SECTION 403 – MASONRY
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ICC 600
SECTION 403 – MASONRY 403.1 General Requirements.
Masonry walls constructed in accordance with this standard shall comply with the requirements of this section. Alternatively, concrete masonry walls shall be permitted to comply with TMS 403 Direct Design Handbook for Masonry Structures or TMS 402 Building Code Requirements for Masonry Structures. The minimum thickness of exterior masonry walls shall be 8 inches (203 mm). The eave to peak height of roofs for masonry buildings shall not exceed 16 ft. (4.8 m). Interior light frame walls shall be designed and detailed in accordance with Chapter 5. |
GUIDE COMMENTARY
SECTION 403 – MASONRY 403.1 General Requirements.
The design standards TMS 402 and TMS 403 define engineered alternatives to the prescriptive designs offered by ICC 600. As many assumptions needed to be made in the development of the requirements and tables of ICC 600, some of which may produce conservative results, a full engineered analysis may offer more economy on specific projects. As an alternative, there are software packages that incorporate the engineered methods of TMS 402 and TMS 403 that offer streamlined design solutions. The Direct Design Software published by the National Concrete Masonry Association is also a very useful tool for analyzing masonry structures for all code required loading conditions. https://ncma.org/software/direct-design/ Similarly, determination of the wind speeds for use with provisions and tables of ICC 600 can be accomplished by interpolating Figure 301(1). Alternatively, an easier and more accurate way to determine wind speed for a project location is by entering the address of the site into the link below, which will provide an exact wind speed in accordance with ASCE 7-16. These wind speeds should be verified with local jurisdictions, which may have modifications to these standard wind speed maps. https://hazards.atcouncil.org/ |
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403.2 Materials for masonry.
403.2.1 Masonry units.
403.2.2 Mortar.
Mortar shall be either Type M or S in accordance with ASTM C270. |
403.2 Materials for masonry.
4.4.1 Masonry units. Additional information on concrete masonry units meeting the requirements of ASTM C90 is available at the following links: https://ncma.org/resource/astm-specifications-for-concrete-masonry-units/ https://ncma.org/resource/typical-sizes-and-shapes-of-concrete-masonry-units/ 403.2.2 Mortar.
The combination of Type M or S mortar in conjunction with using concrete masonry units meeting the requirement of ASTM C90 produces a minimum net area compressive strength for the masonry assembly of 2,000 psi. This specified masonry compressive strength (f’m) is used in the development of the prescriptive designs, details, and tabulated values provided in ICC 600. Additional information on masonry mortars is available at the following link: https://ncma.org/resource/mortars-for-concrete-masonry/ |
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403.2.3 Metal accessories.
Reinforcing bars, joint reinforcement, anchors, ties, wires, plates, and related metal accessories shall comply with the requirements of TMS 602. Reinforcing bars shall be Grade 60. |
403.2.3 Metal accessories.
Additional information on metal accessories permitted to be used in concrete masonry construction is available at the following links: https://ncma.org/resource/anchors-and-ties-for-masonry/ https://ncma.org/resource/joint-reinforcement-for-concrete-masonry/ https://ncma.org/resource/steel-reinforcement-for-concrete-masonry/ |
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403.2.3.1 Size of reinforcement.
Reinforcing steel shall be No. 4, 5, 6 or 7 for bond beam reinforcement and No. 4 or No. 5 bars for wall vertical reinforcement, unless noted otherwise. |
403.2.3.1 Size of reinforcement.
No. 4, 5, 6, or 7 bars in bond beams and No. 4 or 5 bars vertical in walls are permitted. Where two No. 4 bars are required in the same cell, one No. 6 bar may be substituted under certain conditions per the footnotes of Table 403(2) and one No. 7 bar substituted where two No. 5 bars are required in the same cell per the footnotes of Table 403(5). The footnotes of the same tables allow a similar substitution of one No. 6 bar for two No. 4 bars and one No. 7 bar for two No. 5 bars in bond beams. This applies to bars located within the same cell or course of masonry. Bars required separately in the top and bottom of a lintel or in different cells are not permitted to be combined into one. |
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FIGURE GC-403.2.3.3 BENDING LIMITS OF REINFORCEMENT FOR ALIGNMENT
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403.3 Masonry construction.
