CHBC · California Historical Building Code

What constitutes a complete and continuous load path?

Q: Does CHBC let me use smaller seismic forces than the regular code when checking load paths?

Yes. CHBC allows using seismic forces up to 0.75 of regular-code forces and caps base shear at 0.30 W (Risk Cat I/II) or 0.40 W (Risk Cat III/IV) for evaluation purposes ( § 8-706.1 ).

In plain terms for a homeowner: the CHBC requires that every part of your historic building that could be pushed or pulled in an earthquake be connected, end-to-end, down to the ground so forces can flow safely out of the building; an architect or engineer must document that continuous route and check connectors and members against the CHBC-specified seismic demands.

Ask a question free See coverage

Last reviewed: July 6, 2026

What the code requires — 2–4 sentences

A complete and continuous load path, including connections, from every part or portion of the structure to the ground must be provided for the required forces — and the building must be verified to be tied together so it can perform as a unit under earthquake forces. This is the explicit requirement of § 8-706.3.

The single most important rule: every element that sees seismic or wind force must have an unbroken route (through members and connectors) that transmits that force down to the ground. § 8-706.3

Requirements in detail

1) What “complete and continuous load path” means (plain terms)

Complete — every part or portion of the structure that could attract lateral or vertical seismic/wind force must be included (no omitted members). See § 8-706.3.
Continuous — there must be no interruption in the chain of force transfer: framing, diaphragms, collectors, struts/crossties, anchors, continuity connectors and foundations must form an unbroken route from the element to the ground. The CHBC requires the load path to include connections. See § 8-706.3 and the CEBC definitions of continuity components.
Verify as a unit — the building must be shown to be “adequately tied together to perform as a unit” under earthquake forces (explicit language in § 8-706.3).

2) Components that are commonly part of the load path (terms & how CHBC treats them)

Diaphragms/collectors — transfer in-plane diaphragm forces to vertical elements (CHBC references lateral load regulations — see Section 8-706 generally).
Anchors / hold‑downs / continuity connectors — components that provide continuity along crossties/struts and connect wall anchors into diaphragms and foundations — defined in CEBC guidance cited by CHBC.
Wall anchorage systems — the set of anchors, rods, straps, plates, hold‑downs, subdiaphragms, crossties, struts and continuity connectors that comprise the load path for out-of-plane wall forces (CEBC definitions used when CHBC refers to unreinforced masonry evaluation).

3) How large are the “required forces” you must design/verify for?

The CHBC modifies the seismic forces used for evaluation; key numerical directions (decision‑relevant) are:

Decision item	Code value / rule	Why it matters	Code Reference
Maximum seismic forces allowed for evaluation	Need not exceed 0.75 × the regular code seismic forces	Limits the seismic demand used when verifying the load path	§ 8-706.1, Exception 1
Seismic base shear cap — Risk Cat I/II	Need not exceed 0.30 W (W = building weight)	Upper bound on base shear used for verification	§ 8-706.1, Exception 3
Seismic base shear cap — Risk Cat III/IV	Need not exceed 0.40 W	Upper bound for higher-risk occupancies	§ 8-706.1, Exception 4
Requirement to include gravity load path	Evaluate and include all parts of the load path for gravity loads	Gravity path evaluation is part of structural adequacy review	§ 8-705.1

(These numeric limits affect the magnitude of the forces the load path must resist — the CHBC text sets these bounds; the code does not replace the need for engineering design of connectors and members.)

4) Verification & evaluation expectations

The CHBC expects an architect or engineer to survey and document the structural framing, reinforcement and anchorage used for lateral resistance (see § 8-703.1). Verification of the load path uses that survey information.
When materials/members do not meet regular code detailing, their ultimate capacity and inelastic performance must be considered; any members likely to fail and lead to collapse must be strengthened (see § 8-706.2.1). This affects whether the existing connections can be relied on as part of the load path.

Exceptions & special cases

CHBC reduces required seismic forces in many cases: you may evaluate using up to 0.75 of regular-code seismic forces, and base shear caps of 0.30 W or 0.40 W depending on Risk Category — see § 8-706.1. These limits change the demand your load path must meet.
Parapets and exterior decoration and some nonstructural features may be treated separately: CHBC requires investigation and anchorage verification but allows exceptions where features are judged not a life‑safety hazard (see § 8-706.4 and § 8-706.5). If such features are required to resist seismic forces, they still must have a load path to ground or be anchored to a member that does.
For nonstructural components evaluated under ASCE 41, CHBC allows using ASCE 41 forces or not exceeding 0.75 × regular-code seismic forces (§ 8-706.5.2).

