CBC · California Building Code

Seismic design requirements for masonry: SDC, anchorage and special rules

For homeowners: the California Building Code requires masonry (including chimneys) to be reinforced and anchored for earthquakes based on your seismic zone — small chimneys need four vertical bars, ties at prescribed spacing, and two anchored straps at each level above 6 ft unless the chimney sits fully inside exterior walls or your site is in the lowest seismic categories; the CBC gives exact sizes and spacing you must follow.

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Last reviewed: July 5, 2026

What the code requires — 2-4 sentences

Masonry seismic design in the CBC is governed by the requirement that masonry structures comply with Chapter 7 of TMS 402 as modified by the CBC (see § 2106) and by specific masonry-chimney rules in Chapter 21A (see § 2113.3 and § 2113.4). The CBC adds minimum reinforcement, tie and spacing rules for seismic detailing (see § 2106A.1.4 and associated TMS modifications). For chimneys, the CBC prescribes how many vertical bars, horizontal ties and seismic anchorage straps are required depending on Seismic Design Category (SDC) and chimney dimensions (§ 2113.3, § 2113.4).

Requirements in detail

1) High‑level rule: follow TMS 402 as modified by the CBC

  • Masonry structures and components must comply with Chapter 7 of TMS 402 as applicable to the structure’s Seismic Design Category (SDC) as required by § 2106.

2) CBC modifications to TMS (minimum reinforcement & spacing)

  • The CBC replaces/augments TMS provisions so that the total area of reinforcement in reinforced masonry walls shall be not less than 0.003 times the sectional area of the wall, with neither horizontal nor vertical reinforcement less than one‑third of the total. Horizontal and vertical reinforcement spacing shall be not more than 24 in. center-to-center (exceptions for certain nonbearing/freestanding walls). These minimums are the CBC amendment captured in § 2106A.1.4.

3) Lateral ties and column/vertical tie detailing (CBC stricter requirements)

  • Lateral ties that enclose vertical reinforcement must be at least 3/8 in. diameter; vertical spacing limits are the lesser of: 8 longitudinal bar diameters, 24 lateral tie bar diameters, 8 in., or one‑half of the least cross‑sectional dimension of the member. Lateral ties must be embedded in grout and placed within specified distances to footings/slab and adjacent flexural reinforcement per CBC TMS modifications (§ 2106 and its amendments).

4) Chimney-specific seismic reinforcement and anchorage (Chapter 21A: § 2113)

  • SDC applicability:

    • SDC A or B: seismic reinforcement for chimneys is not required. (§ 2113.3)
    • SDC C or D: chimneys shall be reinforced and anchored per the chimney provisions (§ 2113.3 referencing § 2113.3.1, § 2113.3.2 and § 2113.4). (§ 2113.3)
    • SDC E or F: chimneys must meet the full reinforced masonry requirements of §§ 2101–2108 and be anchored per § 2113.4. (§ 2113.3)

  • Vertical reinforcement for chimneys (§ 2113.3.1):

    • Chimneys up to 40 in. (1016 mm) wide: provide four No. 4 continuous vertical bars anchored in the foundation (placed between wythes or in hollow unit cells and grouted). For chimneys wider than 40 in., add two No. 4 vertical bars for each additional 40 in. or fraction thereof. (§ 2113.3.1)

  • Horizontal reinforcement / ties for chimneys (§ 2113.3.2):

    • Place vertical reinforcement enclosed within 1/4‑in. ties (or equivalent) spaced not more than 18 in. on center in concrete, or placed in bed joints of unit masonry at not less than every 18 in. vertical height. Provide two such ties at each bend in the vertical bars. (§ 2113.3.2)

  • Seismic anchorage of chimneys (§ 2113.4):

    • Chimneys and their foundations must be anchored at each floor, ceiling or roof line more than 6 ft (1829 mm) above grade with two 3/16‑in. × 1‑in. straps embedded not less than 12 in. into the chimney. Straps shall be hooked around outer bars, extend 6 in. beyond the bend, and each strap fastened to not less than four floor joists with two 1/2‑in. bolts. (§ 2113.4)

Markdown table — decision‑relevant dimensions/values

Item Value / Limit Code Reference
Follow TMS 402 (with CBC mods) Masonry must comply with Chapter 7 of TMS 402 as modified § 2106
Minimum reinforcement, reinforced walls Area ≥ 0.003 × wall sectional area; horizontal and vertical ≥ 1/3 each; spacing ≤ 24 in. § 2106A.1.4
Lateral tie diameter (columns) ≥ 3/8 in. (9.5 mm) § 2106 (TMS mod)
Lateral tie vertical spacing (columns) ≤ min{8 longitudinal bar diameters, 24 lateral tie bar diameters, 8 in., 1/2 least cross‑section} § 2106 (TMS mod)
Chimney vertical bars (baseline) 4 × No. 4 bars for chimney ≤ 40 in. width § 2113.3.1
Additional vertical bars for chimney +2 × No. 4 for each additional 40 in. (or fraction) beyond 40 in. § 2113.3.1
Chimney horizontal ties 1/4‑in. ties (or equivalent), ≤ 18 in. o.c.; two ties at each bend § 2113.3.2
Seismic anchorage straps 2 straps, 3/16‑in. × 1‑in.; embed ≥ 12 in.; extend 6 in. beyond bend; fasten to ≥ 4 joists with two 1/2‑in. bolts § 2113.4
Where anchorage not required SDC A or B; or fireplace constructed fully within exterior walls § 2113.4 (Exception)

Exceptions & special cases

  • SDC A or B: no seismic reinforcement required for chimneys (see § 2113.3).
  • If a masonry fireplace/chimney is constructed completely within the exterior walls, seismic anchorage is not required (exception to § 2113.4).
  • CBC modifies TMS minimums; for some nonbearing freestanding site walls or interior nonbearing nonshear partitions the horizontal reinforcing spacing and grout rules differ (see exception in § 2106A.1.4 / 7.4.4.1).

