Long Beach Municipal Code Ch. 18.69 Voluntary Earthquake Hazard Reduction in Existing Wood Frame…

A. Purpose. The provisions of this chapter are intended to promote public safety and welfare by reducing the risk of earthquake-induced damage to existing wood-framed residential buildings. The voluntary minimum standards contained in this chapter shall substantially improve the seismic performance of these residential buildings but will not necessarily prevent all earthquake damage. When fully followed, these standards will strengthen the portion of the structure that is most vulnerable to earthquake damage.

Prior to 1960, most wood frame residential buildings were built with raised wood floors supported by short wood stud walls known as cripple walls. These cripple walls are typically braced with weak seismic materials such as Portland cement plaster or horizontal wood siding. In addition, wood frame buildings built under Building Codes in effect prior to July 1938 were not required to be bolted to their foundations. Recent earthquakes have shown that if a building has weak cripple walls or is unbolted, it may fall off its foundation even in moderate earthquakes.

Fallen buildings have collapsed, caught fire or needed extensive repairs to restore their occupancy.

This chapter sets prescriptive standards for strengthening of under floor enclosures, if permitted by the Building Official, without requiring construction documents prepared by a registered design professional licensed by the State of California. This chapter also provides a design standard for the use of alternate materials or an alternate method of construction in lieu of the prescriptive standards.

Construction documents for strengthening using alternate materials or methods shall be prepared by a registered design professional licensed by the State of California.

B. Scope. The provisions of this chapter may be applied to light wood frame Group R occupancies, with no more than four (4) dwelling units when they contain one (1) or more of the structural weaknesses specified in Section 18.69.030.

The provisions of this chapter do not apply to the buildings or elements thereof listed below. These buildings or elements require analysis by a registered design professional licensed by the State of California in accordance with Chapter 16 of the California Building Code adopted in Chapter 18.40 or other approved standards to determine appropriate strengthening.

1. Buildings with a lateral-force-resisting system using poles or columns embedded in the ground.

2. Cripple walls that exceed four (4) feet in height.

3. Buildings exceeding three (3) stories in height and any three (3) story building with cripple wall studs exceeding fourteen (14) inches in height.

4. Buildings, or portions thereof, constructed on a concrete slab on grade or constructed on or into a slope steeper than one (1) unit vertical in three (3) units horizontal (33.3% slope).

5. Buildings where the Building Official determines that conditions exist that are beyond the scope of the requirements of this chapter.

The standard details approved by the Building Official and these prescriptive provisions are not intended to be the only acceptable strengthening methods permitted. Alternate details and methods shall be permitted when approved by the Building Official. Qualified historical buildings shall be permitted to use alternate building regulations or deviations from this chapter in order to preserve their original or restored architectural elements and features. See California Code of Regulations, Title 24, Part 8 (California Historical Building Code) for these standards.

C. Alternative design procedures. When analysis by a registered design professional is required or provided for a building within the scope of this chapter, such analysis shall be in accordance with all requirements of this code except as provided in this chapter. The design shall provide strengthening for any structural weakness listed in Section 18.69.030 that is at least equivalent to that provided by the prescriptive requirements of this chapter with respect to strength, deflection and capacity. The Building Official may require that sufficient evidence be submitted to substantiate such equivalence. The base shear may be determined in accordance with the following:

V = 0.1375 W(69-1)

Where:

V = the total design lateral force or shear at the base

W = the total seismic dead load defined in Section 12.7.2 of ASCE 7-16.

(ORD-25-0019 § 1(Exh. A), 2025; ORD-22-0033 § 1(Exh. A), 2022; ORD-19-0031 § 1(Exh. A), 2019; ORD-16-0026 § 1(Exh. A), 2016)

For the purpose of this chapter, in addition to the applicable definitions, symbols and notations in this code, certain additional terms are defined as follows:

"Adhesive anchor" means a fastener placed in hardened concrete or masonry that derives its holding strength from a chemical adhesive compound placed between the wall of the hole and the embedded portion of the anchor.

"Anchor side plate" means a metal plate or plates used to connect a sill plate to the side of a concrete or masonry stem wall.

"Cripple wall" means a wood-framed stud wall extending from the top of the foundation to the underside of the lowest floor framing.

