CBC · California Building Code

What anchorage and out-of-plane wall requirements apply for seismic forces?

The CBC requires that roofs, floors and walls be tied together so seismic shaking cannot push walls out of the building — structural walls must be anchored to roofs and supporting floors and connections must resist the earthquake out‑of‑plane loads set by ASCE 7 (as referenced in CBC § 1604.8.2). Decks attached to walls must be positively anchored (not by toenails) and designed for both vertical and lateral loads (§ 1604.8.3). Appendix retrofit rules add prescriptive anchor spacings and minimums when you are working on existing masonry buildings.

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Last reviewed: July 5, 2026

What the code requires — 2–4 sentences

The CBC requires buildings, and portions of buildings, to be anchored so roofs, floors, walls and foundations form a continuous load path to resist uplift, sliding and seismic out‑of‑plane forces (see § 1604.8 and § 1604.8.1) . Structural (vertical or shear) walls must be anchored to the roof and all floors or members that laterally support them; those connections must be capable of resisting the horizontal and out‑of‑plane earthquake forces established by ASCE 7 (ASCE 7 §1.4.4 for SDC A and §12.11 for other SDCs) as adopted by the CBC in § 1604.8.2 . Decks attached to exterior walls must be positively anchored for both vertical and lateral loads and not by toenails or withdrawal‑susceptible nails (§ 1604.8.3) .

Requirements in detail

1) General anchorage objective

Code statement: roof-to-wall and wall/column-to-foundation anchorage is required to resist uplift and sliding from prescribed loads (§ 1604.8.1) .
Practical implication: provide continuous connections (anchors, straps, hold‑downs, anchor bolts) that develop required tensile, shear and overturning forces into the diaphragm and foundation.

2) Structural walls — anchorage and out‑of‑plane forces

Walls that carry vertical load or lateral shear must be anchored to roof and to all floors and members that support or are supported by the wall; connections must resist horizontal forces resulting from prescribed loads (§ 1604.8.2) .
The CBC defers the magnitude and distribution of required earthquake out‑of‑plane loads to ASCE 7: Section 1.4.4 for buildings in Seismic Design Category A and Section 12.11 for buildings in all other SDCs (§ 1604.8.2) .
For masonry walls formed with hollow units or cavity walls, required anchors must be embedded in a reinforced, grouted structural element of the wall (explicit requirement in § 1604.8.2) .
Where an alternate/minimum value is adopted in some CBC text, anchorage of concrete or masonry walls to diaphragms is sometimes given a code minimum out‑of‑plane strength design force of not less than 280 lb/linear ft (4.09 kN/m) of wall (see alternate/appendix language in the CBC materials) .

3) Decks and attachments

Decks supported by attachment to an exterior wall must be positively anchored to the primary structure and designed for applicable vertical and lateral loads (§ 1604.8.3) .
Such attachment shall not rely on toenails or nails subject to withdrawal; if positive connection to the primary structure cannot be verified at inspection, decks must be self‑supporting (§ 1604.8.3) .
Connections of cantilevered framing to exterior walls must be designed for:
1. Reactions from dead + live loads (or snow where applicable) acting on all portions of the deck, and
2. Reactions from dead + live (or snow) acting on the cantilevered portion with no live/snow load on the remainder — both per § 1604.8.3 referencing Table 1607.1 and § 1608 for snow loads .

Key decision values & references (quick table)

Decision item	Typical value / rule	Where to check (Code Reference)
Need for anchorage of roof to walls and walls to foundations	Required to resist uplift and sliding from prescribed loads	§ 1604.8.1
Structural wall anchorage to roof/floors	Required; connections must resist horizontal/out‑of‑plane earthquake forces	§ 1604.8.2
Magnitude of earthquake out‑of‑plane load	Determined by ASCE 7: §1.4.4 (SDC A) and §12.11 (other SDCs); CBC references ASCE 7	§ 1604.8.2
Masonry hollow/cavity wall anchor requirement	Anchors must be embedded in a reinforced grouted structural element	§ 1604.8.2
Minimum out‑of‑plane strength design force quoted in CBC alternate text	Not less than 280 lb/linear ft (4.09 kN/m) for concrete/masonry to diaphragms (where that language applies)	CBC alternate/appendix wording shown in 1604 A.8.2
Deck attachment — prohibited fasteners	Attachment shall not be by toenails or nails subject to withdrawal	§ 1604.8.3
Deck cantilever connection design forces	Design for dead + live (or snow) acting on whole deck and on cantilever per § 1604.8.3	§ 1604.8.3; Table 1607.1 and §1608
Maximum spacing for some retrofit anchors (existing URM guidance)	Anchors (bolts through wall) — max spacing 6 ft (per Appendix guidance for existing buildings)	Appendix A, § A113.1.2–A113.1.3

Exceptions & special cases

If during inspection a positive connection of a deck to the primary structure cannot be verified, the deck must be made self‑supporting instead of relying on unseen anchors (§ 1604.8.3) .
The CBC references ASCE 7 for the specific out‑of‑plane seismic force levels (so the designer must consult ASCE 7 §1.4.4 or §12.11 depending on SDC) — the CBC itself does not restate those detailed force equations in § 1604.8.2 .
For existing reinforced concrete or masonry buildings and unreinforced masonry (URM) retrofit work, Appendix A (Guidelines for Seismic Retrofit of Existing Buildings) provides additional prescriptive minima and installation practices (for example, minimum anchor forces, anchor spacings, crossties, development into diaphragms, and special inspection requirements) — see Appendix A sections A113 and A206 for details and limits (these apply when doing retrofit/alteration work covered by the Existing Building provisions) .
Masonry wall anchors in hollow or cavity walls must be developed into a reinforced grouted element of the wall (no edge‑only anchors into voids) (§ 1604.8.2) .

