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Concrete Masonry Veneer Details

  • November 2018

INTRODUCTION

A wall constructed with two or more wythes of masonry can technically be classified in one of three ways, depending on how each individual wythe is designed and detailed. These three wall systems are composite, noncomposite or veneer walls. A true veneer is nonstructural—any contribution of the veneer to the wall’s out-of plane load resistance is neglected.

Building Code Requirements for Masonry Structures (ref. 1) defines veneer as a masonry wythe which provides the exterior finish of a wall system and transfers out-of-plane loads directly to the backing, but is not considered to add load resisting capacity to the wall system.

Noncomposite walls, on the other hand, are designed such that each wythe individually resists the loads imposed on it. Bending moments (flexure) due to wind or gravity loads are distributed to each wythe in proportion to its relative stiffness.

Composite walls are designed so that the wythes act together as a single member to resist structural loads. This requires that the two masonry wythes be connected by masonry headers or by a mortar or grout filled collar joint and wall ties to help ensure adequate load transfer between the two wythes.

The primary function of anchored veneers is to provide an architectural facade and to prevent water penetration into the building. As such, the structural properties of veneers are neglected in veneer design. The veneer is assumed to transfer out-of-plane loads through the anchors to the backup system. Building Code Requirements for Masonry Structures Chapter 6 (ref. 1) includes requirements for design and detailing anchored masonry veneer.

A masonry veneer with masonry backup and an air space between the masonry wythes is commonly referred to as a cavity wall. The continuous air space, or cavity, provides the wall with excellent resistance to moisture penetration and wind driven rain as well as a convenient location for insulation. This TEK addresses concrete masonry veneer with concrete masonry backup.

DESIGN CONSIDERATIONS

Masonry veneers are typically composed of architectural units such as: concrete or clay facing brick; split, fluted, glazed, ground face or scored block; or stone veneer. Most commonly, anchored masonry veneers have a nominal thickness of 4 in. (102 mm), although 3 in. (76 mm) veneer units may be available as well.

Although structural requirements for veneers are minimal, the following design considerations should be accounted for: crack control in the veneer, including deflection of the backup and any horizontal supports; adequate anchor strength to transfer applied loads; differential movement between the veneer and backup; and water penetration resistance.

The continuous airspace behind the veneer, along with flashing and weeps, must be detailed to collect any moisture that may penetrate the veneer and direct it to the outside. A minimum 1 in. (25 mm) air space between wythes is required (ref. 1), and is considered appropriate if special precautions are taken to keep the air space clean (such as by beveling the mortar bed away from the cavity or by placing a board in the cavity to catch and remove mortar droppings and fins while they are still plastic). Otherwise, a 2 in. (51 mm) air space is preferred. As an alternative, proprietary insulating drainage products can be used.

Although veneer crack control measures are similar to those for other concrete masonry wall constructions, specific crack control recommendations have been developed for concrete masonry veneers. These include: locating control joints to achieve a maximum panel length to height ratio of 11/2 and a maximum spacing of 20 ft (6,100 mm), as well as where stress concentrations occur; incorporating joint reinforcement at 16 in. (406 mm) on center; and using Type N mortar for maximum flexibility. See CMU-TEC-009-23, Crack Control Strategies for Concrete Masonry Construction (ref. 2) for more detailed information.

Because the two wythes in a veneer wall are designed to be relatively independent, crack control measures should be employed as required for each wythe. It is generally not necessary for the vertical movement joints in the veneer wythe to exactly align with those in the backup wythe, provided that the ties allow differential in-plane lateral movement.

