Assembly 3:
Wood-Framed Wall with Anchored Masonry Veneer

Assembly 3:
Wood-Framed Wall with Anchored Masonry Veneer

General Info

This Chapter 3 assembly is a rainscreen design approach with wood-framed wall structure and anchored masonry veneer. The components of this assembly, from interior to exterior, are described in Fig. 3-1. This assembly is appropriate for many applications including low- or mid-rise residential or commercial buildings. An example application of this assembly is shown in Fig. 3-2. Benefits and special considerations for this assembly are discussed in Table 3-1.

Building Enclosure Control Functions and Critical Barriers

As noted in the introductory chapter of this guide, an above-grade wall assembly should provide control of water, air, heat, vapor, sound, and fire to serve as an effective and durable environmental separator. Control of these elements is provided by critical barriers such as a water-shedding surface (WSS), water-resistive barrier (WRB), air barrier system (AB), thermal envelope, and vapor retarder (VR). Refer to Fig. i-8 of the introductory chapter for a list of primary building enclosure control functions and associated critical barriers.

Fig. 3-3 illustrates the critical barrier locations for this assembly. The critical barriers for typical Chapter 3 assembly details are also provided adjacent to each detail at the end of this chapter.

As shown in Fig. 3-3, the WSS critical barrier occurs at the anchored masonry veneer with most watershedding occurring at the wall face, while some water will be stored within the masonry veneer to be released at a later time. The WRB and AB critical barriers occur at the same location exterior of the wall sheathing. As a result, a single membrane is typically used to provide these two critical barriers and is commonly referred to in this chapter as the air and water-resistive barrier (AB/WRB). The thermal envelope includes the cavity insulation. The VR critical barrier is located at the interior (warm side) of the wood-framed structure.

The following sections provide more information and discuss best practices for critical barriers specific to this assembly.

Water-Shedding Surface (WSS)

The water-shedding surface is a critical barrier that controls water.

The anchored masonry veneer cladding, including both mortar joints and masonry veneer units, is the primary WSS of this assembly. Additional components include sheet-metal flashings and drip edges, sealant joints, and fenestration systems as shown on the assembly details included at the end of this chapter.

To promote water shedding at the masonry cladding, joints between masonry units should be appropriately installed with a tooled concave (preferred) or “V” shape.

When finished, the WSS critical barrier should be free of gaps except where providing drainage and/or ventilation. Movement joints and joints around windows and penetrations should be continuously sealed with a backer rod and sealant or counterflashed with a sheet-metal flashing to deflect wind-driven rain and shed water away from the rainscreen cavity.

Water-Resistive Barrier (WRB)

The water-resistive barrier is a critical barrier that controls water.

In this assembly, the WRB critical barrier is primarily a vapor-permeable mechanically attached sheet membrane, a self-adhered sheet membrane, or a fluid-applied membrane (that also functions as the AB). A vapor-permeable WRB membrane allows this assembly to dry to the exterior. Drying ability to the exterior is not only beneficial during the service life of the building but also helps relieve construction-related moisture that may occur at wood framing or wood-based sheathing products. A vapor-permeable mechanically attached sheet membrane is depicted in the details at the end of this chapter. An example of this WRB membrane type is shown in Fig. 3-4.

The AB/WRB layer must be continuous across the wall face to serve as an effective critical barrier. In addition to the AB/WRB field membrane, the WRB critical barrier also includes fluid-applied or flexible flashing membranes, sealants, sheet-metal flashings, and interfaces with fenestration systems (e.g., windows and doors) as shown in the detail drawings that follow this chapter discussion. Where sheet-metal flashing components occur, the back leg of the sheet-metal flashing is lapped into the AB/WRB field membrane to encourage water at the WRB layer to drain toward the building exterior.

Masonry veneer ties in this assembly will penetrate the AB/WRB critical barrier and should be detailed based on the membrane manufacturer’s installation requirements. Typically, plate ties are bed in a compatible sealant or fluid-applied flashing product or attached through a self-adhered membrane patch, whereas screw ties with gasketing washers typically do not require any detailing at the AB/WRB plane.

Air Barrier (AB)

The air barrier system is a critical barrier that primarily controls air, heat, and vapor. The AB also controls water, sound, and fire.

In this assembly, the AB system critical barrier is the same field membrane that also serves as the WRB critical barrier. The components described in the above Water-Resistive Barrier (WRB) section are also part of the AB layer, except sheet-metal flashings.

Fig. 3-4 Double eye and pintle plate ties are fastened through compatible self-adhered membrane patches over a mechanically attached sheet air and water barrier membrane.

Fig. 3-4 Double eye and pintle plate ties are fastened through compatible self-adhered membrane patches over a mechanically attached sheet air and water barrier membrane.

Thermal Envelope

The thermal envelope is a critical barrier that controls heat and assists with controlling vapor, sound, and fire.

In this wall assembly, the cavity insulation provides the thermal envelope. At transition details, the thermal envelope also includes parapet cavity insulation and insulation at the roof assembly, slab, and foundation elements. Windows and doors that penetrate this wall are part of the thermal envelope. Exterior insulation may also be used with this assembly as shown in Fig. 3-5 to increase thermal performance.

