14 CHAPTER Wall Systems

Objectives Describe different types of masonry wall systems. Explain the use of ties, flashing, weep holes, lintels, sills, jambs, and expansion joints in masonry wall systems. Explain the effects of moisture condensation in masonry walls and the methods used to resist condensation.

Objectives (Cont.) Describe construction procedures for thin brick veneer, including thin bed set, thick bed set, and precast panels. Explain the design, function, and construction of arches. Describe the joints used for movement in masonry. Understand the function of caps and copings. Install a retaining wall.

Masonry Walls Single-wythe or multiple-wythe Reinforced or unreinforced Provide excellent structural performance Easily maintained and attractive Energy efficient due to high thermal mass

Energy Codes Most energy codes specify U-values Heat flow through a building product based on difference between external and internal temperatures R-value is thermal resistance of heat loss through a building product R = 1/U

Solid Masonry Walls Loadbearing or nonloadbearing

6″ Masonry Walls with SCR brick Nominal thickness of 2 2/3″ produces 16″ in six courses Nominal 6″ wide and 12″ long

Four-Inch RBM Curtain and Panel Walls Exterior nonloadbearing walls Curtain walls Not wholly supported at each story Panel walls Supported at each story and self-supporting between stories Both types must be able to resist lateral forces

Design of Four-Inch Walls Partially reinforced Ladder- or truss-type reinforcement Drainage space on inside of wall Expansion joints Brick Industry Association

Hollow Masonry Walls Walls built using solid or hollow masonry units Separated to form inner and outer wall Two types Cavity walls Masonry bonded walls

Cavity Walls Widely used in low- and high-rise buildings Superior rain penetration resistance, thermal capabilities, sound transmission, and fire resistance Continuous air space 2″ to 3″ wide

Construction of Cavity Walls Exterior wythe Usually a nominal 4″ thick Solid or hollow brick Interior wythe 4″, 6″, or 8″ thick Brick, structural clay tile, or hollow or solid concrete masonry units

Cavity Air space has insulation value and can be filled with insulation material for added reduction of heat transfer Acts as a barrier to moisture Must be kept free of mortar droppings

Weep Holes Required at bottom of cavity wall Mortar opening creates void for moisture inside wall cavity to exit Located immediately above flashing

Flashing Thin, impervious material Usually made of metal Keeps any moisture that might collect in cavity away from inner wall Portland Cement Association

Insulation Rigid boards installed horizontally within air space against cavity face of backup wythe Granular fill is usually poured directly into cavity from bag or from hopper Brick Industry Association

Bonding Adjacent wythes tied together with corrosion-resistant 3/16″ diameter steel or metal ties Ties in alternate courses should be staggered End of ties should be bent to 90° angles Additional ties needed at openings

Flashing Diverts moisture out of cavity through weep holes Continuous flashing at bottom of cavity and wherever cavity is interrupted Over unprotected wall openings At window sills, parapet walls, and spandrels

Weep Holes Must be provided wherever flashing is used Located in joints of outer wythe immediately above flashing Spacing is approximately 2′ O.C maximum Weep holes using wick material should be 16″ O.C. maximum

Expansion Joints Movement of outer brick wythe is greater than that in solid or composite walls Expansion joints are recommended through outer wythe on each side of external corner where walls are 50′ or more in length

Hollow Masonry Bonded Walls Used as foundation and exterior loadbearing walls Not resistant to high moisture

Anchored Veneered Walls Brick and stone masonry facing veneer Veneer is attached, but not bonded to, backing Veneer does not act structurally with rest of wall

Anchored Brick Veneer Construction Nominal 3″ or 4″ thick exterior brick wythe is anchored to backing system with metal ties Clear air space between veneer and backing Wood frame, steel frame, concrete, or masonry backing system Facing of masonry units or other weather-resisting, noncombustible materials

Moisture Resistance Brick veneer wall assemblies are drainage-type walls that resist rain penetration Flashing and weep holes work with air space to resist moisture penetration Brick veneer with wood or metal frame backing is usually built with minimum 1″ air space

Brick Veneer Foundations Brick veneer on frame backing transfers weight of veneer to foundation Foundation brick ledge supporting brick veneer should be at least equal to total thickness of wall assembly Foundations must extend beneath frost line

Masonry Wall Ties Noncorrosive metal ties One tie for every 2 2/3 sq ft of wall area Maximum spacing of 24″ O.C. in either direction Nail must be located within 5/8″ of bend in tie Brick Industry Association

