Exterior-Insulated Stucco Systems

Build durable, fire-resilient, and energy-efficient insulated stucco wall systems with ROCKWOOL stone wool to meet evolving code requirements

Find Products One-Coat Stucco Three-Coat Stucco Why insulate stucco with stone wool?

Stucco has been commonly used in North America as an attractive, durable, fire-resilient, and affordable cladding material. When applied as part of an exterior insulated wall system with stone wool insulation, stucco can support evolving energy code requirements in new and retrofit residential, commercial, and institutional construction.

Stone wool is an excellent choice for high-performance exterior insulated stucco wall assemblies because it has the compressive strength to support the weight of plaster, is noncombustible, has negligible thermal expansion to provide a stable long-term substrate, and offers reliable, long-term energy efficiency.

Continue reading to find solutions for designing a complete exterior insulated stucco wall system with stone wool.

Table of Contents

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Stone Wool Insulation Benefits

Why Stone Wool?

Discover more about integrating stone wool insulation into your exterior-insulated stucco system

What are insulated stucco systems?

Stucco cladding is a rendered construction material commonly made up of a mixture of cement, sand and water, and is currently one of the most commonly applied cladding materials in North America.

As energy code requirements are increasingly driving toward the need for continuous exterior insulation (ci), designing assemblies that combine commonly used cladding materials, like stucco, with a high-performance thermal strategy   contributes to construction of a durable building envelope.

ROCKWOOL stone wool insulation boards have been tested and approved to work in a variety of exterior-insulated stucco solutions.

Stucco Cladding Installation - Amity Construction Completed Buidling Imagery - Residential

 Photo Courtesy of Amity Construction

Stucco System Types

There are multiple ways to approach the design of insulated stucco wall systems. Two common applications of stucco insulated assemblies include one-coat and three-coat systems. Whether you're planning a one- or three-coat stucco application, it can be done either in-field or with panelized solutions.

Click on the links below to learn more about each type of system.

One-Coat Stucco

One-Coat Stucco

Learn more about one-coat stucco with stone wool insulation

Three-Coat Stucco

Three-Coat Stucco

Find assembly details and attachment strategies for three-coat stucco applications

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ROCKWOOL is a proud member of the Stucco Manufacturers Association (SMA) and Wall and Ceiling Alliance (WACA).

Stucco Manufacturers Association (SMA) Wall and Ceiling Alliance (WACA)

ROCKWOOL Stone Wool in Stucco Systems

Stone wool insulation provides multiple benefits for many high-performance exterior wall applications, including those finished with stucco. They work effectively together in fire-rated wall assemblies for improved building and occupant safety, stone wool has high drying potential, excellent pest resistance, provides improved acoustic performance and is inherently durable for long-term performance.

Stone wool insulation provides reliable, long term thermal performance to help meet the goals of your project, and has been evaluated by the International Code Council Evaluation Services for use as a thermal insulation board.

View ICC-ES Report #3773 Find Products

Fire resistant: 

  • Noncombustible stone wool insulation is a critical component in fire-rated wall assemblies, with tested systems per ASTM E119 (CAN/ULC S101)
  • NFPA 285 solutions that may eliminate the need to encapsulate the insulation board at openings
    View one-coat systems
  • Well suited for high-density construction including urban areas with zero- and reduced-lot line installations, WUI (wildland-urban interface) zones, and in noncombustible construction  
  • Resists transfer of heat in a wall assembly that causes layers on the other side to begin burning or smoking, making it part of a strategic solution to a growing risk for all building types
  • ROCKWOOL Comfortboard products are listed in the California State Fire Marshal’s Building Material Listing (BML) as ignition-resistant products for WUI zone construction 
    View the listings
Intertek Logo

See our ASTM E119 1 hour fire-rated wall assemblies for both open frame and sheathed wall construction. Testing includes the industry’s first unrestricted load bearing 1hr. fire-rated assembly (sheathed wall) for one-coat stucco.

