Utilize this section to specify Portland cement plastering for use for wall, ceiling, and soffit finishes. This product is sometimes referred to as “stucco”.
Portland cement plaster for exterior and interior wall and soffit finishes consists of two or more coats of cement-based plaster applied over metal lath or a solid substrate such as concrete or masonry.
Portland cement plaster provides a durable exterior finish that can be left exposed to the weather. Portland cement plaster is susceptible to cracking and to water absorption when used as an exterior finish. Cracking can be minimized by the proper placement of control joints. Water absorption is minimized by the use of a proprietary finish coat or the application of paint.
Numerous manufacturers offer synthetic plaster finishes, Due to the wide variety of available products these are not included in this section but can be added.
A wide range of finishes are available for Portland cement plaster, the most common of which are included in this section. Other finishes can be added.
Corner beads are required to prevent damage to external corners.
Casing beads are placed where plaster stops or abuts dissimilar materials or stops with the edge exposed.
Control joints must be installed to minimize cracking. In general control joints should be placed:
- To limit each area of plaster to 144 square feet or 12 feet on center maximum.
- Vertically above and below each side or openings.
- Horizontally at each floor line.
Portland cement plaster loses up to 4 percent of its original volume as it dries, Thus, even with proper control joint placement cracking often occurs.
In order to prevent damage caused by cracking and water absorption an elastomeric coating can be applied over the plaster.
Hybrid plaster systems consisting of a Portland cement plaster base with a synthetic plaster finish coat provide the benefits of Portland cement plaster with a more weather-resistant finish.