ICC Subscriptions
 
SECTION R606 GENERAL MASONRY CONSTRUCTION

R606.1 General.


Masonry construction shall be designed and constructed in accordance with the provisions of this section or in accordance with the provisions of ACI 530/ASCE 5/TMS 402.

R606.1.1 Professional registration not required.


When the empirical design provisions of ACI 530/ASCE 5/TMS 402 Chapter 5 or the provisions of this section are used to design masonry, project drawings, typical details and specifications are not required to bear the seal of the architect or engineer responsible for design, unless otherwise required by the state law of the jurisdiction having authority.

R606.2 Thickness of masonry.


The nominal thickness of masonry walls shall conform to the requirements of Sections R606.2.1 through R606.2.4.

R606.2.1 Minimum thickness.


The minimum thickness of masonry bearing walls more than one story high shall be 8 inches (203 mm). Solid masonry walls of one-story dwellings and garages shall not be less than 6 inches (152 mm) in thickness when not greater than 9 feet (2743 mm) in height, provided that when gable construction is used, an additional 6 feet (1829 mm) is permitted to the peak of the gable. Masonry walls shall be laterally supported in either the horizontal or vertical direction at intervals as required by Section R606.8.

R606.2.2 Rubble stone masonry wall.


The minimum thickness of rough, random or coursed rubble stone masonry walls shall be 16 inches (406 mm).

R606.2.3 Change in thickness.


Where walls of masonry of hollow units or masonry bonded hollow walls are decreased in thickness, a course of solid masonry shall be constructed between the wall below and the thinner wall above, or special units or construction shall be used to transmit the loads from face shells or wythes above to those below.

R606.2.4 Parapet walls.


Unreinforced solid masonry parapet walls shall not be less than 8 inches (203 mm) in thickness and their height shall not exceed four time their thickness. Unreinforced hollow unit masonry parapet walls shall be not less that 8 inches (203 mm) in thickness, and their height shall not exceed three times their thickness. Masonry parapets in areas subject to wind loads of 30 pounds per square foot (1.44 kN/m2) located in Seismic Design Category D1, or D2, or on townhouses in Seismic Design Category C shall be reinforced in accordance with Section R606.11.

R606.3 Corbeled masonry.


Solid masonry units shall be used for corbeling. The maximum corbeled projection beyond the face of the wall shall not be more than one-half of the wall thickness or one-half the wythe thickness for hollow walls; the maximum projection of one unit shall not exceed one-half the height of the unit or one-third the thickness at right angles to the wall. The top course of corbels shall be a header course when the corbeled masonry is used to support floor or roof-framing members.

R606.3.1 Support conditions.


Cavity wall or masonry veneer construction may be supported on an 8-inch (203 mm) foundation wall, provided the 8-inch (203 mm) wall is corbeled with solid masonry to the width of the wall system above. The total horizontal projection of the corbel shall not exceed 2 inches (51 mm) with individual corbels projecting not more than one-third the thickness of the unit or one-half the height of the unit. The top course of all corbels shall be a header course.

R606.4 Allowable stresses.


Allowable compressive stresses in masonry shall not exceed the values prescribed in Table R606.4. In determining the stresses in masonry, the effects of all loads and conditions of loading and the influence of all forces affecting the design and strength of the several parts shall be taken into account.

R606.4.1 Combined units.


In walls or other structural members composed of different kinds or grades of units, materials or mortars, the maximum stress shall not exceed the allowable stress for the weakest of the combination of units, materials and mortars of which the member is composed. The net thickness of any facing unit that is used to resist stress shall not be less than 1.5 inches (38 mm).

R606.5 Piers.


The unsupported height of masonry piers shall not exceed ten times their least dimension. When structural clay tile or hollow concrete masonry units are used for isolated piers to support beams and girders, the cellular spaces shall be filled solidly with concrete or Type M or S mortar, except that unfilled hollow piers may be used if their unsupported height is not more than four times their least dimension. Where hollow masonry units are solidly filled with concrete or Type M, S or N mortar, the allowable compressive stress shall be permitted to be increased as provided in Table R606.4.

R606.5.1 Pier cap.


Hollow piers shall be capped with 4 inches (102 mm) of solid masonry or concrete or shall have cavities of the top course filled with concrete or grout or other approved methods.

