CHBC · California Historical Building Code
How does CHBC treat solid‑backed vs independent‑wythe stone masonry and required testing?
For homeowners: The California Historical Building Code lets some historic stone walls be evaluated like solid brick walls — but only after an expert inspects and tests the wall to prove the wythes are bonded (solid collar joints or headers/anchors) or that the wall core is essentially solid and tied together with epoxied steel connectors spaced no more than 4 feet apart; un‑interlocked stones must be pull‑tested to confirm strength. **§ 8-805.2.1, § 8-805.2.2, § 8-805.2.3**
Last reviewed: July 6, 2026
What the code requires — 2-4 sentences
The CHBC allows historic stone masonry to be treated as solid brick masonry when certain inspection and testing conditions are met. For solid‑backed stone masonry the code requires verification of solid collar joints or equivalent header action or anchors (§ 8-805.2.1) . For independent‑wythe stone masonry the code requires the core to be essentially solid, steel ties epoxied in drilled holes at floors/roof and at not more than 4 feet (1219 mm) on center, plus a reinforcing element at or near the top of the wall (§ 8-805.2.2) . Testing of stone masonry follows the CEBC/brick‑masonry approach but requires pull tests for stones that are not interlocked (§ 8-805.2.3) .
The single most important rule: Stone walls may be judged and designed like solid brick masonry only when representative inspection/testing confirm the physical continuity (collars/headers/anchors or a solid core plus tied wythes) required by the CHBC. § 8-805.2.1 / § 8-805.2.2
Requirements in detail
Key defined terms (first use bolded)
- Solid‑backed stone masonry — stone backed with brick masonry or stone wythes that effectively overlap to provide header action; eligible to be treated as solid brick masonry when verified (§ 8-805.2.1) .
- Independent wythe stone masonry — stone with face wythes that act independently (not tied by headers); may still be treated as solid if the core is essentially solid and ties are installed per the code (§ 8-805.2.2) .
- Collar joints — mortar joints between wythes; must be solid where required to establish composite action for solid‑backed walls (§ 8-805.2.1) .
- Steel ties — steel connectors epoxied into drilled holes between outer stone wythes for independent wythe walls; spacing and locations are prescribed in § 8-805.2.2 .
Decision‑relevant dimensions, values and tests
| Feature | Requirement / Value | Code Reference |
|---|---|---|
| Treatment as solid brick masonry | Allowed when representative testing/inspection verify required bonding (collar joints, header lap or anchors) for solid‑backed, or solid core + ties for independent wythe | § 8-805.2, § 8-805.2.1, § 8-805.2.2 |
| Solid collar joints / header lap | Representative testing/inspection must verify solid collar joints between stone and brick and a reasonable number of stones lap with the brick wythes as headers, OR presence of steel anchors | § 8-805.2.1 |
| Equivalent header courses | Solid stone wythes that effectively overlap to provide header courses may be treated as solid brick masonry | § 8-805.2.1 |
| Core condition for independent wythe | Core must be essentially solid (representative testing/inspection) | § 8-805.2.2 |
| Steel ties — location & spacing | Epoxied in drilled holes between outer stone wythes at floors and roof and not to exceed 4 feet (1219 mm) on center in each direction between floors and roof | § 8-805.2.2 |
| Reinforcing at top | A reinforcing element shall exist or be provided at or near the top of all stone masonry walls | § 8-805.2.2 |
| Type of testing | Testing similar to 2010 CEBC brick‑masonry requirements; for stones not interlocked, pull‑out tests of representative stones are required and shear area is calculated after the test | § 8-805.2.3 |
| Default allowable shear (existing solid masonry) | Existing solid masonry may be allowed a maximum ultimate shear strength of 9 pounds per square inch (62.1 kPa) without testing when an architect/engineer documents inspection and condition — for unreinforced masonry meeting other limits (see § 8-805.1) | § 8-805.1 |
Notes on testing procedure: The CHBC points designers to the CEBC (California Existing Building Code) / IEBC procedures for representative coring, shear tests, and reporting; § 8-805.2.3 specifies that for stone, where stones are not interlocked, representative stones shall be pulled outward from the wall and the shear area recalculated for the test result .
How the two conditions differ, succinctly
- Solid‑backed: proof of collar joints, header lap or anchors establishes composite action so the wall is treated as solid brick masonry (§ 8-805.2.1) .
- Independent wythe: even if face wythes are independent, testing can permit treatment as solid if the core is essentially solid and steel ties epoxied per spacing/locations are provided, plus top reinforcement (§ 8-805.2.2) .
Exceptions & special cases
- If stone wythes themselves effectively overlap to act as header courses (i.e., the stone wythes are interlocked), they may be treated as solid brick masonry without additional anchors (§ 8-805.2.1) .
- The CHBC ties its stone‑masonry testing requirements to the CEBC (2010) brick‑masonry testing approach; where CEBC provides alternatives (nondestructive testing, coring protocols), those approaches are the accepted path unless CHBC text specifies otherwise (§ 8-805.2.3) .
- A reinforcing element is mandatory at/near the top of independent‑wythe stone walls even if ties are installed; this may be a bond beam, steel cap, or equivalent element per the design authority (§ 8-805.2.2) .
Common mistakes
- Assuming any multiwythe stone wall is “composite” without verifying solid collar joints or header action — the CHBC requires representative inspection/testing to prove this (§ 8-805.2.1) .