View Open Framing Design Listing
ASTM E119 Solutions
View Sheathed Wall Design Listing
ASTM E119 Unrestricted Loading Solution

Sound absorbent: 

  • The non-direction fiber orientation and increased mass of stone wool insulation effectively reduces exterior sound transmission across the wall system, creating quieter, more comfortable spaces.
  • ROCKWOOL has developed a series of assemblies tested for Sound Transmission Class (STC – ASTM E90) and Outdoor-Indoor Sound Attenuation (OITC – ASTM E1332) to support the design of healthy and comfortable buildings.
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Relevant Resources
Acoustic solutions with stucco
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1.0 MB

Durable: 

  • Dimensionally stable: changes in temperature have a negligible impact, making stone wool a stable substrate.
  • ROCKWOOL Comfortboard® has a high maximum-use temperature of 1200°F, meaning it won’t warp or crack as a result of exposure to reflected light or ambient temperatures.
    • Permits the use of darker finishes from stucco manufacturers 
  • Stone wool is proven to resist termites and other insects, even in regions with very heavy pest pressure on building structures  
  • Stone wool boards may be exposed to UV light for up to three years with no significant negative effects — providing greater flexibility with project schedules, even in hot, sunny climates.
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Dimensional Stability of Rigid Board Insulation Products
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Resistance of ROCKWOOL Insulation to Termites
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Resistance of ROCKWOOL insulation to UV
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Vapor permeable and moisture resistant:

  • Stone wool insulation is moisture resistant and vapor permeable, allowing for a high drying potential and mitigating the risk of mold and mildew while reducing the risk of condensation within the wall assembly, contributing to healthy, comfortable indoor environments.
  • When used in exterior walls, the vapor permeability of stone wool minimizes the risk of decay, rot, deterioration, or corrosion, supporting the durability of the assembly. 
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Controlling Vapor Flow in Mass Walls in Hot-Humid, Mixed Humid and Warm Marine Climates
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10 facts about moisture and stone wool insulation
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Sustainable: 

  • Stone wool insulation is manufactured from one of the world’s most abundant raw materials without the use of blowing agents or toxic flame retardants. And because of its ability to support high-performance assemblies that reduce energy consumption, stone wool can contribute towards LEED credits for your project.
LEED Solutions Guide
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LEED Calculator
Request a LEED Certificate
It is predicted over the next decade, 2/3 of stucco used in the U.S. will be an insulated system. Due to verifiable code compliance, one-coat stucco will make up a significant portion of the future stucco market.

Stucco Manufacturers Association 2019 U.S. Stucco Market Report

One-Coat Stucco

One-coat stucco installations can be traced back to the 1970s energy crisis and are often applied over rigid insulation boards and lath for energy efficiency to help meet thermal code requirements. This approach must adhere to stucco manufacturer (system holder) instructions as they are not generically described in the building code.

  • One-coat stucco systems are proprietary, with each system owned be a stucco manufacturer (system holder)
  • Combines the scratch and brown coats into a single layer
  • Features a minimum 3/8” thickness of material that is embedded into lath
  •  Completed with a separate finishing coat to offer a wide range of finish colors and textures
  • Can provide labor efficiencies when compared to a traditional three-coat application
  • Reduces the weight load from the cladding on the assembly by approximately 50 percent
One-coat system testing

ROCKWOOL has tested one-coat assemblies for both hourly fire ratings and acoustic performance. Click the links below for test data and a list of one-coat insulated stucco systems incorporating stone wool insulation.

Fire and Acoustic Tested Solutions
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Find one-coat systems
Find one-coat systems
APPROVAL - National One Coat Stucco Association Lath Standard
The National One Coat Stucco Association (NOCSA) has approved the use of mineral wool board insulation within the NOCSA Standard for Installation and Furring of Plaster Base (Lath) for Vertical Construction.

One-Coat Stucco Systems

Through partnerships with stucco one-coat system manufacturers within the North American market, ROCKWOOL stone wool insulation is a component of code compliant plastering systems that may be installed over open framing or various approved sheathing surfaces.

These systems provide increased energy efficiency that creates a long-lasting exterior cladding for residential and commercial projects. These systems are used as alternatives per ICC-ES Acceptance Criteria for Cementitious Exterior Wall Coatings (AC11) to code prescribed conventional stucco systems compliant with ASTM C926. The stucco systems outlined below must be installed in accordance with the code, ASTM C1063, and the manufacturer’s published installation instructions, as applicable.  

 

 

Stucco Cladding Installation - Ci Labs Testing Imagery Direct Applied Stucco Installation

Western Blended Products

Western 1-Kote Mineral Wool Insulation Exterior Stucco System is an NFPA 285 compliant, complete stucco assembly for residential and commercial buildings. All W1K Systems are code-compliant stucco assemblies that may be installed over open framing or various approved sheathing surfaces.  

