Introduction & Usage

Introduction & Usage

Masonry has been used successfully in building construction in the Northwest region (Washington, Oregon, and Idaho) for many decades as both the primary structural system and as a cladding. Masonry has withstood the test of time not only because of its natural resistance to fire, water, impact, and organic growth, but also because of its design versatility.

Historically, structural mass masonry wall assemblies were commonplace, primarily due to their superior fire resistance, durability, and weatherability. Over time, such assemblies have given way to alternate structural framing materials. By definition, mass structures inherently address the many above-grade wall functions, including control of water, air, heat, sound, and fire. Replacing the mass structure increases the complexity of the wall design as follows:

  • Wall cavity and/or exterior insulation may be necessary for thermal and sound control.
  • An air barrier is necessary to limit the uncontrolled exchange of air—and consequently the uncontrolled exchange of moisture (primarily vapor), heat, sound, and pollutants that move with air—between the interior and exterior environments.
  • Moisture control is rethought to ensure that moisture-sensitive structural and insulation components are protected.

Traditional decorative and durable cornice and cornerstone elements and built-in drip edges at strategic locations were typical of mass masonry structures and responsible for deflecting much of the water cascading down the face of these buildings. These design elements have been either eliminated or traded for more modularized and economized veneer units that, while reminiscent of historic mass masonry construction detailing, do not have the same water-deflecting characteristics. Fortunately, most veneer assemblies are able to accommodate the added moisture ingress due to a concealed drainage cavity and flashings. The result is a similar material aesthetic, fire resistivity, and durability, yet a flatter and simpler appearance lacking the intrinsic ability to deflect water away from the masonry-clad wall face and away from areas most sensitive to water entry, e.g., wall penetrations such as vents, windows, and doors.

Though the evolution of the above-grade wall design has led to more complex overall assemblies, product selection, and code compliance than in previous years, it has also demonstrated the durable and accommodating nature of modern above-grade wall assemblies to the local climate conditions of the Northwest region.

As a result, the focus of this guide is to provide comprehensive design and construction detailing information for 8 primary above‑grade wall assembly options successfully used in the Northwest climate that are composed of clay or concrete masonry as an adhered or anchored veneer or single-wythe CMU wall application. The focus for each assembly is to clarify the overall above-grade wall building enclosure design as it relates to managing heat, air, and moisture (both liquid water and vapor) transfer between the interior environment and exterior environment and to demonstrate the constructibility of these structures to ensure long-term durability. Cladding considerations including attachment and installation methods are also addressed. Each assembly within this guide is addressed specific to the Northwest region, including Washington, Oregon, and Idaho and considers local climate, codes, and building preferences and practices.

Fig. i-1 Historic masonry structure. Washington State Historical Research Center in Tacoma, WA, constructed in 1911.

Fig. i-1 Historic masonry structure. Washington State Historical Research Center in Tacoma, WA, constructed in 1911.

Fig. i-2 Modern masonry veneer structure, Wenatchee Valley College Music and Art Center, constructed in 2012.

Fig. i-2 Modern masonry veneer structure, Wenatchee Valley College Music and Art Center, constructed in 2012.

How to Use This Guide

This introductory chapter showcases the 8 primary above-grade wall assemblies that are the focus of this guide. This introduction also contains technical references and supporting information for general topics that apply to the featured above-grade wall assemblies.

Each subsequent chapter is dedicated to one of the primary above-grade wall assemblies and provides assembly-specific discussion, guidance, photos, and/or diagrammatic illustrations. Two- and three-dimensional details and cutaway wall sections are provided at the end of each chapter, summarizing the chapter content and illustrating its use in real-world applications.

The sections following the 8 assembly chapters contain additional information regarding thermal modeling parameters, published industry references, and product resources.

The information presented within this guide is not meant to be exhaustive of all assembly variations, product performance properties, or detailing approaches but rather represents a selection of the best practices and preferences used in the Northwest region.

Guide Assemblies

Assembly Comparison Matrix

The Table i-1 Assembly Comparison Matrix is provided to assist designers with assembly selection. Comparison categories are those generally considered for both commercial and/or residential applications and include:

  • Recommended Occupancy Type
  • Building Enclosure Design Approach and Recommended Exposure
  • Long-Term Wall Assembly Durability
  • Typical Wall Thickness
  • Typical Cladding Design Compliance
  • Thermal Performance Considerations
  • Special Construction Considerations
  • Constructibility Ease with Limited/No Access to Exterior
  • Fire Resistivity Considerations
  • Maintenance Considerations
  • Price Per Square Foot

Pricing Analysis

A pricing analysis is provided for each assembly within this guide and demonstrates the relative price per square foot. Pricing is for components outboard of the wall sheathing for framed or CMU backup wall assemblies. For exterior-exposed CMU wall systems, pricing includes all components except interior finishes and steel framing (where it occurs). Pricing is based on a 10,000- square-foot wall area and is valued for the 2015–2016 calendar year.

Overall pricing is included within the Assembly Comparison Matrix beginning. A pricing breakdown and additional related discussion is included in a summary table at the end of each assembly chapter.

Online Availability

Available online are downloadable digital versions of two- and three-dimensional assembly details and cutaway sections as well as sample project specifications. Ongoing additions to references and resources included within this guide can also be accessed.

The remaining sections within this introduction serve as a reference for topics consistent among many of the chapter assemblies. These topics include building enclosure system and loads; identification of building enclosure control functions and critical barriers; assembly design approaches; thermal performance and energy code compliance; sheet-metal components; movement joints; as well as cleaning, repellents, and coatings.

Building Enclosure System

The building enclosure (building envelope) is a system of materials, components, and assemblies physically separating the interior environment from the exterior environment(s). As an environmental separator, the building enclosure can be grouped into three subcategories: support, control, and finish. Support satisfies structural requirements whereas finish satisfies interior and exterior aesthetics.

As an environmental separator, the building enclosure controls heat, air, and moisture transfer and, along with the heating and ventilation systems, helps maintain a comfortable and healthy indoor environment.

The elements of the building enclosure include roofs, above- and below-grade walls, windows, doors, skylights, exposed floors, the basement/slab-on-grade floor, and all of the interfaces and details in between. Typical building enclosure elements are depicted in Fig. i-4. As the focus of this guide is specific to the 8 primary assemblies described in the previous sections, only design considerations for above-grade walls are addressed here. Where appropriate, detailing considerations are also discussed and included for roof, floor-line, and foundation assembly transitions as well as fenestration openings within the above-grade wall.

Fig. i-4 Many building enclosure elements are visible in this photo, including a roof, above-grade walls, windows, doors, and floors (i.e., soffits).

Fig. i-4 Many building enclosure elements are visible in this photo, including a roof, above-grade walls, windows, doors, and floors (i.e., soffits).

Building Enclosure Loads

Over the lifespan of a building, the building enclosure will be subjected to a wide range of interior and exterior environmental loads. Exterior environmental loads include solar radiation, rain, snow, ice, hail, vapor condensation, wind, temperature, relative humidity, insects, pests, and fungi. Interior environmental loads include temperature, relative humidity, and vapor condensation as well as water and water vapor associated with human activities and potential defects in appliances, sprinklers, and interior plumbing.

The impact of rain on and flow over the exterior surface of the building—as well as differences in temperature, air water vapor content, and air pressures between the interior and exterior environments—creates the most critical loads acting on the enclosure. Fire, smoke, and noise separation must also be considered; however, they are beyond the scope of this guide.

The location or climate zone in which the building is constructed dictates the magnitude and duration of these environmental loads on the building enclosure. Every climate zone carries unique design, construction, and maintenance considerations. As depicted in Fig. i-5 and defined by ASHRAE 90.1, three climate zones exist in the Northwest: Zone 5, Zone 6, and Marine Zone 4. These climate zones impose a wide range of environmental loads, including rainfall as shown in Fig. i-6 and Fig. i-7. In the Northwest, rainfall loads span from areas of significant precipitation and cooler temperatures near the western Washington peninsula, the Oregon coast, and the higher elevations of Idaho; more extreme temperatures occur both in winter and summer months in dryer areas in eastern Washington and Oregon and southern Idaho.

Fig. i-5 United States ASHRAE climate zone map.

Fig. i-5 United States ASHRAE climate zone map.

Control Functions and Critical Barriers

A primary function of the building enclosure is to control (or rather appropriately manage) environmental loads. Various materials are used within enclosure assemblies and details to perform different control functions depending on their material properties and placement. The following control functions are typically considered: water (precipitation and ground), water vapor, air, heat, sound, fire, light, and contaminants. The interior and exterior finish can also be considered as part of the control function. For the purpose of this guide, the primary control functions of water, air, heat, and vapor are addressed in greater detail. Consideration of sound, fire, light, and contaminants may be related to the concepts discussed within this guide but are not covered in detail.

