CHBC · California Historical Building Code

How does CHBC allow archaic wood framing types and fasteners to be used or assigned values?

In plain terms: the CHBC lets qualified historic buildings keep or reinstall old framing (like balloon or single‑wall), traditional joinery, and old fasteners. A licensed architect or structural engineer must inspect, test as needed, and assign allowable strengths — and the code even allows square/cut nails to be credited with up to 50% more shear capacity than wire nails, provided the assignment is documented and accepted by the enforcing agency.

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Last reviewed: July 6, 2026

What the code requires — plain English (controlling §)

The California Historical Building Code lets qualified historical buildings keep or re‑install original wood framing types and fasteners and allows an engineer or architect to assign allowable stresses based on the codes that were in effect when the member was built — see § 8-807.3. The CHBC also requires that strength values for archaic materials be assigned based on similar codified materials or tests, and that such assignments be documented and concurred with by the enforcing agency — see § 8-802.

The single most important rule: existing or replacement historic wood framing and historical fasteners may be used when the responsible architect/engineer documents their allowable stresses and ties those values to historical practice, testing, or equivalent codified materials.

Requirements in detail

Who assigns the values

  • The architect or structural engineer in responsible charge must assign allowable stresses or strength levels for archaic wood materials. § 8-802 explains the methodology and that assignments are subject to the enforcing agency’s concurrence.
  • A structural survey documenting existing conditions, fastener types/spacing, deterioration and construction details is required (see references to the structural survey requirement in the Archaic Materials chapter).

What old framing types are explicitly allowed

  • Archaic framing types such as balloon framing and single‑wall construction may be used or reinstalled if properly researched. § 8-807.3.
  • Traditional joinery (for example dovetail and mortise and tenon) may be used structurally if well made. § 8-807.3.

Lumber and species allowances

  • Lumber used need not bear grade marks; indigenous and nonstandard species (low‑grade pine/fir, boxwood, local hardwoods) may be used where historically appropriate. § 8-807.3.
  • Assigned strength values should be based on comparable codified materials or testing and must not exceed stated limits without adequate testing and approval. § 8-802.

Fasteners and shear values

  • Wood fasteners such as square or cut nails are permitted; for shear the CHBC allows a maximum increase of 50 percent over the shear capacity of wire nails when square/cut nails are used. § 8-807.3.
  • For diaphragm/shear values, existing sheathing and fasteners are to be evaluated and assigned shear resistance appropriate to the fasteners and materials functioning together — see § 8-807.1 (diaphragms) and § 8-807.2 (lath & plaster).

Documentation, testing & agency concurrence

  • Investigation and testing are expected when applicable. Assigned values must be supported by the structural survey, tests, or comparison to codified materials, and are subject to the enforcing agency’s concurrence. § 8-802 and cross references in the Archaic Materials chapter.

Decision‑relevant quick lookup table

Decision factor What CHBC allows / limit Code Reference
Who assigns allowable stresses Architect/Engineer in responsible charge assigns values § 8-802
Basis for assigned values Based on similar codified materials or tests; subject to agency concurrence § 8-802
Archaic framing types allowed Examples: balloon, single wall (may be used/replaced if researched) § 8-807.3
Traditional wood joinery Dovetail, mortise & tenon permitted structurally if well made § 8-807.3
Lumber grade marks Grade marks not required for lumber selected for use § 8-807.3
Species allowed Nonstandard/indigenous species permitted where historically used § 8-807.3
Fastener allowance for shear Square/cut nails allowed; max +50% shear over wire nails § 8-807.3
Diaphragm/shear evaluation Assign shear values per fasteners & sheathing; structural survey required § 8-807.1 and § 8-807.2

Exceptions & special cases

  • Assigned strength values must not exceed the levels provided in the CHBC subsections without adequate testing and enforcing‑agency concurrence. § 8-802.
  • If higher strengths are proposed (for example to match modern loads or allow code‑required upgrades), specific testing (material samples, pullout tests, laboratory tests) is required and the architect/engineer must document the basis. § 8-802.
  • Historic framing that contributes to life‑safety hazards (e.g., falling ornamentation, parapets) may require strengthening even if kept in‑place; investigate per § 8-706 series.

Common mistakes

  • Treating CHBC allowance as unconditional: the engineer/architect must assign and document values — not the enforcing agency alone. § 8-802.
  • Ignoring the required structural survey and fastener documentation — diaphragm shear depends on fastener type/spacing. § 8-807.1.
  • Applying the +50% fastener benefit without verifying that the square/cut nails are actually performing as assumed (age, corrosion, installation quality matters). § 8-807.3.
  • Using non‑graded lumber without documenting species, condition, and assigned properties — grade marks are not required, but the basis for strength must be documented. § 8-807.3 and § 8-802.
  • Exceeding assigned allowable stresses in design calculations because the CHBC permits archaic materials — remember assigned values are typically conservative and must be justified. § 8-802.