Common mistakes

Relying on “visual continuity” without verifying connector capacity or corrosion/deterioration. CHBC requires the load path “including connections”; presence alone is not enough. § 8-706.3.
Omitting out‑of‑plane wall anchorage, crossties or subdiaphragm components from the load-path check (CEBC definitions make these part of a wall anchorage system). If out‑of‑plane forces are possible, the anchorage system must be considered.
Treating veneers, cornices or decorative elements as non-issues — CHBC explicitly requires these nonstructural features be evaluated and anchored if they pose a life-safety hazard (§ 8-706.5).
Applying full regular-code seismic forces without checking CHBC limits (0.75 multiplier and base shear caps) — this can produce overly conservative or inconsistent evaluations if not acknowledged. See § 8-706.1.

Worked example — tracing and sizing a demand for the load path (concrete scenario)

Scenario summary (simple, conservative): A historical commercial building is evaluated for seismic lateral resistance. The building weight is W = 200 kips (200,000 lb). The structure is Risk Category III.

Step 1 — establish design/base shear demand per CHBC:

For Risk Category III, CHBC caps base shear at 0.40 W (see § 8-706.1, Exception 4).
Base shear V = 0.40 × 200 kips = 80 kips.

Step 2 — identify load-path collectors and endpoints:

Diaphragm transfers in-plane shear to wall lines → walls transfer shear down to foundation via anchors, rods or straps (these components are part of the wall anchorage system as defined in the CEBC). Confirm diaphragm continuity, collector chords, crossties/struts and continuity connectors are present and documented.

Step 3 — split demand to critical connectors (illustrative):

Suppose a primary shear wall line is to resist 40 kips of the 80-kip base shear (the other 40 kips taken by opposite wall line). If two hold-down anchors connect that wall to the foundation, each anchor would need to be able to resist the uplift/force it is assigned — e.g., 20 kips each if forces are shared equally. (Note: CHBC requires the path exist and be verified; actual connector selection/sizing is an engineering design task using these demands and connector manufacturer capacities.)

Step 4 — verification steps per CHBC practice:

Document framing, diaphragms, anchors, continuity connectors and foundations (survey per § 8-703.1) and show connections and force transfer routes.
Compare connector capacities (manufacturer ratings or calculations) against assigned forces (e.g., 20 kips). Where existing connectors are degraded or undersized, propose strengthening so the unbroken path exists and is adequate. CHBC expects evaluation of inelastic capacity where detailing differs from regular-code requirements (§ 8-706.2, § 8-706.2.1).

Important note: CHBC provides the requirement to provide and verify the load path and sets the seismic force bounds used in evaluation. CHBC does not prescribe specific connector capacities or detailed hold‑down schedules — those are to be calculated by the design professional using the CHBC-specified demand and appropriate engineering practice.

Related provisions

§ 8-706.1 — Seismic forces, R-value basis and exceptions (0.75 multiplier; base shear caps).
§ 8-706.2 — Existing building performance; use of ultimate capacity and consideration of ductility/reserve strength.
§ 8-705.1 — Gravity loads evaluation must include all parts of the load path.
§ 8-706.4 — Parapets and exterior decoration anchorage investigation; exceptions when not a life hazard.
§ 8-706.5 and § 8-706.5.2 — Nonstructural features evaluation and acceptable seismic force levels (ASCE 41 or 0.75×).
CEBC Appendix (definitions used by CHBC for masonry anchorage): Continuity connector, wall anchorage system, crosstie, strut (see CEBC definitions referenced for wall anchorage systems).

Code references

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

CHBC § 8-706.3 High relevance — show source text
8-706.3 Load path. A complete and continuous load path, including connections, from every part or portion of the structure to the ground shall be provided for the required forces. It shall be verified that the structure is adequately tied together to perform as a unit when subjected to earthquake forces.

8-706.4 Parapets. Parapets and exterior decoration shall be investigated for conformance with regular code requirements for anchorage and ability to resist prescribed seismic forces.

An exception to regular code requirements shall be permitted for those parapets and decorations which are judged not to be a hazard to life safety.

8-706.5 Nonstructural features. Nonstructural features of historical structure, such as exterior veneer, cornices and decorations, which might fall and create a life safety hazard in an earthquake, shall be evaluated. Their ability to resist seismic forces shall be verified, or the feature shall be strengthened with improved anchorage when appropriate.

