REPAIR HOLE IN LATH AND PLASTER WALL WINDOWS

When the heat diminished, and the lime and water were thoroughly mixed, the lime putty that resulted was used to make plaster. As the lime absorbed the water, heat was given off. When building a house, plasterers traditionally mixed bags of quick lime with water to “hydrate” or “slake” the lime. Evidence of plaster behind trim is often an aid to dating historic houses, or to discerning their physical evolution. Woodwork was then nailed to the “grounds” after the walls were plastered. Installing these grounds so that they were level and plumb made the job much easier because the plasterer could work from a level, plumb, straight surface.

REPAIR HOLE IN LATH AND PLASTER WALL WINDOWS

But sometime in the first half of the 19th century, builders began installing wooden plaster “grounds” around windows and doors and at the base of the wall. Obtaining a plumb, level wall, while working against built-up moldings, must have been difficult. Generally the woodwork was prime-painted before plastering. In early America, the windows, doors, and all other trim were installed before the plaster was applied to the wall. Not only did the basic plastering material change, but the method of application changed also. Gypsum and lime plasters were used in combination for the base and finish coats during the early part of the 20th century gypsum was eventually favored because it set more rapidly and, initially, had a harder finish.

Manufacturing changes at the end of the 19th century made it possible to use gypsum as a plastering material. The lime came from ground-and-heated limestone or oyster shells the aggregate from sand and the fiber from cattle or hog hair. Lime plaster was made from four ingredients: lime, aggregate, fiber, and water. Until the end of the 19th century, plasterers used lime plaster. Plasterers in North America have relied on two materials to create their handiwork–lime and gypsum. Old plaster walls, like this one painted a faded red in a Greek Revival mansion in upstate New York, have a textural, handmade quality that modern materials can’t match. While minor repairs can be undertaken by building owners, most repairs will require the assistance of a plasterer. Plastering is a skilled craft, requiring years of training and special tools. To repair plaster, a building owner must often enlist the help of a plasterer. This system is generally better suited to historic preservation projects than dry wall. Veneer systems include a coat or coats of wet plaster–although thinly applied–which can, to a greater extent, simulate traditional hand-troweled or textured finish coats. Thus, a veneer plaster system is discussed rather than dry wall. Finally, this Brief describes a replacement option when historic plaster cannot be repaired. Dry wall repairs are not included here, but have been written about extensively in other contexts. The approaches described in this Brief stress repairs using wet plaster, and traditional materials and techniques that will best assist the preservation of historic plaster walls and ceilings–and their appearance. For both reasons, plaster walls and ceilings contribute to the historic character of the interior and should be left in place and repaired if at all possible. Plaster can also serve as a plain surface for irreplaceable decorative finishes. Of more concern to preservationists, however, original lime and gypsum plaster is part of the building’s historic fabric–its smooth troweled or textured surfaces and subtle contours evoke the presence of America’s earlier craftsmen. A building owner needs to think carefully about the condition of the plaster that remains plaster is often not as badly damaged as it first appears. It resists fire and reduces sound transmission. First, three-coat plaster is unmatched in strength and durability. But there are practical and historical reasons for saving it. Historic plaster may first appear so fraught with problems that its total removal seems the only alternative. This variety and the adaptability of the material to nearly any building size, shape, or configuration meant that plaster was the wall surface chosen for nearly all buildings until the 1930s or 40s. Plaster could be treated in any number of ways: it could receive stenciling, decorative painting, wallpaper, or whitewash. It provided a durable surface that was easy to clean and that could be applied to flat or curved walls and ceilings.

Technical Preservation Services (TPS), Heritage Preservation Services Division, National Park Service prepares standards, guidelines, and other educational materials on responsible historic preservation treatments to a broad public.Ī versatile material, plaster could be applied over brick, stone, half-timber, or frame construction. This publication has been prepared pursuant to the National Historic Preservation Act of 1966, as amended, which directs the Secretary of the Interior to develop and make available information concerning historic properties.

Repair hole in lath and plaster wall