If you need to apply the E/F‑category rule: chimneys in SDC E/F must be designed to the full reinforced masonry sections (§§ 2101–2108) and anchored per § 2113.4; those full provisions (e.g., development length, splice rules, special wall detailing) are in those sections and TMS as adopted/modified by the CBC. § 2113.3 points to §§ 2101–2108 for SDC E/F.

Common mistakes

  • Applying chimney anchorage only at roof level and omitting anchors at intermediate floor/ceiling lines more than 6 ft above grade (anchorage is required at each such line unless exception applies). § 2113.4.
  • Using only joint reinforcement (ladder/mesh) as principal reinforcement—CBC explicitly prohibits joint reinforcement as principal reinforcement where minimum reinforcement is required. § 2106A.1.4 (7.4.4.1.5).
  • Forgetting grout requirements and preventing grout from bonding to the flue liner; the code requires grout but that grout must not bond to the flue liner so the liner can thermally expand (see § 2113.3.1).
  • Wrong strap embedment or bolting: straps must be embedded ≥12 in., hooked around outer bars, extend 6 in. beyond the bend and be fastened to at least four floor joists with two 1/2‑in. bolts per strap (§ 2113.4).
  • Misreading SDC: treating SDC C/D the same as E/F (E/F require full §§ 2101–2108 design, not just the chimney rules in § 2113). § 2113.3.

Worked example — apply the rule with numbers

Scenario: A masonry chimney on a house located in SDC D (so § 2113 rules apply). Chimney width = 60 in. (1524 mm). Determine vertical bars, ties, and anchors.

  1. SDC D: chimneys must be reinforced and anchored per § 2113.3 and § 2113.4.
  2. Vertical reinforcement (§ 2113.3.1): base requirement = four No. 4 continuous vertical bars for chimney ≤ 40 in. Since the chimney is 60 in., that is 40 in. + (60 − 40) = 20 in. extra → for each additional 40 in. or fraction thereof add two No. 4 bars. 20 in. is a fraction of 40 in., so add 2 bars. Total vertical bars = 4 + 2 = 6 No. 4 bars, anchored into the foundation and grouted. (§ 2113.3.1)
  3. Horizontal ties (§ 2113.3.2): use 1/4‑in. ties (or equivalent) spaced at not more than 18 in. on center vertically (and provide two ties at each bend). (§ 2113.3.2)
  4. Anchorage (§ 2113.4): provide two 3/16‑in. × 1‑in. straps at each floor/ceiling/roof line more than 6 ft above grade. Embed each strap ≥ 12 in. into the chimney, hook around the outer bars, extend 6 in. beyond the bend, and fasten to at least four floor joists with two 1/2‑in. bolts. (§ 2113.4)

This example shows layout and count: for a 60‑in. chimney in SDC D you would specify 6 No.4 verticals, 1/4‑in. ties ≤18 in. o.c., and the two prescribed seismic straps at each required level. Citations: § 2113.3.1, § 2113.3.2, § 2113.4.

Related provisions (CBC sections)

  • § 2106 — Seismic design requirements for masonry (adopt/modify TMS 402).
  • § 2106A.1.4 — CBC modifications to TMS 402 (minimum reinforcement requirements for walls).
  • § 2113.3 — Seismic reinforcement rules for masonry chimneys (SDC applicability, vertical/horizontal reinforcement).
  • § 2113.4 — Seismic anchorage requirements for masonry chimneys (strap size, embedment, fastening).
  • § 2103 (grouting & grout placement references used in chimney reinforcement). § 2113.3.1 references grout per § 2103.3.
  • § 2111 — Masonry fireplace seismic reinforcement and anchorage rules (parallel chimney/fireplace rules).
  • § 1705 — Special inspection requirements for masonry construction (quality assurance and special inspections referenced to TMS).

Code references

Grounded in the retrieved California Building Code — click a citation to read the verbatim passage:

  • CBC § 2113.2 High relevance — show source text

    2113.2 Footings and foundations. Footings for masonry chimneys shall be constructed of concrete or solid masonry not less than 12 inches (305 mm) thick and shall extend not less than 6 inches (152 mm) beyond the face of the foundation or support wall on all sides. Footings shall be founded on natural undisturbed earth or engineered fill below frost depth. In areas not subjected to freezing, footings shall be not less than 12 inches (305 mm) below finished grade.

    2113.3 Seismic reinforcement. In structures assigned to Seismic Design Category A or B, seismic reinforcement is not required. In structures assigned to Seismic Design Category C or D, masonry chimneys shall be reinforced and anchored in accordance with Sections 2113.3.1, 2113.3.2 and 2113.4. In structures assigned to Seismic Design Category E or F, masonry chimneys shall be reinforced in accordance with the requirements of Sections 2101 through 2108 and anchored in accordance with Section 2113.4.