403.3.1 General. Masonry construction shall be in accordance with TMS 602. |
403.3 Masonry construction.
403.3.1 General. This chapter refers to concrete masonry buildings of the configurations permitted In Chapter 1 of ICC 600. For buildings with the first story walls concrete masonry and a single story of light frame above, refer to Chapter 6 of ICC 600. |
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403.3.2 Cleanout for grouted cells.
Cleanout openings shall be provided for cells containing spliced reinforcement where the grout pour exceeds 64 inches (1626 mm) in height. Exception: Cleanout openings are not required in cells containing vertical reinforcement where footing dowels are not required by Section 402.3.1, provided vertical wall reinforcement from above reaches within 12 inches (305 mm) of the floor slab below. |
403.3.2 Grouting and Cleanouts.
Cleanouts are not required for grout pour heights of 64 inches or less (normally referred to as low lift grouting) because the buildup of mortar droppings inside the cell generally is not sufficient to interfere with the encasement of the reinforcement in grout. For grout pour heights greater than 64 inches (normally referred to as high lift grouting), cleanouts are required at splices at foundation and floor levels. The exception in ICC 600 indicates that cleanouts are not required in cells containing reinforcement where no footing dowels are required and that the reinforcement reaches within 12 inches of the floor slab below (see Section 402.3.1). This exception is permitted because the weight provided by the foundation is not required for uplift resistance. Additional information on grouting concrete masonry construction is available at the following link: https://ncma.org/resource/grouting-concrete-masonry-walls/ |
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403.3. 3 Bottom course opening.
Where cleanout openings are required, an opening shall be provided in the bottom course of the masonry cell to be filled. Cleanout openings shall have a minimum opening dimension of 3 inches (76 mm). |
403.3. 3 Bottom course opening.
In cases where adjacent vertical cells are to be grouted, TMS 602 allows for a single cleanout to be used, provided that cleanout gives access to both cells for mortar dropping removal. |
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403.4 Reinforcing.
403.4.1 General. Masonry walls shall be reinforced in accordance with Figure 403(4) and the following: 403.4.1.1 A minimum of one bar of the size used for vertical wall reinforcement shall be provided on each side of openings wider than 6 feet (1829 mm). Where vertical reinforcement is interrupted by an opening, a minimum of one-half of the equivalent area of reinforcement interrupted by the opening shall be placed within 16 inches (406 mm) of each side of the opening. 403.4.1.2 The maximum spacing of vertical wall reinforcement shall not exceed 10 ft (3 m). The maximum spacing of the vertical reinforcement shall be the same for each story.
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403.4 Reinforcing.
403.4.1 General. See ICC 600 Figure 403(4) for a summary of wall reinforcement requirements. 403.4.1.1 See ICC Figure 403(4) for an example of these prescriptive reinforcement requirements. 403.4.1.2 TMS 402 limits the maximum spacing of reinforcement in reinforced masonry to 10 feet. Requiring the same spacing of vertical reinforcement in each story level is to provide load path continuity through the alignment of the vertical reinforcement from one story to the next. This means that the most stringent spacing in each story would govern as the spacing for all stories. However, ICC 600 makes provision where vertical reinforcement may be offset in certain cases, if needed, as shown in Figure 403(6).
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403.4.1.3 A vertical reinforcing bar of the size used for vertical wall reinforcement shall be provided in each corner, including interior corners and corners created by changes in wall direction or offsetting of walls such as at projected bays and inset porches.
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403.4.1.3 No commentary.
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403.4.1.4 Vertical wall reinforcement shall be lap spliced to foundation dowels at locations specified in Section 402.3. Lap splices shall be in accordance with Section 403.2.3.2.
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403.4.1.4 Bars in lap splices do not need to be in contact with each other. In accordance with TMS 402, they may be spaced as far apart as one-fifth the required length of the lap but not more than 8 inches. The bars even may be placed in separate, adjacent cells as long as both cells are grouted for the full length of the splice. Splices are not required to be tied; however tying is often used as a means to hold bars in place.