8-706.5.1 Partitions and ceilings of corridors and stairways serving an occupant load of 30 or more shall be investigated to determine their ability to remain in place when the building is subjected to earthquake forces.

8-706.5.2 Seismic forces used to evaluate and improve nonstructural components and their anchorage, where required, shall comply with ASCE 41 or need not exceed 0.75 times the seismic forces prescribed by the requirements of the regular code.

14 2025 CALIFORNIA HISTORICAL BUILDING CODE

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

8-8 ARCHAIC MATERIALS AND METHODS OF CONSTRUCTION

SECTION 8-801 — PURPOSE, INTENT AND SCOPE

8-801.1 Purpose. The purpose of the CHBC is to provide regulations for the use of historical methods and materials of construction that are at variance with regular code requirements or are not otherwise codified, in buildings or structures designated as qualified historical buildings or properties. The CHBC require enforcing agencies to accept any reasonably equivalent alternatives to the regular code when dealing with qualified historical buildings or properties.

8-801.2 Intent. It is the intent of the CHBC to provide for the use of historical methods and materials of construction that are at variance with specific code requirements or are not otherwise codified.

8-801.3 Scope. Any construction type or material that is, or was, part of the historical fabric of a structure is covered by this chapter. Archaic materials and methods of construction present in a historical structure may remain or be reinstalled or be installed with new materials of the same class to match existing conditions.

SECTION 8-802 — GENERAL ENGINEERING APPROACHES

Strength values for archaic materials shall be assigned based upon similar conventional codified materials, or on tests as hereinafter indicated. The archaic materials and methods of construction shall be thoroughly investigated for their details of construction in accordance with Section 8-703. Testing shall be performed when applicable to evaluate existing conditions. The architect or structural engineer in responsible charge of the project shall assign allowable stresses or strength levels to archaic materials. Such assigned strength values shall not be greater than those provided for in the following sections without adequate testing, and shall be subject to the concurrence of the enforcing agency.

SECTION 8-803 — NONSTRUCTURAL ARCHAIC MATERIALS
CHBC § 8-706.1.3 High relevance — show source text
Exceptions:
1. Alternative standards may be used on a case-by-case basis when approved by the authority having jurisdiction. It shall be permitted to exceed the strength limitation of 100 psi in Section A108.2 of the CEBC when test data and building configuration supports higher values subject to the approval of the authority having jurisdiction.
2. CEBC Section A102.2 shall not apply to Qualified Historical Buildings in Risk Category III buildings and other structures whose primary occupancies are public assembly with an occupancy load greater than 300.
8-706.1.3 All deviations from the detailing provisions of the lateral-force-resisting systems shall be evaluated for stability and the ability to maintain load-carrying capacity at the expected inelastic deformations.

8-706.2 Existing building performance. The seismic resistance may be based upon the ultimate capacity of the structure to perform, giving due consideration to ductility and reserve strength of the lateral-force-resisting system and materials while maintaining a reasonable factor of safety. Broad judgment may be exercised regarding the strength and performance of materials not recognized by regular code requirements. (See Chapter 8-8, Archaic Materials and Methods of Construction.)

8-706.2.1 All structural materials or members that do not comply with detailing and proportioning requirements of the regular code shall be evaluated for potential seismic performance and the consequence of non-compliance. All members that would be reasonably expected to fail and lead to collapse or life threatening injury when subjected to seismic demands shall be judged unacceptable, and appropriate structural strengthening shall be developed.

8-706.3 Load path. A complete and continuous load path, including connections, from every part or portion of the structure to the ground shall be provided for the required forces. It shall be verified that the structure is adequately tied together to perform as a unit when subjected to earthquake forces.

8-706.4 Parapets. Parapets and exterior decoration shall be investigated for conformance with regular code requirements for anchorage and ability to resist prescribed seismic forces.

An exception to regular code requirements shall be permitted for those parapets and decorations which are judged not to be a hazard to life safety.

8-706.5 Nonstructural features. Nonstructural features of historical structure, such as exterior veneer, cornices and decorations, which might fall and create a life safety hazard in an earthquake, shall be evaluated. Their ability to resist seismic forces shall be verified, or the feature shall be strengthened with improved anchorage when appropriate.

8-706.5.1 Partitions and ceilings of corridors and stairways serving an occupant load of 30 or more shall be investigated to determine their ability to remain in place when the building is subjected to earthquake forces.

8-706.5.2 Seismic forces used to evaluate and improve nonstructural components and their anchorage, where required, shall comply with ASCE 41 or need not exceed 0.75 times the seismic forces prescribed by the requirements of the regular code.