Wire Ties Must be embedded at least 5/8″ into bed joint from air space At least 5/8″ cover of mortar to exposed face Corrugated ties must penetrate to at least half the veneer thickness and have at least 5/8″ mortar cover

Flashing and Weep Holes Position above grade As close as possible to bottom of wall As close as possible above openings and below sills Weep holes should be in head joints directly above flashing Weep hole spacing No more than 24″ O.C. for holes in which mortar has been completely removed Maximum of 16″ O.C. for holes with wicking material

Lintels Brick veneer backed by wood or metal frame must be supported by lintels over openings Lintel materials Loose steel Stone Precast Concrete Cast stone Reinforced brick

Expansion Joints May be needed to allow for horizontal movement Required in brick veneer when there are Long walls Walls with returns Large openings

Composite Walls Two walls bonded together with masonry or wire ties Vertical collar joint (narrow space between facing and backup units) prevents passage of water

Building an 8″ Composite Wall First course of facing may be either headers or stretchers All facing courses are laid in a full mortar bed with head joints completely filled Facing headers are laid every seventh course Mortar extruded on backside should be cut flush with trowel before it hardens

Building an 8″ Composite Wall (Cont.) Wythes can be bonded across collar joint by parging backside of facing Portland Cement Association

12″ Composite Wall Facing header course is laid overlapping the header block Header block can be laid with recessed notch up or down

Resisting Moisture Condensation Water affects many building materials Condensation can be decreased through ventilation or dehumidification Mechanical devices and heat exchangers remove moisture-laden air

Reinforced Masonry Walls Steel reinforcement embedded in masonry units Structurally bonded by grout core Grouting techniques vary Full bed joints are used

Reinforcing Masonry Walls Maximum spacing of principal reinforcement should not exceed 48″ Primary use of steel reinforcement is in vertical members, lintels, and bond beams

Retaining Walls Reinforced masonry Two common designs Cantilever-Type Gravity Cantilever Cantilever-Type

Grouted Masonry Walls Single- or multi-wythe Similar to reinforced masonry walls but without reinforcements Grout is added to core in loadbearing masonry walls to provide added strength Other uses include filling bond beams and collar joint in two-wythe walls

Thin Brick Veneer Thin brick units approximately 1/2″ to 1″ thick Give appearance of conventional brick wall Most common face size has nominal dimensions of 2 2/3″ × 8″ Adhered veneer

Thin Brick Veneer Classifications Thin bed set Brick Industry Association

Thin Brick Veneer Classifications (Cont.) Thick bed set Brick Industry Association

Thin Brick Faced Precast Panels Forming table creates size and shape of wall panel Thin brick composes exterior face of panel, becomes bonded and embedded into panel when concrete mix is poured into form Constructed indoors and delivered to site Gage Brothers in Sioux Falls, SD

Chases and Recesses Horizontal or vertical spaces for plumbing, heating ducts, electrical wiring, etc. Chases are located inside of wall and are from 4″ to 12″ in width Recesses are limited to 1/3 of wall thickness

Lintels Structural member placed wall opening to support loads above Steel lintels should be supported on either side of opening for at least 4″ Reinforced concrete lintels should have a minimum bearing of at least 8″ at each end Longer lintels should have greater bearing surfaces at ends

Types of Lintels

Detailed Brick Masonry Lintel Brick masonry lintel with stirrups Brick Industry Association

Movement at Lintels Slight movement occurs at location of lintels Control joints are often located at ends Noncorroding metal plate is placed under ends where control joints occur to prevent uncontrolled cracking Full bed of mortar should be used over plate

Arches Masonry units span an opening by transferring vertical loads laterally to adjacent masonry units, and thus to abutments

Arch Terminology

Arch Classifications Arches are normally classified by: Curve of intrados Function, shape, style Arches are also classified as major and minor

Types of Arches Brick Industry Association

Types of Arches (Cont.) Brick Industry Association

Function of Arches Compression stresses are distributed through arch Weight is diverted to abutments Some may require steel reinforcements Brick Industry Association

Arch Design Odd number of units are used so keystone falls at center of crown Arch voussoirs are usually in radial orientation Different shapes and sizes of brick selected based on arch type, dimension, and desired appearance