TABLE R606.4 ALLOWABLE COMPRESSIVE STRESSES FOR EMPIRICAL DESIGN OF MASONRY


CONSTRUCTION; COMPRESSIVE STRENGTH OF UNIT, GROSS AREA
ALLOWABLE COMPRESSIVE STRESSESa GROSS CROSS-SECTIONAL AREAb
Type M or S mortar
Type N mortar
Solid masonry of brick and other solid units of clay or shale; sand-lime or concrete brick:
8,000 + psi
4,500 psi
2,500 psi
1,500 psi


350
225
160
115


300
200
140
100
Groutedc masonry, of clay or shale;
sand-lime or concrete:
4,500+ psi
2,500 psi
1,500 psi


225
160
115


200
140
100
Solid masonry of solid concrete
masonry units:
3,000+ psi
2,000 psi
1,200 psi


225
160
115


200
140
100
Masonry of hollow load-bearing units:
2,000+ psi
1,500 psi
1,000 psi
700 psi


140
115
75
60


120
100
70
55
Hollow walls (cavity or masonry
bondedd) solid units:
2,500+ psi
1,500 psi
Hollow units


160
115
75


140
100
70
Stone ashlar masonry:
Granite
Limestone or marble
Sandstone or cast stone

720
450
360

640
400
320
Rubble stone masonry:
Coarse, rough or random

120

100


For SI:   1 pound per square inch = 6.895 kPa.

a.   Linear interpolation shall be used for determining allowable stresses for masonry units having compressive strengths that are intermediate between those given in the table.

b.   Gross cross-sectional area shall be calculated on the actual rather than nominal dimensions.

c.   See Section R607.

d.   Where floor and roof loads are carried upon one wythe, the gross cross-sectional area is that of the wythe under load; if both wythes are loaded, the gross cross-sectional area is that of the wall minus the area of the cavity between the wythes. Walls bonded with metal ties shall be considered as cavity walls unless the collar joints are filled with mortar or grout.

R606.6 Chases.


Chases and recesses in masonry walls shall not be deeper than one-third the wall thickness, and the maximum length of a horizontal chase or horizontal projection shall not exceed 4 feet (1219 mm), and shall have at least 8 inches (203 mm) of masonry in back of the chases and recesses and between adjacent chases or recesses and the jambs of openings. Chases and recesses in masonry walls shall be designed and constructed so as not to reduce the required strength or required fire resistance of the wall and in no case shall a chase or recess be permitted within the required area of a pier. Masonry directly above chases or recesses wider than 12 inches (305 mm) shall be supported on noncombustible lintels.

R606.7 Stack bond.


In unreinforced masonry where masonry units are laid in stack bond, longitudinal reinforcement consisting of not less than two continuous wires each with a minimum aggregate cross-sectional area of 0.017 square inch (11 mm2) shall be provided in horizontal bed joints spaced not more than 16 inches (406 mm) on center vertically.

R606.8 Lateral support.


Masonry walls shall be laterally supported in either the horizontal or the vertical direction. The maximum spacing between lateral supports shall not exceed the distances in Table R606.8. Lateral support shall be provided by cross walls, pilasters, buttresses or structural frame members when the limiting distance is taken horizontally, or by floors or roofs when the limiting distance is taken vertically.

TABLE R606.8 SPACING OF LATERAL SUPPORT FOR MASONRY WALLS


CONSTRUCTION
MAXIMUM WALL LENGTH TO THICKNESS OR WALL HEIGHT TO THICKNESSa,b
Bearing walls:
Solid or solid grouted
All other

20
18
Nonbearing walls:
Exterior
Interior

18
36


For SI:   1 foot = 304.8 mm.

a.   Except for cavity walls and cantilevered walls, the thickness of a wall shall be its nominal thickness measured perpendicular to the face of the wall. For cavity walls, the thickness shall be determined as the sum of the nominal thicknesses of the individual wythes. For cantilever walls, except for parapets, the ratio of height to nominal thickness shall not exceed 6 for solid masonry, or 4 for hollow masonry. For parapets, see Section R606.2.4.

b.   An additional unsupported height of 6 feet is permitted for gable end walls.

R606.8.1 Horizontal lateral support.


