This product will set to a smooth, hard plaster-like finish that won't shrink. For the best results we recommend using a setting-type joint compound, also called mud. There are a number of products available for replacing damaged white coat. This product does not set quickly so it can be worked for a couple of hours or more before it becomes too stiff to use. Repairing wood lath, as described on this page, requires replacing the wood strips or using drywall as a substitute for the original lath.Ī product called structo-lite is commonly used to restore plaster scratch coat and the brown coat that follows. The methods for repairing it are relatively easy and basically the same as repairing water-damaged drywall. Gypsum-board plaster is basically the same as drywall but with a thick white-coat covering. Masonry can be restored -which can require special skills- to repair damaged lath. Wire mesh lath can be replaced with new mesh which can be difficult. More than anything else the type of lath in the plaster will determine the difficulty involved in repairing it. There are 4 possible types of plaster lath: wood, wire mesh, gypsum board, and masonry like brick or concrete. Instead materials like setting-type joint compound are now used for repairing plaster white coat. Because plaster of Paris is hard to work with and tends to crack easily, it isn't used much any more. The white coat consists of plaster of Paris and lime mixed together to create a hard, smooth finish when it sets. The brown coat is made up of the same basic ingredients as the scratch coat and it's applied in the same manner but the surface is left smooth to help make the next coat -the white coat- easier to smooth and level. This makes the next coat -the brown coat- adhere better and creates a strong bond between the two. While the scratch coat is still wet, it's roughed up with a stiff brush to leave scratches in the surface. This mixture is applied over the lath and pushed into the gaps between the wood strips to form a key that locks the two together. The first wet coat -the scratch coat- is a mixture of sand, Portland cement, and some filler material such as horsehair. The wet plaster is made up of three separate components: the scratch coat the brown coat and the putty coat, also called the white coat. With wood-lath plaster there are two basic components: the wood strips that make up the lath and the wet mixtures of plaster that create the hard, smooth wall surface. With this type of plaster, three different types of mud are applied over a lathing material to build up a smooth wall or ceiling finish. This page contains instructions for repairing and restoring old, damaged three-coat plaster.