EARTHQUAKE HAZARD REDUCTION FOR EXISTING UNREINFORCED MASONRY BEARING WALL BUILDINGS

This Chapter promotes public safety and welfare by reducing the risk of death or injury otherwise resulting from earthquake damage to certain buildings constructed before March 20, 1933, which have insufficient resistance to moderate or strong earthquakes.
The provisions of this Chapter constitute minimum standards for structural seismic resistance established primarily to reduce the risk of loss of life and injury. Compliance with these standards will not necessarily prevent loss of life or injury or prevent earthquake damage to an existing building. This Chapter shall not require existing electrical, plumbing, mechanical, or fire safety systems to be altered unless they constitute a hazard to life or property.
This Chapter provides systematic procedures and standards for identification and classification of these buildings based on their present use. Priorities, time periods, and standards are also established under which these buildings are required to be structurally analyzed and anchored. Where the analysis identifies deficiencies, this Chapter requires the building to be strengthened or demolished. (Ord. 2010-0053 § 83, 2010.)

The provisions of this Chapter shall apply to buildings which, prior to March 20, 1933, were constructed or were under construction and which have unreinforced masonry bearing walls as defined herein. This Chapter shall also apply to buildings for which a building permit was issued prior to March 20, 1933, and which have unreinforced masonry bearing walls as defined herein.

EXCEPTION: This Chapter shall not apply to dwellings and lodging houses defined as Group R-3 Occupancies nor to accessory buildings defined as Group U Occupancies.

(Ord. 2010-0053 § 83, 2010.)

For the purposes of this Chapter, the applicable definitions contained in this Code and the following definitions shall apply:

ESSENTIAL BUILDING. An essential building under the scope of this Chapter is defined as any building conforming to the definition of essential facilities as set forth in this Code.

HIGH-RISK BUILDING. A high-risk building is any building, other than an essential building, having an occupant load of 100 or more as determined by Chapter 10 of this Code.

EXCEPTION: A high-risk building shall not include the following:

1. Any building having exterior walls braced with masonry crosswalls or woodframe crosswalls spaced less than 40 feet (12192 mm) apart in each story. Crosswalls shall be full-story height with a minimum length of 1-1/2 times the story height.
2. Any building used for its intended purpose, as determined by the building official, for less than 20 hours per week.

HISTORICAL BUILDING. A historical building is any building designated as a historical building by the federal, state, or County government or an agency thereof.

LOW-RISK BUILDING. A low-risk building is any building, other than an essential building, having an occupant load of less than 20 as determined by Chapter 10 of this Code.

MEDIUM-RISK BUILDING. A medium-risk building is any building, not classified as a high-risk building or an essential building, having an occupant load of 20 or more as determined by Chapter 10 of this Code. (Ord. 2010-0053 § 83, 2010.)

The rating classifications identified in Table 96-A are hereby established and each building within the scope of this Chapter shall be placed in one such rating classification by the Building Official. The total occupant load of the entire building as determined by Chapter 10 of this Code shall be used to determine the rating classification.

EXCEPTION: For purposes of this Chapter, portions of buildings constructed to act independently when resisting seismic forces may be placed in separate rating classifications.

(Ord. 2010-0053 § 83, 2010.)

The owner of each building within the scope of this Chapter shall, upon service of an order and within the time limits set forth in this Chapter, cause a structural analysis to be made of the building by a licensed civil or structural engineer or architect. If the building does not comply with standards specified in this Chapter and Appendix Chapter A1 of Part 10, Title 24 of the California Code of Regulations, then the owner shall cause the building to be structurally altered to conform to such standards or shall cause the building to be demolished.
The owner of a building within the scope of this Chapter shall comply with the requirements set forth above by submitting plans that comply with the requirements of Section 9608 to the Building Official for review within the stated time limits of the following items:
1. Within 270 days after service of the order, a structural analysis, which is subject to approval by the Building Official and which shall demonstrate that the building meets the minimum requirements of this Chapter; or
2. Within 270 days after service of the order, the structural analysis and plans for structural alterations of the building to comply with this Chapter; or
3. Within 120 days after service of the order, plans for the installation of wall anchors in accordance with the requirements specified in Appendix Chapter A1 of Part 10, Title 24 of the California Code of Regulations; or
4. Within 270 days after service of the order, plans for the demolition of the building. (Ord. 2010-0053 § 83, 2010.)