Applying the concept of control functions, the term critical barrier is commonly used to refer to materials and components that together perform an important function within the building enclosure. A critical barrier must be continuous for the enclosure to perform as designed. It has become common and referenced within building codes to define specific critical barriers within an enclosure assembly, such as a vapor retarder/barrier or an air barrier. Fig. i-8 depicts the link between the concept of control functions and the associated critical barrier. Fig. i-8 also describes primary and secondary relationships.

The use of critical barrier concepts to evaluate assemblies and details is consistent with industry best practices. The concepts are useful to assess specific assemblies and details being considered for a project. The application of the critical barrier concept will help all parties better understand the role and importance or functions of certain materials and details. As a result, the critical barriers of water-shedding surface (WSS), water-resistive barrier (WRB), air barrier (AB), thermal envelope (e.g. thermal insulation), and vapor retarder/barrier (VR) are demonstrated for each chapter assembly and their respective two-dimensional details throughout this guide. Building form and features are also important concepts for controlling water and are only addressed in this introductory chapter to provide general design guidance.

Throughout this guide, the critical barriers for each assembly and accompanying details will be included similar to those shown in Fig. i-9 and Fig. i-10. Placement and continuity of these critical barriers are also shown for each two-dimensional detail in the following chapters.

The next section introduces the two primary assembly design approaches that apply to the assemblies within this guide. Further discussion on each critical barrier and how each applies to the assembly design approaches is discussed in the following sections.

Assembly Design Approaches

Assemblies within this guide provide the control functions as part of either a rainscreen design approach or mass wall design approach.

A rainscreen design approach is shown in Fig. i-9. This design approach assumes that moisture makes its way through the cladding plane while the building is in-service and provides a level of redundancy to protect against water ingress. A rainscreen assembly includes the following characteristics:

  • A continuous WSS (the rainscreen)
  • An air space behind the cladding that is vented and drained to the outside
  • A WRB (drainage plane) such as a sheathing membrane inside of the drainage space (WSS and WRB are separated)
  • Drain holes or gaps through the cladding so that water can leave the cavity, with a flashing at all penetrations and transitions (e.g., base-of-wall, doors, and windows, etc.) to direct draining water to the outside
  • A continuous air-barrier system (AB) to improve the control of rainwater penetration

It is important to note that using rainscreen wall assemblies that exhibit good resistance to water penetration and that are fundamentally less sensitive to moisture ingress does not eliminate the need for implementing proper details and ensuring acceptable construction practices are followed. Improperly executed details are frequently sources of water entry, critically affecting the moisture performance of the assembly and contributing to premature weathering or efflorescence on the masonry veneer system.

The assemblies in Chapters 1, 2, 3, 6, 7, and 8 are a rainscreen design approach.

A mass wall design approach is shown in Fig. i-10. It provides a WSS and WRB within the CMU structure. In recent years, the mass wall design approach has evolved to allow for thinner mass wall assemblies that control water through the use of clear surface-applied water-repellents and water-repellent admixtures.

The assemblies in Chapters 4 and 5 use a mass wall design approach.

Water-Shedding Surface (WSS)

In general, the water-shedding surface (WSS) is the outer surface of assemblies, interfaces, and details that will deflect and/or drain the vast majority of the exterior water from the assembly. In simplest terms, the WSS is the exterior surface of the building enclosure and the first line of defense against water ingress. The WSS reduces the rain load on the underlying elements of the assembly and serves as a solar control function to protect underlying components from ultraviolet (UV) exposure.

For the rainscreen design approach assemblies included within this guide, the WSS is the adhered or anchored masonry veneer. Because claddings can allow a significant amount of water behind the WSS, a means to drain this moisture out of the wall must be provided.

For the mass wall design approach assemblies included within this guide, the WSS is the single-wythe CMU wall structure, which contains surface-applied clear water repellent and water-repellent admixtures within the block and mortar.

For the additional details and transitions shown throughout this guide, the WSS also includes sheet-metal flashings, as well as the exterior face of fenestrations (e.g., windows), the roof membrane of a conventional roof assembly, and the top surface of the insulation of an inverted roof assembly, Example details included at the end of each assembly chapter demonstrate the location of the WSS at typical wall transitions and a window penetration.

Water-Resistive Barrier (WRB)

The water-resistive barrier (WRB) is the second and last line of defense against water ingress. It is the surface within the wall assembly intended to prevent liquid water from traveling further into the assembly and is often relied upon for assemblies to remain watertight.

In rainscreen design approach assemblies that are exterior-insulated, the WRB may be the surface of the insulation if it is taped and sealed, or it may be a sheet- or fluid-applied sheathing membrane installed on the wall sheathing/structure as shown in Fig. i-11. To perform properly, it is critical that the WRB be continuous. For many standard wall assemblies, the WRB will be the sheathing membrane in combination with flashing and sealants at penetrations, i.e., the plane that sheds any incidental moisture out of the assembly to the exterior. Where the WRB is also part of the air-barrier system, it will be made airtight by tapes, sealants, gaskets, and other airtight components. WRB membranes for the rainscreen design approach assemblies within this guide may be designed as either vapor-permeable or vapor-impermeable:

  • A vapor-permeable membrane allows some water vapor to move through the wall assembly, minimizing the risk of condensation inside the wall and on the sheathing and facilitating drying toward the exterior.
  • A vapor-impermeable membrane allows a minimal amount of water vapor to move between the interior and exterior environment. This membrane type is used when the assembly can safely dry toward the interior under any circumstance. In the Northwest, it is recommended that one-half to two-thirds of the assembly’s total nominal insulation R-value is exterior of a vapor-impermeable WRB.

A number of WRB products and systems are commercially available. However, two primary WRB products are shown within this guide for rainscreen design assemblies: sheet membranes (either mechanically attached or self-adhered) and fluid-applied membranes. Examples of these membrane types are shown in Fig. i-12 as well as Fig. i-13. Alternate types are also discussed where applicable in each assembly chapter.

A WRB system includes a WRB field membrane and accessory products such as flexible self-adhered flashing membranes, fluid-applied flashing membranes, sealants, tapes, and fasteners. These components, when combined, form the WRB system and may also perform as an AB system. When selecting a WRB system, the following properties should be considered:

  • Water Vapor Transmission (Vapor Permeance) – A minimum of 10 perms should be designated for vapor-permeable membranes in the Northwest region and a maximum of 1 perm for vapor-impermeable membranes. Minimum water vapor permeance is demonstrated through ASTM E96 when tested with both water and desiccant methods.
  • Water Penetration Resistance – A product that demonstrates no water leakage when tested to 15 psf to ASTM E331.
  • Durability – A product should be resistant to tears and punctures that may occur during installation or wind gusts. The product must also be able to withstand ultraviolet (UV) exposure following installation and prior to cladding attachment.
  • Compatibility – The product selected should have known compatibility with all accessory products such as self-adhered membranes, liquid-applied membranes, sealants, and tapes.
  • Air Barrier Performance – Where the WRB also forms the AB, the performance properties of the AB should also be demonstrated. (Refer to the Thermal Performance and Energy Code Compliance section of this chapter for more discussion).

In the mass wall design assemblies included within this guide, the WRB is the single-wythe CMU wall structure that contains surface-applied clear water repellent and water-repellent admixtures within the block and mortar.

Example details, two-dimensional details, and three-dimensional wall sections included at the end of each assembly chapter demonstrate the general installation of the WRB.

Air-Barrier System (AB)

The air-barrier is a system of materials that controls flow of air through the building enclosure, either inward or outward. Air flow is significant with respect to heat flow (space conditioning), interstitial vapor condensation (water vapor transported by bulk air flow), and rain penetration control. AB systems should be impermeable to air flow, continuous across the building envelope, able to withstand the forces that act upon them (e.g., mechanical pressures, wind pressures, and stack effect), and durable over the life expectancy of the building enclosure.

For a rainscreen design approach, there are many types of AB products and systems available on the market today. A typical practice within the Northwest is to use a dual-function field membrane that has the performance properties of both an AB and a WRB. When this membrane is paired with accessory products (e.g., self-adhered flexible flashings, fluid-applied flashings, sealants, and/or tapes) and is detailed for airtightness, an AB system is provided.

Where the AB system is provided through the use of a mechanically attached sheet, it is attached to the structure with furring strips, masonry ties, cladding support clips, or washer head fasteners as recommended by the air barrier membrane manufacturer. Attachment provides long-term resistance to the pillowing effects of air pressure differentials. Where a self-adhered sheet membrane or fluid-applied membrane is used, the membrane bonds directly to the exterior sheathing or substrate for continuous support.