Lateral support in the horizontal direction provided by intersecting masonry walls shall be provided by one of the methods in Section R606.8.1.1 or Section R606.8.1.2.

R606.8.1.1 Bonding pattern.


Fifty percent of the units at the intersection shall be laid in an overlapping masonry bonding pattern, with alternate units having a bearing of not less than 3 inches (76 mm) on the unit below.

R606.8.1.2 Metal reinforcement.


Interior nonload-bearing walls shall be anchored at their intersections, at vertical intervals of not more than 16 inches (406 mm) with joint reinforcement of at least 9 gage, or ¼ inch (6.4 mm) galvanized mesh hardware cloth. Intersecting masonry walls, other than interior nonloadbearing walls, shall be anchored at vertical intervals of not more than 8 inches (203 mm) with joint reinforcement of at least 9 gage and shall extend at least 30 inches (762 mm) in each direction at the intersection. Other metal ties, joint reinforcement or anchors, if used, shall be spaced to provide equivalent area of anchorage to that required by this section.

R606.8.2 Vertical lateral support.


Vertical lateral support of masonry walls in Seismic Design Category A, B or C shall be provided in accordance with one of the methods in Section R606.8.2.1 or Section R606.8.2.2.

R606.8.2.1 Roof structures.


Masonry walls shall be anchored to roof structures with metal strap anchors spaced in accordance with the manufacturer’s instructions, ½-inch (12.7 mm) bolts spaced not more than 6 feet (1829 mm) on center, or other approved anchors. Anchors shall be embedded at least 16 inches (406 mm) into the masonry, or be hooked or welded to bond beam reinforcement placed not less than 6 inches (152 mm) from the top of the wall.

R606.8.2.2 Floor diaphragms.


Masonry walls shall be anchored to floor diaphragm framing by metal strap anchors spaced in accordance with the manufacturer’s instructions, ½-inch-diameter (12.7 mm) bolts spaced at intervals not to exceed 6 feet (1829 mm) and installed as shown in Figure R606.10(1), or by other approved methods.

R606.9 Lintels.


Masonry over openings shall be supported by steel lintels, reinforced concrete or masonry lintels or masonry arches, designed to support load imposed.

R606.10 Anchorage.


Masonry walls shall be anchored to floor and roof systems in accordance with the details shown in Figure R606.10(1), R606.10(2) or R606.10(3). Footings may be considered as points of lateral support.

FIGURE R606.10(1) ANCHORAGE REQUIREMENTS FOR MASONRY WALLS LOCATED IN SEISMIC DESIGN CATEGORY A, B OR C AND WHERE WIND LOADS ARE LESS THAN 30 PSF











NOTE: Where bolts are located in hollow masonry, the cells in the courses receiving the bolt shall be grouted solid.

For SI:   1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kN/m2.

FIGURE R606.10(2) REQUIREMENTS FOR REINFORCED GROUTED MASONRY CONSTRUCTION IN SEISMIC DESIGN CATEGORY C











For SI:   1 inch = 25.4 mm, 1 foot = 304.8 mm.

FIGURE R606.10(3) REQUIREMENTS FOR REINFORCED MASONRY CONSTRUCTION IN SEISMIC DESIGN CATEGORY D1 OR D2











NOTE: A full bed joint must be provided. All cells containing vertical bars are to be filled to the top of wall and provide inspection opening as shown on detail “A.” Horizontal bars are to be laid as shown on detail “B.” Lintel bars are to be laid as shown on Section C.

For SI:   1 inch = 25.4 mm, 1 foot = 304.8 mm.

R606.11 Seismic requirements.


The seismic requirements of this section shall apply to the design of masonry and the construction of masonry building elements located in Seismic Design Category D1 or D2. Townhouses in Seismic Design Category C shall comply with the requirements in Section R606.11.2. These requirements shall not apply to glass unit masonry conforming to Section R610 or masonry veneer conforming to Section R703.7.

R606.11.1 General.


Masonry structures and masonry elements shall comply with the requirements of Sections R606.11.2 through R606.11.4 based on the seismic design category established in Table R301.2(1). Masonry structures and masonry elements shall comply with the requirements of Section R606.11 and Figures R606.10(1), R606.10(2) and R606.10(3) or shall be designed in accordance with ACI 530/ASCE 5/TMS 402.