14 2025 CALIFORNIA HISTORICAL BUILDING CODE

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

8-8 ARCHAIC MATERIALS AND METHODS OF CONSTRUCTION

SECTION 8-801 — PURPOSE, INTENT AND SCOPE
CHBC § 8-706 High relevance — show source text
SECTION 8-706 — LATERAL LOAD REGULATIONS

8-706.1 Seismic forces. Strength-level seismic forces used to evaluate the structure for resistance to seismic loads shall be based on the R -values tabulated in the regular code for similar lateral-force-resisting systems including consideration of the structural detailing of the members where such R -values exist. Where such R -values do not exist, an appropriate R -value shall be rationally assigned considering the structural detailing of the members.

Exceptions:
1. The forces need not exceed 0.75 times the seismic forces prescribed by the regular code requirements.
2. For Risk Category I, II or III structures, near-fault increases in ground motion (maximum considered earthquake ground motion of 0.2 second spectral response greater than 150 percent at 5 percent damping) need not be considered when the fundamental period of the building is 0.5 seconds in the direction under consideration.
3. For Risk Category I or II structures, the seismic base shear need not exceed 0.30W.
4. For Risk Category III or IV structures, the seismic base shear need not exceed 0.40W.
8-706.1.1 When a building is to be strengthened with the addition of a new lateral force resisting system, the R -value of the new system can be used when the new lateral force resisting system resists at least 75 percent of the building’s base shear regardless of its relative rigidity.

8-706.1.2 Evaluation and seismic improvement of unreinforced masonry bearing wall buildings shall comply with the California Existing Building Code (CEBC), Appendix Chapter A1 2013 Edition, and as modified by the CHBC.

Exceptions:
1. Alternative standards may be used on a case-by-case basis when approved by the authority having jurisdiction. It shall be permitted to exceed the strength limitation of 100 psi in Section A108.2 of the CEBC when test data and building configuration supports higher values subject to the approval of the authority having jurisdiction.
2. CEBC Section A102.2 shall not apply to Qualified Historical Buildings in Risk Category III buildings and other structures whose primary occupancies are public assembly with an occupancy load greater than 300.
8-706.1.3 All deviations from the detailing provisions of the lateral-force-resisting systems shall be evaluated for stability and the ability to maintain load-carrying capacity at the expected inelastic deformations.

8-706.2 Existing building performance. The seismic resistance may be based upon the ultimate capacity of the structure to perform, giving due consideration to ductility and reserve strength of the lateral-force-resisting system and materials while maintaining a reasonable factor of safety. Broad judgment may be exercised regarding the strength and performance of materials not recognized by regular code requirements. (See Chapter 8-8, Archaic Materials and Methods of Construction.)

8-706.2.1 All structural materials or members that do not comply with detailing and proportioning requirements of the regular code shall be evaluated for potential seismic performance and the consequence of non-compliance. All members that would be reasonably expected to fail and lead to collapse or life threatening injury when subjected to seismic demands shall be judged unacceptable, and appropriate structural strengthening shall be developed.