"Expansion anchor" means a mechanical fastener placed in hardened concrete or assembled masonry, designed to expand in a self-drilled or pre-drilled hole of a specified size and engage the sides of the hole in one or more locations to develop shear and/or tension resistance to applied loads without grout, adhesive or drypack.

"Perimeter foundation" means a foundation system which is located under the exterior walls of a building.

"Snug-tight" is as tight as an individual can torque a nut on a bolt by hand using a wrench with a ten (10) inch long handle and the point at which the full surface of the plate washer is contacting the wood member and slightly indents the wood surface.

"Unreinforced masonry" means and includes adobe, burned clay, concrete or sand-lime brick, hollow clay or concrete block, hollow clay tile, rubble, cut stone, and unburned clay masonry walls in which the area of reinforcement is less than fifty percent (50%) of the minimum steel ratios required for reinforced masonry.

(ORD-25-0019 § 1(Exh. A), 2025; ORD-22-0033 § 1(Exh. A), 2022; ORD-19-0031 § 1(Exh. A), 2019; ORD-16-0026 § 1(Exh. A), 2016)

A. Sill plates or floor framing which are supported directly on the ground without an approved foundation system.

B. A perimeter foundation system which is constructed of wood posts supported on isolated pad footings.

C. Perimeter foundation systems that are not continuous.

EXCEPTIONS:

1. Existing single-story exterior walls not exceeding ten (10) feet in length forming an extension of floor area beyond the line of an existing continuous perimeter foundation.

2. Porches, storage rooms and similar spaces not containing fuel burning appliances.

D. A perimeter foundation system which is constructed of unreinforced masonry.

E. Sill plates which are not connected to the foundation or are connected with less than what is required by Subsection 18.69.040.C.1.

F. Cripple walls that are not braced in accordance with the requirements of Subsection 18.69.040.D and Table 69-A.

(ORD-25-0019 § 1(Exh. A), 2025; ORD-22-0033 § 1(Exh. A), 2022; ORD-19-0031 § 1(Exh. A), 2019; ORD-16-0026 § 1(Exh. A), 2016)

A. General.

1. Scope. The structural weaknesses noted in Section 18.69.030 shall be strengthened in accordance with the requirements of this section. Strengthening work shall be allowed to include both new construction and alteration of existing construction. Except as provided herein, all strengthening work and materials shall comply with the applicable provisions of this code. Alternate methods of strengthening shall be allowed provided such systems are designed by a registered design professional and approved by the Building Official.

2. Condition of existing wood materials. All existing wood materials which will be a part of the strengthening work shall be in a sound condition and free from defects which substantially reduce the capacity of the member. Any wood material found to contain fungus infection shall be removed and replaced with new material. Any wood material found to be infested with insects or to have been infested shall be strengthened or replaced with new materials to provide a net dimension of sound wood at least equal to its undamaged original dimension.

3. Floor joists not parallel to foundations. Floor joists framed perpendicular or at an angle to perimeter foundations shall be restrained by either a nominal two-inch wide continuous rim joist or a nominal two (2) inch wide full depth blocking between alternate joists in one- and two-story buildings, and between each joist in three (3) story buildings. Blocking for multistory buildings must occur at each joist space above a braced cripple wall panel.

Existing connections at the top edge of an existing rim joist or blocking need not be verified. The bottom edge connection to either the foundation sill plate or top plate of a cripple wall shall be verified unless a supplemental connection is provided. The minimum existing bottom edge connection shall consist of 8d toenails spaced six (6) inches apart for a continuous rim joist or three (3) 8d toenails per block. When this minimum bottom edge connection is not present, or is not verified, a supplemental connection shall be provided.

When an existing continuous rim joist or the minimum existing blocking does not occur, new one and one-eighth (1-⅛) inch wood structural panel blocking installed tightly between floor joists and nailed with 10d common nails at four (4) inches on center to the sill or wall top plate shall be provided at the inside face of the cripple wall. In lieu of one and one-eighth (1-⅛) inch wood structural panel blocking, tight-fitting, full or near full depth two (2) inches nominal width lumber blocking shall be allowed provided it does not split during installation. New blocking is not required where it will interfere with vents or plumbing that penetrates the wall.