- Installing ties but not epoxying them in drilled holes as required (the code explicitly requires epoxied ties for independent wythes) (§ 8-805.2.2) .
- Using the CEBC/IEBC brick‑masonry testing procedures without performing the pull tests for representative non‑interlocked stones — CHBC requires pull‑out testing for those stones and recalculation of shear area after the test (§ 8-805.2.3) .
- Overlooking the top reinforcing element requirement for independent‑wythe walls; ties alone are not enough per § 8-805.2.2 .
Worked example — concrete scenario applying the rule with numbers
Scenario: A historic building has a 12‑foot‑high exterior stone wall composed of two separate stone face wythes with an untidy core (some rubble, some voids). You are asking whether it can be treated as solid for seismic evaluation.
Step 1 — Inspection/testing: Perform representative core inspections and identify that the core is NOT uniformly bonded; several areas show voids and some stones are not interlocked. Under § 8-805.2.2 the wall therefore does not yet qualify as essentially solid without corrective action (testing/repair) .
Step 2 — Retrofit to meet CHBC conditions:
- Install steel ties epoxied into drilled holes at the floor and roof lines and at intermediate locations so spacing does not exceed 4 feet (1219 mm) on center in each direction between floors and roof. For a 12 ft tall wall between floor and roof you would place ties at roughly 0 ft (floor), 4 ft, 8 ft, and 12 ft (roof) vertical spacing to meet the “not to exceed 4 ft o.c.” requirement (§ 8-805.2.2) .
- Provide a reinforcing element at or near the top (for example, a steel bond beam or reinforced concrete cap) per § 8-805.2.2 .
Step 3 — Testing:
- Conduct representative testing per CEBC brick‑masonry methods and, for any stones that are not interlocked, perform pull‑out tests pulling those representative stones outward and recalculate shear area per § 8-805.2.3 .
Step 4 — Result: If tests + inspection demonstrate the core is effectively made solid by grout/ties (or was essentially solid to begin with) and tie spacing + top reinforcement meet the code, the wall may be treated as solid brick masonry for allowable shear/stress calculations and seismic evaluation as described in § 8-805.1 and the referenced CEBC/IEBC procedures .
Related provisions
- § 8-805.2 — Stone masonry general statement and linkage to the specific subsections .
- § 8-805.2.1 — Solid‑backed stone masonry criteria (collar joints, headers, anchors) .
- § 8-805.2.2 — Independent‑wythe stone masonry criteria (solid core, epoxied steel ties ≤ 4 ft (1219 mm) o.c., top reinforcement) .
- § 8-805.2.3 — Testing procedures for stone masonry, including pull tests for non‑interlocked stones .
- § 8-805.1 — Treatment of existing solid masonry (including the 9 psi / 62.1 kPa maximum ultimate shear allowance without testing under specified inspection) — referenced in the stone masonry subsections as the target treatment category .
- § 8-805.3 — Reconstructed walls (relevance when walls are rebuilt or heavily repaired) .
Code references
Grounded in the retrieved California Historical Building Code — click a citation to read the verbatim passage:
CHBC § 8-804 High relevance — show source text
SECTION 8-804 — ALLOWABLE CONDITIONS FOR SPECIFIC MATERIALS
Archaic materials which exist and are to remain in qualified historical buildings or structures shall be evaluated for their condition and for loads required by this code. The structural survey required in Section 8-703 of the CHBC shall document existing conditions, reinforcement, anchorage, deterioration and other factors pertinent to establishing allowable stresses, strength levels and adequacy of the archaic materials. The remaining portion of this chapter provides additional specific requirements for commonly encountered archaic materials.
SECTION 8-805 — MASONRY
For adobe, see Section 8-806.
8-805.1 Existing solid masonry. Existing solid masonry walls of any type, except adobe, may be allowed, without testing, a maximum ultimate strength of 9 pounds per square inch (62.1 kPa) in shear where there is a qualifying statement by the architect or engineer that an inspection has been made, that mortar joints are filled and that both brick and mortar are reasonably good. The shear stress above applies to unreinforced masonry, except adobe, where the maximum ratio of unsupported height or length to thickness does not exceed 13, and where minimum quality mortar is used or exists. Wall height or length is measured to supporting or resisting elements that are at least twice as stiff as the tributary wall. Stiffness is based on the gross section. Shear stress may be increased by the addition of 10 percent of the axial direct stress due to the weight of the wall directly above. Higher-quality mortar may provide a greater shear value and shall be tested in accordance with Appendix A, Chapter A1 of the California Existing Building Code (CEBC) 2010 edition, and as modified by the CHBC.
8-805.2 Stone masonry.
8-805.2.1 Solid-backed stone masonry. Stone masonry solidly backed with brick masonry shall be treated as solid brick masonry as described in Section 8-805.1 and in the 2009 International Existing Building Code [®] (IEBC [®] ), provided representative testing and inspection verifies solid collar joints between stone and brick and that a reasonable number of stones lap with the brick wythes as headers or that steel anchors are present. Solid stone masonry where the wythes of stone effectively overlap to provide the equivalent header courses may also be treated as solid brick masonry.
