Stucco is a successful go-to for many businesses’ facilities, however in recent years it’s caught some heat from quality issues due to improper application. There are several types of stucco, but all can be grouped into three categories: three-coat, one-coat, and EIFS (exterior insulating and finish systems). It’s surprising how many construction professionals aren’t keen on the differentiation of one from the other. To weigh out the options on your next project, the below will paint a picture to help you form your next decision of which stucco is the best fit in any upcoming work.
The three coats involve (1) lath, (2) scratch, and (3) brown. Although there is also a ‘finish’ coat, this isn’t included in the three steps because all types of stucco require it. The first coat, the lath, includes paper, metal wire and some corner protection so that there is no water absorption. The wire used has unique features that is best suited for cement to adhere to it. When placed, it should be positioned with a small gap off the wall so that the cement can settle behind it and make the wire and cement all one unit. With proper strengthening to the corners, this step can be a strong foundation to a lasting finish.
Next, the scratch coat is applied with a scarifier and produces horizontal scratches on the cement it spreads evenly at about 3/8 of an inch thick. The roughness of the scratches created allows the following brown coat to stick well.
This last step is then completed with the same technique as the scratch coat. However, instead of a scratcher, a new instrument is used – a darby. This is a long trowel that is used to make a smooth, even surface, with the same thickness of the scratch coat. Following the brown, the top coat is applied, whether the stucco is synthetic or traditional stucco.
• The multi-layer system provides a thicker, long-lasting, durable option.
• Time consuming installation process, in effect adding cost
• Improper installation is a risk due to the complexity of the process. This has the potential to lead to major problems including water infiltration and structural damage.
• Stucco is designed for us in dry climates and is not recommended for regions where there is heavy precipitation or constant exposure to water.
Many claim that one-coat is the most ideal and efficient means of a stucco system. Basically, it consists of all the layers of the three-coat into one. One-coat can be finished in a variety of ways including premixed colored cement stucco finish coats, elastomeric coatings and paints or even acrylic textured finishes—allowing some interesting customization potential.
• Fire-resistant, zero flame spread and zero smoke developed
• Less time investment for installation and lower labor/material cost
• Thinner depth in stucco can create structural issues such as wood damage and leads, ultimately leading to mold and mildew problems. In the Northeast, stucco failure is very common due to high levels of precipitation.
EIFS: Exterior Insulation and Finish Systems (Synthetic Stucco)
EIFS, a system popular in Europe originally for repairs, has become a common option in North American construction consisting of many layers, summarized by The Balance as follows:
1. “An Optional Water-Resistive Barrier that is generally fluid applied and covers the substrate.
2. Adhesive to attach insulation board to the supporting structure (in some cases mechanical fasteners may be used).
3. Foam insulation board that’s secured to the exterior wall surface substrate, most often with adhesive.
4. Base Coat, an acrylic or polymer-based cement material that’s applied to the top of the insulation, then reinforced with glass fiber reinforcement mesh.
5. Reinforcement Mesh, that is embedded in the base coat material.
6. Finish, a textured finish coat that is decorative and protective.”
• Traditional stucco is much more prone to cracking than synthetic, with long cracks that aren’t seen with EIFS.
• Newer EIFS has water drainage systems to keep moisture from becoming trapped internally, helping to avoid mold issues.
• There are several case studies proving the energy savings associated with EIFS-clad facilities.
• Similar to other types of stucco, EIFS is best suited in areas of dry, hotter climates. If used in a wet, rainy area, the material will be susceptible to damage, despite any thorough installation process.
• Manufacturers’ systems are all different that require unique installation techniques. Due to these technical challenges, there is an increased risk of problems with installation (a big determinant of the system’s success)