Wall ties may be joint reinforcement or wire wall ties. Wall ties for veneers transfer lateral loads to the structural wythe and also allow differential inplane movement between wythes. This second feature is particularly important when the two wythes are of materials with different thermal and moisture expansion characteristics (such as concrete masonry and clay brick), or in an insulated cavity wall which tends to have differential thermal movement between the wythes. When horizontal joint reinforcement is used to tie the two wythes together, hot-dipped ladder type reinforcement is preferred over truss type, because the ladder shape accommodates differential in-plane movement and facilitates placing vertical reinforcement, grout and loose fill insulation. Because veneers rely on the backup for support, wall ties must be placed within 12 in. (305 mm) of control joints and wall openings to ensure the free ends of the veneer are adequately supported. More information on ties for veneers can be found in TEK 03-06C, Concrete Masonry Veneers (ref. 4).

The distance between the inside face of the veneer and the outside face of the masonry backup must be a minimum of 1 in. (25 mm) and a maximum of 4 1/2 in. (114 mm). For glazed masonry veneer, because of their impermeable nature, a 2 in. (51 mm) wide airspace is recommended with air vents at the top and bottom of the wall to enhance drainage and help equalize air pressure between the cavity and the exterior of the wall. Vents can also be installed at the top of other masonry veneer walls to provide natural convective air flow within the cavity to facilitate drying. For vented cavities, it is prudent to create baffles in the cavity at the building corners to isolate the cavities from each other. This helps prevent suction being formed in the leeward cavities.

REFERENCES

  1. Building Code Requirements for Masonry Structures, ACI
    530-02/ASCE 5-02/TMS 402-02. Reported by the Masonry
    Standards Joint Committee, 2002.
  2. CMU-TEC-009-23, Crack Control Strategies for Concrete
    Masonry Construction, Concrete Masonry and Hardscapes
    Association, 2023.
  3. TEK 03-06C, Concrete Masonry Veneers, Concrete
    Masonry and Hardscapes Association, 2012.

Rolling Door Details for Concrete Masonry Construction

  • August 2018

INTRODUCTION

Openings in concrete masonry walls utilize lintels and beams to carry loads above the openings. When openings incorporate rolling doors (also referred to as overhead coiling doors or coiling doors), wind loads on the door are transferred to the surrounding masonry through the door guides and fasteners.

In some instances, the rolling doors have been designed for specific wind load applications, and are heavily dependent on the structural integrity of the door jamb members as they are attached to building walls at jamb locations. This TEK discusses the forces imposed on a surrounding concrete masonry wall by rolling doors, and includes recommended details for jamb construction. Lintel design, to carry the loads imposed on the top of the opening, are covered in Allowable Stress Design of Concrete Masonry Lintels and Precast Concrete Lintels for Concrete Masonry Construction (refs. 1, 2).

LOADS EXERTED BY ROLLING DOORS

Architects and building designers should determine the loads that rolling doors exert on the wall around the opening. Dead loads include the weight of the door curtain, counterbalance, hood, operator, etc., that is supported by the wall above the opening. Live loads result from wind that acts on the door curtain. Rolling doors are available with windlocks, which prevent the door curtain from leaving the guides due to wind loading. On doors without windlocks, the only wind load force that the curtain exerts on the guides is normal to the opening. For doors with windlocks, there is an additional load parallel to the opening (see Figures 1 and 2 for face-mounted and jambmounted doors, respectively). This load is the catenary tension that results when the curtain deflects sufficiently to allow the windlocks to engage the windbar in the guide. This force acts to pull the guides toward the center of the opening. The door is exposed to a additive wind loads, from both inside and outside the building.

Calculating the parallel force involves several variables, the most prominent of which are the width of the opening and the design wind load. It is also important to note that the door must withstand both positive and negative wind loads. Including these forces in the design of the jamb and its supporting structure can help prevent a jamb failure and allow the building to fully withstand its specified wind load requirements. The rolling door manufacturer can provide a guide data sheet for quantifying the loads imposed by the overhead coiling doors due to the design wind load.

The following conditions need to be considered:

  • The wall above the door opening must be designed to support the total hanging dead load. The face of wallmounted doors may extend above the opening for 12 to 30 in. (305-762 mm). The door guide wall angles must be mounted to the wall above the opening to support the door. When the door has a hood to cover the coiled door and counter-balance, some provision must be made to fasten the top of the hood and hood supports to the masonry wall. See also Fasteners for Concrete Masonry (ref.3).
  • Reinforcement in jambs is recommended to adequately distribute the forces imposed by the door.
  • Reinforcement locations should be planned such that the reinforcement does not interfere with expansion anchor placement.