    2113.3.1 Vertical reinforcement. For chimneys up to 40 inches (1016 mm) wide, four No. 4 continuous vertical bars anchored in the foundation shall be placed in the concrete between wythes of solid masonry or within the cells of hollow unit masonry and grouted in accordance with Section 2103.3. Grout shall be prevented from bonding with the flue liner so that the flue liner is free to move with thermal expansion. For chimneys greater than 40 inches (1016 mm) wide, two additional No. 4 vertical bars shall be provided for each additional 40 inches (1016 mm) in width or fraction thereof. 2113.3.2 Horizontal reinforcement. Vertical reinforcement shall be placed enclosed within [1] / 4 -inch (6.4 mm) ties, or other reinforcing of equivalent net cross-sectional area, spaced not to exceed 18 inches (457 mm) on center in concrete, or placed in the bed joints of unit masonry, at not less than every 18 inches (457 mm) of vertical height. Two such ties shall be provided at each bend in the vertical bars.

    2113.4 Seismic anchorage. Masonry chimneys and foundations shall be anchored at each floor, ceiling or roof line more than 6 feet (1829 mm) above grade with two [3] / 16 -inch by 1-inch (4.8 mm by 25 mm) straps embedded not less than 12 inches (305 mm) into the chimney. Straps shall be hooked around the outer bars and extend 6 inches (152 mm) beyond the bend. Each strap shall be fastened to not less than four floor joists with two [1] / 2 -inch (12.7 mm) bolts.

    Exception: Seismic anchorage is not required for the following:

    1. In structures assigned to Seismic Design Category A or B.
    2. Where the masonry fireplace is constructed completely within the exterior walls.
  • CBC § 3.1 High relevance — show source text

    R1003.2 Footings and foundations. Footings for masonry chimneys shall be constructed of concrete or solid masonry not less than 12 inches (305 mm) thick and shall extend not less than 6 inches (152 mm) beyond the face of the foundation or support wall on all sides. Footings shall be founded on natural undisturbed earth or engineered fill below frost depth. In areas not subjected to freezing, footings shall be not less than 12 inches (305 mm) below finished grade.

    R1003.3 Seismic reinforcing. Masonry or concrete chimneys shall be constructed, anchored, supported and reinforced as required in this chapter. In all structures regulated by this code assigned to Seismic Design Category C, D 0, D 1 or D 2 masonry and concrete chimneys shall be reinforced and anchored as detailed in Sections R1003.3.1, R1003.3.2 and R1003.4. In Seismic Design Category A or B, reinforcement and seismic anchorage are not required.

    R1003.3.1 Vertical reinforcing. For chimneys up to 40 inches (1016 mm) wide, four No. 4 continuous vertical bars, anchored in the foundation, shall be placed in the concrete, or between wythes of solid masonry, or within the cells of hollow unit masonry, and grouted in accordance with Section R608.1.1. Grout shall be prevented from bonding with the flue liner so that the flue liner is free to move with thermal expansion. For chimneys more than 40 inches (1016 mm) wide, two additional No. 4 vertical bars shall be installed for each additional 40 inches (1016 mm) in width or fraction thereof.

    R1003.3.2 Horizontal reinforcing. Vertical reinforcement shall be placed enclosed within [1] / 4 -inch (6.4 mm) ties, or other reinforcing of equivalent net cross-sectional area, spaced not to exceed 18 inches (457 mm) on center in concrete, or placed in the bed joints of unit masonry, at not less than every 18 inches (457 mm) of vertical height. Two such ties shall be installed at each bend in the vertical bars.

    R1003.4 Seismic anchorage. Masonry and concrete chimneys and foundations in all structures regulated by this code assigned to Seismic Design Category C, D 0, D 1 or D 2 shall be anchored at each floor, ceiling or roof line more than 6 feet (1829 mm) above grade, except where constructed completely within the exterior walls. Anchorage shall conform to the requirements in Section R1003.4.1. R1003.4.1 Anchorage. Two [3] / 16 -inch by 1-inch (5 mm by 25 mm) straps shall be embedded not less than 12 inches (305 mm) into the chimney. Straps shall be hooked around the outer bars and extend 6 inches (152 mm) beyond the bend. Each strap shall be fastened to not less than four floor joists with two [1] / 2 -inch (12.7 mm) bolts. **R1003.4.1.1 Cold-formed steel framing.

  • CBC § 802.3 High relevance — show source text

    Decorative materials 419, 802.3, 806 Floor finish 804, 805 Foam plastic insulation 2603.3, 2603.4 Foam plastic trim 806.6.1, 2604.2 Insulation 807 Light-transmitting plastics 2606 Signs 402.6.4, 2611 Site-fabricated stretch systems 803.10 Trim 806.6, 806.7 Wall and ceiling finishes 803 Wet location 1210 Intermodal Shipping Container 3114 Interpretation, Code 104.1

    Jails [see Institutional (see Group I-3)] 308.5, 408 Joint Gypsum board 2508.5 Lumber sheathing 2308.11.10 Waterproofing 1805.3.3 Joints, Fire-resistant Systems 715 Special inspection 1705.18

    Kiosks 402.6.2

    Kitchens 303.3, 306.2 Accessibility 1133A, 11B-212 Dimensions 1209 Means of egress 1016.2 Occupant load Table 1004.5 Sinks Chapter 29

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    INDEX

    Marquees 3106, H113 Construction 3106.5

    Drainage, water 3201.4 Live load Table 1607.1, 1607.14 Prohibited location 3106.4