Additional thermal envelope discussion is provided in the Thermal Performance and Energy Code Compliance section of this chapter and the introductory chapter.

Insulation Selection

The cavity insulation in this assembly is a vapor-permeable fiberglass or mineral fiber batt insulation product.

When exterior insulation is used with this assembly, it is semi-rigid mineral fiber board insulation, which is hydrophobic, tolerates moisture, and has free-draining capabilities. Its vapor permeance allows it to be acceptable for use exterior of a vapor-permeable AB/WRB membrane. The semi-rigid properties of the insulation allow it to be fit tightly around intermittent attachments such as masonry ties. Vapor-impermeable exterior insulation such as XPS or polyisocyanurate is not recommended for use in this assembly because it limits assembly drying to the exterior.

Vapor Retarder (VR)

The VR 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.

The VR critical barrier of this assembly is located on the interior (warm side) and is typically at the face of or just behind the interior gypsum board. The VR for this assembly should comply with Section 1405.3 of the governing International Building Code (IBC). In the Northwest, typical VR products include PVA vapor-retarding primer, asphalt-coated kraft paper, or a polyamide film retarder membrane. These products are further discussed in the Introductory chapter.

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.

Sheathing Selection

The exterior sheathing of this assembly is typically a wood- or gypsum-based product and is designated by structural requirements. Where wood-based products are used, plywood is generally recommended for its moisture tolerance. Where gypsum board is used, a product resistant to organic growth and moisture is recommended. Fiberglass-faced gypsum board products should be also used; paper face products should be avoided.

Drainage, Ventilation, and Water Deflection

The anchored masonry veneer is expected to shed most water it is exposed to; however, some moisture is expected to penetrate the cladding and enter the rainscreen cavity. This moisture is drained through the rainscreen cavity and exits the rainscreen system where flashings are provided.

Drainage and Ventilation

A 2-inch-deep rainscreen cavity between the anchored masonry veneer and exterior insulation should be provided to encourage drainage and ventilation. At a minimum, a 1-inch gap may be provided and is also the minimum code-allowable depth. However, the risk that mortar droppings will reduce the drainage and ventilation within the rainscreen cavity is increased with smaller cavities. A 1-inch cavity should only be provided where a strict quality control program is implemented to ensure mortar droppings do not block the cavity. Fig. 3-13 demonstrates a typical rainscreen cavity for this assembly.

Where the rainscreen cavity is reduced, such as at window rough openings with return brick, a compressible free-draining filler is recommended; semi-rigid mineral fiber board insulation may be used. In any case, mortar should not be packed within these cavities.

The rainscreen cavity is ventilated through vents located at the top and bottom coursing of each wall section. Top vents typically occur just below parapet blocking and below intermittent bearing elements such as floor line shelf-angles. Bottom vents also serve as weeps to assist with drainage of the rainscreen cavity. These vents/weeps are typically located just above bearing elements such as loose lintels, floor line shelf-angles, or foundation walls.

Vents and weeps should be spaced a maximum of 24 inches on-center (e.g., every 2 to 3 masonry units) and filled with a cellular or mesh product that fills the head joint of a standard brick unit. It is important that weep fillers extend into the bed joint of the course to facilitate drainage. Weep tubes should not be used at vent/weep locations because they provide far less ventilation and are blocked easily with debris. An example of a weep/vent and vent at a floor line shelf angle condition are shown in Fig. 3-14.

Mortar collection nets are recommended at all veneer-bearing locations to prevent mortar from blocking the rainscreen cavity and vents/weeps. It is best practice to use a trapezoidal-shaped open-weave, moisture-tolerant net.

Sheet-Metal Components

Sheet-metal components for this assembly are reflected throughout the details located at the end of this chapter. Cross-cavity sheet-metal components are typically located at all bearing elements such as the head of a penetration (e.g., window head), floor line shelf-angles, and foundation. These flashings assist with draining the rainscreen cavity and also serve to protect fluid-applied or flexible flashing membranes that may exist beneath them. Counterflashing sheet-metal components assist only with watershedding and are typically located at windowsill and parapet top conditions; they protect the cavity from water ingress while still allowing for cavity ventilation.

Refer to the Introductory chapter for general recommendations on sheet-metal flashing products, including design considerations and materials.

Fig. 3-14 Cross-cavity sheet-metal flashing with weep/vent above the flashing and vent below the flashing. Staggering the weep/vent locations reduces the likelihood of exposing the vent below the flashing to drainage from the weep location above.

Fig. 3-14 Cross-cavity sheet-metal flashing with weep/vent above the flashing and vent below the flashing. Staggering the weep/vent locations reduces the likelihood of exposing the vent below the flashing to drainage from the weep location above.

