Rosie on the House: Understanding Arizona stucco applications and repairs

Stucco is one of the most common topics we receive questions about at Rosie on the House. It is one of the most popular exterior home finishes in Arizona.

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

Different stucco systems

Three-coat stucco system

Let’s start with the basics. The three-coat stucco system is the granddaddy of stucco systems. This system consists of three separate cementitious layers over a paper-backed lath, on a solid substrate such as sheathing. The lath is typically a wire mesh to which the first layer, or scratch coat, is applied. This coat is purposely rough to allow the second coat to adhere. The second layer, the brown coat, is applied after the scratch coat is dry. This layer is smoother and designed to accept the final or finished coat. The finish layer is only applied after the brown coat cures. This is where the texturing occurs.

One thing that should be noted is a consistent fact about cementitious stucco products: they all crack to some degree. That being said, the three-coat system allows cracks to show up in the scratch and brown layers, which makes it easier to repair, and the finish layer applied with fewer cracks likely to happen. Notice we said, “less likely” — again, stucco cracks.

One-coat stucco system

The next and more popular stucco system is the one-coat. You may hear it referred to as a “Western one-coat.” The name is a misnomer. The system is two coats of cement, fibers, proprietary chemicals and water applied over a metal mesh, which is then applied over a rigid foam sheathing board. This system combines the scratch and brown coats into one coat upon which the finish or texture coat is applied. As with the three-coat system, the base coat needs to dry and the cracks repaired before the finish coat is applied.

Exterior insulation finishing system

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

There are some other concerns about combining EIFS and traditional home construction methods. EIFS polymers are not designed to breathe and trap moisture in the framing. Commercial construction methods allow the moisture to dissipate before reaching the interior surface of the EIFS components.

Each stucco manufacturer’s components vary. Some include fiberglass or other fibers in the mix, along with different polymers. The fibers and polymers are designed to minimize cracking. Minimize, not eliminate.

Stucco finishes

The final coat is the coat that will include the finish style of the stucco.

Dozens upon dozens of finishes are usually differentiated by specific geographic location. We will focus on Arizona and stick to the most common styles.

The smoothest style without texture is not popular here because the smallest cracks are visible. A coarser sand finish coat, known as a “sand” finish, is more common. This helps make the hairline cracks less visible while accentuating the contemporary lines of a home’s design.

Here is where it gets complicated.

“I’ll do this my way” finishes vary from applicator to applicator. That is company to company and region to region in Arizona. The general characteristic is a more random finish layer that adds a lot of texture to the stucco surface. Dedrick calls his “River Sand” texture.” Others call their textures “Random,” “Skip Trowel,” “Spanish Lace,” or a proprietary name specific to a stucco company.

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

The bottom line is you need to look at samples of different finishes to decide what will work and look best for your project. Looking at and touching a tactile sample is recommended over a picture.

Decorative features

Many homes have decorative features around the windows, doorways and arches, including cornices and many different design profiles. These add-on pieces are typically wired to the base lath system to secure them to the home. They can include built-in lath to make the stucco application easier to secure.

These features can add significant stylized features to your home. Dedrick emphasizes that correctly securing them to the base lath is crucial for reducing separation or cracking.

Expansion joints can help the stucco system expand and contract, thereby minimizing cracking.

Repairs

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

Concrete cracks, and as stucco is a concrete product, it also cracks. If there are cracks in your stucco, follow these rules of thumb to fix them.

1. The location of the crack, its size (length and width) and direction are important. You need to determine if the crack is a result of structural issues. These are usually cracks that are wider than the thickness of a nickel, or 1/8-inch, have surfaces on either side that are no longer in the same plane, or wide cracks that are roughly on a 45-degree angle from an opening such as a window, door or arch. If any of these are the case, you may need to engage a licensed professional to be sure there are no underlying problems to address before engaging in repairs.

2. If the crack doesn’t meet the above criteria, Dedrick says to start by cleaning the crack of dust and small debris. Using a putty knife will make sure all loose material is removed.

3. Select the caulk. Dedrick uses a sand caulk, which is exactly as it sounds. It is a caulking tube mixed with sand and caulk. This will make matching the texture easier. Fill the cracks with caulk and paint.

Dedrick reminds us that sometimes cracks need a finish coat applied to assimilate the cracking repairs. Usually, the entire wall will need to be refinished to match the existing finish style. Be prepared to repaint, as well.

Industry training

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

The second level of training is job site safety. Residential and commercial construction sites are subject to safety rules designed to protect workers. All hires, experienced or not, should understand the principles of scaffolding safety, both construction and usage, tie-off safety, and in Arizona, heat safety can be a serious issue.