    Roof construction 3106.3 Masonry Chapter 21A Adhered veneer 1404.11

    Adobe 2109 Anchorage 1604.8.2 Anchored veneer 1404.7

    Architectural cast stone 2103.1

    Calculated fire resistance 722.4 Chimneys 2113 Construction 2104 Dampproofing 1805.2.2 Design, methods 2101.2, 2107, 2108, 2109

    Fire resistance, calculated 722.3.2,

    722.3.4

    Fireplaces 2111 Floor anchorage 1604.8.2 Foundation walls 1807.1.5

    Foundations, adobe 2109.2.4.5 Glass unit 2110

    Heaters 2112

    Inspection, special 1705.4 Joint reinforcement 2103.4

    Materials 603.1, 2103 Penetrations 714 Quality assurance 2105 Rodentproofing Appendix F Roof anchorage 1604.8.1 Seismic provisions 2106 Serviceability 1604.3.4 Supported by wood 2104.1.1, 2304.13 Surface bonding 2103.2.2 Veneer 1404.11, 1404.7, 2101.2.1,

    2308.10.10 Wall anchorage 1604.8.2 Waterproofing 1805.3.2 Mass Notification Systems 917 Mass Timber 508, 509, 602, 703, 718, 722 Materials

    Alternates 104.2.3

  • CBC § 2.2.8 High relevance — show source text

    R301.2.2.8 Cold-formed steel framing in Seismic Design Categories D 0 , D 1 and D 2 . In Seismic Design Categories D 0, D 1 and D 2 in addition to the requirements of this code, cold-formed steel framing shall comply with the requirements of AISI S230.

    R301.2.2.9 Masonry chimneys. In Seismic Design Categories D 0, D 1 and D 2, masonry chimneys shall be reinforced and anchored to the building in accordance with Sections R1003.3 and R1003.4.

    R301.2.2.10 Seismic restraint of appliances and equipment. In Seismic Design Categories D 0, D 1 and D 2 and in townhouses in Seismic Design Category C, appliances and equipment that are designed to be fixed in position shall be supported and braced or anchored to the structure in accordance with the component manufacturer’s recommendations or per Section R301.2.2.10.1.

    Exceptions: Seismic support, bracing and anchorage are not required for the following:

    1. Suspended mechanical ducts, electrical conduit, automatic sprinkler systems and plumbing systems.
    2. Where the appliance or equipment is bearing on an elevated floor or roof and the housing height is not greater than 1.5 times the width of the housing base in either direction.
    3. Where the installed weight of a suspended appliance or equipment is 50 pounds (22.7 kg) or less.
    4. Where the installed weight is 400 pounds (181.4 kg) or less and the bottom of the appliance or equipment is 4 feet (1219 mm) or less above the adjacent floor level.

    R301.2.2.10.1 Seismic restraint resistance. Supports, bracing and anchorage of appliances and equipment in Seismic Design Categories D 0, D 1 and D 2, and in townhouses in Seismic Design Category C, shall resist a horizontal force equal to onethird times the operating weight of the component, acting in any direction. Bracing shall comply with the following:

    1. Components supported at the base shall be braced with strapping at points within the upper one-third of the component’s vertical dimensions, or the component anchorage shall be designed to resist overturning.
    2. Components suspended from the structure shall be braced to the structure using either flexible or rigid bracing. Flexible bracing such as wires or straps shall be provided in each of the four orthogonal directions. Rigid bracing such as struts or bars may be provided in two orthogonal directions.

    R301.2.3 Snow loads. Ground snow loads shall be determined in accordance with Figure R301.2(3) or shall be determined in accordance in with Section 1608 of the California Building Code . Wood-framed construction, cold-formed, steel-framed construction and masonry and concrete construction, and structural insulated panel construction in regions with allowable stress design ground snow loads, p g(asd ), 70 pounds per square foot (3.35 kPa) or less, shall be in accordance with Chapters 5, 6 and 8. Buildings in regions with allowable stress design ground snow loads, p g(asd), greater than 70 pounds per square foot (3.35 kPa) shall be designed in accordance with accepted engineering practice.

  • CBC § 4.8 High relevance — show source text

    2113 A .4 Seismic anchorage. Masonry chimneys and foundations shall be anchored at each floor, ceiling or roof line more than 6 feet (1829 mm) above grade with two [3] / 16 -inch by 1-inch (4.8 mm by 25 mm) straps embedded not less than 12 inches (305 mm) into the chimney. Straps shall be hooked around the outer bars and extend 6 inches (152 mm) beyond the bend. Each strap shall be fastened to not less than four floor joists with two [1] / 2 -inch (12.7 mm) bolts.

    Exception: Seismic anchorage is not required for the following:

    1. In structures assigned to Seismic Design Category A or B.
    2. Where the masonry fireplace is constructed completely within the exterior walls.

    2113 A .5 Corbeling. Masonry chimneys shall not be corbeled more than half of the chimney’s wall thickness from a wall or foundation, nor shall a chimney be corbeled from a wall or foundation that is less than 12 inches (305 mm) in thickness unless it projects equally on each side of the wall, except that on the second story of a two-story dwelling, corbeling of chimneys on the exterior of the enclosing walls is permitted to equal the wall thickness. The projection of a single course shall not exceed one-half the unit height or one-third of the unit bed depth, whichever is less.