8-805.2.2 Independent wythe stone masonry. Stone masonry with independent face wythes may be treated as solid brick masonry as described in Section 8-805.1 and the CEBC, provided representative testing and inspection verify that the core is essentially solid in the masonry wall and that steel ties are epoxied in drilled holes between outer stone wythes at floors, roof and not to exceed 4 feet (1219 mm) on center in each direction, between floors and roof. A reinforcing element shall exist or be provided at or near the top of all stone masonry walls.
2025 CALIFORNIA HISTORICAL BUILDING CODE 15
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ARCHAIC MATERIALS AND METHODS OF CONSTRUCTION
8-805.2.3 Testing of stone masonry. Testing of stone masonry shall be similar to the 2010 CEBC requirements for brick masonry, except that representative stones which are not interlocked shall be pulled outward from the wall and shear area appropriately calculated after the test.
CHBC § 8-805.2 High relevance — show source text
8-805.2 Stone masonry.
8-805.2.1 Solid-backed stone masonry. Stone masonry solidly backed with brick masonry shall be treated as solid brick masonry as described in Section 8-805.1 and in the 2009 International Existing Building Code [®] (IEBC [®] ), provided representative testing and inspection verifies solid collar joints between stone and brick and that a reasonable number of stones lap with the brick wythes as headers or that steel anchors are present. Solid stone masonry where the wythes of stone effectively overlap to provide the equivalent header courses may also be treated as solid brick masonry.
8-805.2.2 Independent wythe stone masonry. Stone masonry with independent face wythes may be treated as solid brick masonry as described in Section 8-805.1 and the CEBC, provided representative testing and inspection verify that the core is essentially solid in the masonry wall and that steel ties are epoxied in drilled holes between outer stone wythes at floors, roof and not to exceed 4 feet (1219 mm) on center in each direction, between floors and roof. A reinforcing element shall exist or be provided at or near the top of all stone masonry walls.
2025 CALIFORNIA HISTORICAL BUILDING CODE 15
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ARCHAIC MATERIALS AND METHODS OF CONSTRUCTION
8-805.2.3 Testing of stone masonry. Testing of stone masonry shall be similar to the 2010 CEBC requirements for brick masonry, except that representative stones which are not interlocked shall be pulled outward from the wall and shear area appropriately calculated after the test.
8-805.3 Reconstructed walls. Totally reconstructed walls utilizing original brick or masonry, constructed similar to original, shall be constructed in accordance with the regular code. Repairs or infills may be constructed in a similar manner to the original walls without conforming to the regular code.
SECTION 8-806 — ADOBE
8-806.1 General. Unburned clay masonry may be constructed, reconstructed, stabilized or rehabilitated subject to this chapter. Alternative approaches which provide an equivalent or greater level of safety may be used, subject to the concurrence of the enforcing agency.
8-806.2 Moisture protection. Provisions shall be in place to protect adobe structures from deterioration due to moisture penetration. Adobe shall be maintained in reasonably good condition. Particular attention shall be given to moisture content of adobe walls. Unmaintained walls or ruins shall be evaluated for safety based on their condition and stability. Additional protection measures may be appropriate subject to the concurrence of the enforcing agency.
8-806.3 Height to thickness ratio. Unreinforced new or existing adobe walls meeting these criteria need not be evaluated for out of plane failure. Where existing dimensions do not meet these conditions, additional strengthening measures, such as a bond beam, may be appropriate. Existing sod or rammed earth walls shall be considered similar to the extent these provisions apply.
- One-story adobe load-bearing walls shall not exceed a height-to-thickness ratio of 6.
- Two-story adobe buildings or structures’ height- to-thickness wall ratio shall not exceed 6 at the ground floor and 5 at the second floor, and shall be measured at floor-to-floor height when the second floor and attic ceiling/roof are connected to the wall as described below.
CHBC § 2.5 High relevance — show source text
**_ Two cores shall be taken from each building for each 5,000 square feet (465 m [2] ) of the masonry wall area or fraction thereof. The approved agency shall perform or observe the coring of the masonry walls and sample locations shall be subject to approval of the registered design professional.
Core samples shall comply with the following: 1. Cored no sooner than 7 days after grouting of the selected area; 2. Be a minimum of 3 [ 3] / 4 inches (96 mm) in nominal diameter; and 3. Sampled in such a manner as to exclude any masonry unit webs, mortar joint, or reinforcing steel. If all cells contain rein- forcement, alternate core locations or means to detect void or delamination shall be selected by the registered design professional and approved by the building official.
Visual examination of all cores shall be made by an approved agency and the condition of the cores reported as required by the California Administrative Code. Shear test shall test both joints between the grout core and the outside wythes or face shell of the masonry 28 days after grouting of the sample area using a shear test apparatus acceptable to the enforcement agency. Core samples shall not be soaked before testing. Core samples to be tested shall be stored in sealed plastic bags or non-absorbent containers immediately after coring and for at least 5 days prior to testing. The average unit shear value for each pair of cores (4 shear tests) from each 5,000 square feet of wall area (or less) on the cross section of the cores shall not be less than 2.5 √ f ′ m psi.
All cores shall be submitted to an approved agency for examination, including core specimens where an outside wythe or face shell separates from the grout core prior to shear testing, including during the coring operation. At this condition, a shear value of zero shall be assigned to the separated joint interface and the average unit shear value shall include this result. The approved agency shall report the location where each core was taken, the findings of their visual examination of each core, identify which cores were selected for shear testing, and the results of the shear tests. Additional cores shall be permitted to be taken at the direction of the registered design professional and with approval of the enforcement agency.