Worked example — applying the fastener shear allowance

Scenario: a historic floor diaphragm is evaluated. The structural survey determines the diaphragm shear resistance using existing wire nails yields a nominal shear capacity of 200 pounds per linear foot (plf) for a specific detail.

Step 1 — Engineer documents the wire‑nail base shear: 200 plf (from survey/testing or table lookup).

Step 2 — If the contractor proposes to use historic square nails, CHBC § 8-807.3 permits using square/cut nails with a maximum shear increase of 50 percent over wire nails.

Calculation:

  • Base (wire nails): 200 plf
  • Allowed maximum with square/cut nails: 200 × (1 + 0.50) = 300 plf

Step 3 — The architect/engineer must record the basis (field observation or test showing square nails are present and properly embedded), place the assigned 300 plf in the project calculations, and submit this documentation for enforcing‑agency concurrence per § 8-802.

Key caveats:

  • If fasteners are corroded or poorly driven, the increase is not appropriate without testing. § 8-807.3 and § 8-802.

Related provisions

  • § 8-802 — General engineering approaches; assignment basis, testing, and enforcing‑agency concurrence.
  • § 8-703 — Structural survey requirement (investigation and documentation).
  • § 8-807.1 — Existing wood diaphragms or walls; shear resistance values and fastener/spacing evaluation.
  • § 8-807.2 — Wood lath and plaster shear values.
  • § 8-804 — Allowable conditions for specific archaic materials (evaluation and documentation expectations).

Code references

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

  • CHBC § 8-807.3 High relevance — show source text

    8-807.3 Existing wood framing. Existing wood framing members may be assigned allowable stresses consistent with codes in effect at the time of construction. Existing or new replacement wood framing may be of archaic types originally used if properly researched, such as balloon and single wall. Wood joints such as dovetail and mortise and tenon types may be used structurally, provided they are well made. Lumber selected for use and type need not bear grade marks, and greater or lesser species such as low-level pine and fir, boxwood and indigenous hardwoods and other variations may be used for specific conditions where they were or would have been used.

    Wood fasteners such as square or cut nails may be used with a maximum increase of 50 percent over wire nails for shear.

    SECTION 8-808 — CONCRETE

    8-808.1 Materials. Natural cement concrete, unreinforced rubble concrete and similar materials may be utilized wherever that material is used historically. Concrete of low strength and with less reinforcement than required by the regular code may remain in place. The architect or engineer shall assign appropriate values of strength based on testing of samples of the materials. Bond and development lengths shall be determined based on historical information or tests.

    8-808.2 Detailing. The architect or engineer shall carefully evaluate all detailing provisions of the regular code which are not met and shall consider the implications of these variations on the ultimate performance of the structure, giving due consideration to ductility and reserve strength.

    16 2025 CALIFORNIA HISTORICAL BUILDING CODE

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

    ARCHAIC MATERIALS AND METHODS OF CONSTRUCTION

    SECTION 8-809 — STEEL AND IRON

    The hand-built, untested use of wrought or black iron, the use of cast iron or grey iron, and the myriad of joining methods that are not specifically allowed by code may be used wherever applicable and wherever they have proven their worth under the considerable span of years involved with most qualified historical buildings or structures. Uplift capacity should be evaluated and strengthened where necessary. Fixed conditions or midheight lateral loads on cast iron columns that could cause failure should be taken into account. Existing structural wrought, forged steel or grey iron may be assigned the maximum working stress prevalent at the time of original construction.

    SECTION 8-810 — HOLLOW CLAY TILE

    The historical performance of hollow clay tile in past earthquakes shall be carefully considered in evaluating walls of hollow clay tile construction. Hollow clay tile bearing walls shall be evaluated and strengthened as appropriate for lateral loads and their ability to maintain support of gravity loads. Suitable protective measures shall be provided to prevent blockage of exit stairways, stairway enclosures, exit ways and public ways as a result of an earthquake.

    SECTION 8-811 — VENEERS

    8-811.1 Terra cotta and stone. Terra cotta, cast stone and natural stone veneers shall be investigated for the presence of suitable anchorage. Steel anchors shall be investigated for deterioration or corrosion. New or supplemental anchorage shall be provided as appropriate.

    8-811.2 Anchorage. Brick veneer with mechanical anchorage at spacings greater than required by the regular code may remain, provided the anchorages have not corroded. Nail strength in withdrawal in wood sheathing may be utilized to its capacity in accordance with code values.

    SECTION 8-812 — GLASS AND GLAZING

  • CHBC § 8-806.4 High relevance — show source text

    8-806.4 Nonload-bearing adobe. Nonload-bearing adobe partitions and gable end walls shall be evaluated for stability and anchored against out-of-plane failure if necessary.

    8-806.5 Bond beam. Where provided, a bond beam or equivalent structural element shall be located at the top of all adobe walls, and at the second floor for two-story buildings or structures. The size and configuration of the structural element shall be sufficient to provide an effective brace for the wall, to tie the building together and to connect the wall to the floor or roof.