    2113 A .6 Changes in dimension. The chimney wall or chimney flue lining shall not change in size or shape within 6 inches (152 mm) above or below where the chimney passes through floor components, ceiling components or roof components.

    2113 A .7 Offsets. Where a masonry chimney is constructed with a fireclay flue liner surrounded by one wythe of masonry, the maximum offset shall be such that the centerline of the flue above the offset does not extend beyond the center of the chimney wall below the offset. Where the chimney offset is supported by masonry below the offset in an approved manner, the maximum offset limitations shall not apply. Each individual corbeled masonry course of the offset shall not exceed the projection limitations specified in Section 2113 A .5.

    2113 A .8 Additional load. Chimneys shall not support loads other than their own weight unless they are designed and constructed to support the additional load. Masonry chimneys are permitted to be constructed as part of the masonry walls or concrete walls of the building.

    2113 A .9 Termination. Chimneys shall extend not less than 2 feet (610 mm) higher than any portion of the building within 10 feet (3048 mm), but shall be not less than 3 feet (914 mm) above the highest point where the chimney passes through the roof.

    2113 A .9.1 Chimney caps. Masonry chimneys shall have a concrete, metal or stone cap, sloped to shed water, a drip edge and a caulked bond break around any flue liners in accordance with ASTM C1283.

    2113 A .9.2 Spark arrestors. [SFM] All chimneys attached to any appliance or fireplace that burns solid fuel shall be equipped with an approved spark arrester. The spark arrestor shall meet all of the following requirements: 1.

  • CBC § 3.1 High relevance — show source text

    2113 A .3.1 Vertical reinforcement. For chimneys up to 40 inches (1016 mm) wide, four No. 4 continuous vertical bars anchored in the foundation shall be placed in the concrete between wythes of solid masonry or within the cells of hollow unit masonry and grouted in accordance with Section 2103 A .3. Grout shall be prevented from bonding with the flue liner so that the flue liner is free to move with thermal expansion. For chimneys greater than 40 inches (1016 mm) wide, two additional No. 4 vertical bars shall be provided for each additional 40 inches (1016 mm) in width or fraction thereof.

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    MASONRY

    2113 A .3.2 Horizontal reinforcement. Vertical reinforcement shall be placed enclosed within [1] / 4 -inch (6.4 mm) ties, or other reinforcing of equivalent net cross-sectional area, spaced not to exceed 18 inches (457 mm) on center in concrete, or placed in the bed joints of unit masonry, at not less than every 18 inches (457 mm) of vertical height. Two such ties shall be provided at each bend in the vertical bars.

    2113 A .4 Seismic anchorage. Masonry chimneys and foundations shall be anchored at each floor, ceiling or roof line more than 6 feet (1829 mm) above grade with two [3] / 16 -inch by 1-inch (4.8 mm by 25 mm) straps embedded not less than 12 inches (305 mm) into the chimney. Straps shall be hooked around the outer bars and extend 6 inches (152 mm) beyond the bend. Each strap shall be fastened to not less than four floor joists with two [1] / 2 -inch (12.7 mm) bolts.

    Exception: Seismic anchorage is not required for the following:

    1. In structures assigned to Seismic Design Category A or B.
    2. Where the masonry fireplace is constructed completely within the exterior walls.

    2113 A .5 Corbeling. Masonry chimneys shall not be corbeled more than half of the chimney’s wall thickness from a wall or foundation, nor shall a chimney be corbeled from a wall or foundation that is less than 12 inches (305 mm) in thickness unless it projects equally on each side of the wall, except that on the second story of a two-story dwelling, corbeling of chimneys on the exterior of the enclosing walls is permitted to equal the wall thickness. The projection of a single course shall not exceed one-half the unit height or one-third of the unit bed depth, whichever is less.

    2113 A .6 Changes in dimension. The chimney wall or chimney flue lining shall not change in size or shape within 6 inches (152 mm) above or below where the chimney passes through floor components, ceiling components or roof components.

  • CBC § 13.79 High relevance — show source text

    The approved agency shall report the location where each core was taken, the findings of their visual examination of each core, iden- tify which cores were selected for shear testing, and the results of the shear tests. Additional cores shall be permitted to be taken at the direction of the registered design professional and with approval of the enforcement agency.

    Exceptions: 1. Core sampling and testing is not required for non-bearing nonshear masonry walls, not exceeding a total wall height of 12 feet above top of foundation, built with single-wythe hollow unit concrete masonry that attaches opposite face shells using webs cast as single unit, when designed using an f ′ m not exceeding 2,000 psi (13.79 MPa). 2. An infrared thermographic survey or other nondestructive test procedures, shall be permitted to be approved as an alterna- tive system to detect voids or delamination in grouted masonry in lieu of core sampling and testing. [OSHPD 1 & 4] Infrared thermographic surveys or other nondestructive test procedures shall also include core tests with a minimum of two cores taken from each building for each 10,000 square feet (930 m [2] ) of the wall.

    SECTION 2106 A —SEISMIC DESIGN

    2106 A .1 Seismic design requirements for masonry. Masonry structures and components shall comply with the requirements in Chapter 7 of TMS 402 depending on the structure’s seismic design category.