Common mistakes

Using toenails or standard ring‑shank nails as the only connection for decks — the CBC expressly prohibits relying on toenails or nails subject to withdrawal for deck anchorage (§ 1604.8.3) .
Failing to embed anchors in a reinforced grouted element when anchoring hollow‑unit or cavity masonry walls — leads to inadequate development of tension forces (§ 1604.8.2) .
Designing out‑of‑plane anchorage without consulting the correct ASCE 7 section for the building’s Seismic Design Category (the CBC points to ASCE 7 §1.4.4 for SDC A and §12.11 for other SDCs) — result: wrong force magnitudes and distributions (§ 1604.8.2) .
Relying solely on edge sheathing or edge‑fastening of plywood/steel decking to ledgers for wall anchorage in retrofit work — Appendix A warns this is not acceptable unless analysis demonstrates capacity and field verification/special inspection is provided .
Forgetting to design deck cantilever connections for the two separate load cases listed in § 1604.8.3 (whole deck loads and cantilevered portion loads) .

Worked example — concrete/masonry wall anchored to roof diaphragm

Scenario: 30 ft long reinforced masonry wall at the roof line in a building where the CBC alternate language applies and the designer uses the CBC minimum out‑of‑plane strength design force of 280 lb/linear ft (4.09 kN/m) for anchorage to the diaphragm.

Step 1 — total required anchorage force at the roof line:

Minimum out‑of‑plane design force = 280 lb/linear ft (code alternate/appendix wording) .
Wall length = 30 ft → total required anchorage = 280 lb/ft × 30 ft = 8,400 lb.

Step 2 — choose anchor spacing (use Appendix guidance when doing retrofits or conservative spacing):

Appendix A guidance for some wall anchor installations uses a maximum spacing of 6 ft for anchors through URM (see A113.1.2) .
Using 6‑ft spacing → number of anchors = 30 ft / 6 ft = 5 anchors.

Step 3 — required capacity per anchor:

Required capacity = 8,400 lb / 5 anchors = 1,680 lb per anchor (tension capacity required, neglecting redistribution and safety factors that a designer must apply per ASCE 7 and material standards).

Notes and cautions:

This arithmetic uses the CBC alternate minimum (280 lb/ft) shown in the CBC materials; where the project is governed by the main CBC text the designer must calculate out‑of‑plane forces per ASCE 7 §1.4.4 or §12.11 (as referenced in § 1604.8.2) and apply the appropriate load combinations and factors (§ 1604.8.2) .
Anchor selection must consider embedment, masonry grout and bond beam requirements (anchors in hollow units must be embedded in reinforced grouted elements per § 1604.8.2) and must be detailed so loads are developed into the diaphragm per Appendix A development rules when retrofit provisions apply .
Special inspection or testing of existing anchors may be required when relying on existing elements — see Appendix A retrofit provisions for testing/field verification requirements .

Related provisions (quick reference)

§ 1604.8 — Anchorage; general requirement that buildings be provided with anchorage per the following subsections .
§ 1604.8.1 — General anchorage of roof to walls and walls/columns to foundations; resist uplift and sliding .
§ 1604.8.2 — Structural walls: anchor to roof and floors; ASCE 7 referenced for earthquake out‑of‑plane loads; masonry hollow unit anchor embedment requirement .
§ 1604.8.3 — Decks: positive anchorage required; prohibition on toenails; design for vertical and lateral loads and cantilevered reaction conditions .
§ 1609 — Wind design requirements (wind and out‑of‑plane interaction) — see referenced note in § 1604.8.2 .
§ 1613 — Earthquake design requirements (overall CBC earthquake chapter referenced by § 1604.8.2) .
Appendix A (Existing Building Code) — A113 (wall anchorage minima and spacing), A206 (development of anchors into diaphragms), and other retrofit guidance for URM/reinforced masonry walls — applicable when retrofit/alteration rules are used .
ASCE 7 — §1.4.4 (for SDC A) and §12.11 (for other SDCs) are the specific external references the CBC uses to set out‑of‑plane seismic loads for walls (see § 1604.8.2) .

Code references

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

CBC § 1604.6 High relevance — show source text
1604.6 In-situ load tests. The building official is authorized to require an engineering analysis or a load test, or both, of any construction whenever there is reason to question the safety of the construction for the intended occupancy. Engineering analysis and load tests shall be conducted in accordance with Section 1708.