Exceptions: 1. Core sampling and testing is not required for nonbearing nonshear masonry walls, not exceeding a total wall height of 12 feet above top of foundation, built with single-wythe hollow unit concrete masonry that attaches opposite face shells using webs cast as single unit, when designed using an f ′ m not exceeding 2,000 psi (13.79 MPa). 2. An infrared thermographic survey or other nondestructive test procedures, shall be permitted to be approved as an alter- native system to detect voids or delamination in grouted masonry in lieu of core sampling and testing.
2115.5 Seismic design.
2115.5.1 TMS 402, Section 5.4.1.4. Replace TMS 402, Section 5.4.1.4 Items (a), (b), (d) & (e) by the following: (a) Vertical reinforcement shall be enclosed by lateral ties at least [3] / 8 in. (12.7 mm) in diameter.
CHBC § 2.3.10. Medium relevance — show source text
SECTION A106—MATERIALS REQUIREMENTS
[BS] A106.1 Condition of existing materials. Existing materials used as part of the required vertical load-carrying or seismic forceresisting system shall be evaluated by on-site investigation and: determined to be in good condition (free of degraded mortar, degraded masonry units or significant cracking); or shall be repaired, enhanced, retrofitted or removed and replaced with new materials. Mortar joint deterioration shall be patched by pointing or repointing of the eroded joint in accordance with Section A106.2.3.10. Existing significant cracks in solid unit unreinforced and solid grouted hollow unit masonry shall be repaired.
[BS] A106.2 Existing unreinforced masonry.
[BS] A106.2.1 General. Unreinforced masonry walls used to support vertical loads or seismic forces parallel and perpendicular to the wall plane shall be tested as specified in this section. Masonry that does not meet the minimum requirements established by this chapter shall be repaired, enhanced, removed and replaced with new materials, or alternatively, shall have its structural functions replaced with new materials and shall be anchored to supporting elements.
[BS] A106.2.2 Lay-up of walls. Unreinforced masonry walls shall be laid in a running bond pattern.
[BS] A106.2.2.1 Header in multiple-wythe solid brick. The facing and backing wythes of multiple-wythe walls shall be bonded so that not less than 10 percent of the exposed face area is composed of solid headers extending not less than 4 inches (102 mm) into the backing wythes. The clear distance between adjacent header courses shall not exceed 24 inches (610 mm) vertically or horizontally. Where backing consists of two or more wythes, the headers shall extend not less than 4 inches (102 mm) into the most distant wythe, or the backing wythes shall be bonded together with separate headers for which the area and spacing conform to the foregoing. Wythes of walls not meeting these requirements shall be considered to be veneer, and shall not be included in the effective thickness used in calculating the height-to-thickness ratio and the shear capacity strength of the wall. Exception: Where S D 1 is 0.3 g or less, veneer wythes anchored and made composite with backup masonry are permitted to be used for calculation of the effective thickness.
[BS] A106.2.2.2 Lay-up patterns. Lay-up patterns other than those specified in Section A106.2.2.1 are allowed if their performance can be justified.
[BS] A106.2.3 Testing of masonry.
[BS] A106.2.3.1 Concrete masonry units and structural clay load-bearing tile. Grouted or ungrouted hollow concrete masonry units shall be tested in accordance with ASTM C140. Grouted or ungrouted structural clay load-bearing tile shall be tested in accordance with ASTM C67.
APPENDIX A-6 2025 CALIFORNIA EXISTING BUILDING CODE
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APPENDIX A—GUIDELINES FOR THE SEISMIC RETROFIT OF EXISTING BUILDINGS
[BS] A106.2.3.2 In-place mortar joint shear tests. Mortar joint shear test values, v to, shall be obtained by one of the following:
- ASTM C1531.
CHBC § 5.3 Medium relevance — show source text
- The type of interior wall and ceiling materials, and framing.
- The extent and type of existing wall anchorage to floors and roof where used in the design.
- The extent and type of parapet corrections that were previously performed, if any.
- Repair details, if any, of cracked or damaged unreinforced masonry walls required to resist forces specified in this chapter.
- All other plans, sections and details necessary to delineate required retrofit construction.
- The design procedure used shall be stated on both the plans and the permit application.
- Details of the anchor prequalification program required by Section A107.5.3, if used, including location and results of all tests.
- Quality assurance requirements of special inspection for all new construction materials and for retrofit construction including: anchor tests, pointing or repointing of mortar joints, installation of adhesive or mechanical anchors, and other elements as deemed necessary to ensure compliance with this chapter.
[BS] A105.4 Structural observation, testing and inspection. Structural observation, in accordance with Section 1704.6 of the Cali- fornia Building Code, shall be required for all structures in which seismic retrofit is being performed in accordance with this chapter. Structural observation shall include visual observation of work for compliance with the approved construction documents and confirmation of existing conditions assumed during design. Structural testing and inspection for new and existing construction materials shall be in accordance with the building code, except as modified by this chapter. Special inspection as described in Section A105.3, Item 10, shall be provided equivalent to Level 3 as prescribed in TMS 402, Table 3.1(2).