Movement Joints

For this assembly, anchored clay masonry will expand over time as a result of irreversible moisture gain, and the mortar joints will shrink slightly overtime. In the support system, the wood-framed members will shrink due to moisture loss. To avoid veneer damage, breaks must be provided in the veneer to compensate for differential movement between the cladding and support wall. Expansion joints also must be provided to allow for overall expansion of the clay masonry veneer; control joints must be provided for shrinkage where concrete masonry veneer units are used.

Differential movement between the wall structure and veneer is accommodated with a horizontal gap between the veneer and elements that are directly attached to the wall structure, such as shelf angles, parapet blocking, and windows. Locations where this gap should occur are indicated with an asterisk (*) in the details at the end of this chapter. At each horizontal gap, either a backer rod and sealant joint or a cross-cavity sheet-metal flashing should be placed. The sizing and location of vertical movement joints will vary depending on the expected differential movement between the wall and veneer. It is the Designer of Record’s responsibility to appropriately locate and size each joint. In general, a minimum gap dimension of 3/8 of an inch should be provided.

Expansion/shrinkage of the veneer or differential movement between the veneer, penetrations, and different cladding materials is accommodated with vertical joints in the veneer system. Vertical gaps minimize stresses between the veneer and other components and provide crack control for the masonry veneer. It is the Designer of Record’s responsibility to appropriately locate and size each joint. In general, a minimum gap dimension of 3/8 of an inch should be provided.

Refer to the Introductory chapter for more information on locating movement joints and sealant joint best practices.

Expansion joints (clay masonry veneer) or control joints (concrete masonry veneer) minimize stresses within the veneer and also between dissimilar materials such as at window jamb to veneer interfaces.

Structural Considerations

The wood framing provides the primary structure of this assembly. It is the responsibility of the Designer of Record to ensure that all structural elements are designed to meet project-specific loads and local governing building codes. Generic placement of the framing members and support elements are demonstrated within the details of this chapter and are provided for diagrammatical purposes only.

Masonry Ties

Masonry ties are used to connect the veneer to the wood-framed backup wall and should be designed to resist the out-of-plane loads applied to the wall, typically wind and seismic. At the same time, ties must be flexible to allow the veneer to move in-plane relative to the wood-framed wall.

Building codes provide prescriptive requirements for masonry ties secured to wood-framed walls, including spacing, size, placement and anchor type. These requirements are summarized in Table 3-4 and are based on ACI-530 provisions. The use of these prescriptive requirements is limited to masonry veneer assemblies with a weight less than 40 psf, a cavity depth no more than 4.5 inches, and where the ASCE-7 wind velocity pressure (qz) is less than 55 psf (previously wind speed less than 130 mph). Wall assemblies that exceed these criteria require the design professional to evaluate the building loads and materials and rationally design the anchorage system accordingly. The majority of masonry tie manufacturers have empirical testing data available to support the use of their anchorage systems when the cavity depth or loads exceed these criteria.

Prescriptive spacing requirements for anchored masonry veneers in Table 3-4 include special requirements for Seismic Design Categories D, E, and F and high wind zones with velocity pressures (qz) between 40 and 55 psf. These higher seismicity and wind speed areas are common to some parts of the Northwest and are dependent on the geography and building occupancy category. Refer to local building code requirements to ensure seismicity and wind speed criteria are properly evaluated for the building occupancy and site conditions.

Typical tie types for reference are shown in Fig. 3-15. For wood-framed walls, the code does not restrict the use of any tie type; however, based on local best practices, double eye and pintle type ties—whether a plate or screw type—are preferred. Double eye and pintle ties are available from a number of manufacturers in a variety of sizes to meet project requirements in the Northwest.

Adjustable triangular wire ties are acceptable but may not be preferred by installers because the vertical tie orientation can complicate the exterior insulation installation process by requiring vertical orientation of insulation boards. Do not use corrugate masonry ties due to their limited corrosion resistance. Non-adjustable surface-mounted ties are also not recommended.

To prevent pull-out or push-through of the tie, tie embedment should be a minimum 1.5 inches into the veneer, with at least 5/8 of an inch mortar or grout cover at the outside face. The mortar bed thickness is to be at least twice the thickness of the anchor. To prevent excess movement between connecting parts of adjustable tie systems, limit clearance between components to less than 1/16 of an inch. The vertical offset of an adjustable pintle tie may not exceed 1.25 inches.

Masonry tie should be fastened directly to the wood framing through the exterior sheathing. Masonry anchors are not to be fastened to the sheathing alone. The code requires the use of 8d common nails or fasteners with equivalent pull-out strength. However, in Seismic Design Categories D, E, and F , the code requires the use of 8d ring-shank nails or No. 10 corrosion-resistant screws with a nominal minimum shank diameter of 0.190 inches. It is recommended to use No. 10 corrosion-resistant screws or better. While the code allows a horizontal anchor spacing up to 32 inches on-center, it is recommended that anchors be placed at 16 inches on-center horizontally to align with the typical stud spacing.