R606.11.1.1 Floor and roof diaphragm construction.


Floor and roof diaphragms shall be constructed of structural wood sheathing panels, attached to wood framing in accordance with Table R602.3(1) or to cold-formed steel floor framing in accordance with Table R505.3.1(2) or to cold-formed steel roof framing in accordance with Table R804.3. Additionally, sheathing panel edges perpendicular to framing members shall be backed by blocking, and sheathing shall be connected to the blocking with fasteners at the edge spacing. For Seismic Design Categories C, D1 and D2, where the width-to-thickness dimension of the diaphragm exceeds 2-to-1, edge spacing of fasteners shall be 4 inches (102 mm) on center.

R606.11.2 Seismic Design Category C.


Townhouses located in Seismic Design Category C shall comply with the requirements of this section.

R606.11.2.1 Design of elements not part of the lateral force-resisting system.


R606.11.2.1.1 Load-bearing frames or columns.


Elements not part of the lateral-force-resisting system shall be analyzed as to their effect on the response of the system. Such frames or columns shall be adequate for vertical load carrying capacity and induced moment due to the design story drift.

R606.11.2.1.2 Masonry partition walls.


Masonry partition walls, masonry screen walls and other masonry elements that are not designed to resist vertical or lateral loads, other than those induced by their own weight, shall be isolated from the structure so that vertical and lateral forces are not imparted to these elements. Isolation joints and connectors between these elements and the structure shall be designed to accommodate the design story drift.

R606.11.2.1.3 Reinforcement requirements for masonry elements.


Masonry elements listed in Section R606.11.2.1.2 shall be reinforced in either the horizontal or vertical direction as shown in Figure R606.10(2) and in accordance with the following:

1.   Horizontal reinforcement. Horizontal joint reinforcement shall consist of at least two longitudinal W1.7 wires spaced not more than 16 inches (406 mm) for walls greater than 4 inches (102 mm) in width and at least one longitudinal W1.7 wire spaced not more than 16 inches (406 mm) for walls not exceeding 4 inches (102 mm) in width; or at least one No. 4 bar spaced not more than 48 inches (1219 mm). Where two longitudinal wires of joint reinforcement are used, the space between these wires shall be the widest that the mortar joint will accommodate. Horizontal reinforcement shall be provided within 16 inches (406 mm) of the top and bottom of these masonry elements.

2.   Vertical reinforcement. Vertical reinforcement shall consist of at least one No. 4 bar spaced not more than 48 inches (1219 mm). Vertical reinforcement shall be located within 16 inches (406 mm) of the ends of masonry walls.

R606.11.2.2 Design of elements part of the lateral-force-resisting system.


R606.11.2.2.1 Connections to masonry shear walls.


Connectors shall be provided to transfer forces between masonry walls and horizontal elements in accordance with the requirements of Section 2.1.8 of ACI 530/ASCE 5/TMS 402. Connectors shall be designed to transfer horizontal design forces acting either perpendicular or parallel to the wall, but not less than 200 pounds per linear foot (2919 N/m) of wall. The maximum spacing between connectors shall be 4 feet (1219 mm). Such anchorage mechanisms shall not induce tension stresses perpendicular to grain in ledgers or nailers.

R606.11.2.2.2 Connections to masonry columns.


Connectors shall be provided to transfer forces between masonry columns and horizontal elements in accordance with the requirements of Section 2.1.8 of ACI 530/ASCE 5/TMS 402. Where anchor bolts are used to connect horizontal elements to the tops of columns, anchor bolts shall be placed within lateral ties. Lateral ties shall enclose both the vertical bars in the column and the anchor bolts. There shall be a minimum of two No. 4 lateral ties provided in the top 5 inches (127 mm) of the column.

R606.11.2.2.3 Minimum reinforcement requirements for masonry shear walls.


Vertical reinforcement of at least one No. 4 bar shall be provided at corners, within 16 inches (406 mm) of each side of openings, within 8 inches (203 mm) of each side of movement joints, within 8 inches (203 mm) of the ends of walls, and at a maximum spacing of 10 feet (3048 mm).