SECTION A106—MATERIALS REQUIREMENTS
[BS] A106.1 Condition of existing materials. Existing materials used as part of the required vertical load-carrying or seismic forceresisting system shall be evaluated by on-site investigation and: determined to be in good condition (free of degraded mortar, degraded masonry units or significant cracking); or shall be repaired, enhanced, retrofitted or removed and replaced with new materials. Mortar joint deterioration shall be patched by pointing or repointing of the eroded joint in accordance with Section A106.2.3.10. Existing significant cracks in solid unit unreinforced and solid grouted hollow unit masonry shall be repaired.
[BS] A106.2 Existing unreinforced masonry.
[BS] A106.2.1 General. Unreinforced masonry walls used to support vertical loads or seismic forces parallel and perpendicular to the wall plane shall be tested as specified in this section. Masonry that does not meet the minimum requirements established by this chapter shall be repaired, enhanced, removed and replaced with new materials, or alternatively, shall have its structural functions replaced with new materials and shall be anchored to supporting elements.
[BS] A106.2.2 Lay-up of walls. Unreinforced masonry walls shall be laid in a running bond pattern.
[BS] A106.2.2.1 Header in multiple-wythe solid brick. The facing and backing wythes of multiple-wythe walls shall be bonded so that not less than 10 percent of the exposed face area is composed of solid headers extending not less than 4 inches (102 mm) into the backing wythes. The clear distance between adjacent header courses shall not exceed 24 inches (610 mm) vertically or horizontally.
CHBC § 6.895 Medium relevance — show source text
WALL CONSTRUCTION
TABLE R606.9—ALLOWABLE COMPRESSIVE STRESSES FOR EMPIRICAL DESIGN OF MASONRY—continued Col2 Col3 ** CONSTRUCTION; COMPRESSIVE STRENGTH OF UNIT, GROSS AREA** ** ALLOWABLE COMPRESSIVE**
STRESSESa GROSS CROSS-SECTIONAL AREAb** ALLOWABLE COMPRESSIVE**
STRESSESa GROSS CROSS-SECTIONAL AREAb** CONSTRUCTION; COMPRESSIVE STRENGTH OF UNIT, GROSS AREA** ** Type M or S mortar** ** Type N mortar** Masonry of hollow load-bearing units: 2,000 + psi 140 120 1,500 psi 115 100 1,000 psi 75 70 700 psi 60 55 Hollow walls (cavity or masonry bondedd) solid units: 2,500 + psi 160 140 1,500 psi 115 100 Hollow units 75 70 Stone ashlar masonry: Granite 720 640 Limestone or marble 450 400 Sandstone or cast stone 360 320 Rubble stone masonry: Coarse, rough or random 120 100 For SI: 1 pound per square inch = 6.895 kPa.
a. Linear interpolation shall be used for determining allowable stresses for masonry units having compressive strengths that are intermediate between those given in the table.
b. Gross cross-sectional area shall be calculated on the actual rather than nominal dimensions.
c. See Section R606.13.
d. Where floor and roof loads are carried on one wythe, the gross cross-sectional area is that of the wythe under load; if both wythes are loaded, the gross cross-sectional area is
that of the wall minus the area of the cavity between the wythes. Walls bonded with metal ties shall be considered as cavity walls unless the collar joints are filled with mortar
or grout.For SI: 1 pound per square inch = 6.895 kPa.
a. Linear interpolation shall be used for determining allowable stresses for masonry units having compressive strengths that are intermediate between those given in the table.
b. Gross cross-sectional area shall be calculated on the actual rather than nominal dimensions.
c. See Section R606.13.
d. Where floor and roof loads are carried on one wythe, the gross cross-sectional area is that of the wythe under load; if both wythes are loaded, the gross cross-sectional area is
that of the wall minus the area of the cavity between the wythes. Walls bonded with metal ties shall be considered as cavity walls unless the collar joints are filled with mortar
or grout.For SI: 1 pound per square inch = 6.895 kPa.
a. Linear interpolation shall be used for determining allowable stresses for masonry units having compressive strengths that are intermediate between those given in the table.
b. Gross cross-sectional area shall be calculated on the actual rather than nominal dimensions.
c. See Section R606.13.
d. Where floor and roof loads are carried on one wythe, the gross cross-sectional area is that of the wythe under load; if both wythes are loaded, the gross cross-sectional area is
that of the wall minus the area of the cavity between the wythes.CHBC § 63.5 Medium relevance — show source text
Tension bolts
a. Bolts extending entirely through unreinforced masonry walls secured with
bearing plates on far side of a three-wythe minimum wall with at least 30
square inches (19 350 mm2) of area4,5
b. All thread rod extending to the exterior face of the wall installed in adhesive9|5,400 lbs (24 010 N) per bolt6
2,700 lbs (12 009 N) per bolt for two-wythe walls6
3,600 lbs (16 014 N) per bolt| |5. Shear bolts
Bolts embedded a minimum of 8 inches (203 mm) into unreinforced masonry
walls and centered in a 21/2-inch-diameter (63.5 mm) hole filled with dry-pack or
nonshrink grout. Through bolts with first 8 inches (203 mm) as noted above and
embedded all thread rod as noted in Item 4.b5,7,9|1/2 inch (12.7 mm) diameter = 1,050 lbs (4671 N)6
5/8 inch (15.9 mm) diameter = 1,500 lbs (6672 N)6
3/4 inch (19 mm) diameter = 2,250 lbs (10 008 N)6| |6. Infilled walls
Reinforced masonry infilled openings in existing unreinforced masonry walls.