Other types of AB systems include:

  • Sealed Sheathing: This option includes exterior gypsum board or plywood with sealed seams (either joint sealant or tape) to provide the AB field membrane. The AB at the sheathing is transfered to window rough openings, penetrations, and across shelf-angle attachments with flexible self-adhered flashing membrane or liquid-applied flashings. A separate WRB field membrane is required for use with this AB system.
  • Closed-Cell Spray Polyurethane Foam (CCSPF): Spray foam insulation may be installed over the exterior wall sheathing to form the AB system. This system relies on flexible self-adhered membrane flashings at rough openings and transitions to complete the AB system. Use of an exterior CCSPF insulation also provides the WRB, thermal envelope, and VR critical barriers.
  • Rigid Exterior Insulation: This option includes exterior rigid board insulation such as extruded polystyrene (XPS) insulation or foil-faced expanded polystyrene (EPS) or polyisocyanurate. Board seams are sealed and/or taped to form the AB system as well as the WRB. Fluid-applied or self-adhered membrane flashings are used to complete the AB and WRB system at transitions. This system also provides the thermal envelope and VR critical barriers.
  • Airtight Drywall Approach (ADA): This option relies on interior gypsum board and additional air-sealing strategies to form an AB system at the interior plane of the enclosure. This approach is traditionally a single-family residential air‑sealing strategy and can be difficult to execute successfully at transitions such a wall-to-roof lines, complex framing structures, partition walls, and service penetrations. Air-sealing strategies for this approach are typically concealed, making quality control review and system repair difficult. This approach is not recommend for the commercial structures or multifamily structures to which this guide applies.

For the mass wall design approach assemblies within this guide, the single-wythe CMU wall structure may provide the AB system.

Performance requirements for air barrier materials and air barrier systems specific to both rainscreen design approach and mass wall design approach assemblies are further discussed in the Thermal Performance and Energy Code Compliance section of this introductory chapter.

Example details included at the end of each assembly chapter demonstrate the location of a continuous air barrier at typical wall transitions and a window penetration.

Fig. i-6 & i-7

Fig. i-8 List of primary building enclosure control functions and associated critical barriers.

Fig. i-8 List of primary building enclosure control functions and associated critical barriers.

Fig. i-11 Typical window head two-dimensional detail with primary critical barriers.

Fig. i-11 Typical window head two-dimensional detail with primary critical barriers.

 

Fig. i-22 XPS insulation behind anchored masonry veneer.

Fig. i-22 XPS insulation behind anchored masonry veneer.

Fig. i-13 Fluid-applied air and water-resistive barrier membrane example.

Fig. i-13 Fluid-applied air and water-resistive barrier membrane example.

Fig. i-14 Polyamide film vapor retarder installed over a wood-framed wall with cavity batt insulation.

Fig. i-14 Polyamide film vapor retarder installed over a wood-framed wall with cavity batt insulation.

Thermal Envelope

Placement and continuity of thermal insulation is an important factor of a thermally efficient building enclosure. While not typically considered a critical barrier but more of a control function, the thermal insulation materials and line of insulation continuity (commonly referred to as the thermal envelope) are useful to identify. This barrier consists of insulation and other low-conductivity elements within an assembly or detail. Identification of these low-conductivity materials helps identify thermal bridges or any thermal discontinuities that should be addressed by design.

For a rainscreen design approach, the primary resistance to heat flow will be provided by thermal insulation (whether cavity or exterior insulation). Wood framing components will provide some insulating value, whereas steel stud framing will not.

For the mass wall design approach assemblies of this guide, the thermal insulation is either interior of the CMU structure or integral at CMU cores.

The Thermal Performance and Energy Code Compliance section of this chapter includes additional discussion related to the thermal envelope. It provides information on prescriptive thermal performance requirements of the energy code, how to address metal fasteners such as masonry veneer ties or cladding support clips that may penetrate exterior insulation, effective thermal performance of above-grade wall systems, special thermal performance discussion for concrete masonry unit (CMU) structures, insulation products, and air leakage as it’s required by energy code.

Example details included at the end of each assembly chapter demonstrate the location of the thermal envelope at typical wall transitions and a window penetration.

Vapor Retarder (VR)

The vapor retarder/vapor diffusion critical barrier is a layer that retards or greatly reduces (e.g., vapor barrier) the flow of water vapor due to vapor pressure differences across enclosure assemblies. In the Northwest region, a vapor retarder is typically placed on the warm side of the insulation (high vapor pressure side).

A vapor retarder may not be necessary within some assembly designs in the Northwest region. Continuity of the vapor retarder is not necessary to adequately control vapor diffusion in most cases. Small holes, gaps, or tears are not critical, unlike in the air barrier. Section 1405.3 of the International Building Code (IBC) provides VR requirements for Northwest Climate Zones 5, 6, and Marine 4.

Vapor diffusion control is not to be confused with bulk air flow control (air barrier). Continuity and sealing of air barrier details is very important; if the same material is being used to control both vapor diffusion and air flow material continuity and air sealing is critical.

Common VR types used within above-grade wall structures in the Northwest region:

  • Polyvinyl Acetate (PVA) Vapor-Retarding Primer: This applied coating requires a substrate for application. It is typically applied to the face of interior gypsum board prior to the finish paint.
  • Asphalt-Coated Kraft Paper: This sheet good is typically a facer to the wall cavity batt insulation and is located behind the interior gypsum board.
  • Polyamide Film: This sheet good product is located behind the interior gypsum board. It is installed after wall cavity batt installation.

Building Form and Features

Building form and features including roof overhangs, balconies, canopies, and other protruding elements, etc., also play a critical barrier function whereby these elements deflect rain and provide shading from the sun and buffering from wind as shown similar in Fig. i-15. The protection provided by these components may allow for alternative water control strategies to be utilized at protected areas. For this reason, deflection elements can be considered as part of the critical barrier analysis. Conversely, balconies and other exterior architectural elements can also act as water-trapping features, unless carefully designed to prevent trapping water. The criticality of building form also depends on climate, and on rainfall in particular; therefore, building form and features are more critical in regions of greater rainfall (refer to Fig. i-7). Building form and features are not addressed within above-grade wall assemblies included within the remaining chapters of this guide but are important design components that should be considered on a project-specific basis.

The building thermal envelope is defined by the International Energy Conservation Code (IECC) as “the basement walls, exterior walls, floor, roof, and any other building elements that enclose conditioned space or provide a boundary between conditioned space and exempt or unconditioned spaces.” Note that the building envelope is sometimes referred to as the building enclosure.

Fig. i-15 ICHS Shoreline Medical and Dental Clinic, constructed in 2014, features large roof overhangs and canopies above entrances to deflect rain away from the above-grade enclosure components and shade the interior environment from the sun.

Fig. i-15 ICHS Shoreline Medical and Dental Clinic, constructed in 2014, features large roof overhangs and canopies above entrances to deflect rain away from the above-grade enclosure components and shade the interior environment from the sun.

Thermal Performance and Energy Code Compliance

The energy performance of buildings in the Northwest is governed by:

  • State of Washington (except Seattle) – 2012 Washington State Energy Code (WSEC), based on the 2012 International Energy Conservation Code (IECC) with amendment, effective July 1, 2013
  • City of Seattle, Washington – 2012 Seattle Energy Code (SEC), based on the 2012 WSEC with amendments, effective December 27, 2013
  • State of Oregon – 2014 Oregon Energy Efficiency Specialty Code (OEESC), based on the 2009 IECC with amendments, effective July 1, 2014
  • State of Idaho – 2012 International Energy Conservation Code (IECC) without amendments, effective January 1, 2015

In general, these energy codes address the minimum requirements for both the thermal envelope and air barrier system critical barriers of the opaque above-grade wall assemblies included within this guide.

Within this guide, discussions related to the energy code focus on the above-listed codes and their commercial energy code compliance provisions; residential provisions are not explicitly addressed. Definitions of residential and commercial buildings may be found within the Definitions chapter of each of the codes listed above.

The energy codes that govern in the Northwest define the prescriptive thermal performance of above-grade walls that form the thermal envelope. Under commercial provisions, prescriptive performance requirements for opaque above-grade walls are differentiated in the IECC based codes by,

  • Climate zone (Zone Marine 4, Zone 5, or Zone 6), as shown in Fig. i-16
  • Occupancy (All Other or Group R)
  • Classification (i.e., mass, metal building, metal-framed, or wood-framed and other).

Table i-2 summarizes the prescriptive above-grade wall thermal envelope requirements as they apply to the assemblies of this guide. Requirements include both minimum R-value (located above each U-factor) and maximum U-factor. Minimum R-value requirements are for nominal insulation and include continuous insulation (ci), which is discussed in the Continuous Insulation section of this chapter. U-factors define the maximum thermal transmittance of the assembly when insulation and other bridging elements that are required to be considered by the governing code—such as framing members and, in some cases, cladding attachments and supports—are considered. For the purpose of this guide, the prescriptive U-factor has also been provided as an equivalent assembly effective R-value and is shown in parentheses ( ) below each U-factor in Table i-2. For simplicity, the R-value is the inverse of the U-factor.