8-706.3 Load path. A complete and continuous load path, including connections, from every part or portion of the structure to the ground shall be provided for the required forces. It shall be verified that the structure is adequately tied together to perform as a unit when subjected to earthquake forces.
CHBC § 25.4 High relevance — show source text
Use single-story hold-down force where edges of braced wall panels do not align; a
continuous load path to the foundation shall be maintained.
c. Where hold-down connectors from stories above align with stories below, use cumulative hold-down force to size middle- and bottom-story hold-down connectors.
d. Interpolation between braced wall lengths is permitted.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.479 kPa, 1 pound-force = 4.448 N.
NP = Not Permitted.
NA = Not Applicable.
a. One- and two-family dwellings in Seismic Design Category D2 exceeding two stories shall be designed in accordance with accepted engineering practices.
b. Hold-down force is minimum allowable stress design load for connector providing uplift tie from wall framing at end of braced wall panel at the noted story to wall framing
at end of braced wall panel at the story below, or to foundation or foundation wall. Use single-story hold-down force where edges of braced wall panels do not align; a
continuous load path to the foundation shall be maintained.
c. Where hold-down connectors from stories above align with stories below, use cumulative hold-down force to size middle- and bottom-story hold-down connectors.
d. Interpolation between braced wall lengths is permitted.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.479 kPa, 1 pound-force = 4.448 N.
NP = Not Permitted.
NA = Not Applicable.
a. One- and two-family dwellings in Seismic Design Category D2 exceeding two stories shall be designed in accordance with accepted engineering practices.
b. Hold-down force is minimum allowable stress design load for connector providing uplift tie from wall framing at end of braced wall panel at the noted story to wall framing
at end of braced wall panel at the story below, or to foundation or foundation wall. Use single-story hold-down force where edges of braced wall panels do not align; a
continuous load path to the foundation shall be maintained.
c. Where hold-down connectors from stories above align with stories below, use cumulative hold-down force to size middle- and bottom-story hold-down connectors.
d. Interpolation between braced wall lengths is permitted.| |R602.10.7 Ends of braced wall lines with continuous sheathing. Each end of a braced wall line with continuous sheathing shall
have one of the conditions shown in Figure R602.10.7.
FIGURE R602.10.7—END CONDITIONS FOR BRACED WALL LINES WITH CONTINUOUS SHEATHING
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound = 4.45 N.
END CONDITION 1
CONTINUOUSLY SHEATHED
BRACED WALL LINE
RETURN
PANEL
HOLD-
DOWN
DEVICE
HOLD-DOWN
DEVICE
BRACED WALL PANEL AT
END OF BRACED WALL LINE
BRACED WALL PANEL AT
END OF BRACED WALL LINE
FIRST BRACED
WALL PANEL
RETURN
PANEL
* SEE REQUIREMENTS
48″ MINIMUM BRACED WALL PANEL
AT END OF BRACED WALL LINE
FIRST BRACED
WALL PANEL
D*
10′
CHBC § 5.5 High relevance — show source text
5|2,300|—| |D2
a||5.5|11.0|16.5|22.0|27.5|3,900|6,200| |D2
a|Three-story
dwelling|NP|NP|NP|NP|NP|NA|NA| |For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.479 kPa, 1 pound-force = 4.448 N.
NP = Not Permitted.
NA = Not Applicable.
a. One- and two-family dwellings in Seismic Design Category D2 exceeding two stories shall be designed in accordance with accepted engineering practices.
b. Hold-down force is minimum allowable stress design load for connector providing uplift tie from wall framing at end of braced wall panel at the noted story to wall framing
at end of braced wall panel at the story below, or to foundation or foundation wall. Use single-story hold-down force where edges of braced wall panels do not align; a
continuous load path to the foundation shall be maintained.
c. Where hold-down connectors from stories above align with stories below, use cumulative hold-down force to size middle- and bottom-story hold-down connectors.
d. Interpolation between braced wall lengths is permitted.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.479 kPa, 1 pound-force = 4.448 N.
NP = Not Permitted.
NA = Not Applicable.
a. One- and two-family dwellings in Seismic Design Category D2 exceeding two stories shall be designed in accordance with accepted engineering practices.
b. Hold-down force is minimum allowable stress design load for connector providing uplift tie from wall framing at end of braced wall panel at the noted story to wall framing
at end of braced wall panel at the story below, or to foundation or foundation wall. Use single-story hold-down force where edges of braced wall panels do not align; a
continuous load path to the foundation shall be maintained.
c. Where hold-down connectors from stories above align with stories below, use cumulative hold-down force to size middle- and bottom-story hold-down connectors.
d. Interpolation between braced wall lengths is permitted.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.479 kPa, 1 pound-force = 4.448 N.
NP = Not Permitted.
NA = Not Applicable.
a. One- and two-family dwellings in Seismic Design Category D2 exceeding two stories shall be designed in accordance with accepted engineering practices.
b. Hold-down force is minimum allowable stress design load for connector providing uplift tie from wall framing at end of braced wall panel at the noted story to wall framing
at end of braced wall panel at the story below, or to foundation or foundation wall. Use single-story hold-down force where edges of braced wall panels do not align; a
continuous load path to the foundation shall be maintained.
c. Where hold-down connectors from stories above align with stories below, use cumulative hold-down force to size middle- and bottom-story hold-down connectors.
d.
California Historical Building Code High relevance — show source text
; 2′6″ C.R.S. with 1″ cover on
both top and bottom flanges; 12′ span
simply supported.|115 psf|29 min|||7|1, 5,
13|1/4| |F/C-6-RC-31|6″|6″ deep (3450 psi) concrete deck; 4″ ×
13/4″ × 5 lbs R.S.J.; 2′6″ C.R.S. with 1″ cover
on both top and bottom flanges; 12′ span
simply supported.|25 psf|3 hrs
35 min|||7|1, 2|31/2| |F/C-6-RC-32|6″|6″ deep (4460 psi) concrete deck; 4″ ×
13/4″ × 5 lbs R.S.J.; 2′ C.R.S. with 1″ cover
on both top and bottom flanges; 12′ span
simply supported.|60 psf|4 hrs
30 min|||7|1, 10|41/2| |F/C-6-RC-33|6″|6″ deep (4360 psi) concrete deck; 4″ × 13/4″
× 5 lbs R.S.J.; 2′ C.R.S. with 1″ cover on
both top and bottom flanges; 13′1″ span
restrained.|60 psf|2 hrs|||7|1, 3|2| |F/C-6-RC-34|61/4″|61/4″ thick; 43/4″ (5120 psi) concrete core;
1″ T&G board flooring;1/2″ plaster under-
coat; 4″ × 3″ × 10 lbs R.S.J.; 3′ C.R.S. flush
with top surface concrete; 12′ span simply
supported; 2″ × 1′3″ clinker concrete
insert.|100 psf|4 hrs|||7|1, 7|4| |F/C-6-RC-35|61/4″|43/4″ (3600 psi) concrete core; 1″ T&G
board flooring;1/2″ plaster undercoat; 4″ ×
3″ × 10 lbs R.S.J.; 3′ C.R.S. flush with top
surface concrete; 12′ span simply
supported; 2″ × 1′3″ clinker concrete
insert.|100 psf|2 hrs
30 min|||7|1, 5|21/2| |F/C-6-RC-36|61/4″|43/4″ (2800 psi) concrete core; 1″ T&G
board flooring;1/2″ plaster undercoat; 4″ ×
3″ × 10 lbs R.S.J.; 3′ C.R.S.
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.
CHBC § 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.