    8-806.6 Repair or reconstruction. Repair or reconstruction of wall area may utilize unstabilized brick or adobe masonry designed to be compatible with the constituents of the existing adobe materials.

    8-806.7 Shear values. Existing adobe may be allowed a maximum strength level of 12 pounds per square inch (82.7 kPa) for shear.

    8-806.8 Mortar. Mortar may be of the same soil composition as that used in the existing wall, or in new walls as necessary to be compatible with the adobe brick.

    SECTION 8-807 — WOOD

    8-807.1 Existing wood diaphragms or walls. Existing wood diaphragms or walls of straight or diagonal sheathing shall be assigned shear resistance values appropriate with the fasteners and materials functioning in conjunction with the sheathing. The structural survey shall determine fastener details and spacings and verify a load path through floor construction. Shear values of Tables 8-8-A and 8-8-B.

    8-807.2 Wood lath and plaster. Wood lath and plaster walls and ceilings may be utilized using the shear values referenced in Section 8-807.1.

    8-807.3 Existing wood framing. Existing wood framing members may be assigned allowable stresses consistent with codes in effect at the time of construction. Existing or new replacement wood framing may be of archaic types originally used if properly researched, such as balloon and single wall. Wood joints such as dovetail and mortise and tenon types may be used structurally, provided they are well made. Lumber selected for use and type need not bear grade marks, and greater or lesser species such as low-level pine and fir, boxwood and indigenous hardwoods and other variations may be used for specific conditions where they were or would have been used.

    Wood fasteners such as square or cut nails may be used with a maximum increase of 50 percent over wire nails for shear.

    SECTION 8-808 — CONCRETE

    8-808.1 Materials. Natural cement concrete, unreinforced rubble concrete and similar materials may be utilized wherever that material is used historically. Concrete of low strength and with less reinforcement than required by the regular code may remain in place. The architect or engineer shall assign appropriate values of strength based on testing of samples of the materials. Bond and development lengths shall be determined based on historical information or tests.

    8-808.2 Detailing. The architect or engineer shall carefully evaluate all detailing provisions of the regular code which are not met and shall consider the implications of these variations on the ultimate performance of the structure, giving due consideration to ductility and reserve strength.

    16 2025 CALIFORNIA HISTORICAL BUILDING CODE

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

    ARCHAIC MATERIALS AND METHODS OF CONSTRUCTION

    SECTION 8-809 — STEEL AND IRON

  • CHBC § 25.4 High relevance — show source text

    Where the required cladding fastener penetration into wood material exceeds3/4 inch and is not more than 11/2 inches, a minimum 2-inch nominal wood furring or an
    approved design shall be used.
    e. Foam sheathing shall have a minimum compressive strength of 15 psi in accordance with ASTM C578 or ASTM C1289.
    f. Furring shall be spaced not greater than 24 inches on center in a vertical or horizontal orientation. In a vertical orientation, furring shall be located over wall studs and attached with
    the required fastener spacing. In a horizontal orientation, the indicated 8-inch and 12-inch fastener spacing in furring shall be achieved by use of two fasteners into studs at 16 inches
    and 24 inches on center, respectively.|For SI: 1 inch = 25.4 mm, 1 pound per square foot (psf) = 0.0479 kPa, 1 pound per square inch = 0.00689 MPa.
    DR = Design Required, o.c. = on center.
    a. Wood framing and furring shall be spruce-pine-fir or any wood species with a specific gravity of 0.42 or greater in accordance with ANSI/AWC NDS.
    b. Nail fasteners shall comply with ASTM F1667, except nail length shall be permitted to exceed ASTM F1667 standard lengths.
    c. The thickness of wood structural panels complying with the specific gravity requirements of Note a shall be permitted to be included in satisfying the minimum required
    penetration into framing.
    d. Where the required cladding fastener penetration into wood material exceeds3/4 inch and is not more than 11/2 inches, a minimum 2-inch nominal wood furring or an
    approved design shall be used.
    e. Foam sheathing shall have a minimum compressive strength of 15 psi in accordance with ASTM C578 or ASTM C1289.
    f. Furring shall be spaced not greater than 24 inches on center in a vertical or horizontal orientation. In a vertical orientation, furring shall be located over wall studs and attached with
    the required fastener spacing. In a horizontal orientation, the indicated 8-inch and 12-inch fastener spacing in furring shall be achieved by use of two fasteners into studs at 16 inches
    and 24 inches on center, respectively.|For SI: 1 inch = 25.4 mm, 1 pound per square foot (psf) = 0.0479 kPa, 1 pound per square inch = 0.00689 MPa.
    DR = Design Required, o.c. = on center.
    a. Wood framing and furring shall be spruce-pine-fir or any wood species with a specific gravity of 0.42 or greater in accordance with ANSI/AWC NDS.
    b. Nail fasteners shall comply with ASTM F1667, except nail length shall be permitted to exceed ASTM F1667 standard lengths.
    c. The thickness of wood structural panels complying with the specific gravity requirements of Note a shall be permitted to be included in satisfying the minimum required
    penetration into framing.
    d. Where the required cladding fastener penetration into wood material exceeds3/4 inch and is not more than 11/2 inches, a minimum 2-inch nominal wood furring or an
    approved design shall be used.
    e. Foam sheathing shall have a minimum compressive strength of 15 psi in accordance with ASTM C578 or ASTM C1289.
    f. Furring shall be spaced not greater than 24 inches on center in a vertical or horizontal orientation.

