Hanging In There

Suspended Plaster Ceilings

Image Credit: CTA Architects

Cast plaster is a relatively lightweight decorative material that can be used to give a space beautiful ornamentation. While sanded lime plasters were traditionally used for walls, ceilings, and other flat surfaces, gypsum plaster castings can take on nearly any shape and be fitted together to produce intricate arrangements. The use of molds allowed for repetitive shapes, such as rosettes or coffers, to be quickly fabricated and installed, though occasionally more elaborate castings could also be mass-produced such as in this former vaudeville theater in the East Village of New York City (Figure 1).

Figure 1: Cast plaster ceiling of the Village East Cinema located in New York City’s East Village.

Castings are typically suspended from a gridded system of iron framing anchored into the structure above. The castings are attached with embedded wire or fiber-reinforced plaster that wraps around the iron creating plaster wads (Figure 2). Wire-reinforcement is generally preferred since fibers can break down over time, especially when exposed to air or moisture. One of the complications of working with suspended cast plaster is that it is generally impossible to know whether the wads connecting the ornament to the structure contain wire reinforcement until the wads break. Fortunately, each casting typically has multiple wads connecting it to the structure so that, if one is damaged, the others can continue to support the weight of the plaster. But regular inspections are key to ensure that damage doesn’t go unchecked until catastrophic loss occurs.

Figure 2: Black iron grid suspended from ceiling above with multiple plaster wads connecting each casting.

Because suspended ceilings create a cavity between the decorative ceiling and the slab above, these spaces were frequently used to run services and equipment. This practice can lead to destabilization of the ceiling when the framing is altered around ducts or conduit, or when wads are damaged by impact, or when leaks from piping or sprinklers damage the plaster itself. If the space above is large enough, catwalks were frequently installed to provide safe access for workers. But this can lead to over-confidence when individuals decide to walk on the grid iron to reach less accessible areas (Figure 3), forgetting that the actual floor below them is often several stories down. The holes and cracks caused by these activities need to be carefully examined to determine how widespread the damage is before repairs can be completed.

Figure 3: Hole through ceiling panel from worker walking on black iron in attic.