Horizontal joint reinforcement shall consist of at least two wires of W1.7 spaced not more than 16 inches (406 mm); or bond beam reinforcement shall be provided of at least one No. 4 bar spaced not more than 10 feet (3048 mm). Horizontal reinforcement shall also be provided at the bottom and top of wall openings and shall extend not less than 24 inches (610 mm) nor less than 40 bar diameters past the opening; continuously at structurally connected roof and floor levels; and within 16 inches (406 mm) of the top of walls.

R606.11.3 Seismic Design Category D1.


All structures in Seismic Design Category D1 shall comply with the requirements of Seismic Design Category C and to the additional requirements of this section.

R606.11.3.1 Design requirements.


Masonry elements other than those covered by Section R606.11.2.1.2 shall be designed in accordance with the requirements of Chapter 1 and Sections 2.1 and 2.3 of ACI 530/ASCE 5/TMS 402 and shall meet the minimum reinforcement requirements contained in Sections R606.11.3.2 and R606.11.3.2.1.

Exception:
Masonry walls limited to one story in height and 9 feet (2743 mm) between lateral supports need not be designed provided they comply with the minimum reinforcement requirements of Sections R606.11.3.2 and R606.11.3.2.1.

R606.11.3.2 Minimum reinforcement requirements for masonry walls.


Masonry walls other than those covered by Section R606.11.2.1.3 shall be reinforced in both the vertical and horizontal direction. The sum of the cross-sectional area of horizontal and vertical reinforcement shall be at least 0.002 times the gross cross-sectional area of the wall, and the minimum cross-sectional area in each direction shall be not less than 0.0007 times the gross cross-sectional area of the wall. Reinforcement shall be uniformly distributed. Table R606.11.3.2 provides the minimum reinforcing bar sizes required for varying thicknesses of masonry walls. The maximum spacing of reinforcement shall be 48 inches (1219 mm) provided that the walls are solid grouted and constructed of hollow open-end units, hollow units laid with full head joints or two wythe of solid units. The maximum spacing of reinforcement shall be 24 inches (610 mm) for all other masonry.

TABLE R606.11.3.2 MINIMUM DISTRIBUTED WALL REINFORCEMENT FOR BUILDING ASSIGNED TO SEISMIC DESIGN CATEGORY D1


NOMINAL WALL THICKNESS
(inches)
MINIMUM SUM OF THE VERTICAL AND HORIZONTAL REINFORCEMENT AREASa
(inches per square foot)
MINIMUM REINFORCEMENT AS DISTRIBUTED IN BOTH HORIZONTAL AND VERTICAL DIRECTIONSb
(inches per square foot)
MINIMUM BAR SIZE FOR REINFORCEMENT SPACED AT 48 INCHES
6
8
10
12
0.135
0.183
0.231
0.279
0.047
0.064
0.081
0.098
#4
#5
#6
#6


For SI:   1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 square inch per foot = 2.12 mm2/mm.

a.   Based on the minimum reinforcing ration of 0.002 times the gross cross-sectional area of the wall.

b.   Based on the minimum reinforcing ration each direction of 0.0007 times the gross cross-sectional area of the wall.

R606.11.3.2.1 Shear wall reinforcement requirements.


The maximum spacing of vertical and horizontal reinforcement shall be the smaller of one-third the length of the shear wall, one-third the height of the shear wall, or 48 inches (1219 mm). The minimum cross-sectional area of vertical reinforcement shall be one-third of the required shear reinforcement. Shear reinforcement shall be anchored around vertical reinforcing bars with a standard hook.

R606.11.3.3 Minimum reinforcement for masonry columns.


Lateral ties in masonry columns shall be spaced not more than 8 inches (203 mm) on center and shall be at least 3/8 inch (9.5 mm) diameter. Lateral ties shall be embedded in grout.

R606.11.3.4 Material restrictions.


Type N mortar or masonry cement shall not be used as part of the lateral-force-resisting system.

R606.11.3.5 Lateral tie anchorage.


Standard hooks for lateral tie anchorage shall be either a 135-degree (2.4 rad) standard hook or a 180-degree (3.2 rad) standard hook.

R606.11.4 Seismic Design Category D2.


All structures in Seismic Design Category D2 shall comply with the requirements of Seismic Design Category D1 and to the additional requirements of this section.

