What is Stucco? Conventional Stucco

Advisory Report - April 2003

What is Stucco? 
Part One of Three:  Conventional Stucco

We have all heard the term and have seen it on multiple reports. In these reports the stucco is most commonly referred to as Conventional, EIFS PB, and Hybrid. Over the next three issues of the Client Advisory Report we will give details of each system. To start we have chosen the oldest form of stucco: Conventional. 

Stucco is a surface coating that provides superior qualities adaptable to, and applicable over, a wide variety of surfaces. It provides a strong, firm, fire and weather resistant membrane. Stucco will not deteriorate, resists rot and fungus, and has proven to be a durable wall covering in both warm and very cold climates. Possessing properties similar to reinforced concrete, stucco provides long term protection to any surface. It is economical and requires little maintenance. Stucco provides several distinct finishes, and all stucco finishes include a wide variety of texture and color options. 

Although stucco-sided homes became popular in twentieth century America, the concept of using cement mixtures in architecture goes back to ancient times. Part of the traditional construction methods in the Mediterranean area, stucco (or mortars), a mixture of lime and sand, has been used for centuries for wall finishing. ‘Stucco’ refers to the branch of the plastering industry that manipulates Portland cement based mortars, usually on exterior surfaces. 

Why is stucco also called "Portland cement"? "Portland" does not refer to a geographic location. Instead, it refers to a kind of hard stone "Portland stone" that a young bricklayer, Joseph Aspdin, of Leeds, England, was trying to imitate over 150 years ago. Aspdin wondered why some kind of exterior surfacing couldn't be used to match the Portland stone-the durable stone that was so popular in those days. He experimented with different limestones and clays and finally found a way to create a hydraulic cement-a cement that hardens even under water and is not affected by exposure to water. Since the stone he was working with was such an inspiration to him, he patented the product as "Portland cement" in 1824. 

The first record of Portland cement in the United States was in 1868. European manufacturers began shipping it here as ballast in huge steam ships at very low freight rates. Portland cement production in the United States began in the 1870's. Today millions of tons are used annually, predominately for concrete, but only a small percentage of the total output is used in the plastering industry. (Northwest Wall and Ceiling Bureau) 

Modern mortar (lime, sand, cement, and water) is even more resistant and it is usually called European Stucco or Real stucco. Other terms used for European (real) stucco are: old stucco, traditional stucco, and conventional stucco. 

Stucco can be considered as a component of a structure’s wall and ceiling assembly. It is usually either the last, or next to last, element to be installed. Stucco is selected because it possesses characteristics which no other component of the wall assembly can provide. Among its major functions, stucco serves as a refining element, as it can conceal and correct minor deviations in the alignment of the other wall system components, and provide a base for decoration. 

Walls made of genuine stucco sound solid when tapped and will be less likely to suffer damage from a hard blow. Also, genuine stucco holds up well in wet conditions. Although it is porous and will absorb moisture, it will dry easily, limiting damage to the structure. 

• Stucco components: (Stucco Systems, Inc.) 

• ubstrate (wood, concrete, plaster, gypsum sheathing) 

• water barrier (building paper) 

• metal lath

• base coat(s) (scratch coat & brown coat) 

• finish coat

Contributed by Kyle Bost
Senior Technical Advisor
U.S. Inspect, LLC