    2106A.1.1 TMS 402, Section 5.4.1.4. Replace TMS 402, Section 5.4.1.4 Items (a), (b), (d) & (e) by the following: (a) Vertical reinforcement shall be enclosed by lateral ties at least [3] / 8 in. ( 9.5 mm ) in diameter. (b) Vertical spacing of lateral ties, over the full height of the column, shall not exceed 8 longitudinal bar diameters, 24 lateral tie bar diameters, 8 inches (203 mm), or one-half the least cross-sectional dimension of the member. (d) Lateral ties shall be embedded in grout. (e) Lateral ties shall be located vertically not more than one-half lateral tie spacing above the top of the footing or slab in any story, and shall be spaced not more than one-half a lateral tie spacing nor 2 inches (51 mm) below the lowest horizontal reinforcement in beam, girder, slab, or drop panel above. The top tie shall be within 2 inches (51 mm) of the top of the column.

    2106A.1.2 TMS 402, Chapter 5. Add TMS 402, Section 5.7 as follows:

    5.7 – Lateral Support of Members

    5.7.1 – Lateral support of masonry may be provided by cross walls, columns, pilasters, counterforts or buttresses where spanning horizontally, or by floors, beams, girts or roofs where spanning vertically. Where walls are supported laterally by vertical elements, the stiffness of each vertical element shall exceed that of the tributary area of the wall.

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  • CBC § 13.79 High relevance — show source text

    Exceptions: 1. Core sampling and testing is not required for non-bearing nonshear masonry walls, not exceeding total wall height of 12 feet above the top of the foundation, built with single-wythe hollow unit concrete masonry that attaches opposite face shells using webs cast as single unit, when designed using an f ′ m not exceeding 2,000 psi (13.79MPa). 2. An infrared thermographic survey or other nondestructive test procedures shall be permitted to be approved as an alterna- tive system to detect voids or delamination in grouted masonry in conjunction with reduced core sampling and testing. A minimum of two cores shall be taken from each building for each 10,000 square feet (930 m [2] ) of the wall.

    SECTION 2106—SEISMIC DESIGN

    2106.1 Seismic design requirements for masonry. Masonry structures and components shall comply with the requirements in Chapter 7 of TMS 402 depending on the structure’s seismic design category.

    2106.1.1 TMS 402, Sections 5.4.1.4. [OSHPD 1R, 2 & 5] Replace TMS 402, Section 5.4.1.4 Items (a), (b), (d) & (e) by the following: a. Vertical reinforcement shall be enclosed by lateral ties at least [3] / 8 inch ( 9.5 mm ) in diameter. b. Vertical spacing of lateral ties, over the full height of the column, shall not exceed 8 longitudinal bar diameters, 24 lateral tie bar diameters, 8 inches (203 mm), or one-half the least cross-sectional dimension of the member.

    d. Lateral ties shall be embedded in grout. e. Lateral ties shall be located vertically not more than one-half lateral tie spacing above the top of the footing or slab in any story, and shall be spaced not more than one-half a lateral tie spacing nor 2 inches (51 mm) below the lowest horizontal reinforcement in beam, girder, slab, or drop panel above. The top tie shall be within 2 inches (51 mm) of the top of the column.

    2106.1.2 TMS 402, Chapter 5. [OSHPD 1R, 2 & 5] Add TMS 402, Section 5.7 as follows:

    5.7 – Lateral Support of Members

    5.7.1 – Lateral support of masonry may be provided by cross walls, columns, pilasters, counterforts or buttresses where spanning horizontally, or by floors, beams, girts or roofs where spanning vertically. Where walls are supported laterally by vertical elements, the stiffness of each vertical element shall exceed that of the tributary area of the wall.

    2106.1.3 TMS 402, Sections 7.4.4.1 and 7.4.5.1. [OSHPD 1R, 2 & 5] Replace TMS 402, Section 7.4.4.1 as follows and delete Section 7.4.5.1:

  • CBC § 0.080 Medium relevance — show source text

    1/4″|4d casing (11/2″ × 0.080″); or
    4d finish (11/2″ × 0.072″)|6|12| |41.3/8″|6d casing (2″ × 0.099″); or
    6d finish (2″ × 0.092″)
    (Panel supports at 24 inches)|6|12| |For SI: 1 inch = 25.4 mm.
    a. Nails spaced at 6 inches at intermediate supports where spans are 48 inches or more. For nailing of wood structural panel and particleboard diaphragms and shear walls, refer
    to Section 2305. Nails for wall sheathing are permitted to be common, box or casing.
    b. Spacing shall be 6 inches on center on the edges and 12 inches on center at intermediate supports for nonstructural applications. Panel supports at 16 inches (20 inches if
    strength axis in the long direction of the panel, unless otherwise marked).
    c. Where a rafter is fastened to an adjacent parallel ceiling joist in accordance with this schedule and the ceiling joist is fastened to the top plate in accordance with this schedule,
    the number of toenails in the rafter shall be permitted to be reduced by one nail.
    d. RSRS is a Roof Sheathing Ring Shank nail meeting the specifications in ASTM F1667.
    e. Tabulated fastener requirements apply where the basic wind speed,V, is less than 140 mph. For wood structural panel roof sheathing attached to gable-end roof framing and
    to intermediate supports within 48 inches of roof edges and ridges, nails shall be spaced at 4 inches on center where the basic wind speed,V, is greater than 130 mph in Expo-
    sure B or greater than 110 mph in Exposure C. Spacing exceeding 6 inches on center at intermediate supports shall be permitted where the fastening is designed per the AWC
    NDS. Where the specific gravity of the wood species used for roof framing is greater than or equal to 0.35 but less than 0.42 in accordance with AWC NDS, fastening of roof
    sheathing shall be with RSRS-03 (21/2″ × 0.131″ × 0.281″ head) nails unless alternative fastening is designed in accordance with AWC NDS. Where the specific gravity of the wood
    species used for roof framing is less than 0.35, fastening of the roof sheathing shall be designed in accordance with AWC NDS.
    f. Fastening is only permitted where the basic wind speed,V, is less than or equal to 110 mph and where fastening is to wood framing of a species with specific gravity greater
    than or equal to 0.42 in accordance with AWC NDS.
    g. Nails and staples are carbon steel meeting the specifications of ASTM F1667. Connections using nails and staples of other materials, such as stainless steel, shall be designed
    by acceptable engineering practice or approved under Section 104.2.3.|For SI: 1 inch = 25.4 mm.
    a. Nails spaced at 6 inches at intermediate supports where spans are 48 inches or more. For nailing of wood structural panel and particleboard diaphragms and shear walls, refer
    to Section 2305. Nails for wall sheathing are permitted to be common, box or casing.
    b. Spacing shall be 6 inches on center on the edges and 12 inches on center at intermediate supports for nonstructural applications.