ACCOMODATING MASONRY REINFORCEMENT AND DOOR FASTENERS

Rolling door contractors and installers sometimes encounter reinforcement in walls at locations where door jamb fasteners have been specified. Arbitrarily changing either the reinforcement location or the fastener location is not recommended, as either can negatively impact performance. Changing the door manufacturer’s recommended jamb fastener locations may reduce the structural performance of the rolling door or possibly void the fire rating.

The typical masonry jamb detail shown in Figure 3 indicates recommended vertical reinforcement locations for concrete masonry jambs to provide an area for the door fasteners. The detail shows a “reinforcement-free zone” to allow for fasteners of either face mounted or jamb-mounted rolling doors. The Door and Access Systems Manufacturers Association International (DASMA) recommends that vertical reinforcement should be within 2 in. (51 mm) of either corner of the wall at the jamb (ref. 4).

EXISTING CONSTRUCTION

Before installing fasteners in existing masonry construction, the following steps should be followed to locate the reinforcement, to avoid interference:

  • If structural drawings are available, the project engineer should review the drawings to determine whether or not the jamb reinforcement locations conflict with the specified door jamb fastener locations.
  • If the building’s structural plans are not available, either drill
    representative “pilot holes” or use a device similar to an electronic stud locator to determine the steel reinforcement locations.

Once the steel reinforcement has been located, if it is concluded that the reinforcement will interfere with installing jamb fasteners, DASMA recommends that one of the following courses of action be taken:

  1. Consider an alternate door jamb mounting or door size to assure that the reinforcement will not interfere with jamb fasteners.
  2. If an alternate door jamb mounting or alternate door size cannot be accomplished, consult a structural engineer to determine a workable solution. One possible solution is to contact the door manufacturer to obtain an alternate conforming hole pattern for the mounting, which would not interfere with the existing reinforcement. Another solution may be to bolt a steel angle to the concrete masonry jambs, which allows the door guides to then be welded or bolted to the steel angle.

FIRE-RATED ROLLING DOOR CONNECTIONS

When installed in a fire-rated concrete masonry wall, rolling steel fire doors must meet the code-required fire rating corresponding to the fire rating of the surrounding wall. For fire testing, the doors are mounted on the jambs of a concrete masonry wall intended to replicate field construction. The fire door guides must remain securely fastened to the jambs and no “through gaps” may occur in the door assembly during the test. Figure 4 shows a representative jamb construction and guide attachment details for a four-hour fire rated assembly. Note that guide configurations and approved jamb construction will vary with individual fire door manufacturer’s listings. Consult with individual manufacturers for specific guide details and approved jamb constructions.

REFERENCES

  1. Allowable Stress Design of Concrete Masonry Lintels
    Based on 2012 IBC/2011 MSJC, TEK 17-01D, Concrete
    Masonry & Hardscapes Association, 2011.
  2. Precast Concrete Lintels for Concrete Masonry
    Construction, TEK 17-02A, Concrete Masonry &
    Hardscapes Association, 2000.
  3. Fasteners for Concrete Masonry, TEK 12-05, Concrete
    Masonry & Hardscapes Association, 2005.
  4. Metal Coiling Type Door Jamb Construction: Steel
    Reinforcement In Masonry Walls, TDS-259. Door and
    Access Systems Manufacturers Association International,
    2005.
  5. Architects and Designers Should Understand Loads
    Exerted By Overhead Coiling Doors, TDS-251. Door and
    Access Systems Manufacturers Association International,
    2005.
  6. International Building Code 2003. International Code
    Council, 2003.
  7. International Building Code 2006. International Code
    Council, 2006.
  8. Common Jamb Construction for Rolling Steel Fire Doors:
    Masonry Construction—Bolted and Welded Guides, TDS-
  9. Door and Access Systems Manufacturers Association
    International, 2005.
  10. Steel Reinforcement for Concrete Masonry, TEK 12-04D,
    Concrete Masonry & Hardscapes Association, 2006.