2025 CALIFORNIA EXISTING BUILDING CODE APPENDIX A-19

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

APPENDIX A-20 2025 CALIFORNIA EXISTING BUILDING CODE

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

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.
California Historical Building Code High relevance — show source text
|100 psf|1 hr
23 min|||7|1, 2|11/3| |F/C-4-RC-9|4″|4″ deep (4370 psi);1/4″ reinforcement bars
at 6″ pitch with3/4″ cover;1/4″ main rein-
forcement bars at 4″ pitch perpendicular
with1/2″ cover; 13′1″ span restrained.|150 psf|2 hrs|||7|1, 3|2| |F/C-4-RC-10|4″|4″ thick (5140 psi) deck;1/4″ reinforce-
ment bars at 71/2″ pitch with7/8″ cover;3/8″
main reinforcement bars at 33/4″ pitch
perpendicular with1/2″ cover; 13′1″ span
restrained.|140 psf|1 hr
16 min|||7|1, 5|11/4| |F/C-4-RC-11|4″|4″ thick (4000 psi) concrete deck;
3″ × 11/2″ × 4 lbs R.S.J.; 2′6″ C.R.S.; flush
with top surface; 4″ × 6″ x 13 SWG mesh
reinforcement 1″ from bottom of slab; 6′6″
span restrained.|150 psf|2 hrs|||7|1, 3|2| |F/C-4-RC-12|4″|4″ deep (2380 psi) concrete deck;
3″ × 11/2″ × 4 lbs R.S.J.; 2′6″ C.R.S.; flush
with top surface; 4″ × 6″ x 13 SWG mesh
reinforcement 1″ from bottom surface;
6′6″ span restrained.|150 psf|1 hr
3 min|||7|1, 2|1| |F/C-4-RC-13|41/2″|41/2″ thick (5200 psi) deck;1/4″ reinforce-
ment bars at 71/4″ pitch with7/8″ cover;3/8″
main reinforcement bars at 33/4″ pitch
perpendicular with1/2″ cover; 13′1″ span
restrained.|140 psf|2 hrs|||7|1, 3|2| |F/C-4-RC-14|41/2″|41/2″ deep (2525 psi) concrete deck;1/4″
reinforcement bars at 71/2″ pitch with7/8″
cover;3/8″ main reinforcement bars at
33/8″ pitch perpendicular with1/2″ cover;
13′1″ span restrained.|150 psf|42 min|||7|1, 5|2/3| |F/C-4-RC-15|41/2″|41/2″ deep (4830 psi) concrete deck;
11/2″ × No.