Additional information on lapping and aligning reinforcing bars in masonry construction is available at the following link: https://ncma.org/resource/grouting-concrete-masonry-walls/ |
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403.4.1.5 A vertical reinforcing bar of the size used for vertical wall reinforcement shall be provided at both ends of each shear segment.
403.4.1.6 Vertical wall reinforcement shall be terminated in the bond beam at the roof level with a standard hook. The hook may be formed by bending the vertical wall reinforcement or by lap splicing to a standard hook. The hook shall extend to the uppermost horizontal reinforcement of the bond beam and shall be embedded a minimum of 6 inches (152 mm) into the bond beam in accordance with Figure 403(5). In multistory construction, vertical wall reinforcement shall extend through bond beams and shall be continuous with the vertical wall reinforcement of the wall above in accordance with Figure 403(6).
Exceptions:
403.4.1.7 Horizontal reinforcement shall be continuous around corners in accordance with Figure 403(3). Where more than one bar is required, only one bar need be continuous around corners.
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403.4.1.5 Providing a vertical reinforcing bar at both ends of a shear wall segment resists overturning forces generated from lateral loads.
403.4.1.6 Note the minimum embedment requirements for dowels into footings and into bond beams in Section 402.3.2. The main reinforcing bar may be fashioned with a hook or a hooked dowel bar may be lap spliced to it. A standard 90-degree hook is commonly used at the roofline where the spacing of the vertical reinforcement is sufficiently large to preclude congestion in the bond beam. Otherwise, a 180-degree hook could be considered.
Additional information for bending and hooking reinforcement in masonry construction is available at the following link: https://ncma.org/resource/splices-development-standard-hooks-2009-2012-ibc/ In multistory construction, wall vertical reinforcement must be continuous from the foundation to the roof. Exceptions: If there is more than one bar in a cell, only one bar needs to be continuous through the bond beam at the elevated floor level, provided only a single bar is required in the upper story. Also, vertical reinforcement between stories may be offset as shown in Figure 403(6), if needed. Note that reinforcement at ends of shear segments may not be offset per Section 403.5.5 of ICC 600. 403.4.1.7 Note that vertical reinforcement at the corners also terminates into the bond beam at the roof level with a standard hook resulting in additional congestion at this location. It is prudent for the bond beam splices to be offset slightly from the corner to avoid this congestion.
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403.4.1.8 Reinforced masonry bond beams shall be provided at the top of the wall and at each elevated story level. The minimum nominal bond beam depth shall be 8 inches (203 mm). The maximum specified depth of horizontal bond beam reinforcement shall not exceed 2.75 in. (70 mm) from the top of the unit.
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403.4.1.8 Reinforcement in bond beams must be placed near the top of bond beam to resist uplift forces generated at the roofline. Bond beam units are produced with reduced web heights to provide for the proper placement of horizontal reinforcement. If manufactured bond beam units are not available, the units may be notched manually. Notches in the face shell of units at corners normally are done manually.
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403.4.1.9 Where girders or girder trusses bearing on masonry, additional vertical reinforcement shall be provided to resist uplift. This reinforcement shall be lap spliced to the bar of the same size terminating in both the bond beam and in the footing with a standard hook. The maximum design uplift shall not exceed 10,800 lb (48,040 N) for one No. 4 (M#13) reinforcing bar; 16,740 lb (74,460 N) for one No. 5 (M#16) reinforcing bar; 23,760 lb (105,690 N) for one No. 6 (M#19) reinforcing bar; or 32,400 lb (144,120 N) for one No. 7 (M#22) reinforcing bar.
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403.4.1.9 Girders and girder trusses are points of uplift and bearing concentration. Uplift capacities of various reinforcement sizes are given in this section. The loads stipulated here are ultimate loads. To convert to allowable stress design loads, multiply values provided by 0.6.
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403.4.1.10 Unless otherwise noted, reinforcing requirements are not additive as a single reinforcing bar may fulfill more than one requirement. In all cases, the most stringent requirement shall apply.