  • CBC § 2.5 Medium relevance — show source text

    Visual examination of all cores shall be made by an approved agency and the condition of the cores reported as required by the Cali- fornia Administrative Code. Shear tests of both joints between the grout core and the outside wythes or face shell of the masonry shall be made 28 days after grouting of the sample area using a shear test apparatus acceptable to the enforcement agency. Core samples shall not be soaked before testing. Core samples to be tested shall be stored in sealed plastic bags or nonabsorbent containers immediately after coring and for at least 5 days prior to testing. The average unit shear value for each pair of cores (4 shear tests) from each 5,000 square feet of wall area (or less) on the cross section of core shall not be less than 2.5 √ f ′ m psi.

    All cores shall be submitted to an approved agency for examination, including core specimens where a face shell separates from the grout core during the coring operation. The approved agency shall report the location where each core was taken, report the find- ings of their visual examination of each core, identify which cores were selected for shear testing, and report the results of the shear

    21-6 2025 CALIFORNIA BUILDING CODE

    on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

    MASONRY

    tests. Additional cores shall be permitted to be taken at the direction of the registered design professional and with approval of the enforcement agency.

    Exceptions: 1. Core sampling and testing is not required for non-bearing nonshear masonry walls, not exceeding total wall height of 12 feet above the top of the foundation, built with single-wythe hollow unit concrete masonry that attaches opposite face shells using webs cast as single unit, when designed using an f ′ m not exceeding 2,000 psi (13.79MPa). 2. An infrared thermographic survey or other nondestructive test procedures shall be permitted to be approved as an alterna- tive system to detect voids or delamination in grouted masonry in conjunction with reduced core sampling and testing. A minimum of two cores shall be taken from each building for each 10,000 square feet (930 m [2] ) of the wall.

    SECTION 2106—SEISMIC DESIGN

    2106.1 Seismic design requirements for masonry. Masonry structures and components shall comply with the requirements in Chapter 7 of TMS 402 depending on the structure’s seismic design category.

    2106.1.1 TMS 402, Sections 5.4.1.4. [OSHPD 1R, 2 & 5] Replace TMS 402, Section 5.4.1.4 Items (a), (b), (d) & (e) by the following: a. Vertical reinforcement shall be enclosed by lateral ties at least [3] / 8 inch ( 9.5 mm ) in diameter. b. Vertical spacing of lateral ties, over the full height of the column, shall not exceed 8 longitudinal bar diameters, 24 lateral tie bar diameters, 8 inches (203 mm), or one-half the least cross-sectional dimension of the member.

  • CBC § 503.7 Medium relevance — show source text

    [BS] 503.7 Anchorage for concrete and reinforced masonry walls. Where the work area exceeds 50 percent of the building area, the building is assigned to Seismic Design Category C, D, E or F and the building’s structural system includes concrete or reinforced masonry walls with a flexible roof diaphragm, the alteration shall comply with Section 304.3.2 by evaluation of the existing condition or by installation of wall anchors at the roof line.

    [BS] 503.8 Anchorage for unreinforced masonry walls in major alterations. Where the work area exceeds 50 percent of the building area, the building is assigned to Seismic Design Category C, D, E or F and the building’s structural system includes unreinforced masonry bearing walls, the alteration shall comply with Section 304.3.2 by evaluation of the existing condition or by installation of wall anchors at the floor and roof lines.

    [BS] 503.9 Bracing for unreinforced masonry parapets in major alterations. Where the work area exceeds 50 percent of the building area, and where the building is assigned to Seismic Design Category C, D, E or F, and the building has parapets constructed of unreinforced masonry, the alteration shall comply with Section 304.3.2 by evaluation of the existing condition or by installation of parapet bracing to resist out-of-plane seismic forces.

    [BS] 503.10 Anchorage of unreinforced masonry partitions in major alterations. Where the work area exceeds 50 percent of the building area, or where the building is assigned to Seismic Design Category C, D, E or F, and the building has unreinforced masonry partitions and nonstructural walls, the alteration work shall include evaluation of the existing condition or removal, anchoring or alteration of any such partitions or walls within the work area and adjacent to egress paths from the work area, to comply with Section 304.3.2.