Fig. i-17 describes the typical process for navigating energy code compliance options and strategies. It also describes how this process relates to assembly specific thermal performance results and discussion included within each assembly chapter.

Prescriptive Compliance Option

Refer to Fig. i-17, which identifies the prescriptive compliance option for energy code compliance. Where a project seeks this compliance option, the above-grade wall assembly must meet one of the following:

  • R-value Compliance Strategy: The minimum nominal insulation R-value(s) listed in Table i-2 are to be met. As an example, for an R-value compliance strategy, a wood-framed wall (such as in Assemblies 3 and 8) in a multifamily residential (Group R) application in the City of Seattle must have a nominal R-21 wall cavity insulation to meet code compliance. This same wall on a Group R building in Oregon may comply with the energy code with a nominal R-21 wall cavity insulation or with R-13 wall cavity insulation plus a nominal R-3.8 continuous insulation.
  • U-Factor Alternative Compliance Strategy: The maximum assembly U-factor listed in Table i-2 is to be met. For this strategy, the project-specific assembly U-factor will need to be determined. Determining this U-factor is further discussed in the Non-prescriptive Compliance Option section of this chapter.

An exception to the compliance strategies is denoted in the footnotes of Fig. i-17. Refer to the Chapter 4 discussion for more information regarding this exception.

Non-prescriptive Compliance Option

Refer to Fig. i-17, which identifies the non-prescriptive compliance option (e.g., a trade-off strategy or whole-building modeling strategy). When a project seeks this compliance option, an above-grade wall assembly’s thermal performance is determined as a U-factor; however, it may or may not be required to meet the prescriptive values shown in Table i-2.

Discussion and numerous tables are available within Northwest energy codes and ASHRAE 90.1 to assist with determining the U-factors of above-grade wall assemblies. Where assemblies are not represented within these resources, various methods are available for calculating the effective thermal performance of the wall and are listed below. Appropriate calculation methods should be confirmed with the local jurisdiction as not all of these methods may be accepted:

  • Parallel Path and Isothermal Planes (refer to the ASHRAE Handbook of Fundamentals): Typically used for assemblies with low-conductivity materials. Where material conductivity varies minimally, a parallel path method is typically used, such as with a wood-framed wall. When material conductivities within the assembly vary moderately, such as in a CMU wall, the isothermal planes method is typically used. These methods should not be relied upon for assemblies with highly conductive materials (e.g., steel studs) or intermittent components such as fasteners or ties through exterior insulation.
  • Zone Method and Modified Zone Method (refer to the ASHRAE Handbook of Fundamentals): Typically used for assemblies with highly conductive elements such as steel studs. These methods are not recommended for determining the performance of assemblies with intermittent fasteners or ties through exterior insulation.
  • Two-Dimensional Computer Modeling: Programs such as Lawrence Berkley National Laboratory’s THERM calculate two-dimensional heat transfer. This method may be used for most above-grade wall assemblies; however, it is not appropriate for assemblies where intermittent fasteners, ties, or cladding supports bridge exterior insulation. An example of a two-dimensional thermal image is shown in Fig. i-18.
  • Three-Dimensional Computer Modeling: Programs such as HEAT3 (buildingphysics.com) calculate three-dimensional heat transfer. This method may be used for all above‑grade assemblies, including those with exterior insulation bridged by fasteners. An example of a 3-dimensional thermal image is shown in Fig. i-19.

Within this guide, three-dimensional computer modeling was employed for Chapters 1 through 3 and 5 through 8 assemblies to demonstrate how typical thermal bridges—like masonry ties, shelf angles, and cladding support systems of various types—contribute to the effective thermal performance of each assembly. Based on modeling results, insulation thicknesses and types as well as cladding support materials and types may be estimated for project-specific assemblies. Through evaluation of the results, numerous options for thermally optimizing each assembly are discussed. Modeling results and discussion are demonstrated in each chapter as an effective R-value but may be converted to a U-factor by dividing 1 by the R-value. Modeling does not account for the impact of thermal mass.

Thermal modeling was undertaken using HEAT3 (buildingphysics.com). Modeling specifics and additional information used to complete the modeling within this guide is provided in Appendix A.

Continuous Insulation

Continuous insulation is referenced in the prescriptive requirements for many assemblies within this guide. Where continuous insulation is required or used to meet code compliance, the definitions of continuous insulation must be carefully considered; definitions vary by jurisdiction within the Northwest region and include:

  • 2012 IECC: No definition is provided. This guide recommends referring to ASHRAE 90.1-2010 and confirming local requirements with the governing jurisdiction.
  • 2012 WSEC and 2012 SEC: “Insulation that is continuous across all structural members without thermal bridges other than service openings and penetrations by metal fasteners with a cross-sectional area, as measured in the plane of the surface, of less than 0.04% of the opaque surface area of the assembly. It is installed on the interior or exterior or is integral to any opaque surface of the building envelope.”
  • 2014 OEESC: “Insulation that is continuous across all structural members without thermal bridges other than fasteners and service openings. It is installed on the interior or exterior or is integral to any opaque surface of the building.”
  • ASHRAE 90.1-2010: “Insulation that is continuous across all structural members without thermal bridges other than fasteners and service openings. It is installed on the interior or exterior or is integral to any opaque surface of the building envelope.”

Based on the above definitions:

  • Continuous insulation can be interior, exterior, or integral to the building envelope, for example, continuous insulation interior of a CMU wall as shown in Chapter 5.
  • Insulation bridged by structural members (e.g., framing or anchored veneer shelf angles) may not be considered continuous and therefore should be clarified with the governing jurisdiction on a project-specific basis.
  • Service openings (e.g., doors, ducts, etc.) have no impact on whether insulation is classified as continuous or not.
  • Fasteners or metal fasteners may need to be considered, as discussed in the next section.

Metal Fasteners

The thermal performance of exterior insulation is reduced when penetrated by fasteners (metal or otherwise). Continuous insulation with no fasteners will perform near its nominal R-value. However, when fasteners—especially metal fasteners, which are highly conductive—penetrate the insulation, the nominal R-value is reduced. For this reason, metal fasteners (including masonry ties and cladding support clips) may need to be considered for energy code compliance.

The definition of a fastener or metal fastener may vary by code and jurisdiction. Continuous insulation is also not directly defined by the IECC. As a result, the local governing jurisdiction should be contacted for determining when fasteners are to be considered. Below, some general clarifications are provided for assistance.

  • Under the 2012 WSEC and 2012 SEC, the fasteners’ cross-sectional area of penetration (as measured in the plane of the surface) and as calculated as a percentage of opaque wall area, must be considered. Where this area of penetration exceeds 0.04%, the penetrated insulation is not considered continuous. For example, if exterior insulation is bridged by a 2-inch-wide double eye and pintle masonry tie at 24 inches on-center vertically and 16 inches on-center horizontally, the cross-sectional penetration area as a percentage is:
    • 0.04% for a 14-gauge backup plate: meets 0.04% and the exterior insulation is considered continuous.
    • 0.06% for a 12-gauge backup plate: exceeds 0.04% and the exterior insulation is not considered continuous, unless (1) an alternative nominal R-value as found for metal penetrations between 0.04% and 0.08% can be selected from Table C402.2, Footnote f, or (2) the effective thermal performance of the wall is calculated and designated as a U-factor to meet the prescriptive U-factor requirements.Note that if the tie spacing was reduced to 16 inches on-center vertically and 16 inches on-center horizontally, the cross-section penetration area (as a percentage) of 14-gauge backup plate tie would be greater than 0.04%. In this case, guidance provided for the 0.06% case above should be considered.
  • Under the 2014 OEESC, fasteners that penetrate continuous insulation have no impact on whether exterior insulation is considered continuous or not.
  • When complying under the 2012 IECC, contact the local governing jurisdiction to confirm metal fastener and continuous insulation requirements.

Mass Wall Considerations

A mass wall has the ability to store thermal energy (i.e., heat) that can be released at a later time, reducing peak heating and cooling loads and increasing occupant thermal comfort. The benefit of thermal mass varies with climate zone and is more beneficial in warmer climates; however, thermal mass can still provide some benefit in cooler climates. Energy codes within the Northwest region take into consideration thermal mass properties by allowing mass wall assemblies to meet lesser prescriptive R-values (greater U-factors) than framed wall types. When complying with the energy code through a whole-building modeling approach, the benefits of thermal mass are directly considered within the building model.

The 2012 IECC, WSEC, and SEC and the 2014 OEESC define a mass wall as “weighing not less than 35 psf of wall area; or not less than 25 psf of wall area if the material weight is not more than 120 pcf.” Under this definition, 6-inch or larger lightweight (103 pcf) CMU or heavier block qualifies as a mass wall, as does a typical concrete backup wall. The classification of a “mass wall” typically encompasses the backup wall structure; veneer inclusions should be confirmed with the local governing jurisdiction. Chapters 1, 4, 5, and 6 assemblies with CMU backup wall structure typically qualify as mass walls.