4. Floor joists parallel to foundations. Where existing floor joists are parallel to the perimeter foundations, the end joist shall be located over the foundation and, except for required ventilation openings, shall be continuous and in continuous contact with any existing foundation sill plate or top plate of the cripple wall. Existing connections at the top edge connection of the end joist need not be verified; however, the bottom edge connection to either the foundation sill plate or the top plate of a cripple wall shall be verified unless a supplemental connection is provided.

The minimum bottom edge connection shall be 8d toenails spaced six (6) inches apart. If this minimum bottom edge connection is not present or is not verified, a supplemental connection shall be provided.

5. Supplemental connections. Supplemental connections shall provide sufficient strength to transfer the seismic forces. Framing anchors of minimum eighteen (18) gage steel and twelve (12) approved fasteners may be considered to meet this requirement when spaced thirty-two (32) inches on center for one (1) story buildings, twenty-four (24) inches on center for two (2) story buildings and sixteen (16) inches on center for three (3) story buildings.

EXCEPTIONS: A supplemental connection is not required when:

a. The structural wood panel sheathing extends from the sill plate to the rim joist or blocking above.

b. The floor sheathing is nailed directly into the sill or top plate of the cripple wall.

6. Single top plate ties. When a single top plate exists in the cripple wall, all end joints in the top plate shall be tied. Ties shall be connected to each end of the discontinuous top plate and shall be equal to one of the following:

a. Three (3) inch by six (6) inch by 0.036-inch thick galvanized steel and nailed with six (6) 8d nails at each end.

b. One and one-half (1½) inch by twelve (12) inch by 0.058-inch galvanized steel nailed with six (6) 16d nails at each end.

c. Two (2) inch by four (4) inch by twelve (12) inch wood blocking nailed with six (6) 16d nails at each end.

B. Foundations.

1. New perimeter foundations. New perimeter foundations shall be provided for structures with the structural weaknesses noted in Subsections 18.69.030.A and 18.69.030.B. Soil investigations or geotechnical studies are not required for this work unless the building shows signs of excessive settlement or creep.

2. Foundation evaluation by a registered design professional. Partial perimeter foundations or unreinforced masonry foundations shall be evaluated by a registered design professional for the force levels noted in Formula (69-1) of this chapter. Test reports or other substantiating data to determine existing foundation material strengths shall be submitted for review. When approved by the Building Official, these foundation systems may be strengthened in accordance with the recommendations included with the evaluation in lieu of being replaced.

EXCEPTION: In lieu of testing existing foundations to determine material strengths and when approved by the Building Official, a new nonperimeter foundation system, designed for the forces noted in Formula (69-1) of this chapter, may be used to resist all exterior wall lateral forces.

3. Details for new perimeter foundations. All new perimeter foundations shall be continuous and constructed according to the standards for new buildings.

EXCEPTIONS:

a. When approved by the Building Official, the existing clearance between existing floor joists or girders and existing grade below the floor need not comply with Section 2304.12.1.1 of the California Building Code adopted in Chapter 18.40. This exception shall not be permitted when buildings are relocated on new foundations.

b. When approved by the Building Official, and when designed by a registered design professional, partial perimeter foundations may be used in lieu of a continuous perimeter foundation.

C. Foundation sill plate anchorage.

1. Existing perimeter foundations. When the building has an existing continuous perimeter foundation, all perimeter wall sill plates shall be connected to the foundation in accordance with Table 69-A and this section. Anchors shall be installed with the plate washer installed between the nut and the sill plate. The nut shall be tightened to a snug-tight condition after curing is complete for adhesive anchors and after expansion wedge engagement for expansion anchors.

The installation of nuts on all anchors shall be subject to verification by the Building Official. Torque testing shall be performed for twenty percent (20%) of all adhesive or expansion anchors.

Minimum test values shall be thirty (30) foot-pounds for one-half inch (½") and forty (40) foot-pounds for five-eighths inch (⅝") diameter anchors.

Anchor side plates shall be permitted when conditions prevent anchor installation vertically through the sill plate. Anchor side plates shall be spaced as required for adhesive or expansion anchors but only one anchor side plate is required on individual pieces of sill plate less than thirty-two inches (32") in length. Wood structural panel shims shall be used on sill plates for single plate anchor side plates when the foundation stem wall is from three-sixteenths inch ( 3/16 ") to three-fourths inch (¾") wider than the sill plate. The shim length shall extend a minimum of two inches (2") past each end of the anchor side plate. Two (2) plate anchor side plates shall be used when the total thickness of the required shim exceeds three-fourths inch (¾").

