The thickness of stucco can vary depending on a number of factors and I think this is what confuses people. Just identifying what system you have installed on your house or building can prove to be another challenge that you need to overcome in order to determine the thickness of your stucco system.
Let's take a look at some of the different systems that are available and see how they "stack up" as far as overall stucco thickness goes.
How Thick Is Stucco In General?
Stucco can range in thickness from 3/8" to 1 1/8" or a little more, depending on a few different variables. The system you are using (3 coat, one coat, EIFS, skim coat, etc.) is the main contributor that determines the overall thickness of the entire stucco system as a whole and is the main variable.
Other factors like the finish being applied and how many finish coats need to be applied, in order to achieve a specific texture, are also variables that will add slightly more depth to the overall thickness of a system.
The base coats will make up the typical depths of stucco that are usually stated for a particular stucco system, when screeds are used. For example, a 3 coat system is typical 7/8 of an inch thick and the scratch and brown coats will be brought to that depth, before any of the finish coats are applied.
A one coat system that should be 1-3/8" thick will utilize 1" foam behind the base coat and that base coat will be 3/8" to achieve that desired 1-3/8" depth that is stated, again, before any finish coat is applied.
On masonry walls (concrete or cinder block walls) the average depth of the base coat is 3/8", provided that the concrete or cinder block walls are smooth and free from major flaws. This, again, will be achieved using the base coat alone, without any finish material being added to the wall.
Finish coats are applied over the base coat(s) which add additional thickness to the walls, which is thicker than the stated depth of that particular system.
A good example of this would be a three coat stucco system which is stated to be 7/8" thick, but the base coats (scratch and brown) will already achieve that 7/8".
The finish coat or coats will then add additional depth to that, which can range from 1/16" for a single coat of finish material like a fine sand finish, using fine sand. If a heavy lace texture was used instead, which requires two coats, you could add an additional 1/4" or more, depending on how heavy the finished texture was applied.
3 Coat Stucco Thickness...
The overall thickness of a three coat stucco system is definitely the thickest, when it comes to the actual stucco materials, which consist of the base coats and the finish coat(s). The typical three coat stucco system will use 7/8" grounds (weep screed, control joints, plaster stop, etc.) which will be filled to that 7/8" with the base coats.
The scratch coat and the brown coat are the two base coats that make up this 7/8" of material and should fill out those grounds. These are "ideally" divided up evenly between the two coats at around 7/16" each, giving us a total depth of 7/8", but varies, which I will explain.
An important thing to remember is that stucco is usually hand applied and with that comes slight variations, which is usually the case when it comes to the depth of the base coats and finish coats.
Scratch Coat: The scratch coat in the three coat stucco system is usually referred to as being around 3/8" thick and this is usually true in most circumstances. If you are using a deep furred wire, however, it will likely be closer to between 7/16" to 1/2", in order to cover the wire, which is what one of the goals for the scratch coat is.
Brown Coat: From my personal experience, the brown coat is usually a tad bit thicker than the scratch coat and ranges from 3/8" - 1/2" thick. This comes back to how much material was used on the scratch coat and then adding additional material to that scratch coat to get the brown coat out to that 7/8" thickness for the grounds.
The finish coat or coats will add additional depth to those base coats and can vary in thickness from 1/16" to 1/4", typically.The finish will determine the additional depth that I am referring to.
For instance, a fine sand finish applied over a three coat wall may add a miniscule 1/16" to the overall depth of the 7/8" from the base coats, while a two coat finish like a heavy lace texture can add closer to a 1/4" in some spots when done using a traditional cement based finish.
Stucco Thickness Over Concrete or Cinder Blocks...
The thinnest out of all of the systems has to be the instances where stucco is applied over concrete or cinder block walls. These typically only need 3/8" of a base coat applied over these types of substrates, if they are flat and sound. A finish coat will then be applied over that 3/8" base coat that will add to the overall depth of that 3/8" which could range from 1/16" - 1/4".
This, again, would be determined based on the type of finish and how many coats were applied, like I talked about earlier.
Walls That Need Additional Attention: If the walls are not flat and require attention before adding a base coat to smooth them out, then this could affect the overall depth that the base coat needs to be.
An example of this would be a wall that has had stone on it and then that stone was removed, leaving irregular chunks of mortar left on the wall. They would have to be ground and/or scraped off to remove the high points and then a thicker base coat would likely have to be applied that could range from 1/2" to 3/4" or more, depending on the prep work that was done.
One Coat Stucco Thickness...
A one coat system has an overall depth of 1-3/8" which is divided by 1" of foam and then 3/8" of a base coat (brown coat). After that base coat is applied, that 1-3/8" depth is achieved and like every other system we have talked about already, the addition of a finish coat or finish coats that are then applied over that, add to that 1-3/8" system.
Other Variables When It Comes To Overall Depth of Stucco:
I covered some of the more common systems and depths that you will find in the majority of most stucco walls, but there are some outliers that have different components used in their systems that alter that "typical" depths that are commonly found.
Stucco Ground Sizes: The companies who make the stucco grounds will have different sizes to accommodate different stucco systems, that will affect the overall depth of the stucco itself. If you visit Stockton Metal's website, you will see that for that particular weep screed, they offer many different ground depths (labeled as X) to accommodate different systems that might be used.
The different sizes can be used to accommodate a rain screen layer, thicker foam, etc. This is oftentimes the case with EIFS systems, some of which utilize a much thicker foam for added insulation properties and thinner layers of adhesives and/or base coat materials, prior to the finish being applied.