Western 1-Kote Mineral Wool Stucco System

Senery / Finestone

Continuously insulated (CI) cement plaster stucco wall systems with aesthetic versatility for commercial and residential construction. Senergy offers a wide range of Stucco Systems with specifications, details and technical support.

Senergy Insulated Stucco Systems Finestone Insulated Stucco Systems

FacadesXi

The FacadesOne Xi Series is a tested and engineered one-coat stucco wall assembly with continuous exterior insulation. Noncombustible and fire-resistant assemblies available with mineral wool insulation board.

FacadesOne Xi Series
During construction of the stucco wall assemblies no cracking was observed after the curing process. Compared to EPS foam, there were no extra efforts or modifications to the stucco mix required when using stone wool insulation.

Kenyon Plastering

Three-Coat Stucco

Three-coat stucco systems have been used for more than 100 years to create long-lasting, attractive, and durable cladding for buildings of all types. The use of continuous insulation (ci) in three-coat systems is becoming more common with evolving building codes that require greater thermal performance from exterior wall assemblies.

  • Three-coat stucco systems are non-proprietary and are designed to meet various code requirements, such as
    • International Building Code (IBC) Chapter 25
    • International Residential Code (IRC) Chapter 7
  • Typically applied in three layers
  • Heavier than one-coat stucco systems
  • Classified as noncombustible under the IBC
Three-coat stucco resources

ROCKWOOL has developed a series of typical walls for exterior insulated stucco systems showing a variety of attachment strategies. They are designed to provide direction regarding methods of construction using ROCKWOOL stone wool insulation products within a stucco insulated wall assembly

Three-Coat Stucco Solutions
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Stucco for the 21st Century
ARTICLE: Walls and Ceiings - Solutions for design professionals to bring your stucco cladding assemblies into code compliance for the 21st century

In a traditional three-coat system, typically the first layer is a 3/8” scratch coat, followed by a 3/8” brown coat, and the assembly is completed with a 1/8” finish coat for a total thickness of 7/8”. The three layers are applied over an approved water resistive barrier (WRB) and metal lath either by hand with a trowel or by machine. 

ROCKWOOL stone wool insulation boards can be used effectively in three-coat stucco systems in a variety assembly types and attachment strategies to meet building code requirements. These can include:

  • Drainmat over thermally broken clip-and-rail
  • Vertical hat channels over Z-girts and stone wool insulation
  • Vertical strapping over stone wool insulation
Download three-coat stucco solutions
Stucco Multiunit Residential - Stock iStock-184341017 - Modern Townhomes stock photo

Stone Wool Insulation Products

ROCKWOOL Comfortboard®

Comfortboard is a rigid, high-density stone wool board designed for exterior continuous insulation applications. It offers improved energy efficiency, increased fire resistance, enhanced acoustic comfort, along with vapor permeance and moisture resistance for a durable enclosure.

Available in two product options;
Comfortboard 80 or Comfortboard 110, providing compressive strength to meet specific structural requirements, these products may also be used below-grade, under concrete slab, in floor-ceiling assemblies, and for sloped roofing applications.

Comfortboard is an approved component of both one-coat and three-coat stucco assemblies. Comfortboard can also be used with ROCKWOOL Comfortbatt thermal batt insulation in a complete insulated stucco assembly to provide increased thermal, fire and acoustic performance. 

Learn more about these stone wool insulation products:

R-Class builder product photos
2021201 RWNA PHO 1120

ROCKWOOL Comfortboard® 80 rigid stone wool exterior continuous insulation board

ROCKWOOL Comfortboard® 80 is a rigid exterior insulation board, providing a continuous layer of insulation around commercial or residential building envelopes.

20200506 RWNA PHO 1611

ROCKWOOL Comfortboard® 110

Comfortboard® 110 is a rigid, high-density, stone wool insulation board used as exterior continuous insulation in residential and commercial applications where enhanced compressive strengths are required.

20221101 RWNA PHO 1181

ROCKWOOL Comfortbatt® semi-rigid thermal batt insulation for exterior wall cavity wood and steel framing

Comfortbatt® is a stone wool insulation thermal batt for use in both new residential construction and renovations. A unique, flexible edge helps maintain R-values.

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