All anchor side plates which use lag or wood screws shall pre-drill the sill plate to prevent splitting as required by Section 12.1 of the 2024 ANSI/AWC NDS.

Lag or wood screws shall be installed in the center of the thickness of the existing sill plate.

Expansion anchors shall not be used in unreinforced masonry or concrete masonry grout of poor quality. Adhesive anchors shall be required when expansion anchors will not tighten to the required torque or their installation causes surface cracking of the foundation wall.

2. Placement of anchors. Anchors shall be placed within twelve inches (12"), but not less than nine inches (9"), from the ends of sill plates and shall be placed near the center of the stud space closest to the required spacing. New sill plates may be installed in pieces when necessary because of existing conditions.

The minimum length of new sill plate pieces shall be thirty inches (30").

EXCEPTION: Where physical obstructions such as fireplaces, plumbing or heating ducts interfere with the placement of an anchor, the anchor shall be placed as close to the obstruction as possible, but not less than nine inches (9") from the end of the plate. Center-to-center spacing of the anchors shall be reduced as necessary to provide the minimum total number of anchors required based on the full length of the wall. Center-to-center spacing shall not be less than twelve inches (12").

3. New perimeter foundations. Sill plates for new perimeter foundations shall be anchored as required by Section 2308.3.1 of the California Building Code adopted in Chapter 18.40.

D. Cripple wall bracing.

1. General. Exterior cripple walls not exceeding four feet (4') in height shall use the prescriptive bracing method listed below. Cripple walls more than four feet (4') in height require analysis by a registered design professional in accordance with Chapter 16 of the California Building Code adopted in Chapter 18.40.

2. Sheathing requirements. Wood structural panel sheathing shall not be less than 15/32 inch thick. When used, plywood panels shall be constructed of five (5) or more plies.

All wood structural panels shall be nailed with 8d common nails spaced four inches (4") on center at all edges and at twelve inches (12") on center at each intermediate support with not less than two (2) nails for each stud. Nails shall be driven so that their head or crown is flush with the surface of the sheathing and shall penetrate the supporting member a minimum of one and one-half inch (1-½"). When a nail fractures the surface, it shall be left in place and not counted as part of the required nailing. A new 8d nail shall be located within two inches (2") of the discounted nail and hand-driven flush with the sheathing surface.

EXCEPTION: No. 6 × 1-½ inch wood screws may be used for sheathing nailing when bracing materials are installed on the interior face of studs and cement plaster or other brittle finishes are on the exterior of the sheathed wall.

All horizontal joints must occur over nominal two inch (2") by four inch (4") blocking installed with the nominal four inch (4") dimension against the face of the plywood. All vertical joints must occur over studs. Vertical joints at adjoining pieces of wood structural panels shall be centered on existing studs such that there is a minimum one-eighth inch (⅛") between the panels.

Nails shall be placed a minimum of one-half inch (½") from the edges of the existing stud. When such edge distance cannot be maintained because of the width of the existing stud, a new stud shall be added adjacent to the existing and connected with 16d common nails at eight inches (8") on center. A minimum of three (3) such nails shall be provided.

3. Distribution and amount of bracing. See Table 69-A for the distribution and amount of bracing required. Bracing for a building with three (3) or more floor levels above cripple wall studs exceeding fourteen inches (14") in height must be designed in accordance with Chapter 16 of the California Building Code adopted in Chapter 18.40.

The braced panel must be at least two (2) times the height of the cripple stud wall but not less than forty-eight inches (48") in width. All panels along a wall shall be nearly equal in length and shall be nearly equally spaced along the length of the wall. Braced panels at ends of walls shall be located as near the end as possible.

Where physical obstructions such as fireplaces, plumbing or heating ducts interfere with the placement of cripple wall bracing, the bracing shall then be placed as close to the obstruction as possible. The total amount of bracing required shall not be reduced because of obstructions, but the required length of bracing need not exceed the length of the wall.

Under floor ventilation openings shall be maintained in accordance with Section 1202.4 of the California Building Code adopted in Chapter 18.40. Braced panels may include under floor ventilation openings when the height of the solid portion of the panel meets or seventy-five percent (75%) of the height of the cripple stud wall.

