This guide examines stucco vs plaster including the differences between types of wall finishes, how each material is used, and how to decide which one is right for exterior & interior home applications.
Two common building materials, stucco and plaster, look very similar once finished. Many people can’t tell the difference between the two; they’re applied with the same technique, have similar thicknesses, and share the same textures. Both are common residential building materials providing durable and long-lasting finishes with superior fire resistance.
Stucco and plaster are low-maintenance and allow for artistic finishes other residential building materials can’t. Today, stucco and plaster are manufactured in large volumes and both used when building many new homes.
What Is the Difference Between Stucco and Plaster?
There are several fundamental differences between stucco and plaster starting with the most basic fact; stucco is an exterior siding material and plaster is an interior wall finish.
Stucco is made of Portland cement, sand, and lime-based materials while plaster is composed of cement, sand, and gypsum.
The two construction materials are powders mixed with water to form a paste. Both include an aggregate such as sand, and both need water to activate the materials allowing it to cure. The important difference between stucco and plaster is the binder that holds both materials together; lime and gypsum.
Stucco paste adheres to exterior sidings such as particleboard or stone and left to dry. Depending on the type of stucco, several layers, or a single layer create the surface, and then it’s textured with the use of tools such as a trowel. Read more about most popular types of stucco finishes here.
Plaster creates a similar paste or mud, and when applied to interior walls and ceilings, creates a decorative finish by way of different tools and sponges. In addition to walls and ceilings, plaster works well for casting decorative elements such as vases, statues, and indoor columns.
Composition of Stucco vs. Plaster
Modern stucco contains Portland cement, sand, and lime with additional materials used for strength or aesthetics. Additives such as acrylic fibers or fiberglass strands, added to the stucco mixture, improve the strength of the stucco, and help prevent cracking and chipping. These additives typically work with one-coat stucco only. Stucco withstands the rigors of weather, unlike plaster.
Plaster contains cement and sand-like stucco but uses gypsum as a binder. The reaction of the gypsum with water gives off heat through crystallization and causes the plaster to harden.
Plaster walls inside a home provide acoustic sound barriers to keep out noise from traffic or other disturbances. Plaster adds dimension and style to indoor rooms with a raised surface similar to stucco and it holds up for years.
Can You Stucco Over Plaster?
With proper preparation of a plaster wall, you can stucco over the plaster. The first step is to clean the plastered wall of dust, dirt, and grime. The raised surface of plaster collects dust and even oils that are carried in the air. It needs to be completely clean before applying a new stucco surface.
Once the plaster is clean and dry, it’s painted with a bonding agent. Be sure the plaster is absolutely dry before applying the bonding agent. Any trapped moisture will remain and possibly lead to cracks, chipping, and mold.
What Is the Best Type of Stucco?
The two main categories of stucco include traditional or cement stucco and newer synthetic stucco. Cement stucco is durable and stands up to harsh outdoor elements. When mixed and applied properly, traditional stucco lasts from 50 to almost 80 years. The process of application includes layers unless the newer one-coat stuccos are used.
One-coat stucco is an efficient system of applying stucco that includes the three-coat stucco layers in one layer. The process is easier to install and faster. One-coat stucco makes a great base for premixed colored cement and elastomeric coatings, stretchy and thick, to allow customized finishes.
Two-coat and Three-coat stucco entails multiple layering with stucco and a finish coat. It’s a tedious process and takes much longer to finish.
Synthetic stucco does not include cement or lime. It’s made from acrylic resin and dries quickly and evenly. Synthetic stucco does not require a mesh base to adhere to, but instead, a foam board attached to the original surface acts as the base for the stucco.
The system of installation used with synthetic stucco, exterior insulation and finish system (EIFS) includes multiple layers. It’s more resistant to water damage versus traditional stucco and, because of the acrylic resin, remains slightly pliable. This pliability aids in preventing cracks and damage from movement under the stucco caused by problems such as shifting sand.
For more related information about house exteriors, visit our page about stucco vs siding.