In the states of Oregon and Washington (excluding the City of Seattle), integrally insulated CMU walls such as the Chapter 4 assembly are exempt from prescriptive performance R-value and U-factors when the following two conditions are met:

  • “At least 50% of block cores are filled with perlite or equivalent fill insulation.” An alternative to perlite is a phenolic resin core foam insulation as shown in Fig. i-20.
  • “Space use includes warehouse (storage and retail), gymnasium, auditorium, church chapel, arena, kennel, manufacturing plant, indoor swimming pool, pump station, water and wastewater treatment facility, storage facility, restroom/concessions, mechanical/electric structures, storage area, and motor vehicle service facility.” In Washington only, “Where additional uses not listed (such as office, retail, etc.) are contained within the building, the exterior walls that enclose these areas may not utilize this exception and must comply with the appropriate mass wall R-value [from the prescriptive compliance table].”

Insulation Products

A variety of insulation products exist on the market today for wall cavities, integral insulation, and continuous (interior or exterior) insulation.

For wall cavities, unfaced fiberglass or mineral fiber batts are most common. High-density versions of either batt can be found and assist with achieving a greater assembly effective R-value without increasing wall depth, especially in wood-framed wall assemblies. Due to the significant reduction in effective thermal performance for steel-framed wall assemblies (typically 40 to 60%), a high-density batt provides little benefit over lower-density batt products. Batt insulation widths and thicknesses range in size to accommodate most standard wood and steel framing depths. Wall cavity insulation may also include sprayed polyurethane foam insulation, which is available in both open- and closed-cell varieties and varies in thermal resistance and vapor permeance.

Where split insulation occurs (e.g., both wall cavity and exterior insulation) it is important to consider the air- and vapor-permeability of the both the selected insulating materials and WRB field membrane. These considerations are discussed in each assembly chapter.

Where continuous insulation is required, several types of board insulation products are available.

  • Semi-Rigid Mineral Fiber (R-4.2/inch): Hydrophobic, tolerates moisture, and has free draining capabilities. This insulation is vapor-permeable, which allows it to be acceptable for use exterior of both vapor-permeable and vapor-impermeable air and water-resistive barrier membranes. The semi-rigid properties of this insulation facilitate a snug fit at board joints and around metal penetrations such as masonry ties and cladding support clips without requiring notching. The density of the semi-rigid insulation should be considered for cladding attachment designs where insulation compression is necessary to support cladding attachment methods. An example of this insulation product type is shown in Fig. i-21.
  • Rigid Extruded Polystyrene (XPS) (R-5 per inch): Moisture-resistant and suitable for wet environments. XPS has a vapor permeance less than 1.0 and is a Class II vapor retarder. As a result, XPS may be used where cavity insulation does not exist or when the cavity stud insulation nominal R-value is 1/2 to 1/3 of the total nominal insulation R-value of the assembly. Rigid board insulation may require notching around intermittent cladding supports or ties to create a snug fit. An example of this insulation product type is shown in Fig. i-22.
  • Rigid Polyisocyanurate (R-5.0 to 5.7 per inch): When used as continuous exterior insulation, typically includes a foil facer or moisture-tolerant facing to protect the insulation core. Faced polyisocyanurate insulation has a vapor permeance of approximately 0.01 and is a Class II vapor retarder. As a result, polyisocyanurate may be used where cavity insulation does not exist or when the cavity stud insulation nominal R-value is 1/2 to 1/3 of the total nominal insulation R-value of the assembly. Rigid board insulation may require notching around intermittent cladding supports or ties to create a snug fit.
  • Closed-cell Spray Foam Insulation (R-5.5 to R-6 per inch): may be used as exterior or interior insulation and eliminates the need for a separate air and vapor barrier. This insulation option should be installed after all wall penetrations and cladding supports are in place. To avoid excessive heat buildup during installation, closely follow the manufacturer’s installation instructions. Closed-cell spray foam insulation has a vapor permeance less than 1.0 at 2-inch or greater thicknesses and provides a Class II vapor retarder. As a result, closed-cell spray foam insulation may be used where cavity insulation does not exist or when the cavity stud insulation nominal R-value is 1/2 to 1/3 of the total nominal insulation R-value of the assembly.

Integral insulation, which may be used within the assemblies of this guide, may be loose-fill such as perlite but is commonly provided by a expanding foam-in-place insulation product. Foam-in-place insulation is typically injected through ports drilled within the CMU mortar joints. An example of foam-in-place insulation is shown in Fig. i-20.

Air Leakage

Energy codes within the Northwest have mandatory air leakage requirements. Requirements include a continuous air barrier throughout the building thermal envelope (i.e., surrounding conditioned and semi-heated spaces). The air barrier must be continuously sealed and supported by the structure (e.g., with fasteners or adhered to the sheathing). Air barrier compliance options for each Northwest code are provided below. All members of the design and construction team should be familiar with the air barrier requirements specific to their jurisdiction.

  • Under the 2012 WSEC and 2012 SEC, once the whole-building air barrier system is complete, the rate of air leakage must be determined by performing a whole-building air leakage test such as that shown in Fig. i-23. The maximum allowable air leakage rate is 0.40 cfm/ft2 at 0.3 in-H20 (75 Pa) when tested to ASTM E779. Failure to comply with the maximum leakage rate requires a visual inspection and repair of the discontinuous air barrier areas to the extent practicable under 2012 code provisions. Industry research has demonstrated this code-maximum air leakage target is not prohibitively difficult to meet.
  • Under the 2012 IECC and 2014 OEESC, air leakage testing is one of three air barrier compliance options. The remaining two options require that materials or assemblies meet specific air permeance performance and meet specific installation requirements.

The following checklist items can increase the success rate for the design and installation of a continuous air barrier in all jurisdictions.

Design Checklist

  • Select appropriate air barrier materials and systems. An air barrier material has an air permeance less than 0.004 cfm/ft2 at 1.57 psf (75 Pa) when tested to ASTM E2178. An air barrier assembly has an air permeance of less than 0.04 cfm/ft2 at 1.57 psf (75 Pa) when tested to ASTM E2357 and ASTM E283. Section C402.4 of the 2012 IECC, WSEC, and SEC and Section 502.4 of the 2014 OEESC include a number of materials and assemblies that meet these requirements. The Air Barrier Association of America (ABAA) also lists several commercially available compliant air barrier membranes and systems online at www.airbarrier.org.
  • Ensure that a continuous line representing the plane of airtightness can be drawn across all assemblies, details, and transitions between assemblies. Details included within this guide demonstrate this practice; an example is shown in Fig. i-11.
  • Clearly delineate the air barrier boundary on the construction documents. This practice is typically performed on the floor plans for each building level and on each building section as shown in Fig. i-24. This delineation is required by the 2012 SEC for compliance.
  • Identify air barrier installation, testing, and installer qualification requirements in the project manual. Include general air barrier system requirements in a Division 1 section. Also include air barrier requirements in related Division 7 sections. Air barrier master specifications related to Division 1 and 7 are available online from ABAA.

Construction/Installation Checklist

  • Use installers with air barrier installation experience to perform air barrier–related installations.
  • Build freestanding mock-ups of all project-specific typical and unique air barrier details. Retain building mock-ups for training and reference purposes throughout the course of construction.
  • Perform qualitative diagnostic air leakage testing of mock-up installations to identify deficiencies. Correct deficiencies and retest to demonstrate that deficiencies have been resolved. Refer to ASTM E1186 for air leakage site detection practices. An example of diagnostic air leakage testing is demonstrated in Fig. i-25.
  • Implement a quality control program. Develop a checklist of items requiring review prior to covering the air barrier with additional elements such as exterior insulation and cladding.
  • Provide third-party quality assurance reviews of installed air barrier detailing and provide periodic diagnostic air leakage testing to ensure airtight transitions, especially between roof-to-wall and roof-to-foundation detailing.
  • Execute whole-building air leakage testing prior to covering (when possible). This limits the need to remove building elements, such as cladding, to correct deficiencies.

Within the IECC-based codes, opaque thermal envelope assembly requirements are grouped into “Zone 5 and Marine 4” and “Zone 6”. Although IECC-designated climate Zones 5, 6, and Marine 4 all occur within the state of Washington, the Washington State Building Code Council has determined that all zones must meet the “Zone 5 and Marine 4” requirements. This determination is reflected in Table i-2.

Fig. i-16 Northwest region (Washington, Oregon, and Idaho Climate zones including Zone Marine 4, Zone 5, and Zone 6.

Fig. i-16 Northwest region (Washington, Oregon, and Idaho Climate zones including Zone Marine 4, Zone 5, and Zone 6.

Project-specific thermal performance values for opaque above-grade wall assemblies should be used for energy code compliance and should be determined from a source that is approved by the local governing jurisdiction. Sources may include the Appendices of the WSEC and SEC, ASHRAE 90.1, COMcheck, thermal modeling, or other industry resources.