When the minimum amount of bracing prescribed in Table 69-A cannot be installed due to obstructions along any wall, the bracing must be designed by a registered design professional in accordance with Subsection 18.69.010.C.

4. Stud space ventilation. When bracing materials are installed on the interior face of studs forming an enclosed space between the new bracing and existing exterior finish, each braced stud space must be ventilated. Adequate ventilation and access for future inspection shall be provided by drilling on two inch (2") to three inch (3") diameter round hole through the sheathing nearly centered between each stud at the top and bottom of the cripple wall. Such holes should be spaced a minimum of one (1) inch clear from the sill or top plates. In stud spaces containing sill bolts, the hole shall be located on the center line of the sill bolt but not closer than one inch (1") clear from the nailing edge of the sheathing.

When existing blocking occurs within the stud space, additional ventilation holes shall be placed above and below the blocking or the existing block shall be removed and a new nominal two inch (2") by four inch (4") block installed with the nominal four inch (4") dimension against the face of the plywood. For stud heights less than eighteen inches (18"), only one (1) ventilation hole need be provided.

5. Existing under floor ventilation. Existing under floor ventilation shall not be reduced without providing equivalent new ventilation as close to the existing as possible. New sheathing may be installed around existing vent openings in braced panels when the length of the panel is increased a distance equal to the length of the vent opening or one stud space minimum.

EXCEPTION: For residential buildings with a post and pier foundation system where a new continuous perimeter foundation system is being installed, ventilation shall be provided in accordance with this title.

(ORD-25-0019 § 1(Exh. A), 2025; ORD-22-0033 § 1(Exh. A), 2022; ORD-19-0031 § 1(Exh. A), 2019; ORD-16-0026 § 1(Exh. A), 2016)

A. Inspection by the Department. All work shall be subject to inspection by the Building Official including, but not limited to:

1. Placement and installation of new adhesive or expansion anchors or anchor side plates installed in existing foundations;

2. Placement of required blocking and framing anchors;

3. Installation and nailing of new cripple wall bracing. The torque testing of sill plate anchors per Subsection 18.69.040.C.1 shall be performed by the Building Inspector.

B. Special inspection. Special inspection is not required for sill plate anchors installed in existing foundations regulated by the provisions of this chapter. Any work may be subject to special inspection when required by the Building Official or when so designated by the registered design professional of record.

C. Structural observation. Structural observation is not required for work done under the prescriptive provisions of this chapter. When construction documents for strengthening are prepared by a registered design professional and alternate materials or methods are used, structural observation shall be provided as required in Section 1704.6 of the California Building Code adopted in Chapter 18.40.

D. Registered design professional of record's statement. When an alternative design is provided per Subsection 18.69.010.C, the responsible registered design professional of record shall place the following statement on the approved construction document:

1. "I am responsible for this building's seismic strengthening design for the under floor cripple walls and sill bolting in compliance with the minimum seismic resistance standards of Chapter 18.69 of the Long Beach Municipal Code."

or when applicable:

2. "The registered special inspector, required as a condition of the use of structural design stresses requiring continuous inspection, will be responsible to me."

TABLE 69-A SILL PLATE ANCHORAGE AND CRIPPLE WALL BRACING 1,2,3

1 Plate washers for use with adhesive or expansion anchors shall be two inches by two inches by three-sixteenths inch for one-half-inch diameter anchors and two and one-half inches by two and one-half inches by one-fourth inch for five-eighths-inch diameter anchors.

2 Existing sill plate anchor bolts shall be permitted to provide all or a portion of the sill plate connection requirement if:

2.1 The anchor bolt is cast in concrete and in sound condition,

2.2 The diameter size and maximum spacing meets or exceeds the requirements of this table,

2.3 A new plate washer conforming to Footnote 1 is installed, and

2.4 The sill plate is connected to a snug-tight condition and torque tested per Subsection 18.69.040.C.1.

3 Anchor side plates shall be permitted when conditions prevent anchor installation vertically through the sill plate.

(ORD-25-0019 § 1(Exh. A), 2025; ORD-22-0033 § 1(Exh. A), 2022; ORD-16-0026 § 1(Exh. A), 2016)