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403.4.1.10 A single bar can accommodate loads of multiple origins. For example, a reinforcing bar may resist flexural tension due to out-of-plane loads concurrently with vertical uplift tension. In all cases the bar should be sized according to the most stringent individual load considered, unless otherwise stipulated.
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403.4.2 Vertical wall reinforcing.
Masonry walls shall be vertically reinforced in accordance with Table 403(2) or Table 403(5). |
403.4.2 Vertical wall reinforcing.
Table 403(2) is calculated using No. 4 bars and Table 403(5) is calculated using No. 5 bars. The No. 4 bar tables and the No. 5 bar tables were separated for clarity. |
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403.5 Exterior shear walls.
Exterior shear walls shall comply with the requirements of Section 403.5.1 through 403.5.6. |
403.5 Exterior shear walls.
Shear walls are walls that resist the shear loads from wind loads on perpendicular walls. These horizontal loads are normally referred to as in-plane loads. The shear segments (or shear wall segments) are the portions of the shear wall that are actually designed to resist the shear (in-plane) loads. Figure 403(7) of ICC 600 provides illustrated examples of shear walls and shear wall segments. |
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403.5.1 Shear segments.
Required shear segment lengths shall be determined from Tables 403(3) and 403(4) or Tables 403(6) and 403(7) as required in accordance with Figure 403(7). The required shear segment length shall apply to each line of resistance in a building. When using Table 403(3) or Table 403(6) and the building contains one or more interior shear walls, the distance to the first interior shear wall shall be used in determining the length-to-width ratio for use in the table. The building length used shall be the distance between adjacent shear walls. The distance between adjacent shear walls shall not exceed 2 times the building width. The minimum shear segment length shall be 2 feet (610 mm). |
403.5.1 Shear segments.
For design, interior shear walls collect loads from two sides of the structure, and therefore may require more reinforcement or longer lengths than exterior shear walls. The maximum distance between two parallel shear walls is 2 times the building width. This is due to wood roof and floor diaphragm capacity and deflection limitations. Shear segments (portions of a shear wall that are designed to resist the shear) are 2 feet minimum. Any wall length less than 2 feet is considered too flexible to provide effective shear resistance. |
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403.5.2 Multiple shear segments.
Shear segment lengths shown in Tables 403(3), 403(4), 403(6), and 403(7) are for a single shear segment of the specified length. Shear walls may be divided into multiple smaller segments if:
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403.5.2 Multiple shear segments.
When multiple shear segments in a shear wall are used, the longest shear segment cannot be any longer than 4 times the shortest because longer shear segments are stiffer and take a higher percentage of the load than the shorter, more flexible segments. The longest shear segment would then automatically be the longest shear segment in the wall. No shear segments less than one-fourth the length of the longest segment can be included as counting toward the minimum cumulative shear segment length required by the tables. This would include shear segments provided for other reasons such as the minimum required 2-foot shear segments at corners or a minimum required 2-foot shear segment inserted to maintain the maximum clear space of openings. Note that the cumulative shear segment length determined from these tables is minimum only. More length may be required as the maximum nominal clear distance between shear segments is 18 ft. See Section 403.5.4 and Figure 403(4) of ICC 600. |
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403.5.3 Openings.
Shear wall piers and shear segments shall not contain openings, other than incidental utility penetrations, with a maximum horizontal or vertical dimension of 5 inches (127 mm) for piers and 12 inches (305 mm) for portions of shear segments above and below piers. The total area of openings in any single shear segment shall not exceed 144 square inches (929 cm2). |
403.5.3 Openings.
Only small utility-type openings of the size indicated here are allowed in shear segments. If the opening is located in a shear wall pier (the portion between openings) the opening size allowed is even less. See Figure 403(7). |
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403.5.4 Arrangement.