Table i-2 Northwest energy codes - prescriptive compliance values for opaque above-grade wall assemblies within this guide.

Table i-2 Northwest energy codes – prescriptive compliance values for opaque above-grade wall assemblies within this guide.

When looking at actual heat loss calculations (e.g., mechanical equipment sizing or energy modeling) the assembly effective R-value with all fasteners should be considered.

Fig. i-17 Energy Code Compliance Flow Chart. Use this chart to navigate selection of an energy code compliance strategy and use of the modeling results within this guide.

Fig. i-17 Energy Code Compliance Flow Chart. Use this chart to navigate selection of an energy code compliance strategy and use of the modeling results within this guide.

The term “thermal bridging” is not defined by the energy codes that govern the Northwest region (Washington, Oregon, and Idaho). However, the 2013 ASHRAE Handbook of Fundamentals recognizes thermal bridging as “passing highly conductive materials through insulation layers.”

Fig. i-20 Foam-in-place CMU core insulation.

Fig. i-20 Foam-in-place CMU core insulation.

Fig. i-21 Semi-rigid mineral fiber board insulation prior to anchored masonry veneer installation.

Fig. i-21 Semi-rigid mineral fiber board insulation prior to anchored masonry veneer installation.

Fig. i-22 XPS insulation behind anchored masonry veneer.

Fig. i-22 XPS insulation behind anchored masonry veneer.

Although masonry is defined as a noncombustible cladding material, the use of a combustible air and water-resistive barrier or foam plastic insulation within a wall cavity can trigger fire propagation considerations and requirements. Depending on the local jurisdiction, IBC Section 1403.5 regarding vertical and lateral flame propagation as it relates to a combustible water-resistive barrier may require acceptance criteria for NFPA 285. The use of foam plastic insulation within a wall cavity should also be addressed for IBC Chapter 26 provisions.

Fig. i-23 Blower door setup during whole-building air leakage testing of building with an anchored masonry veneer above-grade wall assembly.

Fig. i-23 Blower door setup during whole-building air leakage testing of building with an anchored masonry veneer above-grade wall assembly.

For above-grade wall assemblies in the Northwest, vapor-impermeable exterior insulation and vapor-impermeable air and water-resistive barrier membranes may be used when the assembly insulation is located exterior of the air and water-resistive barrier or when the exterior insulation is 1/2 to 2/3 of the total nominal insulation R-value in the assembly. This reduces the risk of condensation development within the wall cavity. Vapor-impermeable products and greater insulation R-value splits may be considered but should be carefully evaluated based on project-specific characteristics.

Fig. i-24 Whole-building section. The continuous air barrier pressure boundary is denoted in red.

Fig. i-24 Whole-building section. The continuous air barrier pressure boundary is denoted in red.

Fig. i-25 A smoke pencil is used to conduct diagnostic air leakage testing while a building is under positive air pressure. Smoke exits the building through a discontinuity at the head of the window rough opening.

Fig. i-25 A smoke pencil is used to conduct diagnostic air leakage testing while a building is under positive air pressure. Smoke exits the building through a discontinuity at the head of the window rough opening.

Sheet Metal Components

Sheet-metal components deflect liquid water and are used In both rainscreen and mass wall design approaches and typically occur above and below wall penetrations, as parapet caps, and as counterflashing elements to protect flashing membranes. In a rainscreen design approach, cross-cavity sheet-metal flashings deflect water within the rainscreen cavity back to the exterior environment while still allowing cavity ventilation.

Design Considerations

The location of sheet metal flashings should be carefully planned for each project but, at minimum, should be located:

  • Above and below wall penetrations such as windows, doors, electrical outlets, fixtures, and pipe penetrations. This applies to both rainscreen design approach assemblies and where practicable in mass wall design approach assemblies.
  • At perpendicular wall interfaces such as parapet-to-wall or roof-to-wall saddle conditions and at parapet tops. This applies to both rainscreen and mass wall design approaches.
  • For a rainscreen design approach, at every floor line for buildings three stories or greater in height. Regardless of building height, it is best practice to locate sheet metal flashings at every floorline. Examples are depicted in Fig. i-26 and Fig. i-27.
  • At vertical support elements of anchored masonry veneer assemblies and at movement joints designed to accommodate vertical differential movement in a rainscreen design approach.

Sheet-metal flashing profiles should include a projected hemmed drip edge and positive slope. For cross cavity sheet metal flashings, a minimum 4-inch-tall back leg should be provided and should be shingle lapped into the WRB system. Where serving as a counterflashing, the sheet metal should counterflash cladding a minimum of 1.5 inches (where possible) and project a minimum of half an inch beyond the cladding face to avoid blocking ventilation. The vertical location of the sheet-metal flashing in relation to the masonry veneer must be considered. Adequate spacing between the sheet metal and veneer above and below will ensure building movement does not affect the sheet-metal flashing profile or its function.

In a rainscreen design approach, folded end dams assist with deflecting water away from the rainscreen cavity and should be provided at all flashing terminations (e.g., at the ends of a window head flashing).

Where sheet-metal laps occur, laps should either be fully sealed with a high-quality silicone or butyl-based sealant or may be soldered. Laps within sheet-metal parapet coping should be standing-seam.

It is a best practice to construct masonry veneer sheet-metal flashings from stainless steel. Stainless steel is relatively inert to the corrosiveness of mortar and provides a similar level of durability and longevity as the masonry veneer. Prefinished galvanized sheet-metal products may be used in masonry veneer applications; however, they may require replacement before the masonry veneer does.

Cross-Cavity Alternate

Where exterior insulation is used, cross-cavity sheet-metal flashings create a thermal bridge. An alternate to a sheet-metal flashing at anchored veneer assemblies is to provide a flexible self-adhered flashing membrane that is fully supported by the insulation and lapped into the WRB as shown in Fig. i-27. This flexible membrane is shingle-lapped over the bearing element (typically a standoff shelf angle) and onto a sheet-metal drip flashing.

A cross-cavity flashing and through-wall flashing are commonly used interchangeably; however, there is a technical difference. A cross-cavity flashing is integrated with the WRB and extends through the rainscreen cavity. A through-wall flashing extends through the entire depth of the wall, such as one might find at the base of a CMU wall.

Fig. i-26 Assembly 8, Detail 8b-D. Typical floor line cross-cavity sheet-metal flashing. The flashing helps drain the rainscreen cavity above and deflects water away from the top of the cavity below while still allowing for drainage and ventilation in each cavity. Space above and below the sheet metal flashing also allows for movement within the veneer as well as differential movement between the veneer and wall structure.

Fig. i-26 Assembly 8, Detail 8b-D. Typical floor line cross-cavity sheet-metal flashing. The flashing helps drain the rainscreen cavity above and deflects water away from the top of the cavity below while still allowing for drainage and ventilation in each cavity. Space above and below the sheet metal flashing also allows for movement within the veneer as well as differential movement between the veneer and wall structure.

Fig. i-27 Assembly 2, Detail 2-D. Typical floor line condition at standoff shelf-angle. This alternate detail approach includes a flexible self-adhered membrane in lieu of sheet metal to divert drainage at the rainscreen cavity.

Fig. i-27 Assembly 2, Detail 2-D. Typical floor line condition at standoff shelf-angle. This alternate detail approach includes a flexible self-adhered membrane in lieu of sheet metal to divert drainage at the rainscreen cavity.

Movement Joints

Over time, volumetric changes will occur within any above-grade wall assembly and can be the result of changes in temperature, moisture, elastic deformation, settlement, and creep. The amount of movement that occurs will depend on the building materials used within the wall assembly as well as on the intensity of the influencing mechanism (e.g., temperature change). In general, wood frame members, concrete, CMU, and stone will shrink, whereas clay masonry will expand. If steel studs or a CMU backup wall are used and are properly protected, minimal volume change is expected.

Different materials within each above-grade wall assembly may also move differently in relation to one another as shown by the example in Fig. i-29. If not properly designed for, differential movement can cause unwanted cracking, spalling, buckling, settlement, or separation within the building structure or veneer.

For the purpose of this guide, discussion and design of movement joints are considered as they relate to differential movement between the veneer and wall structure and also include control and expansion joints. The consideration for locating and sizing building expansion joints that occur within the wall structure is beyond the scope of this guide but must be appropriately designed for and integrated into the above-grade wall system where they occur.

The discussion of building movement in this guide is meant to be a general reference; it is the responsibility of the Designer of Record to appropriately design for building movement.

Joint Locations

This section identifies general rules for locating movement, expansion, and control joints as they relate to the 8 primary wall assemblies in this guide.