Vertical Supports

Anchored masonry veneers are supported vertically by the building’s foundation or other structural components. There are generally three methods of supporting masonry veneers:

  • Structural bearing (foundations, floor slabs, structural beams)
  • Intermediate supports (continuous or standoff shelf angles)
  • Supports at openings (loose lintel, shelf angle, reinforced masonry lintel, precast concrete lintel)

A structural bearing support and lintel are both shown in Fig. 3-16.

While the function of each support method is different, they must each be designed to eliminate the possibility of cracking and deflection within the veneer. Selection of the appropriate support method should consider the design loads, material type, moisture control, movement provisions, and constructibility.

For wood-framed backings, anchored masonry veneer supported vertically by noncombustible construction may be installed up to a height of 30 feet. Wherever the masonry veneer is supported by wood construction, it must be supported every 12 feet. Best practice for commercial wood-framed construction is to support the lowest portion of the masonry cladding directly on the concrete foundation wall.

When intermediate support is needed above 30 feet, provide vertical support at each floor slab, not exceeding a vertical spacing of 12 feet. When fastening to the floor slab, the masonry must be isolated from the wood construction and should be supported by steel shelf angles anchored directly to the wood-framed rim joist at each floor slab. Do not support the veneer through the vertical wall studs above or below the floor slab. The floor slab design should be sufficient to limit floor deflection to less than L/600 or 0.3 inches, whichever is less. As noted in the above Movement Joints section, a joint should be provided beneath the angle and sealed with elastomeric silicone sealant.

Masonry cladding must also be supported at openings within the veneer, such as windows and doors. This may be done with shelf angles for larger openings, or with loose lintels at smaller openings. Galvanized steel angles are typically used as lintels, except where architectural design dictates the use of reinforced masonry or precast concrete lintels for appearance. Steel angle lintels should span the opening and bear a minimum of 6 inches onto the adjacent masonry at the jambs of the opening.

Table 3-4 Minimum spacing for anchored masonry veneer ties.

Table 3-4 Minimum spacing for anchored masonry veneer ties.

Fig. 3-15 Brick tie types. Top row, left to right: standard double eye and pintle plate tie, thermally optimized double eye and pintle screw tie. Bottom row, left to right: corrugated masonry tie, adjustable L-bracket, non-adjustable surface mounted tie.

Fig. 3-15 Brick tie types. Top row, left to right: standard double eye and pintle plate tie, thermally optimized double eye and pintle screw tie. Bottom row, left to right: corrugated masonry tie, adjustable L-bracket, non-adjustable surface mounted tie.

Fig. 3-16 This masonry veneer bears on the continuous shelf angle at the right and the concrete foundation element at the left.

Corrosion Resistance

To avoid premature cladding replacement, the durability and longevity of metal components within this assembly should match that expected of the masonry veneer cladding system. Metal components within this assembly include veneer ties, vertical support ledgers and lintels, sheet-metal flashings, and fasteners.

Veneer ties should be hot-dipped galvanized carbon steel that complies with ASTM A 153 Class B-2 or stainless steel that complies with AISI Type 304 or 316 such as that shown in Table 3-4. Steel support angles such as ledger angles and lintels should be a minimum G185 hot-dipped galvanized. Sheet-metal flashing components should be manufactured of ASTM A167 Type 304 or 316 stainless steel, which is non-staining and resistant to the alkaline content of mortar materials.

Whereas the use of stainless steel sheet-metal flashing components is not always economically feasible or aesthetically desirable, prefinishing sheet-metal may be considered. Where used, the base sheet metal should receive a minimum G90 hot-dipped galvanized coating in conformance with ASTM A653 or minimum AZ50 galvalume coating in conformance with ASTM A792. It is recommended that the exposed top finish of the sheet metal be coated with an architectural-grade coating conforming to AAMA 2605.

Fasteners used with all metal components should be corrosion-resistant, either galvanized steel or stainless steel. Consideration should be given to the fastener selection when used with preservative-treated wood to prevent galvanic corrosion.

Masonry Veneer

There are several types of anchored masonry veneer products that may be used with this assembly. Those most typical within the Northwest include facing brick made of clay or shale. Concrete facing brick and concrete masonry units are also used.

When using facing brick made from clay or shale, anchored veneer units should comply with ASTM C216 and be severe weather (SW) grade. When using concrete facing brick, anchored veneer units should comply with ASTM C1634. Hollow concrete masonry units used for veneer applications are typically 4-inches deep and should comply with ASTM C90.

Mortar designed for the anchored masonry veneer units should conform to ASTM C270, and type selected should be appropriate for the veneer application; Type N mortar is acceptable for most anchored masonry veneer applications. When selecting mortar, the lowest compressive strength (softest) mortar that satisfies the project requirements should be used.

Appropriate product selection of masonry veneer unit and mortar materials is necessary to provide a durable and water-resistive cladding system. The veneer units and mortar joints should also be installed in conformance with industry standard best practices and manufacturer requirements. The specifics of architectural characteristics and structural properties of the veneer unit, mortar, and reinforcing should be designed and reviewed by a qualified Designer of Record.

Various industry resources are available to assist with veneer design and installation methods and are listed in the References section of this guide.

