Stucco Is Stucco, Except When It Isn’t

It used to be that stucco was stucco. And by that I mean a Portland cement plaster finish material. But the word stucco has been used in a plethora of products and so stucco is not always stucco.

The word stucco is Latin with Germanic roots, whatever that means. The Italian use of the word actually translates best as “filler”, but the conjugated verb stuccare refers generically to plaster. Thus the typical definition of stucco in modern English is refined lime cement plaster.

Today in construction there are many products that contain the word stucco and below are a few of them:

• Stucco - Most of the time that the word stucco is used in modern construction it refers to a 3-coat exterior cladding that is found in residential and commercial applications throughout the U.S. and in many countries around the world. The most common installation over wood framing consists of one or two layers of building paper (a vapor permeable weather barrier), metal lathing, a scratch coat of portland cement plaster, a brown coat of portland cement plaster, and a final finishing coat of portland cement plaster usually containing pigment to provide the final color and texture of the surface. The scratch coat is applied with sufficient force at an approximate thickness of 3/8-inch to become embedded into the metal lath which creates a metal reinforced cementitious base coat which is then “scratched” using a special tool. The “scratched” surface of the base coat provides a mechanical “key” to aid in the bonding of the “brown” coat which is also applied at a thickness of 3/8-inch. The final color coat is applied at 1/8-inch and depending on technique employed, can allow for a variety of textures. The final thickness of the 3-coat stucco system is ideally 7/8-inch. Portland Cement Association
• One-Coat Stucco - According to the National One Coat Stucco Association (NOCSA), “the term One Coat Stucco refers to a blend of Portland cement, sand, fibers, special proprietary chemicals and water. One Coat Stucco combines the scratch and brown coat into a single application of 3/8″ to 1/2″ thick.” On top of the base coat, a finish coat is applied - so really, “one coat stucco” is actually two coat stucco. The Evaluation Service, ICC-ES, is a non-profit corporation that evaluates various building products and methods of application. According to the various building code bodies in the U.S., now consolidated into the International Code Council, the evaluation reports issued by ICC-ES determine the compliance of given products and systems with accepted codes. As such, there is an evaluation report (ER-3899) that addresses one coat stucco products by several manufacturers available for download. The products listed in that specific report are Western 1-Kote Exterior Stucco System, Master Wall One Coat Stucco System, Dryvit Stucco Plus System and Sto One-coat Stucco System. There are many manufacturers of one coat stucco products today and accordingly, several more evaluation reports. NOCSA Technical Information
• EIFS - Exterior Insulating Finish System. Also called EFIS or Exterior Finish Insulation System. EIFS can also be called Synthetic Stucco. EIFS assemblies consist of an EPS foam substrate, a reinforced layer of adhesive and fiberglass reinforcing mesh, with a final topcoat of a polymer-based or polymer-modified finish material. These products also require an evaluation report for use. There are numerous reports under the 07240 division at the ICC-ES website for various EIFS products. Unfortunately, many in the industry have found it difficult to differentiate between various products and often one hears the terms “one coat stucco” and “EIFS” used interchangeably because often a manufacturer makes both types of products. To add to the confusion, there are hybrid systems that used portland cement or modified portland cement over EPS foam substrates. In fact, EPS foam is often used as a form for 3-coat systems at windows, and other openings. And Ultrakote manufactures a one coat stucco system that according to ER-4658 can be used in an open framing system over an EPS foam substrate. So even though EPS foam is used as a base for the finishing material, only EIFS is really EIFS. Article from forensic expert Brian Erickson, Wikipedia entry on EIFS
• Stucco Panels - These are prefabricated panels installed similar to hardboard siding that are composed of fiber reinforced portland cement. So this product is stucco, but it is siding, so it isn’t exactly stucco, depending on how one defines the term. Fiber Cement Siding at Wikipedia.
• Liquid Stucco - This isn’t stucco at all. “Liquid Stucco is a highly unique, permanent, ceramic-based exterior coating system designed to beautify, protect and insulate your home.” [Liquid Stucco, Inc.] The product is installed over a number of substrates including wood, siding, metal and, well - stucco. Liquid is definitely not stucco.
• Stucco Veneziano - This is the fancy name for Venetian Plaster which is a decorative paste plaster for interior applications that delivers a highly decorative, glossy finish that resembles marble. Marmorino Venetian Plasters USA

There can be a lot of variation in terms of material composition, application and installation of many products that people refer to as stucco. Many people also refer generically to sugary carbonated beverages as “coke”. But that doesn’t necessarily mean that it is the proprietary trademarked product of The Coca-Cola Company.

24 June 2007 | Construction, Consulting, Experts, General | Comments

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