“From the underside, much of the ceiling sounded okay,” Lisa Easton reports. The initial sounding results seemed promising. ![]() While waiting for a significant amount of pigeon droppings to be removed from the attic, a sound-testing exercise was conducted on the surface side of the plaster ceiling in an effort to detect any areas of imminent collapse. These were removed, repainted and secured back into place using a conservation method called pinning. About 150 pieces were found to be insecure or unstable. Sound testing involves tapping a rubber mallet against the plaster ornament. Using JTI’s telescopic lift to avoid the need for scaffolding, the HPCS team sound-tested hundreds of plaster ornament throughout the building. and sister company, Historic Plaster Conservation Services USA. Tiedemann is president of John Tiedemann Inc. Easton contacted Ray Tiedemann to conduct an evaluation of the cast plaster ornament and the wood lath and plaster ceiling. Ann & Holy Trinity, Father John summoned Lisa Easton of Easton Architects LLP, the church’s go-to architect. Immediately after the plaster ornament crashed to the floor at St. This deterioration takes place over many decades and is exacerbated by wide fluctuations in temperature, by building micro-movements and vibrations which cause the plaster keys and lugs to abrade, and by disturbance from the installation of various mechanical systems.Īs a matter of pure fact, from the day that a wood lath and plaster ceiling is installed, it begins to experience this process of slow, unrelenting deterioration. Usually, this can be best seen in the attic where many observers fear to tread.Įventually, the plaster matrix becomes friable (powdery and weak), and the plaster keys and lugs that hold the ceiling suspended in place are either broken or rendered so weak that they can barely do their job. One can tell this is happening by observing the effervescent salt deposits on the warm surface of a plaster ceiling. The formation of the salts causes expansion which breaks down the plaster. ![]() The main culprit is moisture from humidity, which moves through the plaster dissolving and mobilizing salts. The major cause of the demise of a wood lath and plaster ceiling is ongoing systemic deterioration. As a result, a wood lath and plaster ceiling is designed to function as a suspended system-not an adhered system-held up by the keys and lugs formed by the plasterer. Second, when the wood lath dries, it shrinks away from the plaster, creating a gap that gives the assembly the flexibility it needs. First, the lath is pre-wet so that it doesn’t suck moisture from the plaster and prevent the important chemical reaction that must take place when the plaster cures. The strips of wood lath are soaked in water before being nailed to the joists for a couple of reasons.
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