plaster Use

EnlargeCeiling medallion

Graham Residence, 1873

Racine, Wisconsin. Decorative plaster ceiling medallions could be quite ornate such as this one found in the Graham Residence. Source: WHI - archives. View the original source document: WHI 40381

Plaster was used to create decorative designs on ceilings and walls in 19th- and early 20th-century homes and commercial buildings. Artisans used plaster to create ceiling medallions, cornices, coffered ceilings and raised relief decorations. These interior finishes were often quite ornate, especially in Victorian-era and Colonial Revival style dwellings. Ornate plaster was often used in spaces most often used to entertain guests, such as living rooms, dining rooms and parlors.

Plaster medallions were typically added to the center of a ceiling, often where a chandelier was hung. Medallions varied from a simple relief of a circle to ornate floral and wreath designs. These designs were often based on classical elements such as acanthus leaves, egg and dart molding and Greek fret bands.

EnlargePlaster cornice

Milwaukee County. Decorative plaster cornices were yet another way to elevate the interior room design. Source: WHS - State Historic Preservation Office.

Plaster was also used on ceilings to build up a cornice around the perimeter of the ceiling. Plaster cornices are generally more ornate in design than crown moldings. Plaster cornices were often designed to match the room's medallion.

EnlargeCoffered ceiling

Wisconsin Historical Society Headquarters, 1900

Madison, Wisconsin. Coffered ceilings such as the one at the Wisconsin Historical Society Headquarters Building was a popular in many revival style buildings. Source: WHI - archives. View the original source document: WHI 57048

In some cases an entire ceiling was coffered using plaster. Coffered ceilings were especially popular in commercial buildings such as bank lobbies, post office lobbies and department stores. Coffering units were cast in a shop or on site. They were typically installed with hanging wires to form the finished ceiling. The ceiling design varied in depth, panel shape and ornamental complexity during different time periods. Coffered ceilings could be installed flat or curved, like domes or barrel vaults. Coffers on domed or barrel ceilings differed from row to row so they would appear identical from various site lines.

Identify Causes of Your Decorative Plaster Deterioration

The decorative plaster in your historic house or building can last indefinitely if it is well maintained. However, the plaster can peel, crack and loosen from the wall or ceiling over time, especially if your building is exposed to temperature extremes. The most common problem associated with decorative plaster is moisture infiltration. Your plaster can be damaged by moisture in a variety of ways, but the most common causes are a leaking roof and leaky plumbing.

You can also damage plaster if you add synthetic sidings or sealers to the exterior walls of your building. These sidings and sealers will reduce your building’s ability to “breathe” and release moisture, resulting in condensation. Plaster can also be damaged through foundation settling or other structural movement in your building. Generally, if your decorative plaster is deteriorating, you are likely facing problems that affect other parts of your historic building as well.

Repair or Replace Your Damaged Decorative Plaster

You can repair decorative plaster using compatible plaster mixtures and patching kits that are widely available. You can use these products to effectively seal small cracks and holes in your plaster. If the deterioration of your plaster is caused by the plaster pulling away from the wall or ceiling lath, you will need to use appropriate anchor screws to reattach the plaster.

If you need to replace sections of missing or deteriorated plaster molding, or if you have intricate designs to replicate, you should hire a mason with experience in decorative plaster. For extensive repairs, plaster professionals will typically mark the profiles of the damaged or missing pieces, create molds and pour plaster into the molds to harden and then finish the pieces.

Follow Best Practices

Follow these best practices to preserve and maintain your decorative plaster features:

  • Keep water out of your building. The best way to prevent plaster deterioration is to keep water out of your building by maintaining your roof, gutters and downspouts. Plaster can be easily damaged by water, whether from a leaky roof or from condensation. Do not apply sealers or synthetic sidings that will trap moisture in your building and cause condensation.
  • Repair minor cracks or holes with plaster patching kits. If your decorative plaster has only minor cracks or chips, you can use plaster patching mixtures and kits to make repairs.
  • Hire a professional for extensive plaster repairs or replacement. If your decorative plaster decoration has missing pieces or extensive deterioration, you should hire a professional to do repair or replacement work. These types of plaster repair often require specific tools and expertise to create molds that are used to replicate the missing or damaged pieces.