Clear Water Repellents

A clear water repellent should be applied to the anchored masonry veneer of this assembly. Refer to the Introductory chapter for more information on selecting an appropriate clear water repellent and best practice installation guidelines.

Details

Typical Lintel at Window Head (Detail 3-A)

Assembly 3 Detail 3A Critical BarriersLEGEND

  1. Typical Assembly:
    – interior gypsum board
    – vapor retarder
    – wood-framed wall with batt insulation
    – exterior sheathing
    – vapor-permeable sheet-applied AB/WRB field membrane
    – air cavity
    – anchored masonry veneer
    – clear water repellent
  2. Masonry veneer anchor over flexible self-adhered membrane patch
  3. Continuous mortar collection mesh
  4. Continuous AB sealant
  5. Hot-dipped galvanized steel lintel (loose or anchored)
  6. Vapor-permeable sheet-applied or fluid-applied AB/WRB head prestrip membrane
  7. Weep at maximum 24 inches on-center
  8. Sheet-metal head flashing with 1/2-inch hemmed drip edge and end dams beyond
  9. Sealant over backer rod
  10. AB sealant over backer rod, tie to continuous seal at window perimeter
  11. Flanged window

Detail Discussion

  • AB and WRB continuity is provided by the sheet-applied AB/WRB field membrane, sheet-applied or fluid applied AB/WRB rough opening head prestrip membrane, continuous AB sealant, and AB sealant transition to the window.
  • A flanged window is depicted. Consider using a non-flanged window unit to facilitate future window repair and replacement without the need to remove the anchored masonry veneer. Refer to window strap anchor detailing in Chapter 2 details when a non-flanged window is used.
  • Refer to the introductory chapter of this guide for lip brick detailing options which can minimize the appearance of the sheet-metal flashing shown in this detail.
  • Weeps located above the lintel provide rainscreen cavity ventilation and drainage. The mortar collection mesh keep weeps clear of mortar droppings.

Assembly 3 Detail 3A

Typical Precast Window Sill (Detail 3-B)

Assembly 3 Detail 3B Critical BarriersLEGEND

  1. Typical Assembly:
    – interior gypsum board
    – vapor retarder
    – wood-framed wall with batt insulation
    – exterior sheathing
    – vapor-permeable sheet-applied AB/WRB field membrane
    – air cavity
    – anchored masonry veneer
    – clear water repellent
  2. Flanged window
  3. Sealant over backer rod
  4. Intermittent minimum 1/4-inch shims
  5. Intermittent minimum 1/4-inch shims behind sill flange for drainage
  6. Sloped precast concrete sill
  7. Fluid-applied AB/WRB sill membrane (or flexible self-adhered flashing membrane)
  8. Masonry veneer anchor over flexible self-adhered membrane patch per AB/WRB field membrane manufacturer recommendations
  9. Continuous AB sealant. Tie to continuous seal at window perimeter.
  10. Continuous back dam angle at rough opening sill, minimum 1 inch tall. Fasten window through back dam angle per window manufacturer recommendations.

Detail Discussion

AB and WRB continuity is provided by the sheet-applied AB/WRB field membrane, fluid-applied AB/WRB sill membrane (or flexible self-adhered flashing membrane), and AB sealant transition to the window.

A flanged window is depicted. Consider using a non-flanged window unit to facilitate future window repair and replacement without the need to remove the anchored masonry veneer. Refer window strap anchor detailing in Chapter 2 details when a non-flanged window is used.

Do not place a sheet-metal flashing below the precast sill. It can prematurely degrade the mortar bed beneath the precast element.

Assembly 3 Detail 3B

Typical Brick Return at Window Jamb (Detail 3-C)

Assembly 3 Detail 3C Critical BarriersLEGEND

  1. Typical Assembly:
    – interior gypsum board
    – vapor retarder
    – wood framed wall with batt insulation
    – exterior sheathing
    – vapor-permeable sheet-applied AB/WRB field membrane
    – air cavity
    – anchored masonry veneer
    – clear water repellent
  2. Flanged window
  3. Sealant over backer rod
  4. Minimum 1/2 inch drainage path, fill with free draining compressible material
  5. Vapor-permeable sheet-applied or fluid-applied AB/WRB jamb prestrip membrane
  6. Masonry veneer anchor over flexible self-adhered membrane patch per AB/WRB field membrane manufacturer recommendations

Detail Discussion

  • AB and WRB continuity is provided by the sheet-applied AB/WRB field membrane, sheet-applied or fluid-applied AB/WRB rough opening sill membrane, and AB sealant transition to the window.
  • Maintain a clear drainage cavity between the brick return and AB/WRB by placing a free draining material such as semi-rigid mineral fiber board insulation between the masonry veneer and sheet-applied AB/WRB jamb prestrip. Do not fill this space with mortar.
  • When exterior insulation is used with this assembly, consider the Chapter 2 rough opening details with sheet-metal jamb trim and sill flashing. Chapter 2 details are a thermally improved alternate to returning the masonry veneer at the jamb which reduce the exterior insulation thickness at the window perimeter.

