Stucco; also know as Portland Cement Plaster has been used on a wide variety of building in the US for over 150 years. In fact, variations of stucco go back as far as Roman times and some of the applications are still in use today. The term Portland Cement Plaster refers to a blend of cement, lime or masonry cement, sand and water. These materials are mixed in a prescribed formula by the applicator on the building site and then applied by hand or machine. Some of the advantages of Stucco include:
- Versatility of design; stucco can be applied to curved wall surfaces, window bands and quoins for aesthetic appeal.
- Curb appeal; Stucco can blend in with or standout with the surrounding structures because of the wide variety of finish styles [textures] and colors available.
- Water Resistance; properly mixed and applied stucco with the appropriate weather barrier is classified as a concealed weather-barrier system.
- Durability; stucco can endure the wet/dry and freeze/thaw cycles in all parts of the country. Stucco has high abuse and impact resistance.
- Stucco is a low maintenance and low life cycle cost wall cladding.
- Stucco is a fire rated wall assembly available in 1 or 2 hour ratings.
- Code approved; stucco is listed in the IBC, IRC and the UBC.
There are two basic stucco systems the traditional three coat system and the newer one coat system. One Coat Stucco could be called two coat stucco because the term ‘One Coat’ refers only to the base coat and not the finish coat that is required to complete the application. It is important that the system selection be done by a design professional who can balance the project requirements with the project budget.
Interior Gypsum Plaster
The primary purpose of gypsum plaster is fire protection. The secondary purpose is decorative. The use of gypsum plaster in buildings goes back as far as the Romans who required plaster in buildings for life safety reasons. Prior to the introduction of gypsum drywall in the 40s all interior walls and ceilings in buildings were plastered. Before the introduction of gypsum lath and metal lath the gypsum plaster was applied over thin strips of wood [lath] that were fastened to the wood studs. Today there are several plaster systems to choose from instead of gypsum drywall. These plaster systems are considered a premium wall finish when compared to the cost of drywall however, these systems offer longer term durability, a monolithic surface and the ability to be applied to curves and arches, things that are not possible with gypsum drywall boards.
Conventional Plaster System
Conventional plaster systems are the ultimate in interior wall and ceiling finishes. Skilled craftsmen generally install this system in two or three coats. The basecoat is used to level and correct any irregularities in the lath or masonry substrate or to achieve the necessary thickness for fire or acoustical ratings. Gypsum basecoat plasters for conventional systems come in a wide variety from neat [no sand], mill mixed with light weight aggregate, to a special high strength gypsum plaster. Finish coats are generally made of gypsum plaster, lime, or gauging plaster depending upon the desired texture.
Veneer Plaster System
A veneer plaster system is made up of a thin coat [3/32″ to 1/8″] of specially formulated plaster that is trowel applied over a 48″x96″ gypsum base that is specifically made for this plaster application. The advantages of a veneer plaster system are faster application time, a much harder and impact resistant surface compared to conventional drywall and the surface can be painted in as little as 24 hours. The veneer finish can be integrally colored [pastels are recommended] to eliminate the extra step of painting.
Gypsum Plaster Columns and Partitions for Fireproofing
The use of metal lath and gypsum plaster as a fireproofing material has been well established through extensive testing and field experience. The advantage of using this material instead of convention drywall is the ability to meet the architectural requirement as well as the fireproofing requirement. A good example would be round structural steel columns or partitions that are set on a radius. Fire rating test reports are available from several agencies such as Underwriters Laboratory and the National Board of Fire Underwriters.
Buildings are classified as to building type and occupancy usage according to the code authority adopted by the city in which the building is to be constructed. The most common code authorities in use today are the International Building Code [IBC], the Uniform Building Code [UBC], the Standard Building Code [SBC], and the Building Officials and Code Administrators [BOCA].
The classification of building type and occupancy is the key to whether or not fireproofing is required.
Spray applied fireproofing is classified as a passive fire protection system because once it is installed it remains in place and ready to perform. Alternative fire protection methods such as sprinkler systems rely on the heat of a fire that reaches a certain temperature to activate a fuse before the system itself becomes active. Sprinkler systems need to be tested on a regular schedule to insure the systems readiness. The percentage of systems that malfunction when tested is significant.
Once it is determined that sprayed fireproofing is required, the decision as to what type of product is best for the project must be made. Spray fireproofing materials in use today include:
- Low, Medium, and High Density Cementitious.
- Low and Medium Density Mineral Fiber.
- Interior or Exterior Grade material.
- Intumescent coatings.
Each of these products have specific design characteristics that when specified correctly will meet all of the fireproofing requirements. Underwriters Laboratory has conducted hundreds of fire tests on specific construction assemblies using products from all of the manufacturers of fireproofing materials. These tests are updated and published yearly, taking advantage of new and improved products and reduced thicknesses. This UL publication is the major source for information on standards for fireproofing applications.
Low Density Fireproofing; proven in place performance on interior structural members make these products the most widely used fireproofing material in the world. The products are cost effective because of the ease of spray applications to protect steel and concrete substrates. These products provide the maximum flexibility to fit a wide variety of job site conditions. Typical Use: Interior Concealed Applications.
Medium Density Fireproofing; designed for applications where the potential for physical abuse is a consideration. These products offer an increased bond strength and density over the low density materials. Typical Use: Interior Exposed applications.
High Density Fireproofing; designed for use in applications where environmental or climatic conditions exist. It is a durable product that is excellent for use in high traffic areas such as parking garages. Typical use: Interior of Exterior Exposed Applications.
Intumescent Fireproofing; is a decorative thin filmed fireproofing for structural steel. This material allows the designer to express structure as an art form at interior locations in buildings where fire resistance ratings are required. Typical Use: Interior Exposed Structural Steel.
Ornamental plaster is the term that describes coffers, troughs, cornices and intricate details in ceilings and walls. Ornamental plaster is still used today although the use is mostly limited to restoration work on historic buildings. In the days when all buildings were plastered ornamental shapes were common even in houses. Over time the expense and tastes in decorating style gradually eliminated ornamental plaster. Today there is a small resurgence in the use of this material. Plaster type ornamental shapes are now made in a factory rather than hand made on site. These shapes can be produced from plaster or a variety of other materials suited for a particular application. Genuine ornamental plaster is still available although it is expensive and experienced craftsman that perform this kind of work are hard to find.
The term Venetian Plaster refers to a very old technique for decorating walls and ceilings. Originally this material was made from crushed marble and limestone. The beauty of this type of finish is the fact that each application is unique to the craftsman that performed the work. Just as nature makes each piece of granite or marble different so too does the craftsman that applies the Venetian Plaster; each application is the result of the applicators skill and imagination. Venetian Plaster is applied in one or more layers of colored material to produce a finish of blended colors with exceptional depth. The finishes can be waxed to develop a soft sheen or a high gloss appearance.