1604.7 Preconstruction load tests. Materials and methods of construction that are not capable of being designed by approved engineering analysis or that do not comply with the applicable referenced standards, or alternative test procedures in accordance with Section 1707, shall be load tested in accordance with Section 1709.

1604.8 Anchorage. Buildings and other structures, and portions thereof, shall be provided with anchorage in accordance with Sections 1604.8.1 through 1604.8.3, as applicable. 1604.8.1 General. Anchorage of the roof to walls and columns, and of walls and columns to foundations, shall be provided to resist the uplift and sliding forces that result from the application of the prescribed loads. 1604.8.2 Structural walls. Walls that provide vertical load-bearing resistance or lateral shear resistance for a portion of the structure shall be anchored to the roof and to all floors and members that provide lateral support for the wall or that are supported by the wall. The connections shall be capable of resisting the horizontal forces that result from the application of the prescribed loads. The required earthquake out-of-plane loads are specified in Section 1.4.4 of ASCE 7 for walls of structures assigned to Seismic Design Category A and to Section 12.11 of ASCE 7 for walls of structures assigned to all other seismic design categories. Required anchors in masonry walls of hollow units or cavity walls shall be embedded in a reinforced grouted structural element of the wall. See Sections 1609 for wind design requirements and 1613 for earthquake design requirements. 1604.8.3 Decks. Where supported by attachment to an exterior wall, decks shall be positively anchored to the primary structure and designed for both vertical and lateral loads as applicable. Such attachment shall not be accomplished by the use of toenails or nails subject to withdrawal. Where positive connection to the primary building structure cannot be verified during inspection, decks shall be self-supporting. Connections of decks with cantilevered framing members to exterior walls or other framing members shall be designed for both of the following:
1. The reactions resulting from the dead load and live load specified in Table 1607.1, or the snow load specified in Section 1608, in accordance with Section 1605, acting on all portions of the deck.
2. The reactions resulting from the dead load and live load specified in Table 1607.1, or the snow load specified in Section 1608, in accordance with Section 1605, acting on the cantilevered portion of the deck, and no live load or snow load on the remaining portion of the deck. 1604.9 Wind and seismic detailing. Lateral force-resisting systems shall meet seismic detailing requirements and limitations prescribed in this code and ASCE 7 Chapters 11, 12, 13, 15, 17 and 18 as applicable, even where wind load effects are greater than seismic load effects.
Exception: References within ASCE 7 to Chapter 14 shall not apply, except as specifically required herein.

1604.10 Loads on storm shelters. Loads and load combinations on storm shelters shall be determined in accordance with ICC 500.

SECTION 1605—LOAD COMBINATIONS
CBC § 1604.5. High relevance — show source text
Where a separated portion of a building or structure provides required access to, required egress from or shares life safety systems, designated seismic systems, emergency power systems, or emergency and egress lighting systems with another portion having a higher risk category, or provides required electrical, communications, mechanical, plumbing or conveying support to another portion assigned to Risk Category IV, both portions shall be assigned to the higher risk category. Exception: Where a storm shelter designed and constructed in accordance with ICC 500 is provided in a building, structure or portion thereof normally occupied for other purposes, the risk category for the normal occupancy of the building shall apply unless the storm shelter is a designated emergency shelter in accordance with Table 1604.5. 1604.5.2 Photovoltaic (PV) panel systems. Photovoltaic (PV) panel systems and elevated PV support structures shall be assigned a risk category as follows:
1. Ground-mounted PV panel systems serving only Group R-3 buildings shall be assigned to Risk Category I.
2. Ground-mounted PV panel systems other than those described in Items 1 and 5 shall be assigned to Risk Category II.
3. Elevated PV support structures other than those described in Items 4, 5 and 6 shall be assigned to Risk Category II.
4. Rooftop-mounted PV panel systems and elevated PV support structures installed on top of buildings shall be assigned to the same risk category as the risk category of the building on which they are mounted.
5. PV panel systems and elevated PV support structures paired with energy storage systems (ESS) and serving as a dedicated, stand-alone source of backup power for Risk Category IV buildings shall be assigned to Risk Category IV.
6. Elevated PV support structures where the usable space underneath is used for parking of emergency vehicles shall be assigned to Risk Category IV. 1604.6 In-situ load tests. The building official is authorized to require an engineering analysis or a load test, or both, of any construction whenever there is reason to question the safety of the construction for the intended occupancy. Engineering analysis and load tests shall be conducted in accordance with Section 1708.
1604.7 Preconstruction load tests. Materials and methods of construction that are not capable of being designed by approved engineering analysis or that do not comply with the applicable referenced standards, or alternative test procedures in accordance with Section 1707, shall be load tested in accordance with Section 1709.