CHBC § 3.1 Medium relevance — show source text

2|1/3| |F/C-3-RC-2|31/4″|31/4″ deep (3540 psi) concrete deck;3/8″ main
reinforcement bars at 51/2″ pitch with7/8″
cover;3/8″ main reinforcement bars at 41/2″
pitch perpendicular with1/2″ cover; 13′1″
span restrained.|195
psf|2 hrs|||7|1, 3, 4|2| |F/C-3-RC-3|31/4 ″|31/4″ deep (4175 psi) concrete deck;3/8″ main
reinforcement bars at 51/2″ pitch with7/8″
cover;3/8″ main reinforcement bars at 41/2″
pitch perpendicular with1/2″ cover; 13′1″
span restrained.|195
psf|31
min|||7|1, 5|1/2| |F/C-3-RC-4|31/4″|31/4″ deep (4355 psi) concrete deck;
3/8″ main reinforcement bars at 51/2″ pitch
with7/8″ cover;3/8″ main reinforcement bars
at 41/2″ pitch perpendicular with1/2″ cover;
13′1″ span restrained.|195
psf|41
min|||7|1, 5, 6|1/2|

2025 CALIFORNIA EXISTING BUILDING CODE RESOURCE A-91

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

RESOURCE A—GUIDELINES ON FIRE RATINGS OF ARCHAIC MATERIALS AND ASSEMBLIES

TABLE 3.1—continued FLOOR/CEILING ASSEMBLIES—REINFORCED CONCRETE	Col2	Col3	Col4	Col5	Col6	Col7	Col8	Col9	Col10
ITEM CODE	ASSEMBLY THICKNESS	CONSTRUCTION DETAILS	PERFORMANCE	PERFORMANCE	REFERENCE NUMBER	REFERENCE NUMBER	REFERENCE NUMBER	NOTES	REC. HOURS
ITEM CODE	ASSEMBLY THICKNESS	CONSTRUCTION DETAILS	LOAD	TIME	PRE-BMS-92	BMS-92	POST-BMS-92	POST-BMS-92	POST-BMS-92
F/C-3-RC-5	31/4″	31/4″ thick (3800 psi) concrete deck;3/8″ main reinforcement bars at 51/2″ pitch with7/8″ cover;3/8″ main reinforcement bars at 41/2″ pitch perpendicular with1/2″ cover; 13′1″ span restrained.	195 psf	1 hr 5 min			7	1, 5	1
F/C-4-RC-6	41/4″	41/4″ thick; 31/4″ (4000 psi) concrete deck; 1″ sprayed asbestos lower surface;

CHBC § 3-17 Medium relevance — show source text

Applicants must ensure that when multiple service facilities (i.e., gas, electric, and telecommunications) are installed in close proximity (e.g., in a joint trench), a 12-inch minimum, radial separation is maintained where those facilities transition from below ground to above ground.

3-17 2022 – 2023

Section 3, Electric Service: Underground

3.3.8. (continued)

PG&E allows an exception to that rule when the separation is between PG&E secondary, electric-service conduit and gas-service piping. In this instance, the minimum separation distance may be reduced to 6 inches. Clearances between other facilities can be reduced only when the facility owners reach a mutual agreement.

When electric underground facilities cross under or over gas facilities, the minimum vertical separation between these facilities is 6 inches. The electric and gas facilities should cross at an angle between 45 degrees to 90 degrees. Crossings less than 45 degrees are considered to be parallel and require the minimum horizontal clearance between the two facilities.

12” Minimum

12” Minimum	Col2	Col3	Col4
6” Minimum Bedding Material S G T C 39” Minimum 2” 12” 3” * Increase Minimum Cover to 30” in the Franchise Area. 12” Minimum 4”	6” Minimum Bedding Material S G T C 39” Minimum 2” 12” 3” * Increase Minimum Cover to 30” in the Franchise Area. 12” Minimum 4”	6” Minimum Bedding Material S G T C 39” Minimum 2” 12” 3” * Increase Minimum Cover to 30” in the Franchise Area. 12” Minimum 4”	6” Minimum Bedding Material S G T C 39” Minimum 2” 12” 3” * Increase Minimum Cover to 30” in the Franchise Area. 12” Minimum 4”
			39” Minimum
3”
12”
4”
2”		Bedding Material	Bedding Material

Col1	Col2
24” Minimum Cover*

2”

Figure 3-6 Typical Joint Service Trench

Notes in reference to Figure 3-6 and Figure 3-7.

Trench depth will vary depending on conduit size.

Figure 3-7 PG&E Electric and Gas Service Trench

Soil compaction must meet PG&E’s and any applicable federal, state, county, and local requirements.
All separation and clearance dimensions must be met in Table 3-1 on Page 3-19.