  • For adhered veneers, joint location recommendations vary throughout the industry and should be confirmed with the veneer unit manufacturer for the project specific application. In general, this guide recommends that joints be provided such that each panel of adhered masonry does not exceed 144 square feet. A maximum height/width or width/height ratio of 2.5 to 1 should be maintained. Spacing between joints should not exceed 15 feet in any direction. Refer to Brick Industry Association (BIA) Technical Note 28C and the Latricrete Direct-Adhered Ceramic Tile, Stone, and Thin Brick Facades Technical Design Manual (1998) for additional information. An example of adhered veneer joint locations is shown in Fig. i-28.
  • For anchored clay masonry veneer, provide expansion joints such that long wall sections do not exceed 25 feet apart at occupied space and 15 feet apart at parapet conditions. Joint locations may be reduced to 20 feet at wall sections that have openings. Additional guidance on brick veneer expansion joints may be referenced from BIA Technical Notes 18 and 18A. An example of anchored masonry veneer joint locations is shown in Fig. i-30.
  • For anchored concrete masonry veneer, provide control joints such that long wall sections do not exceed a length to height ratio of 1.5. The maximum wall length between control joints is 26 feet. Additional guidance on concrete masonry veneer control joints may be referenced from Northwest Concrete Masonry Association (NWCMA) Tek Note on Design of Concrete Masonry Veneer for Crack Control.
  • For CMU wall structures, control joints should be spaced every 40 feet or where needed to minimize wall sections to a 3:1 ratio of length to height, whichever is less. Additional guidance on control joints may be referenced from NWCMA Tek Note on Control Joints for Concrete Masonry Crack Control. An example of CMU control joint locations is shown in Fig. i-31.

There is no single set of recommendations for the placement and design of movement joints that will work for all projects. Additionally, joints may be added more frequently than is necessary for aesthetic purposes. In general, the following locations for movement joints within a masonry veneer or structure should be considered in addition to the above.

Vertical Joint Placement

  • Throughout long walls with no openings as described in the previous section
  • At wall offsets and setbacks
  • At or within 10 feet of corners
  • Around openings such as windows and doors
  • At intersections and junctions (at intersections of walls that serve different functions or are different heights/thicknesses or cladding types)
  • At parapets, align with joint placement at the wall area below
  • Where framing methods or materials change (e.g., where a concrete meets steel-framed backup wall)

Horizontal Joint Placement

  • At floor lines, aligned with the top-of-wall and floor interface.
  • Below structural support elements such as shelf angles
  • Between cladding material changes

Note that placement of horizontal joints are also recommended at various locations for a rainscreen design approach to allow for cavity drainage and ventilation. These locations are further discussed and identified within each chapter and with an asterisk (*) in chapter details.

Joint Design

Joints that accommodate vertical movement should either include a sheet metal flashing or a backer rod and sealant joint. Joints that accommodate horizontal movement should receive a backer rod and sealant joint. Movement joints should be designed and constructed to accommodate 3 to 4 times the amount of anticipated movement and should be no narrower than 3/8 of an inch. Movement joints should be free of debris, reinforcing, or other elements that may inhibit movement over the life of the building.

Joint sealants are a critical component of a movement joint and allow the joint to open and close uninhibited while providing a continuous water-shedding surface. Sealant products ideal for use at masonry movement joints have the following properties:

  • Movement Capabilities: A low-modulus (highly elastic) sealant will allow for expansion or compression of the sealant joint without permanent deformation. The sealant product selected should have joint movement capabilities of a minimum 100% extension and 50% compression when tested to ASTM C719.
  • Adhesion to Substrate: The sealant selected should have demonstrated adhesion to porous substrates such as masonry and concrete. Where differing substrates occur at either side of the movement joint (e.g., at metal panel–to-masonry veneer interfaces), the sealant should have acceptable adhesion to both substrates. Sealant adhesion testing prior to and during field installation is highly recommended and should result in cohesive sealant failure (rather than adhesive failure to the substrate).
  • Durability: Movement joints at cladding should be UV-stable as well as durable when exposed to water and temperature fluctuations.
  • Longevity: Masonry is a long-lasting cladding option and will likely outlive the movement sealant joint. To match the durability of the masonry cladding and reduce the replacement frequency of the joint, use a quality silicone sealant. When properly installed, silicone sealants will exhibit 20+ years of acceptable performance. Other sealant options such as hybrid or polyurethane sealants may provide acceptable performance for 10+ years before replacement is required.

Best Practices

The following joint design best practices will ensure long-term performance of a movement joint:

  • Select a quality sealant based on the criteria described in the previous section of this guide.
  • Follow industry-standard best practices for sealant joint installation. This includes joint design and substrate cleaning and priming. As a useful resource, refer to Dow Corning Americas Technical Manual as well as the joint dimensioning described in Fig. i-32.
  • Provide an annual review and repair of joints one year after installation and biannual review thereafter. Areas of adhesive failure or damage should be repaired.

Architectural Considerations

Where there is a desire to minimize the visual appearance of masonry veneer movement joints, the following may be considered:

  • Select a sealant joint color that is similar to the anchored veneer mortar or adhered veneer grout color.
  • Consider details that minimize the visible area of the joint while still accommodating movement. The options included in Fig. i-35 and Fig. i-34 demonstrate using lip brick to minimize horizontal movement joint visibility.
  • Opt for a sanded joint in which mason’s sand is bed into the sealant following tooling as shown in Fig. i-33.
  • Include a provision in the project manual for field mock-ups of typical horizontal and vertical movement joints. Review the mock-ups for joint installation quality, adhesion, and appearance.
  • Hide movement joints at inside building corner.
Fig. i-29 Cross-cavity sheet-metal flashing displacement as a result of wood-framed wall shrinkage and brick anchored veneer expansion.

Fig. i-29 Cross-cavity sheet-metal flashing displacement as a result of wood-framed wall shrinkage and brick anchored veneer expansion.

Fig. i-28 Example of adhered masonry veneer horizontal and vertical movement joints located at floor lines and in alignment with window jambs.

Fig. i-28 Example of adhered masonry veneer horizontal and vertical movement joints located at floor lines and in alignment with window jambs.

Fig. i-30 Example of anchored brick veneer movement joint locations.

Fig. i-30 Example of anchored brick veneer movement joint locations.

Fig. i-31 Example of CMU control joints (vertical joints).

Fig. i-31 Example of CMU control joints (vertical joints).

Fig. i-34 Typical anchored masonry veneer horizontal floor-line movement joint example.

Fig. i-34 Typical anchored masonry veneer horizontal floor-line movement joint example.

Fig. i-35 Anchored masonry veneer horizontal floor-line movement joint example with lip brick.

Fig. i-35 Anchored masonry veneer horizontal floor-line movement joint example with lip brick.

Fig. i-32 Typical joint design.

Fig. i-32 Typical joint design.

Fig. i-33 Typical sanded sealant joint below a window opening.

Fig. i-33 Typical sanded sealant joint below a window opening.

Cleaners, Repellents, and Coatings

In the Northwest region, surface-applied clear water repellents are commonly applied to the surface of masonry veneer claddings and exposed CMU walls for the assemblies featured within this guide. Elastomeric coatings may also be used in targeted applications. The success of a clear water repellent or elastomeric coating is reliant on appropriate product selection, cleaning procedures, and application methods. Although the use of these products provides a number of purposes, as described below, these products do not make up for poor masonry workmanship or detailing. This guide section covers cleaning and best practices for selection and application of clear water sealers and elastomeric coatings.

Cleaning Methods

Debris and contaminants, including oil, grease, dirt, ash, and hydrocarbons, need to be cleaned from new masonry products prior to clear water repellent or elastomeric coating application. A number of cleaning methods are available, including hand, water, or chemical cleaning and abrasion.

Select cleaning procedures based on masonry and mortar colors, texture, and the type of existing debris or contaminants. In general, select the least aggressive cleaning method necessary to remove debris and contaminates. Over-cleaning masonry products or using excessive abrasion can alter the appearance of the masonry veneer or CMU and can encourage premature weathering.

For all cleaning methods, test-clean an inconspicuous area of the wall to confirm the effectiveness and acceptability of the cleaning method. Water clean only when temperatures exceed 40˚F; even warmer temperatures may be required for applications of chemical cleaning products that rely on a chemical reaction to be effective.

ASTM D5703 and BIA Technical Note 20 are helpful resources for determining appropriate cleaning procedures for clay masonry units, whereas NCMA TEK 8-4A provides helpful discussion on cleaning CMU block of various types and finishes. Also consult the masonry unit or CMU manufacturer and cleaning product manufacturer (where applicable) prior to cleaning.

Surface-Applied Clear Water Repellents

A surface-applied clear water repellent is recommended for the assemblies in this guide that include adhered or anchored unglazed clay masonry veneer or exterior-exposed CMU. Application of a clear water repellent can reduce water absorption of masonry veneer and CMU, as demonstrated in Fig. i-36, while preserving or enhancing natural appearance. By reducing how much water the masonry cladding absorbs, less frequent wetting/drying and freezing/thawing cycles are expected to occur, reducing the likelihood of premature weathering and water-related damage and staining.