Modular Layout of Concrete Masonry

  • August 2018

INTRODUCTION

Although concrete masonry structures can be constructed using virtually any layout dimension, for maximum construction efficiency and economy, concrete masonry elements should be designed and constructed with modular coordination in mind. Modular coordination is the practice of laying out and dimensioning structures and elements to standard lengths and heights to accommodate modular-sized building materials. When modular coordination is not considered during the design phase, jobsite decisions must be made—often in haste and at a cost. This TEK provides recommendations for planning masonry construction to minimize cutting of masonry units or using nonstandard unit sizes.

When a project does require non-modular layout, further design and construction issues need to be addressed, including:

Placement of vertical reinforcement—In construction containing vertical reinforcing steel, the laying of units in other than running (half) bond or stack bond interrupts the vertical alignment of unit cells. As a result, reinforcement placement and adequate consolidation of grout becomes difficult, and partial grouting of walls is virtually impossible.

Interruption of bond pattern—In addition to the aesthetic impact a change in bond pattern can create, building codes often contain different design assumptions for masonry constructed in running bond versus other bond patterns. Walls incorporating more than a single bond pattern may present a unique design situation.

Locating control joints—In running bond, control joint construction can be accomplished using only full and half-size units. Similarly, stack bond construction only requires full-size units when control joints are properly spaced and detailed. However, with other bond patterns units may need to be cut if specially dimensioned units are not used or are not available.

MODULAR WALL ELEVATIONS

Standard concrete masonry modules are typically 8 in. (203 mm) vertically and horizontally, but may also include 4-in. (102 mm) modules for some applications. These modules provide overall design flexibility and coordination with other building products such as windows, doors, and other similar elements as shown in Figures 1 and 2.

MODULAR WALL OPENINGS

The rough opening dimensions illustrated in Figure 1 apply to the layout and construction of the masonry. To allow for fastening windows and doors to the masonry, however, the nominal heights and widths of these elements are slightly less.

For conventional construction methods, the widths of masonry openings for doors and windows should generally be 4 in. (102 mm) larger than the door or window width. This allows for 2 in. (51 mm) on each side of the opening for framing. The heights of masonry openings to accommodate windows are typically 8 in. (203 mm) greater than the window height. This opening size allows for 2 in. (51 mm) above and below for framing and 4 in. (102 mm) for installation of a sill at the bottom of the window. Masonry openings for doors are commonly either 2 or 4 in. (51 or 102 mm) greater than the door height, allowing for the door framing as well as the use of a standard sized door.

Thus, door and window widths of 28, 36, 44, and 52 in. (711, 914, 1,118 and 1,321 mm) (and so on in 8 in. (203 mm) increments) do not require the masonry to be cut. Modular window heights are any multiple of 8 in. (203 mm), with a masonry window opening 8 in. (203 mm) greater than the height of the window if a 4-in. (102 mm) sill will be used. Similarly, door heights 2 in. (51 mm) less than any even multiple of eight can be installed without the need for cutting the masonry. For the commonly available 84-in. (2,134 mm) high door, a 4-in. (102 mm) door buck can be placed at the top of the opening. In addition, precast lintels are available in some areas containing a 2 in. (51 mm) notch to accommodate 80-in. (2,032 mm) doors.

Hollow metal frames for doors should be ordered and delivered
for the masonry before the other door frames in the project are scheduled for delivery. For economy, the frames should be set before the walls are built. If the walls are built before the frame are set, additional costs are incurred to set special knock down door frames and attachments.