Assembly 3 Detail 3C

Typical Floor Line with Continuous Shelf Angle (Detail 3-D)

Assembly 3 Detail 3D Critical BarriersLEGEND

  1. Typical Assembly:
    – interior gypsum board
    – vapor retarder
    – wood-framed wall with batt insulation
    – exterior sheathing
    – vapor-permeable sheet-applied AB/WRB field membrane
    – air cavity
    – anchored masonry veneer
    – clear water repellent
  2. Continuous AB sealant
  3. Flexible self-adhered flashing membrane or fluid-applied flashing membrane
  4. Continuous mortar collection mesh
  5. Hot-dipped galvanized steel shelf angle anchored to structure
  6. Rigid XPS insulation, sealed or foamed at perimeter and joints
  7. Weep at minimum 24 inches on-center
  8. Sheet-metal flashing with hemmed drip edge
  9. Sealant over backer rod
  10. Flexible self-adhered or fluid-applied flashing membrane
  11. Masonry veneer anchor over flexible self-adhered membrane patch per AB/WRB field membrane manufacturer recommendations
    * Size joint for project-specific building movement, minimum 3/8-inch wide.

Detail Discussion

  • AB and WRB continuity is provided by the sheet-applied AB/WRB field membrane, flexible self-adhered or fluid-applied flashing membrane, and continuous AB sealant. Use of a flexible self-adhered or fluid-applied flashing membrane behind the lintel reduces the opportunity for air leakage at anchor locations.
  • Mortar collection mesh and weeps are provided to encourage drainage and ventilation of the rainscreen cavity.
  • The floor line is insulated with a rigid board insulation and sealed at the edges to provide both thermal envelope continuity and VR layer continuity.
  • Refer to the Introductory chapter for alternate lip brick details which reduce the visibility of the backer rod and sealant movement joint. Note this joint is necessary for differential movement that will occur between the structure and anchored masonry veneer.

Assembly 3 Detail 3D

Typical Parapet at Conventional Roof System (Detail 3-E)

Assembly 3 Detail 3E Critical BarriersLEGEND

  1. Parapet Assembly
    – conventional roof membrane
    – exterior sheathing
    – vented wood-framed parapet
    – exterior sheathing
    – vapor-permeable sheet-applied AB/WRB field membrane
    – air cavity
    – anchored masonry veneer
    – clear water repellent
  2. Conventional roof assembly
  3. Standing-seam sheet-metal coping with gasketed washer fasteners
  4. High-temperature self-adhered membrane
  5. Compressible filler
  6. Weep at minimum 24 inches on-center
  7. Masonry veneer anchor over flexible self-adhered membrane patch per AB/WRB field membrane manufacturer recommendations
  8. Continuous bead of AB sealant
  9. Closed-cell spray foam insulation plug (AB)
  10. Preservative-treated blocking
  11. Insect screen
    * Size joint for project specific building movement, minimum 3/8 inch wide

Detail Discussion

  • A weep is located at the top masonry course to encourage ventilation of the rainscreen cavity. The sheet-metal parapet cap is offset from the face of the anchored masonry veneer so as not to block the ventilation path. The sheet-metal coping and weep overhang the weeps to protect the masonry veneer opening from wind-driven rain.
  • A compressible filler is used between the anchored masonry veneer and parapet blocking to allow building movement while preventing insects and debris from entering the rainscreen cavity.
  • Parapet cavity insulation is provided to create a continuous thermal envelope at the roof-to-wall transition.
  • AB continuity in this assembly is created by the continuous AB sealant at the parapet and closed cell spray foam insulation within the wood-framed parapet cavity.

Assembly 3 Detail 3E

Parapet Assembly Cutaway Section (Detail 3-F)

LEGEND

  1. Wood-framed wall with batt insulation
  2. Exterior sheathing
  3. Wood-framed parapet
  4. Closed-cell spray foam insulation plug (AB)
  5. Preservative treated blocking, sloped to drain toward roof
  6. Vapor-permeable AB/WRB field membrane
  7. Vapor-permeable sheet-applied or fluid-applied AB/WRB head prestrip membrane
  8. Masonry veneer anchor over flexible self-adhered membrane patch per AB/WRB field membrane manufacturer recommendations
  9. Anchored masonry veneer
  10. Hot-dipped galvanized steel loose or anchored lintel
  11. Sheet-metal head flashing with 1/2-inch hemmed drip edge and end dams beyond
  12. Continuous AB sealant
  13. Conventional roof assembly
  14. High-temperature self-adhered membrane
  15. Standing-seam sheet-metal coping with gasketed washer fasteners
  16. Rigid insulation sealed at perimeter and joints