1604.8 Anchorage. Buildings and other structures, and portions thereof, shall be provided with anchorage in accordance with Sections 1604.8.1 through 1604.8.3, as applicable. 1604.8.1 General. Anchorage of the roof to walls and columns, and of walls and columns to foundations, shall be provided to resist the uplift and sliding forces that result from the application of the prescribed loads. 1604.8.2 Structural walls. Walls that provide vertical load-bearing resistance or lateral shear resistance for a portion of the structure shall be anchored to the roof and to all floors and members that provide lateral support for the wall or that are supported by the wall. The connections shall be capable of resisting the horizontal forces that result from the application of the prescribed loads. The required earthquake out-of-plane loads are specified in Section 1.4.4 of ASCE 7 for walls of structures assigned to Seismic Design Category A and to Section 12.11 of ASCE 7 for walls of structures assigned to all other seismic design categories. Required anchors in masonry walls of hollow units or cavity walls shall be embedded in a reinforced grouted structural element of the wall.
CBC § 4.09 High relevance — show source text
For anchorage of concrete or masonry walls to roof and floor diaphragms, the out-of-plane strength design force shall not be less than 280 lb/linear ft (4.09 kN/m) of wall. Required anchors in masonry walls of hollow units or cavity walls shall be embedded in a reinforced grouted structural element of the wall. See Sections 1609 for wind design requirements and 1613 A for earthquake design requirements. 1604 A .8.3 Decks. Where supported by attachment to an exterior wall, decks shall be positively anchored to the primary structure and designed for both vertical and lateral loads as applicable. Such attachment shall not be accomplished by the use of toenails or nails subject to withdrawal. Where positive connection to the primary building structure cannot be verified during inspection, decks shall be self-supporting. Connections of decks with cantilevered framing members to exterior walls or other framing members shall be designed for both of the following:
1. The reactions resulting from the dead load and live load specified in Table 1607 A .1, or the snow load specified in Section 1608, in accordance with Section 1605 A, acting on all portions of the deck.
2. The reactions resulting from the dead load and live load specified in Table 1607 A .1, or the snow load specified in Section 1608 A, in accordance with Section 1605 A, acting on the cantilevered portion of the deck, and no live load or snow load on the remaining portion of the deck. 1604 A .9 Wind and seismic detailing. Lateral force-resisting systems shall meet seismic detailing requirements and limitations prescribed in this code and ASCE 7 Chapters 11, 12, 13, 15, 17 and 18 as applicable, even where wind load effects are greater than seismic load effects.
Exception: References within ASCE 7 to Chapter 14 shall not apply, except as specifically required herein.

1604 A .10 Loads on storm shelters. Loads and load combinations on storm shelters shall be determined in accordance with ICC 500.

2025 CALIFORNIA BUILDING CODE 16A-9

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STRUCTURAL DESIGN

SECTION 1605 A —LOAD COMBINATIONS

1605 A .1 General. Buildings and other structures and portions thereof shall be designed to resist the strength load combinations specified in ASCE 7, Section 2.3, the allowable stress design load combinations specified in ASCE 7, Section 2.4, or the alternative allowable stress design load combinations of Section 1605 A .2. Exceptions:
CBC § 8.1 High relevance — show source text
1. Elevated PV support structures where the usable space underneath is used for parking of emergency vehicles shall be assigned to Risk Category IV. 1604 A .6 In-situ load tests. The building official is authorized to require an engineering analysis or a load test, or both, of any construction whenever there is reason to question the safety of the construction for the intended occupancy. Engineering analysis and load tests shall be conducted in accordance with Section 1708 A .
1604 A .7 Preconstruction load tests. Materials and methods of construction that are not capable of being designed by approved engineering analysis or that do not comply with the applicable referenced standards, or alternative test procedures in accordance with Section 1707 A, shall be load tested in accordance with Section 1709 A .

1604 A .8 Anchorage. Buildings and other structures, and portions thereof, shall be provided with anchorage in accordance with Sections 1604 A .8.1 through 1604 A .8.3, as applicable. 1604 A .8.1 General. Anchorage of the roof to walls and columns, and of walls and columns to foundations, shall be provided to resist the uplift and sliding forces that result from the application of the prescribed loads. 1604 A .8.2 Structural walls. Walls that provide vertical load-bearing resistance or lateral shear resistance for a portion of the structure shall be anchored to the roof and to all floors and members that provide lateral support for the wall or that are supported by the wall. The connections shall be capable of resisting the horizontal forces that result from the application of the prescribed loads. The required earthquake out-of-plane loads are specified in Section 1.4.4 of ASCE 7 for walls of structures assigned to Seismic Design Category A and to Section 12.11 of ASCE 7 for walls of structures assigned to all other seismic design categories. For anchorage of concrete or masonry walls to roof and floor diaphragms, the out-of-plane strength design force shall not be less than 280 lb/linear ft (4.09 kN/m) of wall. Required anchors in masonry walls of hollow units or cavity walls shall be embedded in a reinforced grouted structural element of the wall. See Sections 1609 for wind design requirements and 1613 A for earthquake design requirements. 1604 A .8.3 Decks. Where supported by attachment to an exterior wall, decks shall be positively anchored to the primary structure and designed for both vertical and lateral loads as applicable. Such attachment shall not be accomplished by the use of toenails or nails subject to withdrawal. Where positive connection to the primary building structure cannot be verified during inspection, decks shall be self-supporting. Connections of decks with cantilevered framing members to exterior walls or other framing members shall be designed for both of the following:
1. The reactions resulting from the dead load and live load specified in Table 1607 A .1, or the snow load specified in Section 1608, in accordance with Section 1605 A, acting on all portions of the deck.
2. The reactions resulting from the dead load and live load specified in Table 1607 A .1, or the snow load specified in Section 1608 A, in accordance with Section 1605 A, acting on the cantilevered portion of the deck, and no live load or snow load on the remaining portion of the deck.
CBC § 12.11.2.2.7 High relevance — show source text
[BS] A206.4 Anchorage at pilasters. Where pilasters are present, the wall anchorage system shall comply with the requirements of this section and Section 12.11.2.2.7 of ASCE 7. The pilasters or the walls immediately adjacent to the pilasters shall be anchored directly to the roof framing such that the existing vertical anchor bolts at the top of the pilasters are bypassed without permitting tension or shear failure at the top of the pilasters.

