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What you need to know about stucco application and repair

Rosie Romero, special to the Arizona Daily Star

Stucco is one of the topics we get asked about most often at Rosie on the House. It is one of the most popular exterior finishes for homes in Arizona.

To help us understand stucco application and repair, stucco expert and long-time Rosie on the House certified partner Doug Dedrick, owner of Stucco Renovations of Arizona, LLC, explains.

Various stucco systems

Let's start with the basics. The three-coat stucco system is the granddaddy of all stucco systems. This system consists of three separate cementitious coats over a paper-backed lath on a solid substrate such as sheathing. The lath is usually a wire mesh to which the first coat, or scratch coat, is applied. This coat is intentionally rough to allow the second coat to adhere. The second coat, the brown coat, is applied after the scratch coat has dried. This coat is smoother and designed to receive the final or finished coat. The top coat is applied only after the brown coat has cured. This is where the texturing occurs.

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One thing to keep in mind is a consistent fact about cementitious stucco products: they all crack to some degree. However, with the three-coat system, cracks may show up in the scratch and brown coat, making it easier to repair and apply the top coat with less cracking. Notice we said “less likely” – again, stucco cracks.

The next and more popular stucco system is the one coat system. You may also hear it called the “Western one coat system.” However, the name is misleading. The system consists of two coats of cement, fiber, proprietary chemicals and water applied to a metal mesh, which is then applied over a rigid foam sheathing board. This system combines the scratch and brown coats into one layer, over which the top or texture coat is applied. As with the three coat system, the base coat must dry and the cracks must be repaired before the top coat is applied.

Thermal insulation composite system

Another system not commonly used in residential construction is the exterior insulation finishing system (EIFS). The polymer-based stucco-like finish is applied over foam insulation that can be thicker than one layer. This is common in commercial construction. Dedrick says this system is quite expensive compared to more traditional stucco systems.

There are other concerns about combining EIFS with traditional home building methods. EIFS polymers are not designed to breathe and trap moisture within the frame. Commercial building methods allow moisture to evaporate before it reaches the interior surface of the EIFS components.

Each stucco manufacturer's components are different. Some include fiberglass or other fibers as well as various polymers in the mix. The fibers and polymers are designed to minimize cracking. Minimize, not eliminate.

Stucco surfaces

The final layer gives the stucco its final style.

Dozens and dozens of styles are usually differentiated by geographic location. We'll focus on Arizona and limit ourselves to the most common styles.

The smoothest style with no texture is not popular here as the smallest cracks are visible. A coarser sand finish layer, known as a “sand” finish, is more common. This helps to make the hairline cracks less visible while emphasizing the modern lines of a home's design.

This is where things get complicated.

“I do it my way” finishes vary from applicator to applicator. This varies from company to company and region to region in Arizona. The general characteristic is a more random finish layer that gives the stucco surface a lot of texture. Dedrick calls his “river sand” texture.” Others call their textures “Random,” “Skip Trowel,” “Spanish Point,” or a trademarked name specific to a particular stucco company.

Another finish that Dedrick uses is called “Cat Face.” It has a smooth finish with small rough spots. This finish is also known as “Santa Fe.”

The bottom line is that you need to look at samples of different finishes to decide what will work and look best for your project. It's better to look at and touch a tactile sample than a picture.

Decorative features

Many homes have decorative elements around windows, doors and arches, including cornices and many different design profiles. These additional pieces are usually wired to the base lath system to attach them to the home. They may include integrated laths to make it easier to attach the moldings.

These elements can add a special style to your home. Dedrick stresses that correct attachment to the base board is crucial to avoid detachments or cracks.

Expansion joints can support the expansion and contraction of the stucco system, thereby minimizing cracking.

Repair

There is a common statement in the construction industry that has almost become a proverb: “We only guarantee concrete against fire and theft.”

Concrete cracks, and since stucco is a concrete product, so does it. If your stucco has cracks, follow these rules of thumb to repair them.

1. The location of the crack, its size (length and width), and direction are important. You need to determine if the crack is the result of structural problems. These are usually cracks that are wider than the thickness of a nickel or 1/8 of an inch, whose surfaces on both sides are no longer in the same plane, or wide cracks that run at approximately a 45-degree angle from an opening such as a window, door, or arch. If any of these cases apply, you may need to call in a licensed professional to make sure there are no underlying problems that need to be addressed before you begin repairs.

2. If the crack does not meet the above criteria, Dedrick recommends first cleaning the crack of dust and small debris. Using a putty knife will ensure that all loose material is removed.

3. Choose the caulk. Dedrick uses a sand caulk, which is exactly what it sounds like. It's a tube of caulk mixed with sand and caulk, which makes it easier to match the texture. Fill the cracks with caulk and paint.

Dedrick reminds us that cracks sometimes need to be treated with a top coat to even out the repairs. Usually, the entire wall needs to be repainted to match the existing style. Be prepared for a repaint, too.

Industry training

Finally, we asked Dedrick what training looks like for someone entering the plastering industry. Dedrick tells us that there are basically two types of training a plasterer needs. The first method is similar to traditional on-the-job training, where a newcomer to the industry learns the intricacies of the trade from an experienced crew. This takes time and, as you might expect, costs money. A solid skill set can be developed over a few years of learning and practice.

The second level of training is on construction site safety. Private and commercial construction sites have safety regulations in place to protect workers. All employees, whether experienced or not, should understand the principles of scaffold safety, both during construction and use, tethering safety, and in Arizona, heat safety can be a serious issue.

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Rosie Romero has been an expert in Arizona's home building and renovation industry for over 40 years and hosts the syndicated radio show “Rosie on the House,” heard Saturday mornings from 10 to 11 a.m. on KNST-AM (790) in Tucson.

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