MODULAR WALL SECTIONS

For door and window openings, the module size for bond patterns and layout are nominal dimensions. Actual dimensions of concrete masonry units are typically 3/8 in. (9.5 mm) less than nominal dimensions, so that the 4 or 8-in. (102 or 203 mm) module is maintained with 3/8 in. (9.5 mm) mortar joints. Where mortar joint thicknesses differ from 3/8 in. (9.5 mm) (as may be specified for aesthetic purposes or with brick construction), special consideration is required to maintain modular design. Figure 3 illustrates this concept.

Typically, concrete masonry units have nominal face dimensions of (height by length) 8 by 16 in. (203 by 406 mm), and are available in nominal widths ranging from 4 in. to 16 in. (102 to 406 mm) in 2-in. (51 mm) increments. In addition to these standard sizes, other unit widths, heights and lengths may be available from concrete masonry producers. The designer should always check local availability of specialty units prior to design.

Incorporating brick into a project, either as a structural component or as a veneer, can present unique modular coordination considerations in addition to those present with single wythe construction. Brick most commonly have a nominal width of 4 in. (102 mm), length varying from 8 to 16 in. (203 to 406 mm) and height from 2 1/2 to 6 in. (64 to 152 mm). The specified dimensions of modular concrete and clay brick are typically 3 5/8 by 2 1/4 by 7 5/8 in. (92 by 57 by 194 mm), but may be available in a wide range of dimensions.

Because of their unique dimensions, concrete and clay brick are usually laid with bed joints that are slightly larger (or sometimes smaller depending upon the actual size of the brick) than the standard 3/8 in. (9.5 mm) mortar joint thickness. For example, common modular brick are laid with a 5/12 in. (11 mm) thick bed joint, thereby providing a constructed height of 2 2/3 in. (68 mm) for one brick and one mortar joint. (Note that a 5/12 in. (11 mm) thick bed joint is within allowable mortar joint tolerances (refs. 1, 2).) The result is that three courses of brick (including the mortar joints) equals one 8-in. (203 mm) high module, thereby maintaining modular coordination (see Figure 3).

MODULAR BUILDING LAYOUTS AND HORIZONTAL COURSING

In addition to wall elevations, sections and openings, the overall plan dimensions of a structure also need to be considered, especially when using units having nominal widths other than 8 in. (203 mm).

Ideally, the nominal plan dimensions of masonry structures should be evenly divisible by 8 in. (203 mm). This allows constructing each course of a wall using only full-length or half length units, which in turn reduces labor and material costs. In addition, maintaining an 8-in. (203 mm) module over the length of a wall facilitates the turning of corners, whereby half of the units from one wall interlock with half of the units from the intersecting wall. As an alternative to cutting units or changing building dimensions, corner block can be used if available. These units are specifically manufactured to turn corners without interrupting bond patterns. Concrete Masonry Corner Details,TEK 05-09A (ref. 4) contains a variety of alternatives for efficiently constructing corners.

METRIC COORDINATION

One additional consideration for some projects is the use of standard sized (inch-pound) masonry units in a metric project. Similar to inch pound units, masonry units produced to metric dimensions are 10 mm (13/32 in.) less than the nominal dimensions to provide for the mortar joints. Thus, the nominal metric equivalent of an 8 by 8 by 16 in. unit is 200 by 200 by 400 mm (190 by 190 by 390 mm net unit dimensions). Since inch-pound dimensioned concrete masonry units are approximately 2% larger than hard metric units, complications can arise if they are incorporated into a structure designed on a 100 mm (3.9 in.) metric module, or vice versa.

REFERENCES

  1. International Building Code. International Code Council,
    2003 and 2006.
  2. Specification for Masonry Structures, ACI 530.1-05/ASCE
    6-05/TMS 602-05. Reported by the Masonry Standards
    Joint Committee, 2005.
  3. Building Code Requirements for Masonry Structures, ACI
    530-05/ASCE 5-05/TMS 402-05. Reported by the Masonry
    Standards Joint Committee, 2005.
  4. Concrete Masonry Corner Details, TEK 05-09A, Concrete
    Masonry & Hardscapes Association, 2004.