After plans are submitted and approved by the Building Official, the owner shall obtain a building permit and then commence and complete the required alteration or demolition within the time limits set forth in Table 96-B. These time limits shall begin to run from the date the order is served in accordance with Section 9606.2, except that the time limit to commence structural alterations or demolition shall begin to run from the date the building permit is issued.
An owner electing to comply with Item 3 of Section 9605.1 is also required to comply with Item 2 or 4 of Section 9605.1 provided, however, that the 270-day period provided for in Item 2 or 4 of Section 9605.1 and the time limits for obtaining a building permit and to complete structural alterations or building demolition set forth in Table 96-B shall be extended in accordance with Table 96-C. Each such extended time limit shall begin to run from the date the order is served in accordance with Section 9606, except that the time limit to commence structural alterations or demolition shall begin to run from the date the building permit is issued. (Ord. 2010-0053 § 83, 2010.)

The Building Official shall, in accordance with the priorities set forth in Table 96-C, issue an order as provided in this Section to the owner of each building within the scope of this Chapter.
Prior to the service of an order as set forth in Table 96-C, a bulletin may be issued to the owner as shown upon the last equalized assessment roll of a building considered by the Building Official to be within the scope of this Chapter. The bulletin may contain information the Building Official deems appropriate. The bulletin may be issued by mail or in person. (Ord. 2010-0053 § 83, 2010.)

Priorities for the service of the order for buildings within the scope of this Chapter shall be in accordance with the rating classification as shown in Table 96-C. Within each separate rating classification, the priority of the order shall normally be based on the occupant load of the building. The owner of buildings housing the largest occupant loads shall be served first. The minimum time period prior to the service of the order as shown in Table 96-C shall be measured from the effective date of this Chapter. The Building Official may, upon receipt of a written request from the owner, order such owner to bring the building into compliance with this Chapter prior to the normal service date for such building set forth in this Chapter. (Ord. 2010-0053 § 83, 2010.)

The order shall be in writing and shall be served either personally or by certified or registered mail upon the owner as shown on the last equalized assessment roll of the building. The order shall specify that the building has been determined by the Building Official to be within the scope of this Chapter and, therefore, is required to meet the minimum seismic standards of this Chapter. The order shall specify the rating classification of the building and shall be accompanied by a copy of Section 9605 which sets forth the owner’s alternatives and time limits for compliance. (Ord. 2010-0053 § 83, 2010.)

The owner of the building may appeal the Building Official’s initial determination that the building is within the scope of this Chapter to the Building Board of Appeals established by Section 105. Such appeal shall be filed with the Board within 60 days from the service date of the order described in Section 9606.3. Any such appeal shall be decided by the Board no later than 90 days after the date that the appeal is filed. Such appeal shall be made in writing and the grounds thereof shall be stated clearly and concisely. Appeals or requests for modifications from any other determinations, orders or actions by the building official pursuant to this Chapter shall be made in accordance with the procedures established in Sections 104.2.7 and 105. (Ord. 2010-0053 § 83, 2010.)

At the time that the Building Official serves the aforementioned order, the Building Official shall also file with the office of the County Recorder a certificate stating that the subject building is within the scope of this Chapter and is a potentially earthquake hazardous building. The certificate shall also state that the owner thereof has been ordered to structurally analyze the building and to structurally alter or demolish the building where compliance with this Chapter has not been demonstrated.
If the building is either demolished, found not to be within the scope of this Chapter, or is structurally capable of resisting minimum seismic forces required by this Chapter as a result of structural alterations or an analysis, the Building Official shall file with the office of the County Recorder a form terminating the status of the subject building as being classified within the scope of this Chapter. (Ord. 2010-0053 § 83, 2010.)