Exception: If existing vertical anchor bolts at the top of the pilasters are used for the anchorage, additional exterior confinement shall be provided as required to resist the total anchorage force.

[BS] A206.5 Combination of anchor types. New anchors used in combination on a single framing member shall be of compatible behavior and stiffness.

[BS] A206.6 Anchorage at interior walls. Existing interior reinforced concrete or reinforced masonry walls that extend to the floor above or to the roof diaphragm shall be anchored for out-of-plane forces per Sections A206.1 and A206.3. Walls extending through

APPENDIX A-22 2025 CALIFORNIA EXISTING BUILDING CODE

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APPENDIX A—GUIDELINES FOR THE SEISMIC RETROFIT OF EXISTING BUILDINGS

the roof diaphragm shall be anchored for out-of-plane forces on both sides, and continuity ties shall be spliced across or continuous through the interior wall to provide diaphragm continuity.

[BS] A206.7 Collectors. Collectors designed in accordance with this section shall be provided at reentrant corners and at interior shear walls. Existing or new collectors shall have the capacity to develop into the diaphragm a force equal to the lesser of the rocking or shear capacity of the reentrant wall or the tributary shear based on 75 percent of the diaphragm design forces specified in Section 12.10 of ASCE 7. The capacity of the collector need not exceed the capacity of the diaphragm to deliver loads to the collector. A connection shall be provided from the collector to the reentrant wall to transfer the full collector internal force. If a truss or beam other than a rafter or purlin is supported by the reentrant wall or by a column integral with the reentrant wall, then an independent secondary column is required to support the roof or floor members whenever rocking or shear capacity of the reentrant wall is less than the tributary shear.

[BS] A206.8 Mezzanines. Existing mezzanines relying on reinforced concrete or reinforced masonry walls for vertical or lateral support shall be anchored to the walls for the tributary mezzanine load. Walls depending on the mezzanine for lateral support shall be anchored per Sections A206.1, A206.2 and A206.3.

Exception: Existing mezzanines that have independent lateral and vertical support need not be anchored to the walls.

SECTION A207—MATERIALS OF CONSTRUCTION

[BS] A207.1 Materials. Materials permitted by the building code, including their appropriate strength or allowable stresses, shall be used to meet the requirements of this chapter.

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APPENDIX A-24 2025 CALIFORNIA EXISTING BUILDING CODE
CBC § A203 High relevance — show source text
[BS] A202.1 Scope. The provisions of this chapter shall apply to wall anchorage systems that resist out-of-plane forces and to collectors in existing reinforced concrete or reinforced masonry buildings with flexible diaphragms. Wall anchorage systems that were designed and constructed in accordance with the 1997 Uniform Building Code or the 2001 or subsequent editions of the California Building Code shall be deemed to comply with these provisions.

SECTION A203—DEFINITIONS

[BS] A203.1 Definitions. For the purpose of this chapter, the applicable definitions in the California Building Code and the following shall apply:

[BS] CONTINUITY CONNECTOR. A component, typically a plate, rod, strap or hold-down, that ensures load path continuity along the full length of a crosstie or strut.

[BS] CROSSTIE. A member or group of members continuous across the main diaphragm that connects opposite wall lines and transfers out-of-plane wall anchorage forces into the diaphragm.

[BS] FLEXIBLE DIAPHRAGM. A roof or floor sheathed with plywood, wood decking (1-by or 2-by) or metal deck without a concrete topping slab.

[BS] STRUT. A member or group of members continuous across a subdiaphragm that transfers out-of-plane wall anchorage forces into the subdiaphragm.

[BS] WALL ANCHORAGE SYSTEM. The components comprising a complete load path for out-of-plane wall forces from the wall to the main diaphragm, typically including anchors embedded in or fastened to the wall; rods, straps, plates, hold-downs or other hardware; subdiaphragms and their chords; crossties; struts; and continuity connectors.

[BS] WALL SEGMENT. Any length of concrete wall with continuous horizontal reinforcing and not interrupted or intersected by a pilaster or vertical construction joint, or any length of reinforced masonry wall with continuous horizontal reinforcing and not interrupted or intersected by a pilaster or vertical control joint.

SECTION A204—SYMBOLS AND NOTATIONS

[BS] A204.1 General. For the purpose of this chapter, the applicable symbols and notations in the California Building Code shall apply.