  • CHBC § 3.00 High relevance — show source text

    120" diameter nail|12|3.00|0.70|DR|DR|2.15|DR|DR|DR| |Wood Framing
    (minimum 11/4- inch
    penetration)b|0.131" diameter nail|6|4.00|2.15|1.20|0.75|4.00|1.35|0.70|DR| |Wood Framing
    (minimum 11/4- inch
    penetration)b|0.131" diameter nail|8|4.00|1.55|0.80|DR|4.00|0.90|DR|DR| |Wood Framing
    (minimum 11/4- inch
    penetration)b|0.131" diameter nail|12|4.00|0.90|DR|DR|2.70|0.50|DR|DR| |Wood Framing
    (minimum 11/4- inch
    penetration)b|0.162" diameter nail|6|4.00|3.55|2.05|1.40|4.00|2.25|1.25|0.80| |Wood Framing
    (minimum 11/4- inch
    penetration)b|0.162" diameter nail|8|4.00|2.55|1.45|0.95|4.00|1.60|0.85|0.50| |Wood Framing
    (minimum 11/4- inch
    penetration)b|0.162" diameter nail|12|4.00|1.60|0.85|0.50|4.00|0.95|DR|DR| |For SI: 1 inch = 25.4 mm, 1 pound per square foot (psf) = 0.0479 kPa.
    DR = Design Required, o.c. = on center.
    a. Wood framing shall be spruce-pine-fir or any wood species with a specific gravity of 0.42 or greater in accordance with ANSI/AWC NDS.
    b. The thickness of wood structural panels complying with the specific gravity requirement of Note a shall be permitted to be included in satisfying the minimum penetration
    into framing.
    c. Nail fasteners shall comply with ASTM F1667, except nail length shall be permitted to exceed ASTM F1667 standard lengths.
    d. Foam sheathing shall have a minimum compressive strength of 15 psi in accordance with ASTM C578 or ASTM C1289.|For SI: 1 inch = 25.4 mm, 1 pound per square foot (psf) = 0.0479 kPa.
    DR = Design Required, o.c. = on center.
    a. Wood framing shall be spruce-pine-fir or any wood species with a specific gravity of 0.42 or greater in accordance with ANSI/AWC NDS.
    b. The thickness of wood structural panels complying with the specific gravity requirement of Note a shall be permitted to be included in satisfying the minimum penetration
    into framing.
    c. Nail fasteners shall comply with ASTM F1667, except nail length shall be permitted to exceed ASTM F1667 standard lengths.
    d. Foam sheathing shall have a minimum compressive strength of 15 psi in accordance with ASTM C578 or ASTM C1289.|For SI: 1 inch = 25.4 mm, 1 pound per square foot (psf) = 0.0479 kPa.
    DR = Design Required, o.c. = on center.
    a.

  • CHBC § 4.00 High relevance — show source text

    10
    wood screw|1|24|4.00|0.90|DR|DR|2.85|DR|DR|DR| |Minimum 1x
    Wood Furringd|Minimum 2x
    Wood Stud|1/4" lag screw|11/2|12|4.00|2.65|1.50|0.90|4.00|1.65|0.80|DR| |Minimum 1x
    Wood Furringd|Minimum 2x
    Wood Stud|1/4" lag screw|11/2|16|4.00|1.95|0.95|0.50|4.00|1.10|DR|DR| |Minimum 1x
    Wood Furringd|Minimum 2x
    Wood Stud|1/4" lag screw|11/2|24|4.00|1.10|DR|DR|3.25|0.50|DR|DR| |For SI: 1 inch = 25.4 mm, 1 pound per square foot (psf) = 0.0479 kPa, 1 pound per square inch = 0.00689 MPa.
    DR = Design Required, o.c. = on center.
    a. Wood framing and furring shall be spruce-pine-fir or any wood species with a specific gravity of 0.42 or greater in accordance with ANSI/AWC NDS.
    b. Nail fasteners shall comply with ASTM F1667, except nail length shall be permitted to exceed ASTM F1667 standard lengths.
    c. The thickness of wood structural panels complying with the specific gravity requirements of Note a shall be permitted to be included in satisfying the minimum required
    penetration into framing.
    d. Where the required cladding fastener penetration into wood material exceeds3/4 inch and is not more than 11/2 inches, a minimum 2-inch nominal wood furring or an
    approved design shall be used.
    e. Foam sheathing shall have a minimum compressive strength of 15 psi in accordance with ASTM C578 or ASTM C1289.
    f. Furring shall be spaced not greater than 24 inches on center in a vertical or horizontal orientation. In a vertical orientation, furring shall be located over wall studs and attached with
    the required fastener spacing. In a horizontal orientation, the indicated 8-inch and 12-inch fastener spacing in furring shall be achieved by use of two fasteners into studs at 16 inches
    and 24 inches on center, respectively.|For SI: 1 inch = 25.4 mm, 1 pound per square foot (psf) = 0.0479 kPa, 1 pound per square inch = 0.00689 MPa.
    DR = Design Required, o.c. = on center.
    a. Wood framing and furring shall be spruce-pine-fir or any wood species with a specific gravity of 0.42 or greater in accordance with ANSI/AWC NDS.
    b. Nail fasteners shall comply with ASTM F1667, except nail length shall be permitted to exceed ASTM F1667 standard lengths.
    c. The thickness of wood structural panels complying with the specific gravity requirements of Note a shall be permitted to be included in satisfying the minimum required
    penetration into framing.
    d. Where the required cladding fastener penetration into wood material exceeds3/4 inch and is not more than 11/2 inches, a minimum 2-inch nominal wood furring or an
    approved design shall be used.
    e.