If the owner of the subject building fails to comply with any order issued by the Building Official pursuant to this Chapter within any of the time limits set forth in Section 9605, then the Building Official shall verify that the record owner of this building has been properly served. If the order has been served on the record owner, then the Building Official may order that the entire building be vacated and that the building remain vacated until such order has been complied with. If compliance with such order has not been accomplished within 90 days after the date the building has been ordered vacated or such additional time as may have been granted by the Building Board of Appeals, then the Building Official may order its demolition in accordance with the provisions of Section 102.1 of this Code. (Ord. 2010-0053 § 83, 2010.)

An owner who has been served with an abatement order as described in Section 9606.6 may request a hearing before the Building Board of Appeals to request postponement of County action leading to demolition, vacation of building, or other abatement procedure. All such requests shall be accompanied by a rehearing fee as specified in Section 105. At such a rehearing, the Board will consider all evidence submitted and after such consideration may find that a postponement is warranted and so order, or may find that further postponement is unwarranted and order any abatement work considered necessary to be performed by a specified date after which date the Building Official shall cause such work to be performed or completed without further notice. Nothing in this Section shall prevent the Board itself or the Building Official from bringing any matter before the Board for rehearing. (Ord. 2010-0053 § 83, 2010.)

Existing walls of adobe construction shall conform with the following:

9607.2.1 Unreinforced adobe masonry walls shall not exceed a height or length-to-thickness ratio of five for exterior-bearing walls and must be provided with a reinforced bond beam at the top, interconnecting all walls. Minimum beam depth shall be 6 inches (152 mm) and a minimum width of 8 inches (203 mm) less than the wall width. Minimum wall thickness shall be 18 inches (457 mm) for exterior-bearing walls and 10 inches (254 mm) for adobe partitions. No adobe structures shall exceed one story in height unless the historic evidence indicates a two-story height. In such cases, the height-to-thickness ratio shall be the same as above for the first floor based on the total two-story height, and the second floor wall thickness shall not exceed the ratio five by more than 20 percent. Bond beams shall be provided at the roof and second-floor levels. (Ord. 2010-0053 § 83, 2010.)

9607.2.2 Foundation footings shall be reinforced concrete under newly reconstructed walls and shall be 50 percent wider than the wall above, soil conditions permitting, except that the foundation wall may be 4 inches (102 mm) less in width than the wall above if a rock, burned brick, or stabilized adobe facing is necessary to provide authenticity. (Ord. 2010-0053 § 83, 2010.)

9607.2.3 Existing unstabilized brick and adobe brick masonry shall have an average compressive strength of 225 pounds per square inch (1551 kPa) when tested in accordance with ASTM C 67. One sample out of five may have a compressive strength of not less than 188 pounds per square inch (1296 kPa). Unstabilized brick may be used where existing bricks are unstabilized and where the building is not susceptible to flooding conditions or direct exposure. Adobe may be allowed a maximum value of 3 pounds per square inch (21 kPa) for shear with no increase for lateral forces. (Ord. 2010-0053 § 83, 2010.)

9607.2.4 Mortar may be of the same soil composition and stabilization as the brick in lieu of cement mortar. (Ord. 2010-0053 § 83, 2010.)

9607.2.5 Nominal tension stresses due to seismic forces normal to the wall may be neglected if the wall meets thickness requirements and shear values allowed by this Section. (Ord. 2010-0053 § 83, 2010.)

9607.4 Alternative materials and state historical building code advisory review.

Alternative materials, design, or methods of construction will be considered as set forth in Section 104.2.8. In addition, when a request for an alternative proposed design, material, or method of construction is being considered, the Department may file a written request for an opinion to the State Historical Building Code Advisory Board for its consideration, advice or findings in accordance with the State Historical Building Code. (Ord. 2010-0053 § 83, 2010.)