SECTION A205—GENERAL REQUIREMENTS

[BS] A205.1 General. The seismic-resisting elements specified in this chapter shall comply with applicable provisions of Section 1613 of the California Building Code and Chapter 12 of ASCE 7, except as modified herein.

[BS] A205.2 Requirements for plans. The plans shall accurately reflect the results of the engineering investigation and design and shall show all pertinent dimensions and sizes for plan review and construction. The following shall be provided:
1. Floor plans and roof plans shall show existing framing construction, diaphragm construction, proposed wall anchors, crossties and collectors. Existing nailing, anchors, crossties and collectors shall be shown on the plans if they are considered part of the lateral force-resisting systems.
2. Typical wall panel details and sections with panel thickness, height, pilasters and location of anchors shall be provided.
3. Details shall include existing and new anchors and the method of developing anchor forces into the diaphragm framing, existing and new crossties, and existing and new or improved support of roof and floor girders at pilasters or walls.
4. The basis for design and the building code used for the design shall be stated on the plans.
CBC § 1.11. High relevance — show source text
The state agency does not adopt sections identified with the following symbol: The Office of the State Fire Marshal’s adoption of this chapter or individual sections is applicable to structures regulated by other state agencies pursuant to Section 1.11.

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APPENDIX A-20 2025 CALIFORNIA EXISTING BUILDING CODE

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APPENDIX A—GUIDELINES FOR THE SEISMIC RETROFIT OF EXISTING BUILDINGS

CHAPTER A2

EARTHQUAKE HAZARD REDUCTION IN EXISTING REINFORCED CONCRETE AND REINFORCED MASONRY WALL BUILDINGS WITH FLEXIBLE DIAPHRAGMS

SECTION A201—PURPOSE

[BS] A201.1 Purpose. The purpose of this chapter is to promote public safety and welfare by reducing the risk of death or injury as a result of the effects of earthquakes on reinforced concrete and reinforced masonry wall buildings with flexible diaphragms. Based on past earthquakes, these buildings have been categorized as being potentially hazardous and prone to significant damage, including possible collapse in a moderate to major earthquake. The provisions of this chapter are minimum standards for structural seismic resistance established primarily to reduce the risk of life loss or injury on both subject and adjacent properties. These provisions will not necessarily prevent loss of life or injury, or prevent earthquake damage to an existing building that complies with these standards.

SECTION A202—SCOPE

[BS] A202.1 Scope. The provisions of this chapter shall apply to wall anchorage systems that resist out-of-plane forces and to collectors in existing reinforced concrete or reinforced masonry buildings with flexible diaphragms. Wall anchorage systems that were designed and constructed in accordance with the 1997 Uniform Building Code or the 2001 or subsequent editions of the California Building Code shall be deemed to comply with these provisions.

SECTION A203—DEFINITIONS

[BS] A203.1 Definitions. For the purpose of this chapter, the applicable definitions in the California Building Code and the following shall apply:

[BS] CONTINUITY CONNECTOR. A component, typically a plate, rod, strap or hold-down, that ensures load path continuity along the full length of a crosstie or strut.

[BS] CROSSTIE. A member or group of members continuous across the main diaphragm that connects opposite wall lines and transfers out-of-plane wall anchorage forces into the diaphragm.

[BS] FLEXIBLE DIAPHRAGM. A roof or floor sheathed with plywood, wood decking (1-by or 2-by) or metal deck without a concrete topping slab.

[BS] STRUT. A member or group of members continuous across a subdiaphragm that transfers out-of-plane wall anchorage forces into the subdiaphragm.

[BS] WALL ANCHORAGE SYSTEM. The components comprising a complete load path for out-of-plane wall forces from the wall to the main diaphragm, typically including anchors embedded in or fastened to the wall; rods, straps, plates, hold-downs or other hardware; subdiaphragms and their chords; crossties; struts; and continuity connectors.
CBC § 12.11.2.2 High relevance — show source text
Where new members are added as crossties, they shall be spaced no more than 24 feet (7315 mm) apart. Where existing girders are used as crossties, their actual spacing shall be deemed adequate even where the spacing exceeds 24 feet (7315 mm), as long as the girders are provided with continuity connectors as required.

Wall anchorage shall not be provided by fastening the edge of plywood sheathing to steel ledgers. Wall anchorage shall not be provided solely by fastening the edge of steel decking to steel ledgers unless analysis demonstrates acceptable capacity. The existing connections shall be subject to field verification and the new connections shall be subject to special inspection.

New wall anchors shall be provided to resist the full wall anchorage design force independent of existing shear or tension anchors.

Exception: Existing cast-in-place anchors shall be permitted as part of the wall anchorage system if the tie element can be readily attached to the anchors, and if the anchors are capable of resisting the total vertical and lateral shear load (including dead load) while being acted on by the maximum wall anchorage tension force caused by an earthquake. Acceptable tension values for the existing anchors shall be established by testing in accordance with Section A205.4.

[BS] A206.3 Development of anchor forces into the diaphragm. Development of the required anchorage forces into roof and floor diaphragms shall comply with the requirements of this section and Section 12.11.2.2 of ASCE 7.

