When it comes to stucco finishes, understanding the perm rating is crucial and if you're considering acrylic stucco for your project, you might be wondering about its perm rating, or if it even has one. Let's explore this aspect of acrylic stucco and see if it has any permeability and if so, how much?
Is There a Perm Rating for Acrylic Stucco?
The answer is yes, acrylic stucco finishes have a permeability rating and these ratings can be influenced by a variety of factors, including the specific type of acrylic stucco used, the size of the aggregate incorporated into the mix and the number of coats applied to the walls.
Factors That Affect Acrylic Stucco's Rating
Understanding the perm ratings of acrylic stucco finishes means looking closely at the products themselves, which you will have to research individually due to the amount of factors that seem to influence the numbers, like:
Standard vs. Specialty Products: A wide range of acrylic finish materials are available on the market, each offering a variety of textures and each having their own, distinct perm ratings.
- Standard Acrylic Stucco: Standard acrylic finishes display a range of perm ratings, directly correlated to the size of the aggregate used in the mix, with finer aggregates often resulting in higher permeability and coarser aggregates generally yielding a more moisture-resistant surface.
- Specialty Acrylic Stucco: Some specialty finishes are designed with specific functional benefits in mind, such as elastomeric products that bridge cracks or formulations enhanced for greater water resistance, each having unique perm ratings that set them apart from standard finish options.
Impact of Aggregate Size: The perm ratings of acrylic finishes are greatly influenced by the size of the aggregate used in them. As an example, finishes that use smaller aggregates tend to have higher perm ratings and this is because the smaller particle size of the aggregate creates a more porous texture, which allows for better moisture transmission through the stucco finish coat layer(s).
To give you one example of what I am talking about, Omega’s (OmegaFlex) acrylic stucco comes with a range of perm ratings for their acrylic finishes:
- Coarse is listed at 11 perms
- Medium at 13 perms
- Fine at 20 perms
- Swirl at 10 perms.
While there are more variables that can influence perm ratings, the data provided by Omega serves as a useful example, illustrating the kind of variation you can expect when looking at perm ratings for one type of finish material.
Effect of Texture: Like I already mentioned, the choice of aggregate in the acrylic stucco also plays a role in determining its overall permeability rating, with different sized aggregates significantly affecting the material's perm rating.
- Sand Finish: Sand finishes are known for their porous surface, which usually results in a higher perm rating and better moisture transmission than smoother finishes.
- Troweled Finish: A troweled finish, known for its smooth appearance and less porous surface, tends to have a lower perm rating, resulting in reduced moisture transmission through the material.
The Number of Coats: A single coat of acrylic stucco will offer a certain amount of breathability, but as additional coats are applied on top, the perm rating tends to decrease, resulting in less moisture passing through the layers.
Here Are Some Examples:
You can view the perm ratings for Omega Stucco's acrylic products, revealing how these ratings can vary significantly from one product to another and across different variations. This will give you a valuable glimpse into the various options out there.
- Omega’s OmegaFlex:
- Coarse: 11 perms
- Medium: 13 perms
- Fine: 20 perms
- Swirl: 10 perms
- Omega’s Akrolastic (Elastomeric): 8 perms
- Omega’s AkroFlex Delta: 21 perms
- Omega’s AkroFlex Semi-Smooth: 15 perms
- Omega’s AkroFlex Malibu:
- Malibu 12: 11 perms
- Malibu 16: 21 perms
- Malibu 20: 31 perms
- Malibu Fine: 14 perms
- Omega’s AkroFlex Desert Series:
- Sahara Sand: 18 perms
- Pebble Beach: 24 perms
- Omega’s AkroSil (Silicone Additive for More Water Resistance): Same as AkroFlex Finishes
Important Notes: The perm ratings provided by Omega for their acrylic stucco products do not specify a particular texture that was used as a control group for these measurements. It is also assumed that the ratings presented are based on the application of a single coat of stucco to the wall.
This assumption is made in the absence of explicit information regarding the number of coats or specific textures that may influence these perm ratings.
Other Manufacturers: Other stucco manufacturers have not provided perm ratings for their acrylic stucco products and despite looking around their website's for any information, I couldn't find any similar data for stucco finishes from other manufacturers.