    [BS] 503.11 Substantial structural alteration. Where the work area exceeds 50 percent of the building area and where work involves a substantial structural alteration, the lateral load-resisting system of the altered building shall satisfy the requirements of Section 1609 of the California Building Code and Section 304.3.2 of this code. Where the building is assigned to Seismic Design Category D or F, supports and attachments for nonstructural components required to serve any portion of the building with a use included in Risk Category IV shall comply with Section 1613 of the California Building Code or shall comply with ASCE 41 using an objective of Position Retention nonstructural performance with the BSE-1E earthquake hazard level.

    Exceptions:

    1. Buildings of Group R occupancy with not more than five dwelling or sleeping units used solely for residential purposes that are altered based on the conventional light-frame construction methods of the California Building Code or in compliance with the provisions of the California Residential Code .
    2. Where the intended alteration involves structural components of the lowest story of a building, only the lateral loadresisting system above that story need not comply with this section.

    [BS] 503.12 Roof diaphragms resisting wind loads in high-wind regions. Where the intended alteration requires a permit for reroofing and involves removal of roofing materials from more than 50 percent of the roof diaphragm of a building or section of a building located where the basic wind speed, V, is greater than 130 mph (58 m/s) in accordance with Figure 1609.3(2) of the California

  • CBC § 3.1 Medium relevance — show source text

    2111 A .3.1 Ash dump cleanout. Cleanout openings, located within foundation walls below fireboxes, where provided, shall be equipped with ferrous metal or masonry doors and frames constructed to remain tightly closed, except when in use. Cleanouts shall be accessible and located so that ash removal will not create a hazard to combustible materials.

    2111 A .4 Seismic reinforcement. In structures assigned to Seismic Design Category A or B, seismic reinforcement is not required. In structures assigned to Seismic Design Category C or D, masonry fireplaces shall be reinforced and anchored in accordance with Sections 2111 A .4.1, 2111 A .4.2 and 2111 A .5. In structures assigned to Seismic Design Category E or F, masonry fireplaces shall be reinforced in accordance with the requirements of Sections 2101 A through 2108 A .

    2111 A .4.1 Vertical reinforcing. For fireplaces with chimneys up to 40 inches (1016 mm) wide, four No. 4 continuous vertical bars, anchored in the foundation, shall be placed in the concrete between wythes of solid masonry or within the cells of hollow unit masonry and grouted in accordance with Section 2103.3. For fireplaces with chimneys greater than 40 inches (1016 mm) wide, two additional No. 4 vertical bars shall be provided for each additional 40 inches (1016 mm) in width or fraction thereof. 2111 A .4.2 Horizontal reinforcing. Vertical reinforcement shall be placed enclosed within [1] / 4 -inch (6.4 mm) ties or other reinforcing of equivalent net cross-sectional area, spaced not to exceed 18 inches (457 mm) on center in concrete; or placed in the bed joints of unit masonry at not less than every 18 inches (457 mm) of vertical height. Two such ties shall be provided at each bend in the vertical bars.

    2111 A .5 Seismic anchorage. Masonry fireplaces and foundations shall be anchored at each floor, ceiling or roof line more than 6 feet (1829 mm) above grade with two [3] / 16 -inch by 1-inch (4.8 mm by 25 mm) straps embedded not less than 12 inches (305 mm) into the chimney. Straps shall be hooked around the outer bars and extend 6 inches (152 mm) beyond the bend. Each strap shall be fastened to not fewer than four floor joists with two [1] / 2 -inch (12.7 mm) bolts.

    Exception: Seismic anchorage is not required for the following:

    1. In structures assigned to Seismic Design Category A or B.
    2. Where the masonry fireplace is constructed completely within the exterior walls.

Frequently asked questions

Do these chimney anchorage rules apply to single‑family homes?

Yes — the chimney anchorage provisions in § 2113.4 apply by SDC: they are not required only in SDC A or B or when the fireplace/chimney is constructed entirely within exterior walls; otherwise they apply to residential buildings in higher SDCs.

What diameter and spacing must lateral ties have for columns and piers?

Lateral ties must be at least 3/8 in. diameter and spacing is limited by the CBC modification: not more than the lesser of 8 longitudinal bar diameters, 24 lateral tie bar diameters, 8 in., or one‑half the least cross‑sectional dimension of the member (§ 2106 TMS modifications).

If my chimney is 100 in. wide, how many vertical No.4 bars are required?

For chimneys: 4 No. 4 bars for the first 40 in., then add 2 No. 4 bars for each additional 40 in. or fraction. For 100 in.: 4 + 2×ceil((100−40)/40) = 4 + 2×2 = 8 No. 4 bars. (§ 2113.3.1)

Can joint reinforcement (ladder-type) be used as the only principal reinforcement?

No. The CBC amendments explicitly state that joint reinforcement shall not be used as principal reinforcement where the minimum reinforcement rules apply — provide full vertical/horizontal reinforcement per § 2106A.1.4 (7.4.4.1.5).

Are the strap sizes and bolt counts negotiable with an engineer?

They are code‑prescribed minimums: two 3/16‑in. by 1‑in. straps embedded ≥12 in., hooked and extending 6 in., each strap fastened to not fewer than four joists with two 1/2‑in. bolts is the CBC requirement in § 2113.4. An engineered design may provide an alternate anchorage system, but it must be approved by the enforcing authority.

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Related in the CBC

Minimum reinforcement: area, spacing, spacing limits and termination requirements

Allowed masonry design methods and DSA/OSHPD prohibitions

Seismic design and reinforcement

California Building Code