  • CHBC § 25.4 High relevance — show source text


    plywood
    sidinge
    except
    Group 5
    Species,
    ANSI/APA
    PRP 210
    sidinge|19/32|19/32|13/4 16
    Gage|185|280|375|475|—|—|—|—|—| |For SI: 1 inch = 25.4 mm, 1 pound per foot = 14.5939 N/m.
    a. For framing of other species: (1) Find specific gravity for species of lumber in ANSI/AWC NDS. (2) For staples find shear value from table for Structural I panels (regardless of
    actual grade) and multiply value by 0.82 for species with specific gravity of 0.42 or greater, or 0.65 for all other species.
    b. Panel edges backed with 2-inch nominal or wider framing. Install panels either horizontally or vertically. Space fasteners maximum 6 inches on center along intermediate
    framing members for3/8-inch and7/16-inch panels installed on studs spaced 24 inches on center. For other conditions and panel thickness, space fasteners maximum 12 inches
    on center on intermediate supports.
    c. 3/8-inch panel thickness or siding with a span rating of 16 inches on center is the minimum recommended where applied directly to framing as exterior siding. For grooved
    panel siding, the nominal panel thickness is the thickness of the panel measured at the point of fastening.
    d. Framing at adjoining panel edges shall be 3 inches nominal or wider.
    e. Values apply to all-veneer plywood. Thickness at point of fastening on panel edges governs shear values.
    f. Where panels are applied on both faces of a wall and fastener spacing is less than 6 inches on center on either side, panel joints shall be offset to fall on different framing
    members, or framing shall be 3 inches nominal or thicker at adjoining panel edges.
    g. In Seismic Design Category D, E or F, where shear design values exceed 350 pounds per linear foot, all framing members receiving edge fastening from abutting panels shall be
    not less than a single 3-inch nominal member, or two 2-inch nominal members fastened together in accordance with Section 2306.1 to transfer the design shear value
    between framing members. Wood structural panel joint and sill plate nailing shall be staggered at all panel edges. See AWC SDPWS for sill plate size and anchorage
    requirements.
    h. Staples shall have a minimum crown width of7/16 inch and shall be installed with their crowns parallel to the long dimension of the framing members.
    i. For shear loads of normal or permanent load duration as defined by the ANSI/AWC NDS, the values in the table shall be multiplied by 0.63 or 0.56, respectively.|For SI: 1 inch = 25.4 mm, 1 pound per foot = 14.5939 N/m.
    a. For framing of other species: (1) Find specific gravity for species of lumber in ANSI/AWC NDS. (2) For staples find shear value from table for Structural I panels (regardless of
    actual grade) and multiply value by 0.82 for species with specific gravity of 0.42 or greater, or 0.65 for all other species.
    b. Panel edges backed with 2-inch nominal or wider framing. Install panels either horizontally or vertically.