There are two primary types of repellents: penetrating or film-forming.

  • Penetrating repellents have the ability to penetrate into the pores of the masonry while still allowing water vapor to diffuse through the masonry veneer. Common penetrating repellents include silicone resins, silanes, and siloxanes.
  • Film-forming repellents, such as acrylics, stearates, and urethanes, form a thin film on the surface of the masonry face and across smaller pores. As a result, film-forming repellents can reduce the drying ability of the masonry cladding.

Of the two repellent types, penetrating repellents are recommended for use within the Northwest.

For unglazed clay masonry and CMU in the Northwest, use a silane/siloxane blend clear water repellent.

  • Silanes penetrate deep into the pores of clay masonry.
  • Siloxanes are deposited closer to the masonry surface.

Both silanes and siloxanes chemically bond to clay masonry, CMU, and mortar in the presence of moisture and alkalinity; as a result, silane/siloxane-based repellents can provide 5 to 10 years of protection, making such blends a durable and relatively longer-lasting water repellent option.

A penetrating silicone-based repellent may also be considered and may provide greater anti-graffiti properties than a silane/siloxane blend. Silicone-based repellents have less chemical bonding ability to clay masonry, mortar, and CMU than silane/siloxane blends have; thus, silicone-based repellents need to be reapplied more frequently than silane/siloxane-based products.

Clear water repellent application to glazed masonry veneers is not recommended. Glazed surfaces reduce the penetrating ability of clear water repellent products, limiting the effectiveness of the application.

When selecting a clear water repellent, the following characteristics/properties are desirable for long-term performance:

  • Suitability for Substrate/Finish: Products selected should be suited for vertical above-grade wall applications and project-specific masonry cladding types. Manufacturer-published literature should indicate that the product is acceptable for the type of masonry substrate and finish (e.g., split-faced CMU, fired clay brick, etc.).
  • High Vapor Permeance: Water repellence test results should indicate 90% or more of the untreated masonry product vapor permeance is retained when tested to ASTM E96.
  • Effective Water Penetration Resistance: ASTM E514 results should indicate an 85% reduction in maximum leakage rate when compared to an untreated wall.
  • Block and Mortar Water-Repellent Admixture Compatibility: Where a clear water repellent is applied over CMU and mortar containing a water-repellent admixture, use a clear water repellent that is compatible with the admixture. Incompatible sealers may be less durable.

Where anti-graffiti repellent properties are desired, use a vapor-permeable silicone-based repellent with penetrating properties. The anti-graffiti repellent should provide similar vapor permeance and water penetration resistance to that listed above. The effectiveness of anti-graffiti properties is demonstrated through ASTM D7089 results, which may be used to compare the ease of graffiti removal.

Clear water repellents should not be used as a replacement for a water-resistive barrier or air barrier within a masonry assembly. Water repellents are also not effective at bridging cracks or filling voids that result from poor joint design/installation or from long-term building movement. Although clear water repellents will increase the masonry’s ability to shed water, a repellent will not prevent efflorescence as a result of water intrusion behind a masonry veneer and will require reapplication to be effective over the long-term service life of the building.

Best Practices

The following general procedures and considerations are the best practices for clear water repellent application:

  • Complete cladding sealant joints (such as around window and door perimeters and at expansion/control joints) prior to application. Provide a minimum 28-day cure on sealant joints prior to cleaning and application.
  • Clean masonry substrates to remove debris and surface contaminants prior to water repellent application.
  • Protect areas that are not to receive water repellent. Prevent contact between clear water repellents and non-masonry products such as asphalt-based products, window glazing, and landscaping.
  • Avoid sealer application when rain threatens, when windy, and when minimum water repellent application temperatures are not met.
  • Perform a mock-up to demonstrate protection, cleaning, and water repellent application procedures and for review of final masonry appearance.
    Plan application extents to determine start and stop application locations; avoid overlap.
  • Apply water repellent in accordance with the repellent manufacturer installation instructions, including application rate. General application requirements may include the following:
    • Begin water repellent application on a dry substrate at lower surfaces, working upward as shown in Fig. i-37. Fully saturate brushes and rollers and provide a continuous stream for spray application. Brush away drips and runs.
    • Allow individual coats to penetrate a minimum of 5 to 15 minutes prior to reapplication where wet-on-wet application is required by some manufacturers,.
    • Schedule reapplication of clear water repellent as prescribed by the manufacturer. Perform reapplication with the same or similarly formulated clear water repellent.

Elastomeric Coatings

Elastomeric coatings reduce the amount of water absorbed by masonry substrates and also provide crack-bridging properties that help reduce water leaks. Elastomeric coatings are typically installed where additional water penetration resistance is desired and where a painted surface is visually acceptable. An example of an elastomeric-coated CMU wall is shown in Fig. i-38. Elastomeric coatings can serve as a water-shedding surface, water-resistive barrier, and air barrier on the exterior face of a masonry substrate when a UV-stable coating is used.

A vapor-permeable silicone or acrylic elastomeric coating with UV resistance and high elongation properties is recommended for a good coating. A vapor-permeable coating will allow the masonry substrate to dry and reduces the likelihood of salt buildup and bubbling or blistering of the coating.

When selecting an elastomeric coating, the following characteristics/properties are desirable for long-term performance:

  • Product Suitability: Products suited for vertical above-grade wall applications with UV resistance
  • Water Penetration Resistance: Resistance to wind-driven rain when tested to ASTM D6904 should result in no leaks.
  • Vapor Permeance: A minimum vapor permeance of 8 perms when measured per by ASTM E96 wet cup method at the manufacturer- recommended dry film thickness.
  • Higher Solids Content: Solids content by volume greater than 50% are commercially available and are determined through ASTM D2697 testing.
  • High Elongation Properties: Elongation properties are determined per ASTM D412 and should exceed 300%.
  • Crack-Bridging Ability: No cracking should occur when tested to ASTM C1305.
  • Validation: Consider products that include an “SWR Institute Validation Program” label on the product data sheet. This label validates performance properties and can be helpful for comparing product options with the program label.

Elastomeric coatings can exhibit staining and may be difficult to clean. Surface staining is largely attributed to surface wetting below horizontal surfaces and penetrations including flashings, windows, and parapets. Therefore, staining can largely be reduced by reducing the amount of water that runs off onto the wall from these dirt-collecting surfaces. The use of sheet-metal drip edges (such as at window and door sills) is recommended to deflect water away from the surface of the masonry coating to help reduce staining.

Best Practices

The following general application procedures and considerations are the best practices for elastomeric coating application:

  • Include consideration for water-shedding and deflection in above-grade wall design. Use minimum 1/2-inch projected drip edges to minimize coating staining and runoff.
  • Provide a minimum 28-day cure for masonry grouts and adjacent concrete surfaces prior to application.
  • Seal all cracks and cladding joints as recommended by the coating manufacturer. Use appropriate joint design and backing where movement joints occur. Typically, cracks or holes 1/16 of an inch wide or greater require treatment.
  • Use block filler when required by the manufacturer. Some manufacturers may allow an additional application of coating in lieu of block filler.
  • Test the coating adhesion to confirm cleaning procedures and priming requirements to the masonry substrate and joint sealants. Use a mock-up for coating review prior to full-scale application.

The remaining chapters within this guide address assembly-specific considerations for the 8 primary above grade wall assemblies.

Fig. i-36 Water droplets form on a brick veneer on which clear water repellent has been applied.

Fig. i-36 Water droplets form on a brick veneer on which clear water repellent has been applied.

Fig. i-37 Clear water repellent application at an anchored masonry veneer.

Fig. i-37 Clear water repellent application at an anchored masonry veneer.

Fig. i-38 Exposed CMU wall coated with elastomeric coating.

Fig. i-38 Exposed CMU wall coated with elastomeric coating.

Guide Task Force

Tonia Sorrell-Neal, LEED-AP
Masonry Institute of Washington
Washington State Conference
of Mason Contractors
Northwest Masonry Institute
Seattle, WA
Tom Young, P.E.
Masonry Institute of Washington
Northwest Concrete Masonry Association
Mill Creek, WA
Bailey Brown, P.E.; Graham Finch, P.Eng.;
and Michael Aoki-Kramer, LEED-AP
RDH Building Science Inc.
Seattle, WA, and Vancouver, BC
Gary Zagelow
Mutual Materials
Durham, OR
Mike Breda
TekTerior
Seattle, WA
Steve Golden
Great Northwest Construction Products
Everett, WA
Kevin Nolan
VaproShield
Gig Harbor, WA
Marc Chavez, FCSI, AIA, CCS, CCCA
ZGF ARCHITECTS LLP
Seattle, WA
James Allard
Masons Supply, Inc.
Portland, OR
Contractor Members of the Washington State Conference of Mason Contractors
Supporters of the Masonry Institute of Washington