One Coat VS Three Coat Stucco | What’s The Difference?

Stucco is a popular choice for exterior walls due to its durability, aesthetic appeal, and versatility. However, choosing between the two main systems—1-coat and 3-coat stucco—can be confusing, especially if you’re new to stucco applications.

Each system has unique features, benefits, and drawbacks that make it better suited for specific types of projects. In this article, we’ll break down the key differences to help you decide which system is the best fit for your needs.

1-Coat Stucco System

The 1-coat stucco system is a more "modern alternative" to traditional stucco, designed for efficiency and speed. Here are its main components and features:

• Layers: The 1-coat system uses a single base coat over the lath, followed by a finish coat. This streamlines the application process and reduces the necessary curing time of an additional base coat.
  
  
• Thickness: The thickness of the base coat is around 3/8", with an additional finish coat that is applied over that at a thickness that ranges from 1/16 of an inch to 1/8 of an inch. When 1 inch foam insulation (foam sheeting) is included in this system, the total overall thickness reaches approximately 1 1/2".
  
  
• Lath: The lath for a one coat system consists of: two-ply paper, 1" foam board for insulation (oftentimes), and 20-gauge wire mesh. This simplifies the installation process, while adding additional insulating benefits due to the foam being used.
  
  
• Base Coat: One coat stucco systems use only one base coat that is around 3/8 of an inch thick. This is pretty thin, as far as base coats go, so you will lose strength in the overall system, mainly in regard to the impact resistance, something that is surely apparent if you live on a golf course.

Advantages of the 1 Coat System:

1. Faster Installation: With fewer layers to apply, the 1-coat system saves time on installation. This is mainly due to the single base coat that is used, saving time on applying an additional base coat and allowing it to cure before applying another.
   
   
2. Added Insulation: The foam board improves energy efficiency slightly, due to the added R-Value it provides with 1" EPS foam. Some one coat systems do not use foam (uninsulated system) but it is fairly rare these days and is more likely to be found on larger commercial projects.
   
   
3. Lower Labor Costs: Fewer layers and quicker application result in reduced labor expenses, in general, but the added cost of the foam and base coat material level that cost out a bit.

Disadvantages of the 1 Coat System:

1. Reduced Impact Resistance: The thinner base coat offers less durability compared to a 3-coat system and impact resistance will be affected by this, possibly leading to smaller repairs that need to be addressed over time.
   
   
2. Foam Reliance: The system depends heavily on the foam board for stability, which makes the walls more susceptible to movement, cracking and impact damage.
   
   
3. Limited Applications: Better suited for residential projects than high-traffic or commercial buildings that might see more impact potential on a daily basis.

3-Coat Stucco System

The 3-coat stucco system is a proven system, known for its strength and versatility. Here’s what sets it apart from the one coat system:

• Layers: Includes a separate scratch coat, brown coat, and finish coat that is applied over the lath. Each layer serves a distinct purpose—the scratch coat fills close to half of the required system thickness needed and provides a strong mechanical bond for the next coat. The brown coat fills in the remaining thickness needed and creates a more leveled off, even surface for the finish coat.
  
  
• Thickness: The combined thickness of a three coat stucco system is approximately 7/8" for the scratch and brown coats, plus the finish coat, which is applied on top of the brown coat. This robust layering adds to the system's durability and impact resistance.
  
  
• Lath: Three coat stucco systems also use two-ply paper and 17-gauge metal lath, which is thicker and stronger, adding greater reinforcement to the system in that area. The heavier gauge wire enhances structural stability, making it ideal for higher-stress prone areas and applications.
  
  
• Base Coats: There are two separate base coats that make up the three coat stucco system and these are the scratch coat and brown coat. This creates the strong foundation for the system.

Advantages of the 3 Coat System:

1. Superior Durability: The thicker base coats provide excellent impact resistance and structural integrity. This system has been used for decades and has a proven record for longevity, if done properly.
   
   
2. Versatile Applications: A three coat system is suitable for both residential and commercial projects, including high-traffic areas where impact damage might occur more frequently.
   
   
3. Material Availability: The base coat materials used in these systems is a lot more available due to the fact that the ingredients used are sold at most home improvement stores. One coat stucco base coat material is more of a specialized material, and is usually bought at a stucco material supply yard.

Disadvantages of the 3 Coat System:

1. Longer Installation Time: The separate base coat layers require more time and material to apply and allowing these coats to dry and cure will also tack on additional time.
   
   
2. Higher Labor Costs: Increased labor is needed for three coat stucco systems, especially when it comes to applying the base coats. The extra layer of the scratch coat and the increased amount of material that is applied to the walls makes up the added labor needed for these systems.
   
   
3. Skilled Application Needed: Applying the base coats and then having to deal with properly hydrated walls as you're applying the base coats to the walls, increases the skill level that is required.

Key Differences at a Glance:

Which System Is Right for You?

The choice between a 1-coat and 3-coat stucco system ultimately depends on your project’s specific needs but can be broken down in two simple choices, for the most part:

• Choose 1-Coat Stucco if your priorities are speed, cost-effectiveness, and a slight increase in energy efficiency. It’s a great option for residential projects where any additional added insulation is important.
  
  
• Opt for 3-Coat Stucco if you are leaning more towards maximum durability, more versatility, and a robust system with a proven record.