  • CHBC § 0.90 High relevance — show source text

    00|0.90|DR|DR|DR| |Minimum
    1× wood
    furringd|Minimum
    2× wood
    stud|No.10
    wood
    screw|1|24|4.00|0.90|DR|DR|DR|2.85|DR|DR|DR|DR| |Minimum
    1× wood
    furringd|Minimum
    2× wood
    stud|1/4″
    lag screw|11/2|12|4.00|2.65|1.90|1.50|0.90|4.00|1.65|1.05|0.80|DR| |Minimum
    1× wood
    furringd|Minimum
    2× wood
    stud|1/4″
    lag screw|11/2|16|4.00|1.95|1.25|0.95|0.50|4.00|1.10|0.65|DR|DR| |Minimum
    1× wood
    furringd|Minimum
    2× wood
    stud|1/4″
    lag screw|11/2|24|4.00|1.10|0.65|DR|DR|3.25|0.50|DR|DR|DR| |For SI: 1 inch = 25.4 mm, 1 pound per square foot = 0.0479 kPa, 1 pound per square inch = 6.895 kPa.
    DR = Design Required.
    o.c. = On Center.
    a. Wood framing and furring shall be Spruce-pine-fir or any wood species with a specific gravity of 0.42 or greater in accordance with AWC NDS.
    b. Nail fasteners shall comply with ASTM F1667, except nail length shall be permitted to exceed ASTM F1667 standard lengths.
    c. The thickness of wood structural panels complying with the specific gravity requirements of Note a shall be permitted to be included in satisfying the minimum required pene-
    tration into framing.
    d. Where the required cladding fastener penetration into wood material exceeds3/4 inch and is not more than 11/2 inches, a minimum 2× wood furring or an approved design shall
    be used.
    e. Foam sheathing shall have a minimum compressive strength of 15 psi in accordance with ASTM C578 or ASTM C1289.
    f. Furring shall be spaced not more than 24 inches on center, in a vertical or horizontal orientation. In a vertical orientation, furring shall be located over wall studs and attached
    with the required fastener spacing. In a horizontal orientation, the indicated 8-inch and 12-inch fastener spacing in furring shall be achieved by use of two fasteners into studs
    at 16 inches and 24 inches on center, respectively.
    g. Cladding weight is the maximum weight of cladding materials in pounds per square foot of wall area. The 3 psf category typically applies to panel and lap siding materials; the
    11 psf category typically applies to conventional three-coat stucco of7/8-inch thickness; and 15 psf to 25 psf categories typically apply to adhered masonry veneers.|For SI: 1 inch = 25.4 mm, 1 pound per square foot = 0.0479 kPa, 1 pound per square inch = 6.895 kPa.
    DR = Design Required.
    o.c. = On Center.
    a.

  • CHBC § 8-801 High relevance — show source text

    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

    Where nonstructural historical materials exist in uses which do not meet the requirements of the regular code, their continued use is allowed by this code, provided that any public health and life safety hazards are mitigated subject to the concurrence of the enforcing agency.

    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.

  • CHBC § 25.4 High relevance — show source text

    The thickness of wood structural panels complying with the specific gravity requirement of Note a shall be permitted to be included in satisfying the minimum penetration
    into framing.
    c. Nail fasteners shall comply with ASTM F1667, except nail length shall be permitted to exceed ASTM F1667 standard lengths.
    d. Foam sheathing shall have a minimum compressive strength of 15 psi in accordance with ASTM C578 or ASTM C1289.|For SI: 1 inch = 25.4 mm, 1 pound per square foot (psf) = 0.0479 kPa.
    DR = Design Required, o.c. = on center.
    a. Wood framing shall be spruce-pine-fir or any wood species with a specific gravity of 0.42 or greater in accordance with ANSI/AWC NDS.
    b. The thickness of wood structural panels complying with the specific gravity requirement of Note a shall be permitted to be included in satisfying the minimum penetration
    into framing.
    c. Nail fasteners shall comply with ASTM F1667, except nail length shall be permitted to exceed ASTM F1667 standard lengths.
    d. Foam sheathing shall have a minimum compressive strength of 15 psi in accordance with ASTM C578 or ASTM C1289.|For SI: 1 inch = 25.4 mm, 1 pound per square foot (psf) = 0.0479 kPa.
    DR = Design Required, o.c. = on center.
    a. Wood framing shall be spruce-pine-fir or any wood species with a specific gravity of 0.42 or greater in accordance with ANSI/AWC NDS.
    b. The thickness of wood structural panels complying with the specific gravity requirement of Note a shall be permitted to be included in satisfying the minimum penetration
    into framing.
    c. Nail fasteners shall comply with ASTM F1667, except nail length shall be permitted to exceed ASTM F1667 standard lengths.
    d. Foam sheathing shall have a minimum compressive strength of 15 psi in accordance with ASTM C578 or ASTM C1289.|For SI: 1 inch = 25.4 mm, 1 pound per square foot (psf) = 0.0479 kPa.
    DR = Design Required, o.c. = on center.
    a. Wood framing shall be spruce-pine-fir or any wood species with a specific gravity of 0.42 or greater in accordance with ANSI/AWC NDS.
    b. The thickness of wood structural panels complying with the specific gravity requirement of Note a shall be permitted to be included in satisfying the minimum penetration
    into framing.
    c. Nail fasteners shall comply with ASTM F1667, except nail length shall be permitted to exceed ASTM F1667 standard lengths.
    d. Foam sheathing shall have a minimum compressive strength of 15 psi in accordance with ASTM C578 or ASTM C1289.|For SI: 1 inch = 25.4 mm, 1 pound per square foot (psf) = 0.0479 kPa.
    DR = Design Required, o.c. = on center.
    a. Wood framing shall be spruce-pine-fir or any wood species with a specific gravity of 0.42 or greater in accordance with ANSI/AWC NDS.
    b. The thickness of wood structural panels complying with the specific gravity requirement of Note a shall be permitted to be included in satisfying the minimum penetration
    into framing.
    c. Nail fasteners shall comply with ASTM F1667, except nail length shall be permitted to exceed ASTM F1667 standard lengths.
    d.