Provide keys or dowels to match reinforcing.|Same as values specified for unreinforced masonry walls| |7. Reinforced masonry
Masonry piers and walls reinforced per the regular code|Same as values specified in the regular code8| |8. Reinforced concrete
Concrete footings, walls and piers reinforced as specified in the regular code
and designed for tributary loads|Same as values specified in the regular code8| |1. Values are for strength level loads as defined in regular code standards.
2. Values may be adjusted for other fasteners when approved by the enforcing authority.
3. In addition to existing sheathing value.
4. Bolts to be1/2-inch (12.7 mm) minimum diameter.
5. Other bolt sizes, values and installation methods may be used provided a testing program is conducted in accordance with regular code standards. Bolt spacing shall not
exceed 6 feet (1830 mm) on center and shall not be less than 12 inches (305 mm) on center.
6. Other masonry based on tests or other substantiated data.
7. Embedded bolts to be tested as specified in regular code standards.
8. Stresses given may be increased for combinations of loads as specified in the regular code.
9. Adhesives shall be approved by the enforcing agency and installed in accordance with the manufacturer’s recommendations. All drilling dust shall be removed from drilled
holes prior to installation.|1. Values are for strength level loads as defined in regular code standards.
2. Values may be adjusted for other fasteners when approved by the enforcing authority.
3. In addition to existing sheathing value.
4. Bolts to be1/2-inch (12.7 mm) minimum diameter.
5. Other bolt sizes, values and installation methods may be used provided a testing program is conducted in accordance with regular code standards. Bolt spacing shall not
exceed 6 feet (1830 mm) on center and shall not be less than 12 inches (305 mm) on center.
6.CHBC § 6-98 Medium relevance — show source text
R606.9 Allowable stresses. Allowable compressive stresses in masonry shall not exceed the values prescribed in Table R606.9. In determining the stresses in masonry, the effects of all loads and conditions of loading and the influence of all forces affecting the design and strength of the several parts shall be taken into account.
TABLE R606.9—ALLOWABLE COMPRESSIVE STRESSES FOR EMPIRICAL DESIGN OF MASONRY Col2 Col3 ** CONSTRUCTION; COMPRESSIVE STRENGTH OF UNIT, GROSS AREA** ** ALLOWABLE COMPRESSIVE**
STRESSESa GROSS CROSS-SECTIONAL AREAb** ALLOWABLE COMPRESSIVE**
STRESSESa GROSS CROSS-SECTIONAL AREAb** CONSTRUCTION; COMPRESSIVE STRENGTH OF UNIT, GROSS AREA** ** Type M or S mortar** ** Type N mortar** Solid masonry of brick and other solid units of clay or shale; sand-lime or concrete brick: 8,000 + psi 350 300 4,500 psi 225 200 2,500 psi 160 140 1,500 psi 115 100 Groutedc masonry, of clay or shale; sand-lime or concrete: 4,500 + psi 225 200 2,500 psi 160 140 1,500 psi 115 100 Solid masonry of solid concrete masonry units: 3,000 + psi 225 200 2,000 psi 160 140 1,200 psi 115 100 6-98 2025 CALIFORNIA RESIDENTIAL CODE
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WALL CONSTRUCTION
TABLE R606.9—ALLOWABLE COMPRESSIVE STRESSES FOR EMPIRICAL DESIGN OF MASONRY—continued Col2 Col3 ** CONSTRUCTION; COMPRESSIVE STRENGTH OF UNIT, GROSS AREA** ** ALLOWABLE COMPRESSIVE**
STRESSESa GROSS CROSS-SECTIONAL AREAb** ALLOWABLE COMPRESSIVE**
STRESSESa GROSS CROSS-SECTIONAL AREAb** CONSTRUCTION; COMPRESSIVE STRENGTH OF UNIT, GROSS AREA** ** Type M or S mortar** ** Type N mortar** Masonry of hollow load-bearing units: 2,000 + psi 140 120 1,500 psi 115 100 1,000 psi 75 70 700 psi 60 55 Hollow walls (cavity or masonry bondedd) solid units: 2,500 + psi 160 140 1,500 psi 115 100 Hollow units 75 70 Stone ashlar masonry: Granite 720 640 Limestone or marble 450 400 Sandstone or cast stone 360 320 Rubble stone masonry: Coarse, rough or random 120 100 For SI: 1 pound per square inch = 6.895 kPa.
a. Linear interpolation shall be used for determining allowable stresses for masonry units having compressive strengths that are intermediate between those given in the table.
b. Gross cross-sectional area shall be calculated on the actual rather than nominal dimensions.
c.CHBC § 3.7.2 Medium relevance — show source text
R606.3.7.2 Masonry laid in stack bond. Where unit masonry is laid with less head joint offset than in Section R606.3.7.1, the minimum area of horizontal reinforcement placed in mortar bed joints or in bond beams spaced not more than 48 inches (1219 mm) apart shall be 0.0007 times the vertical cross-sectional area of the wall.
R606.4 Thickness of masonry. The nominal thickness of masonry walls shall conform to the requirements of Sections R606.4.1 through R606.4.4.