CHBC § 8-705.1 Medium relevance — show source text
8-705.1 Gravity loads. The capacity of the structure to resist gravity loads shall be evaluated and the structure strengthened as necessary. The evaluation shall include all parts of the load path. Where no distress is evident, and a complete load path is present, the structure may be assumed adequate by having withstood the test of time if anticipated dead and live loads will not exceed those historically present.

8-705.2 Wind and seismic loads. The ability of the structure to resist wind and seismic loads shall be evaluated. Wind loads shall be considered when appropriate, but need not exceed 75 percent of the wind loads prescribed by the regular code. The evaluation shall be based on the requirements of Section 8-706.

8.705.2.1 Any unsafe conditions in the lateral-load-resisting system shall be corrected, or alternative resistance shall be provided. When strengthening is required, additional resistance shall be provided to meet the minimum requirements of the CHBC. The strengthening measures shall be selected with the intent of meeting the performance objectives set forth in Section 8-701.2. The evaluation of structural members and structural systems for seismic loads shall consider the inelastic performance of structural members and their ability to maintain load-carrying capacity during the seismic loadings prescribed by the regular code.

8.705.2.2 The architect or engineer shall consider additional measures with minimal loss of, and impact to, historical materials which will reduce damage and needed repairs in future earthquakes to better preserve the historical structure in perpetuity. These additional measures shall be presented to the owner for consideration as part of the rehabilitation or restoration.

2025 CALIFORNIA HISTORICAL BUILDING CODE 13

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

STRUCTURAL REGULATIONS

SECTION 8-706 — LATERAL LOAD REGULATIONS

8-706.1 Seismic forces. Strength-level seismic forces used to evaluate the structure for resistance to seismic loads shall be based on the R -values tabulated in the regular code for similar lateral-force-resisting systems including consideration of the structural detailing of the members where such R -values exist. Where such R -values do not exist, an appropriate R -value shall be rationally assigned considering the structural detailing of the members.

Exceptions:
1. The forces need not exceed 0.75 times the seismic forces prescribed by the regular code requirements.
2. For Risk Category I, II or III structures, near-fault increases in ground motion (maximum considered earthquake ground motion of 0.2 second spectral response greater than 150 percent at 5 percent damping) need not be considered when the fundamental period of the building is 0.5 seconds in the direction under consideration.
3. For Risk Category I or II structures, the seismic base shear need not exceed 0.30W.
4. For Risk Category III or IV structures, the seismic base shear need not exceed 0.40W.
8-706.1.1 When a building is to be strengthened with the addition of a new lateral force resisting system, the R -value of the new system can be used when the new lateral force resisting system resists at least 75 percent of the building’s base shear regardless of its relative rigidity.

8-706.1.2 Evaluation and seismic improvement of unreinforced masonry bearing wall buildings shall comply with the California Existing Building Code (CEBC), Appendix Chapter A1 2013 Edition, and as modified by the CHBC.

Exceptions:

Frequently asked questions

What is the single test I should do to know if a load path is complete?

Trace every element that will get seismic or wind load and confirm, on plans or in the field, that there is an unbroken structural route (members + connectors) from that element down to the foundation/ground; CHBC requires the load path “including connections” from every part to the ground (§ 8-706.3).

Does CHBC let me use smaller seismic forces than the regular code when checking load paths?

Yes. CHBC allows using seismic forces up to 0.75 of regular-code forces and caps base shear at 0.30 W (Risk Cat I/II) or 0.40 W (Risk Cat III/IV) for evaluation purposes (§ 8-706.1).

Are decorative cornices required to be tied into the load path?

CHBC requires nonstructural features (cornices, veneers) to be evaluated and anchored if they could fall and create life-safety hazards; exceptions exist where they are judged not to be a hazard (§ 8-706.5, § 8-706.4).

Who must document the load path for a historical building?

An architect or engineer knowledgeable in historical structures must survey and document framing, reinforcement and anchorage when the structure is evaluated under CHBC (see § 8-703.1).

If I find a missing connector, what does CHBC require?

CHBC requires that the structure be adequately tied together to perform as a unit; missing or inadequate connectors mean the load path is incomplete and strengthening or alternate resistance must be provided (see § 8-706.3 and related sections on strengthening).

Ask about the CHBC

Get cited, plain-English answers on the California Historical Building Code for your project — any code section, any scenario.

Start Free Trial

Related in the CHBC

How to evaluate gravity-load capacity and when may the structure be assumed adequate?

How are parapets and nonstructural features evaluated for seismic hazard?

Gravity loads & load path

California Historical Building Code