3-D Detail Discussion

  • Three-dimensional cutaway sections on the next three pages represent two-dimensional details of this assembly.
  • In all details, WRB and WSS elements are shingle lapped to encourage water shed, in both the rainscreen cavity and at the anchored masonry veneer face.
  • As shown in Detail 3-F, the lintel is placed above the window head and shingle lapped into the AB/WRB field membrane. The continuous AB sealant above this location provides AB continuity between the AB/WRB head prestrip and AB/WRB field membrane.
  • AB continuity is created at the parapet in Detail 3-F with the line of continuous AB sealant at the parapet and closed cell spray foam insulation within the parapet cavity framing. These components assist with transferring the AB critical barrier across the parapet sheathing to the AB at the roof assembly.
  • Terminate the loose lintel and two-piece sheet-metal head flashing in Detail 3-F at a masonry veneer head joint. This allows for an end dam to be formed at the sheet metal termination.
  • Weeps at the floor line lintel, as shown in Detail 2-G, provide both drainage and ventilation of the rainscreen cavity above. Mortar collection mesh helps keep the weeps and base of the rainscreen cavity free of mortar droppings.
  • Detail 3-H describes a typical rough opening with sill back dam angle. The back dam angle creates a sill pan below the window; intermittent shims encourage drainage at the sill and into the rainscreen cavity.

Assembly 3 Detail 3F

Base of Wall Section Model (Detail 3-G)

LEGEND

  1. Wood-framed wall with batt insulation
  2. Rigid XPS thermal insulation, sealed or foamed at perimeter and joints
  3. Exterior sheathing
  4. Flexible self-adhered or fluid-applied flashing membrane
  5. Sheet-metal flashing with hemmed drip edge over hot-dipped galvanized steel shelf angle anchored to rim joist
  6. Flexible self-adhered or fluid-applied flashing membrane
  7. Continuous bead of AB sealant
  8. Vapor permeable AB/WRB field membrane
  9. Continuous mortar collection mesh
  10. Masonry veneer anchor over flexible self-adhered membrane patch per AB/WRB field membrane manufacturer recommendations
  11. Anchored masonry veneer
  12. Sealant over backer rod (movement joint)
  13. Weep at minimum 24 inches on-center

Assembly 3 Detail 3G

Window Jamb / Sill Section Model (3-H)

LEGEND

  1. Continuous back dam angle at rough opening sill, minimum 1-inch tall. Fasten window through back dam angle per window manufacturer recommendations.
  2. Vapor permeable sheet-applied AB/WRB field membrane
  3. Fluid-applied AB/WRB sill membrane (or flexible self-adhered flashing membrane)
  4. Vapor-permeable sheet-applied or fluid-applied AB/WRB jamb prestrip membrane
  5. Intermittent minimum 1/4-inch shims
  6. Continuous AB sealant, tie to continuous seal at window perimeter
  7. Masonry veneer anchor over flexible self-adhered membrane patch per AB/WRB field membrane manufacturer recommendations
  8. Anchored masonry veneer
  9. Flanged window
  10. Precast concrete sill
  11. Sealant between precast sill and window frame. Tie to sealant between window jamb and masonry veneer.

Assembly 3 Detail 3H

Specifications

Thermal Modeling

Thermal Performance and Energy Code Compliance

This chapter assembly is typically classified as a “wood-framed and other” above-grade wall for energy code compliance purposes. Prescriptive energy code compliance values for this assembly are summarized in Table 3-3 and describe:

  • Minimum insulation R-values for a prescriptive R-value compliance strategy.
  • Maximum assembly U-factors for a prescriptive U-factor alternative compliance strategy. Note, the equivalent assembly effective R-value of this maximum U-factor has been calculated and is denoted in parenthesis ( ) for easy comparison to thermal modeling results included within this chapter.

Wood-framed walls are typically constructed with 16-inch on-center stud spacing for standard framing or 24-inches on-center stud spacing for advanced framing methods. Nominal 2×6 framing accommodates up to an R-21 fiberglass or R-23 mineral fiber batt insulation and nominal 2×8 framing up to an R-30 mineral fiber batt insulation. When continuous insulation requirements are to be met, this assembly will have insulation exterior of the wood frame structure and AB/WRB critical barrier, as shown in Fig. 3-5.

When a non-prescriptive compliance option (e.g., a trade-off strategy or whole-building modeling strategy) is used for energy code compliance, this assembly’s effective thermal performance will need to be calculated; however, it may or may not be required to meet the prescriptive values shown in Table 3-3.

Fig. i-17 of the introductory chapter describes the typical process of navigating energy code compliance strategies and options. Thermal modeling results demonstrated within this chapter may be used to assist with estimating insulation and tie selection to achieve a target thermal performance value. Options for thermally optimizing this assembly, as determined through the modeling results are also provided.

Assembly Effective Thermal Performance

Exterior insulation in this assembly may or may not be required to meet project-specific energy code compliance; however, when exterior insulation is used, cladding attachments and supports (e.g., masonry ties and shelf angles) will penetrate the exterior insulation and create areas of thermal bridging (i.e., heat loss). An example of the thermal bridging is described by Fig. 3-6 through Fig. 3-9 and shows the comparative thermal impact of either a continuous or standoff floor line shelf angle. Fig. 3-7 shows a dark blue thermal gradient color (colder temperature) at the floor line edge for the continuous floor line shelf angle, whereas the floor line with a standoff shelf angle is light blue and yellow, indicating warmer temperatures. Thermal bridging reduces the assembly’s effective thermal performance.