R606.4.1 Minimum thickness. The minimum thickness of masonry bearing walls more than one story high shall be 8 inches (203 mm). Solid masonry walls of one-story dwellings and garages shall be not less than 6 inches (152 mm) in thickness where not greater than 9 feet (2743 mm) in height, provided that where gable construction is used, an additional 6 feet (1829 mm) is permit
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ted to the peak of the gable. Masonry walls shall be laterally supported in either the horizontal or vertical direction at intervals as required by Section R606.6.4.
R606.4.2 Rubble stone masonry wall. The minimum thickness of rough, random or coursed rubble stone masonry walls shall be 16 inches (406 mm).
R606.4.3 Change in thickness. Where walls of masonry of hollow units or masonry-bonded hollow walls are decreased in thickness, a course of solid masonry or masonry units filled with mortar or grout shall be constructed between the wall below and the thinner wall above, or special units or construction shall be used to transmit the loads from face shells or wythes above to those below.
R606.4.4 Parapet walls. Unreinforced solid masonry parapet walls shall be not less than 8 inches (203 mm) thick and their height shall not exceed four times their thickness. Unreinforced hollow unit masonry parapet walls shall be not less than 8 inches (203 mm) thick, and their height shall not exceed three times their thickness. Masonry parapet walls in areas subject to wind loads of 30 pounds per square foot (1.44 kPa) located in Seismic Design Category D 0, D 1 or D 2, or on townhouses in Seismic Design Category C shall be reinforced in accordance with Section R606.12.
R606.5 Corbeled masonry. Corbeled masonry shall be in accordance with Sections R606.5.1 through R606.5.3.
R606.5.1 Units. Solid masonry units or masonry units filled with mortar or grout shall be used for corbeling.
R606.5.2 Corbel projection. The maximum projection of one unit shall not exceed one-half the height of the unit or one-third the thickness at right angles to the wall. The maximum corbeled projection beyond the face of the wall shall not exceed:
- One-half of the wall thickness for multiple-wythe walls bonded by mortar or grout and wall ties or masonry headers.
- One-half the wythe thickness for single wythe walls, masonry-bonded hollow walls, multiple-wythe walls with open collar joints and veneer walls.
CHBC § 2104A.1.3.10.2 Medium relevance — show source text
2104A.1.3.10.2 TMS 402, Section 5.1.3.2 Composite action. Replace TMS 402, Section 5.1.3.2.1 by the following:
5.1.3.2.1 Multiwythe masonry designed for composite action shall have wythes connected by collar joints and wall ties.
2104A.1.3.10.3 TMS 602, Article 3.3 B.4 Placing mortar and units – Solid units. Add the following to TMS 602, Article 3.3 B.4: d. Toothing of masonry walls is prohibited. Racking is to be held to a minimum.
2104A.1.3.10.4 TMS 602, Article 3.4 C.2 Wall ties. Replace TMS 602, Article 3.4 C.2 as follows: 2. The two wythes shall be bonded together with wall ties. Ties shall not be less than No. 9 (W1.7) wire in the form of rect- angles 4 inches (102 mm) wide and 2 inches (50.8 mm) in length less than the overall wall thickness. Kinks, water drips or deformations shall not be permitted in the ties. One wythe of the wall shall be built up not more than 16 inches (406 mm) ahead of the other wythe. Ties shall be laid not to exceed 24 inches (610 mm) on center horizontally and 16 inches (406 mm) on center vertically for running bond, and not more than 24 inches (610 mm) on center horizontally and 12 inches (305 mm) on center vertically for other than running bond.
2104A.1.3.10.5 TMS 602, Article 3.5 B Confinement. Add the following to TMS 602, Article 3.5 B: 1. Construct vertical grout barriers or dams of solid masonry across the grout space the entire height of the wall to control horizontal grout flow. Space grout barriers not more than 30 feet (9.14 m) apart.
2104A.1.3.11 Reinforced hollow unit masonry.
2104A.1.3.11.1 TMS 602, Article 2.3 A & 2.3 B Masonry unit materials. Add the following to TMS 602, Articles 2.3 A and 2.3 B: 1. In reinforced hollow unit masonry, place horizontal reinforcement in bond beam units. The depth of the bond beam channel below the top of the unit shall be 1 [1] / 2 inches (38.1 mm) minimum and the width shall be 3 inches (76.2 mm) minimum.
CHBC § 12.7 Medium relevance — show source text
Bolts shall be solidly embedded in grout._ 5. Bent bar anchor bolts shall not be allowed. The maximum size anchor shall be [1] / 2 -inch (12.7 mm) diameter for 6-inch (152 mm) nominal masonry, [3] / 4 -inch (19.1 mm) diameter for 8-inch (203 mm) nominal masonry, [7] / 8 -inch (22.2 mm) diameter for 10-inch (254 mm) nominal masonry, and 1-inch (25.4 mm) diameter for 12-inch (305 mm) nominal masonry. 6. Bolts shall be accurately set with templates or by approved equivalent means and held in place to prevent dislocation during grouting.
2104.2.4 TMS 602, Article 3.5 F.1 Grout key. Replace TMS 602, Article 3.5 F.1 as follows: 1. Between grout pours or where grouting has been stopped more than an hour, a horizontal construction joint shall be formed by terminating grout a minimum of 1 [1] / 2 inches (38.1 mm) and a maximum of one-half the masonry unit height below a mortar joint, except at the top of the wall. Where bond beams occur, the grout pour shall be terminated a minimum of [1] / 2
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inch (12.7 mm) below the mortar joint. Horizontal reinforcement shall be placed in bond beam units with a minimum grout cover of 1 inch (25.4 mm) above reinforcing steel for each grout pour.
