Plastering—one of the oldest crafts in the building trades—remains popular due to the durability and relatively low cost of the material. Plasterers apply plaster to interior walls and ceilings to form fire-resistant and relatively soundproof surfaces. They also apply plaster veneer over drywall to create smooth or textured abrasion-resistant finishes. In addition, plasterers install prefabricated exterior insulation systems over existing walls—for good insulation and interesting architectural effects—and cast ornamental designs in plaster. Stucco masons apply durable plasters, such as polymer-based acrylic finishes and stucco, to exterior surfaces. Plasterers and stucco masons should not be confused with drywall installers, ceiling tile installers, and tapers who use drywall instead of plaster to make interior walls and ceilings.
Plasterers can plaster either solid surfaces, such as concrete block, or supportive wire mesh called lath. When plasterers work with hard interior surfaces, such as concrete block and concrete, they first apply a brown coat of gypsum plaster that provides a base, which is followed by a second, or finish coat, also called "white coat," made of a lime-based plaster. When plastering metal-mesh lath foundations, they apply a preparatory, or "scratch coat" with a trowel. They spread this rich plaster mixture into and over the metal lath. Before the plaster sets, plasterers scratch its surface with a rake-like tool to produce ridges, so that the subsequent brown coat will bond tightly. They then apply the brown coat and the finish, white coat.
Applying different types of plaster coating requires different techniques. When applying the brown coat, plasterers spray or trowel the mixture onto the surface, then finish by smoothing it to an even, level surface. Helpers usually prepare this mixture.
For the finish, or white coat, plasterers themselves usually prepare a mixture of lime, plaster of Paris, and water. They quickly apply this using a "hawk," that is a light, metal plate with a handle, along with a trowel, brush, and water. This mixture, which sets very quickly, produces a very smooth, durable finish.
Plasterers also work with a plaster material that can be finished in a single coat. This "thin-coat" or gypsum veneer plaster is made of lime and plaster of Paris and is mixed with water at the jobsite. This plaster provides a smooth, durable, abrasion-resistant finish on interior masonry surfaces, special gypsum baseboard, or drywall prepared with a bonding agent.
Plasterers create decorative interior surfaces as well. One way that they do this is by pressing a brush or trowel firmly against a wet plaster surface and using a circular hand motion to create decorative swirls. Plasterers sometimes do more complex decorative and ornamental work that requires special skill and creativity. For example, they may mold intricate wall and ceiling designs, such as cornice pieces and chair rails. Following an architect's blueprint, plasterers pour or spray a special plaster into a mold and allow it to set. Workers then remove the molded plaster and put it in place, according to the plan.
Stucco masons usually apply stucco—a mixture of Portland cement, lime, and sand—over cement, concrete, masonry or wire lath. Stucco may also be applied directly to a wire lath with a scratch coat, followed by a brown coat, and then a finish coat. Stucco masons may also embed marble or gravel chips into the finish coat to achieve a pebblelike, decorative finish.
When required, plasterers and stucco masons apply insulation to the exteriors of new and old buildings. They cover the outer wall with rigid foam insulation board and reinforcing mesh, and then trowel on a polymer-based or polymer-modified base coat. They may apply an additional coat of this material with a decorative finish.
Work environment. Most plasters work indoors, except for the few who apply decorative exterior finishes. Stucco masons, however, work outside when applying stucco or exterior wall insulation. Plasterers and stucco masons may work on scaffolds high above the ground.
Plastering and stucco work is physically demanding, requiring considerable standing, bending, lifting, and reaching overhead, sometimes causing neck and upper back cramps. The work can also be dusty and dirty. It can irritate the skin, eyes, and lungs unless protective masks and gloves are used.
| 1. | Apply coats of plaster or stucco to walls, ceilings, or partitions of buildings, using trowels, brushes, or spray guns. |
| 2. | Mix mortar and plaster to desired consistency or direct workers who perform mixing. |
| 3. | Create decorative textures in finish coat, using brushes or trowels, sand, pebbles, or stones. |
| 4. | Apply insulation to building exteriors by installing prefabricated insulation systems over existing walls or by covering the outer wall with insulation board, reinforcing mesh, and a base coat. |
| 5. | Cure freshly plastered surfaces. |
| 6. | Clean and prepare surfaces for applications of plaster, cement, stucco, or similar materials, such as by drywall taping. |
| 7. | Rough the undercoat surface with a scratcher so the finish coat will adhere. |
| 8. | Apply weatherproof, decorative coverings to exterior surfaces of buildings, such as troweling or spraying on coats of stucco. |
| 9. | Install guidewires on exterior surfaces of buildings to indicate thickness of plaster or stucco, and nail wire mesh, lath, or similar materials to the outside surface to hold stucco in place. |
| 10. | Spray acoustic materials or texture finish over walls and ceilings. |
| 11. | Mold and install ornamental plaster pieces, panels, and trim. |
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