Arch Spans Short spans Larger spans Tapered brick is recommended to avoid wide mortar joints at extrados Larger spans Requires less taper of the voussoirs Formed with rectangular brick and tapered mortar joints Mortar joint should be between 1/8″ and 3/4″

Arch Depth Dimension of arch at skewback that is perpendicular to arch axis, except in jack arches Depends on size and orientation of brick used Usually a multiple of the brick’s width Arch depth should increase with increasing arch span

Brick Masonry Arch Construction Two methods Special shapes and uniform joint thickness Units of uniform thickness with varying joint thickness All mortar joints must be completely filled

Centering for Arches Temporary shoring supports masonry Centering is usually made from wood

Jack Arch Construction Supported by steel if opening is over 2′ wide Steel must be bent to the camber Each joint should be same width as entire length of joint End joints are horizontal to radius of arch

Segmental Arch Construction Number of courses is determined by length of extrados Size of brick is determined by length of intrados Rise should be 1/6, 1/8, 1/10, or 1/12 of span

Window and Door Details Details are necessary for mason to plan ahead Relationships between head, jambs, and sill to masonry wall Brick Industry Association

Sills Channel water away from a building Single or multiple units Built in place or prefabricated Made of cut stone, brick, concrete, or metal

Joints for Movement in Masonry Volume changes in masonry material result in movement Joints allow for movement to occur and to prevent cracks Types Expansion joints Control joints Building expansion joints Construction joints

Expansion Joints Separate brick masonry into segments Prevent cracking due to changes in temperature, moisture expansion, elastic deformation, and creep Horizontal or vertical Located so as not to compromise structural integrity Brick Industry Association

Control Joint Creates a plane of weakness in concrete masonry to control location of cracks Vertical opening through concrete masonry wythe Must be located so structural integrity of concrete masonry is not affected

Building Expansion (Isolation) Joint Divides building into separate sections so stresses developed in one section do not affect integrity of remainder of structure Through-the-building joint allows adjoining parts of building to move freely from one another

Construction (Cold) Joint Used where masonry work is interrupted Mason terminates work at a vertical plane and then continues laying brick until that section of wall is complete Next section of wall begins at construction joint Located where least likely to impair strength

Bond Breaks Prevent cracks due to differences in expansion and contraction rates of materials Building paper or flashing separate two surfaces of masonry material Used between floor slabs and foundations Allow each element to move somewhat independently while providing support

Brick Masonry Soffits Enclose a building Provide attractive appearance Large soffits requires expensive forming and shoring Brick masonry soffit may be more efficient for small soffit area Usually reinforced and grouted

Stone Quoins Large square stones used at corners and around openings of building for ornamental purposes Height is odd number of brick courses Length is equal to one or more units used in wall

Garden Walls Freestanding structures Can be perforated Straight walls Pier and panel walls Serpentine walls Can be perforated

Straight Walls Masonry texture and color give character Thickness provides lateral stability against wind and impact loads Different copings

Pier and Panel Walls Series of relatively thin panels 4′ thick, braced by masonry piers Easy to build and economical Ideal for uneven terrain Foundations are required only for piers

Serpentine Walls Serpentine shape provides lateral strength so wall can be built 4″ thick Radius of curvature no more than twice height above grade Depth no less than 1/2 of height

Caps and Copings Channel water away from building Cap is covering within height of wall Coping is covering at top of wall Single or multiple units Tops slope in one direction or both directions Made of brick, precast or cast-in-place concrete, stone, metal, or terra cotta

Corbels Shelf or ledge formed by projecting successive courses of masonry out from face of wall Used to achieve a particular appearance or to provide structural support Horizontal projection should not exceed 1/2 thickness of wall or veneer Projection of single course should not exceed 1/2 of unit height or 1/3 of unit bed depth

Racking Masonry in which successive courses are stepped back from face of wall When racking back to achieve desired dimensions, make sure cores of units are not exposed

Segmental Retaining Walls (SRW) and Hardscape Constructed of high-strength concrete blocks or units made for dry stacking SRW blocks are used to build retaining walls Hardscape is intended for decorative purposes Anchor Wall Systems, Inc.

Retaining Wall Products Some have locking lip on lower back edge Prevent forward movement exerted by earth pressures Straight and beveled front units with uniform or tapered widths

Retaining Wall Installation Prior to construction, prepare a layout plan that considers topography, drainage patterns, soil conditions, and local code restrictions