Lengths of development of anchor loads in wood diaphragms shall be based on existing field nailing of the sheathing unless existing edge nailing is positively identified on the original construction plans or at the site.

[BS] A206.4 Anchorage at pilasters. Where pilasters are present, the wall anchorage system shall comply with the requirements of this section and Section 12.11.2.2.7 of ASCE 7. The pilasters or the walls immediately adjacent to the pilasters shall be anchored directly to the roof framing such that the existing vertical anchor bolts at the top of the pilasters are bypassed without permitting tension or shear failure at the top of the pilasters.

Exception: If existing vertical anchor bolts at the top of the pilasters are used for the anchorage, additional exterior confinement shall be provided as required to resist the total anchorage force.

[BS] A206.5 Combination of anchor types. New anchors used in combination on a single framing member shall be of compatible behavior and stiffness.

[BS] A206.6 Anchorage at interior walls. Existing interior reinforced concrete or reinforced masonry walls that extend to the floor above or to the roof diaphragm shall be anchored for out-of-plane forces per Sections A206.1 and A206.3. Walls extending through

APPENDIX A-22 2025 CALIFORNIA EXISTING BUILDING CODE

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APPENDIX A—GUIDELINES FOR THE SEISMIC RETROFIT OF EXISTING BUILDINGS

the roof diaphragm shall be anchored for out-of-plane forces on both sides, and continuity ties shall be spliced across or continuous through the interior wall to provide diaphragm continuity.

[BS] A206.7 Collectors. Collectors designed in accordance with this section shall be provided at reentrant corners and at interior shear walls.
CBC § 181.4 High relevance — show source text
1. Buildings in which the increase in the demand-capacity ratio is due entirely to the addition of rooftop-supported mechanical equipment individually having an operating weight less than 400 pounds (181.4 kg) and where the total additional weight of all rooftop equipment placed after initial construction of the building is less than 10 percent of the roof dead load. For purposes of this exception, “roof” shall mean the roof level above a particular story.
2. Increases in the demand-capacity ratio due to lateral loads from seismic forces need not be evaluated for the installation of rooftop photovoltaic panel systems where the additional roof dead load due to the system, including ballast where applicable, does not exceed 5 pounds per square foot (psf) (0.2394 kN/m [2] ) and does not exceed 10 percent of the dead load of the existing roof.
[BS] 503.5 Seismic Design Category F. Where the work area exceeds 50 percent of the building area, and where the building is assigned to Seismic Design Category F, the lateral force-resisting system of the altered building shall meet the requirements of Section 1609 of the California Building Code and Section 304.3.2 of this code. Supports and attachments for nonstructural components serving 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.

[BS] 503.6 Bracing for unreinforced masonry parapets on reroofing. Where the intended alteration requires a permit for reroofing and involves removal of roofing materials from more than 25 percent of the roof area of a building assigned to Seismic Design Category D, E or F that has parapets constructed of unreinforced masonry, the work 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] 503.7 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.
CBC § 4.1 High relevance — show source text
[BS] A112.4.1 Seismic force distribution. Seismic forces shall be distributed among the vertical-resisting elements in proportion to their relative rigidities, except that moment-resisting frames shall comply with Section A112.4.2.

[BS] A112.4.2 Moment-resisting frames. Moment resisting frames shall not be used with an unreinforced masonry wall in a single line of resistance unless the wall has piers that have adequate shear capacity to sustain rocking in accordance with Section A112.2.2. The frames shall be designed in accordance with the building code to resist 100 percent of the seismic forces tributary to that line of resistance, as determined from Section A111.2. The story drift ratio shall be limited to 0.0075.

SECTION A113—DETAILED BUILDING SYSTEM DESIGN REQUIREMENTS

[BS] A113.1 Wall anchorage.

[BS] A113.1.1 Anchor locations. Unreinforced masonry walls shall be anchored at the roof and floor levels as required in Section A110.2. Ceilings of plaster or similar materials, where not attached directly to roof or floor framing and where abutting masonry walls, shall either be anchored to the walls at a maximum spacing of 6 feet (1829 mm) or be removed.

[BS] A113.1.2 Anchor requirements. Anchors shall consist of bolts installed through the wall as specified in Table A108.1(2), or an approved equivalent at a maximum anchor spacing of 6 feet (1829 mm). Wall anchors shall be secured to the framing members parallel or perpendicular to the wall to develop the required forces.

2025 CALIFORNIA EXISTING BUILDING CODE APPENDIX A-15

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APPENDIX A—GUIDELINES FOR THE SEISMIC RETROFIT OF EXISTING BUILDINGS

[BS] A113.1.3 Minimum wall anchorage. Anchorage of masonry walls to each floor or roof shall resist a minimum force determined as 0.9 S DS times the tributary weight or 200 pounds per linear foot (2920 N/m), whichever is greater, acting normal to the wall at the level of the floor or roof. Existing wall anchors, if used, must be tested and meet the requirements of Section A107.5.1 or be upgraded.