The maximum clear distance between shear segments shall be 18 feet (5486 mm). A minimum 2-foot (610 mm) shear segment shall be located at each building corner where the wall length is greater than 4 feet (1220 mm) in accordance with Figure 403(4). |
403.5.4 Arrangement.
A 2-foot minimum shear segment is required on each side of each corner in walls that are 4 feet long or longer. This means that there can be no windows or doorways within 2 feet of a corner when designing in accordance with ICC 600. The maximum distance between shear segments is 18 feet to keep from overloading the bond beam, which acts as a drag strut over openings. Therefore, window and doorway openings cannot exceed 18 feet clear. |
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403.5.5 Multistory shear walls.
Shear segments in an upper story shall be located directly over shear segments in the story below and reinforcement at the ends of the shear segment shall be continuous from the bond beam of the upper story through the story below. |
403.5.5 Multistory shear walls.
Shear segments in upper stories must be placed directly over shear segments below. The reinforcement at the end of the shear segment in the upper story must be continuous through the shear segment below, or in the case of the bottom story, all the way to the foundation as illustrated in Figure GC-403.5.5. This means no portion of a shear segment is allowed to extend over an opening below. This generally is not a problem because shear segments in lower stories are larger than the ones in stories above. If reinforcement in the wall below is already there for some other requirement, that bar can satisfy both needs. However, if the reinforcement required in the lower story is greater than that for the story above, the greater amount only needs to be provided in the lower story. Notes: 1. A = Top story and second story effective shear segment length because the top story shear segment reinforcement must extend through the story below. The same reinforcement serves as the shear segment reinforcement for the second story and therefore must extend through the bottom story. 2. B = Bottom story effective shear segment length. The reinforcement in the end cells must extend and be hooked into the foundation. 
Figure GC-403.5.5 Multistory Shear Segments
The design methodology for the tabular shear segment length determination was based on the per foot capacity of a 4 foot long, 10 foot high shear segment as determined assuming a minimum of one bar of the size used in the wall (No. 4 or No. 5) at each end of the segment. If a shear segment in a wall is more than 8 feet in length, then any 2 foot segments cannot be counted as contributing toward the shear resistance. However, even though not counted, minimum 2 foot shear segments still are required in each direction at each corner and spaced no more than 18 feet clear in all walls. Note, these segments can be made longer to keep within the 4:1 criteria. Because in many cases there will be more than one bar at each end of the shear segment because one-half of the vertical reinforcement interrupted by an opening must be provided in the first two cells on each side of the opening, this assumption is conservative. Additionally, any reinforcement other than in the end cells of each segment was not counted as contributing toward the shear resistance, which is also conservative. |
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403.5.6 Nonrectangular buildings.
For nonrectangular buildings, the required length of shear walls shall be determined in accordance with Section 302. |
403.5.6 Nonrectangular buildings.
Portions of L- and T-shaped buildings are analyzed as two separate buildings and the shear wall requirements of the common wall between each building section are added together as this common wall resists load from both sides. However, some portions of the two building sections shield each other, resulting in a reduction in wind loads. Figure 302(1) and Figure 302(2) indicate when this is the case according to the two different orthogonal wind directions. Also note that offsets of up to 4 feet do not need to meet the requirements of L- and T-shaped buildings. The roof diaphragm is able to distribute the loads in these offset lines of resistance without the need for perpendicular shear walls. |
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403.6 Interior shear walls.
403.6.1 Length-to-width ratio of building. Interior shear walls used to decrease the length-to-width ratio of buildings shall comply with the following:
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403.6 Interior shear walls.
403.6.1 Length-to width ratio of building. These provisions for interior shear walls perpendicular to the roof ridge are used when buildings longer than the maximum length to width ratio of the building is exceeded or to reduce roof or floor diaphragm requirements.
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403.6.2 Interior shear wall in bottom story.
When an interior shear wall is used in the bottom story of a multi-story building without an interior shear wall above it, the following procedure shall be used:
3.2 Shear wall without shear wall above it, multiply by 0.35. |
403.6.2 Interior shear wall in bottom story.
When interior shear walls in multi-story buildings are used, alternate upper story shear walls (which have much lower shear loads) can be omitted by using the procedure prescribed in this section. The shear wall spacing is based on the upper story requirements and an additional shear wall is inserted in the story below to further distribute the higher shear loads in that story. |