  • CHBC § 2306.1 High relevance — show source text

    Install panels either horizontally or vertically. Space fasteners maximum 6 inches on center along intermediate
    framing members for3/8-inch and7/16-inch panels installed on studs spaced 24 inches on center. For other conditions and panel thickness, space fasteners maximum 12 inches
    on center on intermediate supports.
    c. 3/8-inch panel thickness or siding with a span rating of 16 inches on center is the minimum recommended where applied directly to framing as exterior siding. For grooved
    panel siding, the nominal panel thickness is the thickness of the panel measured at the point of fastening.
    d. Framing at adjoining panel edges shall be 3 inches nominal or wider.
    e. Values apply to all-veneer plywood. Thickness at point of fastening on panel edges governs shear values.
    f. Where panels are applied on both faces of a wall and fastener spacing is less than 6 inches on center on either side, panel joints shall be offset to fall on different framing
    members, or framing shall be 3 inches nominal or thicker at adjoining panel edges.
    g. In Seismic Design Category D, E or F, where shear design values exceed 350 pounds per linear foot, all framing members receiving edge fastening from abutting panels shall be
    not less than a single 3-inch nominal member, or two 2-inch nominal members fastened together in accordance with Section 2306.1 to transfer the design shear value
    between framing members. Wood structural panel joint and sill plate nailing shall be staggered at all panel edges. See AWC SDPWS for sill plate size and anchorage
    requirements.
    h. Staples shall have a minimum crown width of7/16 inch and shall be installed with their crowns parallel to the long dimension of the framing members.
    i. For shear loads of normal or permanent load duration as defined by the ANSI/AWC NDS, the values in the table shall be multiplied by 0.63 or 0.56, respectively.|For SI: 1 inch = 25.4 mm, 1 pound per foot = 14.5939 N/m.
    a. For framing of other species: (1) Find specific gravity for species of lumber in ANSI/AWC NDS. (2) For staples find shear value from table for Structural I panels (regardless of
    actual grade) and multiply value by 0.82 for species with specific gravity of 0.42 or greater, or 0.65 for all other species.
    b. Panel edges backed with 2-inch nominal or wider framing. Install panels either horizontally or vertically. Space fasteners maximum 6 inches on center along intermediate
    framing members for3/8-inch and7/16-inch panels installed on studs spaced 24 inches on center. For other conditions and panel thickness, space fasteners maximum 12 inches
    on center on intermediate supports.
    c. 3/8-inch panel thickness or siding with a span rating of 16 inches on center is the minimum recommended where applied directly to framing as exterior siding. For grooved
    panel siding, the nominal panel thickness is the thickness of the panel measured at the point of fastening.
    d. Framing at adjoining panel edges shall be 3 inches nominal or wider.
    e. Values apply to all-veneer plywood. Thickness at point of fastening on panel edges governs shear values.
    f.

  • CHBC § 0.164 High relevance — show source text

    8 screw (0.164″ min. dia.)|16″ o.c.| |For SI: 1 inch = 25.4 mm, 1 pound per square foot = 0.479 kPa.
    a. Fastener length shall be sufficient to penetrate the back side of the wood structural panel sheathing by at least1/4 inch. The wood structural panel sheathing shall be not less
    than7/16 inch in thickness.
    b. Spacing of fasteners is per 12 inches of siding width. For other siding widths, multiply “Spacing of Fasteners” above by a factor of 12/s, where “s” is the siding width in inches.
    Fastener spacing shall never be greater than the manufacturer’s minimum recommendations.|For SI: 1 inch = 25.4 mm, 1 pound per square foot = 0.479 kPa.
    a. Fastener length shall be sufficient to penetrate the back side of the wood structural panel sheathing by at least1/4 inch. The wood structural panel sheathing shall be not less
    than7/16 inch in thickness.
    b. Spacing of fasteners is per 12 inches of siding width. For other siding widths, multiply “Spacing of Fasteners” above by a factor of 12/s, where “s” is the siding width in inches.
    Fastener spacing shall never be greater than the manufacturer’s minimum recommendations.|For SI: 1 inch = 25.4 mm, 1 pound per square foot = 0.479 kPa.
    a. Fastener length shall be sufficient to penetrate the back side of the wood structural panel sheathing by at least1/4 inch. The wood structural panel sheathing shall be not less
    than7/16 inch in thickness.
    b. Spacing of fasteners is per 12 inches of siding width. For other siding widths, multiply “Spacing of Fasteners” above by a factor of 12/s, where “s” is the siding width in inches.
    Fastener spacing shall never be greater than the manufacturer’s minimum recommendations.|

    R703.3.4 Minimum fastener length and penetration. Fasteners shall have the greater of the minimum length specified in Table R703.3(1) or as required to provide a minimum penetration into framing as follows:

    1. Fasteners for horizontal aluminum siding, steel siding, particleboard panel siding, wood structural panel siding in accordance with ANSI/APA-PRP 210, fiber-cement panel siding and fiber-cement lap siding installed over foam plastic sheathing shall penetrate not less than 1 [1] / 2 inches (38 mm) into framing or shall be in accordance with the manufacturer’s installation instructions.