[BS] A113.1.4 Anchors at corners. At the roof and floor levels, both shear and tension anchors shall be provided within 2 feet (610 mm) horizontally from the inside of the corners of the walls.

[BS] A113.2 Diaphragm shear transfer. Anchors transmitting shear forces shall have a maximum spacing of 6 feet (1829 mm) and shall have nuts installed over malleable iron or plate washers where bearing on wood, and heavy-cut washers where bearing on steel.

[BS] A113.3 Collectors. Collector elements shall be provided that are capable of transferring the seismic forces originating in other portions of the building to the element providing the resistance to those forces.

[BS] A113.4 Ties and continuity. Ties and continuity shall conform to the requirements of the building code.

[BS] A113.5 Wall bracing.
CBC § 2.2 High relevance — show source text
APPENDIX A-14 2025 CALIFORNIA EXISTING BUILDING CODE

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

APPENDIX A—GUIDELINES FOR THE SEISMIC RETROFIT OF EXISTING BUILDINGS

[BS] FIGURE A112.2.2—ANALYSIS OF URM WALL IN-PLANE SHEAR FORCES

PIER IS OVERSTRESSED IN SHEAR

V a = Allowable shear strength of a pier.

V p = Shear force assigned to a pier on the basis of a relative shear rigidity analysis.

RETURN

V r

V WX

∑ V r

= Rocking shear capacity of pier.

= Total shear force resisted by the wall.

= Rocking shear capacity of all piers in the wall.

[BS] A112.2.3 Shear walls without openings. Shear walls without openings shall be analyzed the same as for walls with openings, except that V r shall be calculated as follows: Equation A1-23 V r = 0.9( P D + 0.5 P w ) D / H

[BS] A112.3 Plywood-sheathed shear walls. Plywood-sheathed shear walls may be used to resist lateral forces for URM buildings with flexible diaphragms analyzed according to provisions of Section A111. Plywood-sheathed shear walls shall not be used to share lateral forces with other materials along the same line of resistance.

[BS] A112.4 Combinations of vertical elements.

[BS] A112.4.1 Seismic force distribution. Seismic forces shall be distributed among the vertical-resisting elements in proportion to their relative rigidities, except that moment-resisting frames shall comply with Section A112.4.2.

[BS] A112.4.2 Moment-resisting frames. Moment resisting frames shall not be used with an unreinforced masonry wall in a single line of resistance unless the wall has piers that have adequate shear capacity to sustain rocking in accordance with Section A112.2.2. The frames shall be designed in accordance with the building code to resist 100 percent of the seismic forces tributary to that line of resistance, as determined from Section A111.2. The story drift ratio shall be limited to 0.0075.

SECTION A113—DETAILED BUILDING SYSTEM DESIGN REQUIREMENTS

[BS] A113.1 Wall anchorage.

[BS] A113.1.1 Anchor locations. Unreinforced masonry walls shall be anchored at the roof and floor levels as required in Section A110.2. Ceilings of plaster or similar materials, where not attached directly to roof or floor framing and where abutting masonry walls, shall either be anchored to the walls at a maximum spacing of 6 feet (1829 mm) or be removed.

[BS] A113.1.2 Anchor requirements. Anchors shall consist of bolts installed through the wall as specified in Table A108.1(2), or an approved equivalent at a maximum anchor spacing of 6 feet (1829 mm). Wall anchors shall be secured to the framing members parallel or perpendicular to the wall to develop the required forces.

2025 CALIFORNIA EXISTING BUILDING CODE APPENDIX A-15

Frequently asked questions

Do I always use 280 lb/ft for wall anchorage design?

No — the 280 lb/ft figure appears in alternate/appendix CBC wording as a minimum for anchoring concrete or masonry walls to diaphragms; the main CBC text requires designers to determine earthquake out‑of‑plane loads using ASCE 7 (§ 1604.8.2) and to use that calculated force unless the project scope or adopting jurisdiction specifically uses the alternate minimum language .

Can I use existing anchor bolts in a hollow masonry wall?

Only if the anchors are embedded in a reinforced grouted structural element or if existing cast‑in‑place anchors are tested and shown capable of resisting the total anchorage force per Appendix A testing/verification rules; otherwise new anchors developed into grouted elements are required (§ 1604.8.2 and Appendix A) .

Are toenails acceptable for deck anchorage?

No. § 1604.8.3 explicitly prohibits accomplishing the required positive attachment of decks to the primary structure by toenails or other nails subject to withdrawal; if a positive connection cannot be verified, the deck must be self‑supporting .

Where do I find the actual out‑of‑plane force formulas to use?

§ 1604.8.2 directs you to ASCE 7: use ASCE 7 §1.4.4 for SDC A and ASCE 7 §12.11 for structures assigned to other seismic design categories; the CBC does not restate those ASCE 7 formulas in § 1604.8.2 .

If I’m retrofitting an old masonry building, which rules matter most?

For retrofits, Appendix A (Guidelines for Seismic Retrofit of Existing Buildings) adds prescriptive requirements and minimums (anchor spacing, test requirements, crosstie/collector details, minimum anchor forces) that supplement § 1604.8.*; follow the Existing Building provisions when they apply to the project .

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