The following requirements with appropriate construction details shall be made part of the submitted plans. (Ord. 2010-0053 § 83, 2010.)

9608.2.1 All unreinforced masonry walls shall be anchored at the roof and all floor levels as specified in Appendix Chapter A1 of Part 10, Title 24 of the California Code of Regulations, or by an approved equivalent method. (Ord. 2010-0053 § 83, 2010.)

9608.2.2 Diaphragm chord stresses of horizontal diaphragms shall be developed in existing materials or by addition of new materials. (Ord. 2010-0053 § 83, 2010.)

9608.2.3 Where trusses and beams other than rafters or joists are supported on masonry, independent secondary columns shall be installed to support vertical loads of the roof or floor members. (Ord. 2010-0053 § 83, 2010.)

9608.2.4 Parapets and exterior wall appendages not capable of resisting the forces specified in this Chapter shall be removed, stabilized, or braced to ensure that the parapets and appendages remain in their original position. (Ord. 2010-0053 § 83, 2010.)

9608.2.5 All deteriorated mortar joints in unreinforced masonry walls shall be pointed with Type S or N mortar. Prior to any pointing, the wall surface must be raked and cleaned to remove loose and deteriorated mortar. Pointing shall be done under the continuous inspection of a registered special masonry or concrete inspector. At the conclusion of the project, the inspector shall submit a written report to the Building Official setting forth the portion of work inspected. (Ord. 2010-0053 § 83, 2010.)

9608.2.6 Repair details of any cracked or damaged unreinforced masonry wall required to resist forces specified in this Chapter. (Ord. 2010-0053 § 83, 2010.)

The following existing construction information shall be made part of the approved plans:
1. The type and dimensions of existing walls and the size and spacing of floor and roof members.
2. The extent and type of existing wall anchorage to floors and roof.
3. The extent and type of parapet corrections which were preformed in accordance with Chapter 34 of this Code.
4. Accurately dimensioned floor plans and masonry wall elevations showing dimensioned openings, piers, wall thickness, and heights.
5. The location of cracks or damaged portions or unreinforced masonry walls requiring repairs.
6. The type of interior wall surfaces and ceilings, and if reinstallation or anchoring of existing plaster is necessary.
7. The general condition of the mortar joints and if the joints need pointing. (Ord. 2010-0053 § 83, 2010.)

Removal and replacement of unreinforced masonry interior or exterior walls with materials and construction conforming to the requirements of this Code for new buildings constitutes compliance with this Chapter. Upon completion of such work, the remainder of the structure is, therefore, subject to the provisions of Chapter 34, “Existing Structures.” Nothing in this Section shall be construed to mean that a building within the scope of this Chapter is not subject to Section 102, “Unsafe Buildings,” or to Chapter 99 of this Code. (Ord. 2010-0053 § 83, 2010.)

TYPE OF BUILDING	CLASSIFICATION
Essential building	I
High-risk building	II
Medium-risk building	III
Low-risk building	IV

REQUIRED ACTION BY OWNER	OBTAIN BUILDING PERMIT WITHIN¹	COMMENCE ALTERATION WITHIN	COMPLETE ALTERATION WITHIN¹
Structural alterations or building demolition	1 year	180 days²	3 years
Wall anchor	180 days	270 days¹	1 year

RATING CLASSIFICATION	OCCUPANT LOAD	EXTENSION OF TIME IF WALL ANCHORS ARE INSTALLED	MINIMUM TIME PERIODS FOR SERVICE OF ORDER
I (Highest priority)	Any	1 year	90 days
II	100 or more	1 year	180 days
III-A	100 or more	1 year	1 year
III-B	More than 50, but less than 100	1 year	2 years
III-C	More than 19, but less than 51	1 year	3 years
IV (Lowest priority)	Less than 20	1 year	4 years