2104.3 Aluminum equipment. [OSHPD 1R, 2 & 5] Grout shall not be handled nor pumped utilizing aluminum equipment unless it can be demonstrated with the materials and equipment to be used that there will be no deleterious effect on the strength of the grout.
SECTION 2105—QUALITY ASSURANCE
2105.1 General. A quality assurance program shall be used to ensure that the constructed masonry is in compliance with the approved construction documents.
The quality assurance program shall comply with the inspection and testing requirements of Chapter 17 and TMS 602. 2105.2 Compressive strength , f ′ m . [OSHPD 1R, 2 & 5] Testing of masonry shall be provided in accordance with TMS 602, Article 1.4 B.
Exception: Where values of f ′ m greater than 2,000 psi (13.79 MPa) are used in the design of reinforced grouted multi-wythe masonry and reinforced hollow unit masonry, they shall be based on prism test results in accordance with TMS 602, Article 1.4 B.3 submitted by the architect or engineer to the enforcement agency which demonstrate the ability of the proposed construction to meet prescribed performance criteria for strength exceed 3,000 psi (20.7 MPa).
CHBC § 12.7 Medium relevance — show source text
Values are for strength level loads as defined in regular code standards.
2. Values may be adjusted for other fasteners when approved by the enforcing authority.
3. In addition to existing sheathing value.
4. Bolts to be1/2-inch (12.7 mm) minimum diameter.
5. Other bolt sizes, values and installation methods may be used provided a testing program is conducted in accordance with regular code standards. Bolt spacing shall not
exceed 6 feet (1830 mm) on center and shall not be less than 12 inches (305 mm) on center.
6. Other masonry based on tests or other substantiated data.
7. Embedded bolts to be tested as specified in regular code standards.
8. Stresses given may be increased for combinations of loads as specified in the regular code.
9. Adhesives shall be approved by the enforcing agency and installed in accordance with the manufacturer’s recommendations. All drilling dust shall be removed from drilled
holes prior to installation.|1. Values are for strength level loads as defined in regular code standards.
2. Values may be adjusted for other fasteners when approved by the enforcing authority.
3. In addition to existing sheathing value.
4. Bolts to be1/2-inch (12.7 mm) minimum diameter.
5. Other bolt sizes, values and installation methods may be used provided a testing program is conducted in accordance with regular code standards. Bolt spacing shall not
exceed 6 feet (1830 mm) on center and shall not be less than 12 inches (305 mm) on center.
6. Other masonry based on tests or other substantiated data.
7. Embedded bolts to be tested as specified in regular code standards.
8. Stresses given may be increased for combinations of loads as specified in the regular code.
9. Adhesives shall be approved by the enforcing agency and installed in accordance with the manufacturer’s recommendations. All drilling dust shall be removed from drilled
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8-9 MECHANICAL, PLUMBING AND ELECTRICAL REQUIREMENTS
SECTION 8-901 — PURPOSE, INTENT AND SCOPE
8-901.1 Purpose. The purpose of the CHBC is to provide regulations for the mechanical, plumbing and electrical systems of buildings designated as qualified historical buildings or properties. The CHBC requires enforcing agencies to accept any reasonable equivalent solutions to the regular code when dealing with qualified historical buildings or properties.
8-901.2 Intent. The intent of the CHBC is to preserve the integrity of qualified historical buildings or properties while providing a reasonable level of protection from fire, health and life safety hazards (hereinafter referred to as safety hazards) for the building occupants.
8-901.3 Scope. The CHBC shall be applied in conjunction with the regular code whenever compliance with the regular code is required for qualified historical buildings or properties.
Frequently asked questions
When can I treat a stone wall as solid brick masonry without testing?
Only when representative inspection/testing verifies the required composite action — for solid‑backed walls that means solid collar joints and header lap or anchors; for independent wythes it means the core is essentially solid and epoxied steel ties and top reinforcement are present — see § 8-805.2.1 and § 8-805.2.2 .
What exactly must be done for independent‑wythe walls to qualify?
Verify by testing/inspection that the core is essentially solid, install steel ties epoxied in drilled holes at floors/roof and spaced no more than 4 ft (1219 mm) o.c., and provide a reinforcing element at or near the top of the wall — see § 8-805.2.2 .
How are non‑interlocked stones tested?
Per § 8-805.2.3, follow the CEBC/brick masonry testing approach, but for stones that are not interlocked perform pull‑out tests of representative stones and recalculate the shear area after the test .
Is there any default shear value if I don’t test?
The CHBC allows existing solid masonry to be assigned a maximum ultimate shear strength of 9 pounds per square inch (62.1 kPa) without testing if an architect/engineer documents the wall condition per § 8-805.1 — but this applies to solid masonry meeting the section’s other criteria, not to independent wythes with voided cores unless they meet the solid‑masonry criteria .
Do ties have to be epoxied or can they be mechanical?
The CHBC specifically requires steel ties epoxied in drilled holes for independent‑wythe stone masonry at the prescribed locations and spacing — see § 8-805.2.2; any alternative method should be justified to and accepted by the enforcing agency .
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