Three-dimensional thermal modeling demonstrates this assembly’s effective thermal performance with various insulation thicknesses, insulation R-values, masonry veneer ties, and standoff shelf angle options. A discussion on the modeling performed for this guide is included in the Introduction Chapter and the Appendix.

Thermal Modeling: Variables

The following are modeling variables specific to this assembly:

  • Framing and Cavity Insulation: 2×6 with R-21 batt insulation or 2×8 with R-30 batt insulation. Modeling results include a full-height wood-framed wall with a floor line. Standard framing allowance for 77% insulated cavity and 23% framing members such as studs, plates, and headers is used.
  • Masonry Ties: Various tie types are considered at 16 inches by 16 inches on-center spacing. Tie types are shown in Fig. 3-10 and include:
    • Thermally optimized screw tie with stainless barrel and carbon steel fastener. Hooks are either hot-dipped galvanized steel or Type 304 stainless steel.
    • Double eye and pintle plate tie (14-gauge). Hooks are either hot-dipped galvanized steel or Type 304 stainless steel to match the tie plate.
  • Exterior Insulation: This assembly with and without exterior insulation is considered and includes insulation materials with either a thermal resistance of R-4.2/inch or R-6/inch in thicknesses of 1, 2, and 3 inches. The R-values selected demonstrate the lower and upper thermal resistance of typical exterior insulation products.
  • Shelf Angle Supports: Hot-dipped galvanized steel shelf angles. Either attached tight to the floor line structure (i.e., continuous shelf angle) as shown in Fig. 3-6 and Fig. 3-7 or offset to the depth of the exterior insulation and supported by intermittent hollow steel sections (HSS) at 4 feet on-center (i.e., standoff shelf angle) as shown similar in Fig. 3-8 and Fig. 3-9.

Thermal Modeling: Results

The results of this modeling are shown in Table 3-2, Fig. 3-11, and Fig. 3-12 and demonstrate the assembly effective R-value under various conditions; Fig. 3-11 and Fig. 3-12 are graphical representations of the results summarized in Table 3-2. Discussion of these results is provided below and key points for thermally optimizing this assembly are italicized in boldface.

  • As shown in Table 3-2, the assembly effective R-value without penetrations, as read from the “Cavity + Exterior Insulation (Without Penetrations)” column, is lesser than if the “Nominal Insulation R-Value (Cavity + Exterior)” values were combined. This difference is due to wood framing that creates thermal bridges through the cavity insulation. When masonry ties are considered as shown in the “Without Shelf Angle” column, the assembly effective R-value is further reduced.
  • As shown in Table 3-2, the assembly effective R-value without penetrations is reduced anywhere between 2 and 12% when masonry tie penetrations are considered. Reducing the frequency of ties will increase the effective thermal performance of the assembly but will also need to be coordinated with structural requirements.
  • Stainless steel plate ties and thermally optimized screw ties reduce the assemblies effective R-value without penetrations by 2 and 7%; whereas, galvanized steel plate ties reduce the effective R-value without penetrations by 3 to 12%. Galvanized steel plate ties provide a lesser effective R-value than both the stainless steel or thermally optimized screw tie options as shown in Fig. 3-11. Both stainless steel and thermally optimized screw ties provide similar effective R-value performance. Whether galvanized steel hooks or stainless steel hooks are used for thermally optimized tie selection makes little difference; however, stainless steel hooks provide better corrosion resistance. Use of a standard all-stainless steel tie option may prove to be a cost-effective option when compared to thermally improved proprietary tie options, and it also provides a highly corrosion-resistant attachment.
  • A shelf angle further reduces the assembly effective R-value after ties are considered as shown in Table 3-2 and Fig. 3-12. When considering ties, continuous shelf angles can reduce the assembly’s effective R-value by 4 to 20%. However, this is reduced to 2 to 13% when a standoff shelf angle is used. As determined from Fig. 3-12, up to an additional half-inch of insulation may be required to achieve the same effective thermal performance for this assembly if a continuous angle is used in lieu of a standoff shelf angle. Use of a standoff shelf angle in lieu of the continuous shelf angle improves the effective thermal performance of this assembly and may allow for thinner insulation thicknesses to meet the same assembly effective R-value.

Project-specific thermal performance values for the opaque above-grade wall assembly of this chapter 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.

Pricing Analysis

A pricing analysis for this assembly is provided on Table 3-5. Pricing demonstrates the relative price per square foot and is based on a 10,000-square-foot wall area with easy drive-up access. Pricing includes all components outboard of the exterior wall sheathing and provides no evaluation for interior finishes (including VR), framing/sheathing, or cavity insulation.

Pricing is valued for the 2015–2016 calendar year.

Table 3-5 Assembly 3 wood-framed wall with anchored masonry veneer pricing analysis.

Table 3-5 Assembly 3 wood-framed wall with anchored masonry veneer pricing analysis.