    2. Fasteners for hardboard panel and lap siding shall penetrate not less than 1 [1] / 2 inches (38 mm) into framing.

    3. Fasteners for vinyl siding and insulated vinyl siding shall be installed in accordance with Section R703.11 or R703.13.

    4. Fasteners for polypropylene siding shall be installed in accordance with Section R703.14.

    5. Fasteners for vertical or horizontal wood siding shall penetrate not less than 1 [1] / 2 inches (38 mm) into studs, studs and wood sheathing combined, or blocking.

    6. Fasteners for siding material installed over foam plastic sheathing shall have sufficient length to accommodate foam plastic sheathing thickness and to penetrate framing or sheathing and framing combined, as specified in Items 1 through 5.

  • CHBC § 2304.10.2.1 High relevance — show source text

    2304.10.2.1 Additional requirements. [DSA-SS and OSHPD 1, 1R, 2, 4 & 5] Fasteners used for the attachment of exterior wall coverings shall be of hot-dipped zinc-coated galvanized steel, mechanically deposited zinc-coated steel, stainless steel, silicon bronze or copper. The coating weights for hot-dipped zinc-coated fasteners shall be in accordance with ASTM A153. The coating weights for mechanically deposited zinc coated fasteners shall be in accordance with ASTM B695, Class 55 minimum.

    2304.10.3 Sheathing fasteners. Sheathing nails or other approved sheathing connectors shall be driven so that their head or crown is flush with the surface of the sheathing.

    2304.10.4 Joist hangers and framing anchors. Connections depending on joist hangers or framing anchors, ties and other mechanical fastenings not otherwise covered are permitted where approved. The vertical load-bearing capacity, torsional moment capacity and deflection characteristics of joist hangers shall be determined in accordance with ASTM D7147.

    2304.10.5 Other fasteners. Clips, staples, glues and other approved methods of fastening are permitted where approved.

    2304.10.6 Fasteners and connectors in contact with preservative-treated and fire-retardant-treated wood. Fasteners, including nuts and washers, and connectors in contact with preservative-treated and fire-retardant-treated wood shall be in accordance with Sections 2304.10.6.1 through 2304.10.6.4. The coating weights for zinc-coated fasteners shall be in accordance

    2025 CALIFORNIA BUILDING CODE 23-21

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

    WOOD

    with ASTM A153. The coating weight for zinc-coated nails shall be in accordance with ASTM A153 Class D or ASTM A641 Class 3S [1 ounce per square foot (305 g/m [2] )]. Stainless steel driven fasteners shall be in accordance with the material requirements of ASTM F1667.

    2304.10.6.1 Fasteners and connectors for preservative-treated wood. Fasteners, including nuts and washers, in contact with preservative-treated wood shall be of hot-dipped zinc-coated galvanized steel, stainless steel, silicon bronze or copper. Staples shall be of stainless steel. Fasteners other than nails, staples, timber rivets, wood screws and lag screws shall be permitted to be of mechanically deposited zinc-coated steel with coating weights in accordance with ASTM B695, Class 55 minimum. Connectors that are used in exterior applications and in contact with preservative-treated wood shall have coating types and weights in accordance with the treated wood or connector manufacturer’s recommendations. In the absence of manufacturer’s recommendations, not less than ASTM A653, Type G185 zinc-coated galvanized steel, or equivalent, shall be used.

    Exception: Plain carbon steel fasteners, including nuts and washers, in SBX/DOT and zinc borate preservative-treated wood in an interior, dry environment shall be permitted.

    2304.10.6.2 Fastenings for wood foundations. Fastenings, including nuts and washers, for wood foundations shall be as required in AWC PWF.

Frequently asked questions

Can I automatically count square nails as stronger than wire nails?

You may use the CHBC allowance to count square or cut nails as giving up to 50% more shear capacity than wire nails, but the responsible architect/engineer must document the condition and basis (observation or test) and include it in the structural survey and calculations. § 8-807.3 and § 8-802.

Do historic joists need modern grade marks to be used under CHBC?

No — CHBC § 8-807.3 expressly allows lumber selected for use to not bear grade marks, but the architect/engineer must assign allowable stresses and document the basis.

If I want to use balloon framing for a new replacement member, is that allowed?

Yes — balloon framing is listed as an archaic type that may be used or reinstalled when properly researched; assigned stresses must be documented by the engineer/architect. § 8-807.3 and § 8-802.

Who decides whether testing is needed to justify an assigned value?

The architect/engineer specifies tests when required; assigned values and any tests/results are subject to the enforcing agency’s concurrence per § 8-802.

Does CHBC let me exceed regular code demands by using more favorable historic values?

No — assigned values must be justified and cannot exceed the CHBC subsections or modern code values without adequate testing and agency concurrence. § 8-802.

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Wood, Concrete, Steel & Other Archaic Materials

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