Plastering and Stuccoing

the finishing of surfaces of structural members and other parts of buildings and other structures (exterior and interior walls, ceilings, partitions, and the like) with a plaster or stucco mortar; the mortar is applied wet to the application surfaces. Because the work is very labor-intensive, in modern industrial construction plastering has in large part been replaced by the facing of surfaces with large dry-plaster sheets and other efficient prefabricated finishing materials.

In wet plastering, the composition of the plaster mortar applied depends on the purpose of the plaster, the material of the surfaces being plastered, and the conditions under which the buildings will be used. For example, lime mortars are used to plaster interior stone walls of rooms with normal humidity (up to 60 percent), and lime-gypsum mortars are used for wood partitions. Cement and lime-cement mortars are used in areas with increased humidity, such as bathrooms, laundries, and bathhouses.

Plastering mortars are usually manufactured at centrally located plants, chiefly in the form of dry mixes that are delivered to construction sites. Mortar-mixing units and mobile plastering stations mounted on motor vehicle trailers are used to prepare the mortars to the required composition at the sites.

In most cases the application of wet plaster is mechanized; plastering machines supply and apply the mortar by means of pumps. Hand plastering is reserved for small jobs and areas difficult to reach. The mortar is supplied through rubber hoses or metal pipes. The type and diameter of the feed line and the capacity of the pump depend on the number of stories in the building, the amount of wet plaster, and the distance over which the mortar must be delivered (up to 200 m horizontally and 40 m vertically). Special nozzles are usually used to apply the mortar to the surface being plastered. The mortar is usually applied in three layers. The first two layers are required for all types of plaster and stucco; the third is required for improved and high-grade types. Electric and pneumatic finishers and power tools are used for the final dressing of the top layer.

In areas where humidity under operating conditions will not exceed 60 percent, surfaces are finished with dry-plaster (gypsum, gympsum-fiber, and wood-fiber) sheets. Gypsum facing sheets, manufactured from construction-grade gypsum with mineral or organic additives and covered with cardboard on two sides, are most frequently used. Sheets produced in the USSR (1978) have lengths of 250, 270, 290, and 330 cm; widths of 120 and 130 cm; and thicknesses of 1.0 and 1.2 cm. Facing sheets must be correctly shaped and undamaged at the corners and edges, and the face side must not show seams where the cardboard is glued. The grading, laying out, and cutting of sheets to dimensions is usually done at centralized workshops at the construction site. Sheets are cemented to rock or concrete surfaces with gypsum glue, gypsum foam, and other mastics; they are attached to wood surfaces with galvanized nails or wood screws. Before wallpapering, the seams between dry-plaster sheets are filled with gypsum mastic.