R606.11.4.1 Design of elements not part of the -lateral-force-resisting system.


Stack bond masonry that is not part of the lateral-force-resisting system shall have a horizontal cross-sectional area of reinforcement of at least 0.0015 times the gross cross-sectional area of masonry. Table R606.11.4.1 provides minimum reinforcing bar sizes for masonry walls. The maximum spacing of horizontal reinforcement shall be 24 inches (610 mm). These elements shall be solidly grouted and shall be constructed of hollow open-end units or two wythes of solid units.

TABLE R606.11.4.1 MINIMUM REINFORCING FOR STACKED BONDED MASONRY WALLS IN SEISMIC DESIGN CATEGORY D2


NOMINAL WALL THICKNESS
(inches)
MINIMUM BAR SIZE
SPACED AT 24 INCHES

6
8
10
12
#4
#5
#5
#6


For SI:   1 inch = 25.4 mm.

R606.11.4.2 Design of elements part of the -lateral-force-resisting system.


Stack bond masonry that is part of the lateral-force-resisting system shall have a horizontal cross-sectional area of reinforcement of at least 0.0025 times the gross cross-sectional area of masonry. Table R606.11.4.2 provides minimum reinforcing bar sizes for masonry walls. The maximum spacing of horizontal reinforcement shall be 16 inches (406 mm). These elements shall be solidly grouted and shall be constructed of hollow open-end units or two wythes of solid units.

TABLE R606.11.4.2 MINIMUM REINFORCING FOR STACKED BONDED MASONRY WALLS IN SEISMIC DESIGN CATEGORY D2


NOMINAL WALL THICKNESS
(inches)
MINIMUM BAR SIZE
SPACED AT 16 INCHES

6
8
10
12
#4
#5
#5
#6


For SI:   1 inch = 25.4 mm.

R606.12 Protection for reinforcement.


All bars shall be completely embedded in mortar or grout. Joint reinforcement embedded in horizontal mortar joints shall not have less than 5/8-inch (15.9 mm) mortar coverage from the exposed face. All other reinforcement shall have a minimum coverage of one bar diameter over all bars, but not less than ¾ inch (19.1 mm), except where exposed to weather or soil, in which case the minimum coverage shall be 2 inches (51 mm).

R606.13 Beam supports.


Beams, girders or other concentrated loads supported by a wall or column shall have a bearing of at least 3 inches (76 mm) in length measured parallel to the beam upon solid masonry not less than 4 inches (102 mm) in thickness, or upon a metal bearing plate of adequate design and dimensions to distribute the load safely, or upon a continuous reinforced masonry member projecting not less than 4 inches (102 mm) from the face of the wall.

R606.13.1 Joist bearing.


Joists shall have a bearing of not less than 1½ inches (38 mm), except as provided in Section R606.13, and shall be supported in accordance with Figure R606.10(1).

R606.14 Metal accessories.


Joint reinforcement, anchors, ties and wire fabric shall conform to the following: ASTM A 82 for wire anchors and ties; ASTM A 36 for plate, headed and bent-bar anchors; ASTM A 510 for corrugated sheet metal anchors and ties; ASTM A 951 for joint reinforcement; ASTM B 227 for copper-clad steel wire ties; or ASTM A 167 for stainless steel hardware.

R606.14.1 Corrosion protection.


Minimum corrosion protection of joint reinforcement, anchor ties and wire fabric for use in masonry wall construction shall conform to Table R606.14.1.

TABLE R606.14.1 MINIMUM CORROSION PROTECTION


MASONRY METAL ACCESSORY
STANDARD
Joint reinforcement, interior walls
ASTM A 641, Class 1
Wire ties or anchors in exterior walls completely embedded in mortar or grout
ASTM A 641, Class 3
Wire ties or anchors in exterior walls not completely embedded in mortar or grout
ASTM A 153, Class B-2
Joint reinforcement in exterior walls or interior walls exposed to moist environment
ASTM A 153, Class B-2
Sheet metal ties or anchors exposed to weather
ASTM A 153, Class B-2
Sheet metal ties or anchors completely embedded in mortar or grout
ASTM A 525, Class G-60
Stainless steel hardware for any exposure
ASTM A 167, Type 304