Petaluma Municipal Code Ch. 17.34 Earthquake Hazard Reduction in Existing Unreinforced

The purpose of this chapter is to promote public safety and welfare by reducing the risk of death or injury that

may result from the e]ects of earthquakes on unreinforced masonry bearing wall buildings.

The provisions of this chapter are intended as minimum standards for structural seismic resistance established

primarily to reduce the risk of life loss or injury. Compliance with these standards will not necessarily prevent loss

of life or injury or prevent earthquake damage to rehabilitated buildings. Building owners who retroZt their

buildings in Petaluma in accordance with the provisions of this chapter shall be deemed to have used an

acceptable standard of care to protect the safety of the public and occupants of the building. This chapter does

not require alteration of existing electrical; accessibility; plumbing; mechanical or Zre safety systems. (Ord. 1882

NCS §1, 1992.)

The provisions of this chapter shall apply to all existing buildings having at least one unreinforced wall as deZned

herein. Structural characteristics to be addressed are parapet stability; wall anchors (roof and [oor systems); shear

anchors (corners) and external hazards.

Exceptions: This chapter shall not apply to the following:

A. Single-Family Detached dwellings.

B. Detached apartment houses containing less than Zve dwelling units which are used solely for residential

purposes.

(Ord. 1882 NCS §1, 1992.)

Alternate materials; designs and methods of construction may be approved by the building o\cial in accordance

with the current "Uniform Code for Building Conservation." (Ord. 1882 NCS §1, 1992.)

For the purpose of this chapter; certain terms are deZned as follows:

"Cross walls" mean interior walls of masonry or wood frame construction with surface Znish of wood lath and

plaster; minimum one-half inch-thick gypsum wallboard or solid horizontal wood sheathing. In order to be

considered as a cross wall within the intent of this chapter; cross walls shall be spaced not more than forty feet

apart in each story; and shall be full story height with a minimum length of one and one-half times the story

height.

"Unreinforced masonry wall" means a masonry wall having all of the following characteristics:

1. Provides the vertical support for a [oor or roof.

2. The total superimposed load is over one hundred pounds per linear foot.

3. The area of reinforcing steel; if any; is less than Zfty percent of that required by Section 2407(h)4B of the

UBC.

"External hazard" means an object attached to or forming the exterior facade of a building which may fall onto

pedestrians or adjacent buildings. Examples of this type of hazard include; but are not limited to; the following:

1. Parapets;

2. Masonry chimneys;

3. Tile rooZng;

4. Masonry or stone wall veneer and wall ornamentation; including cornices or other decorative

appendages;

5. Nonstructural exterior wall panels; such as masonry in-Zll or decorative precast concrete.

(Ord. 1882 NCS §1, 1992.)

A. Service of Order. The building o\cial shall issue an order; as provided in subsection B; to the owner of each

building within the scope of this chapter within sixty days from the e]ective date of this chapter.

B. Contents of Order. The order shall be in writing and shall be served either personally or by certiZed or

registered mail upon the owner. The order shall specify that the building has been determined by the building

o\cial to be within the scope of this chapter and; therefore; is required to meet the minimum standards of this

chapter. The order shall be accompanied by a copy of this chapter and shall specify the time limits for compliance.

C. Appeal From Order. The owner or the owner’s authorized agent may appeal to the city council the building

o\cial’s initial determination that the building is within the scope of this chapter. Such appeal shall be Zled with

the city clerk within sixty days from the service date of the order described in subsection B. Any such appeal shall

be decided by the city council no later than sixty days after the date that the appeal is Zled. Such appeal shall be

made in writing and the ground thereof shall be stated clearly and concisely.

Appeals or requests for modiZcations from any other determinations; orders; or action by the building o\cial

pursuant to this chapter; shall be made in accordance with the appeal procedures established in this chapter.

D. Recordation. At the conclusion of the appeal period; the building o\cial shall Zle with the o\ce of the county

recorder a certiZcate stating that the subject building is within the scope of Chapter 17.34; Earthquake Hazard

Reduction in Existing Unreinforced Masonry Wall Buildings. The certiZcate shall also state that the owner thereof

has been ordered to bring the building into conformance with Chapter 17.34.

E. Termination of Status. As a result of structural alterations or an analysis is found to be structurally capable of

resisting minimum seismic forces required by this chapter; or is demolished; the building o\cial shall Zle with the

o\ce of the county recorder a certiZcate terminating the status of the subject building as being classiZed within

the scope of Chapter 17.34.

Further; the building o\cial shall also notify the California Seismic Safety Commission and/or other agencies

hereafter charged with the maintenance of the California Unreinforced Masonry Building Inventory; that the

subject building has been removed from the city of Petaluma Inventory Of Unreinforced Masonry Buildings; and

instructing the commission and/or agencies to do the same.

F. Enforcement. If the owner fails to comply with any order issued by the building o\cial pursuant to this chapter

within any of the time limits set forth in Section 17.34.110; the building o\cial shall order the entire building

vacated and remain vacated until such order has been complied with. If compliance with such order has not been

accomplished within ninety days after the date the building has been ordered vacated; or by such additional time

as may have been granted by the city council; the building o\cial may initiate proceedings in accordance with the

Uniform Code for the Abatement of Dangerous Buildings.

In addition; the following remedies are available to:

1. The city may seek injunctive relief on behalf of the public to enjoin a building owner’s violation of this

chapter.

2. A building owner violating this ordinance shall be guilty of a misdemeanor and; upon conviction thereof;

shall be punishable by a Zne of not more than Zve hundred dollars or by imprisonment in the Sonoma

County Jail for a term not exceeding six months; or by both such Zne and imprisonment. Such building owner

is guilty of a separate o]ense for each and every day during any portion of which such violation of this

ordinance is committed; continued or permitted by such building owner.

3. These remedies are not exclusive.

(Ord. 1882 NCS §1, 1992.)

A. General. Unreinforced masonry wall buildings subject to this chapter shall undergo structural alterations

necessary to comply with the minimum requirements set forth in this chapter.

As an alternate; said buildings may be demolished subject to the restrictions set forth in the policies and

ordinances of Petaluma.

Buildings which have undergone earthquake hazard reduction work which is deemed by the building o\cial to be

equivalent to the requirements set forth in this chapter need have no additional work performed.

B. Mandatory Requirements.

1. Compliance with standards. Unreinforced masonry buildings shall comply with provisions of this chapter.

Should an owner elect to strengthen a building beyond the mandatory requirements set forth herein; such

additional strengthening work shall comply with other recognized standards (Appendix Chapter 1 of the 1991

UCBC) as approved by the building o\cial.

2. Change in Use. After the e]ective date of this chapter the time limits set forth in Table No. 17.34.110 shall

not apply to any building which will undergo a change of use or occupancy which will result in the building

being classiZed as a Group A Occupancy having an occupant load of one hundred or more. Before such building may be used or occupied as a Group A Occupancy it shall be made to comply with provisions of this

chapter.

C. Responsibility of Owner. As speciZed in Section 17.34.050; the owner shall comply with the requirements set

forth in this subsection by submitting to the building o\cial one of the following:

1. A structural analysis by a civil or structural engineer or architect licensed by the state of California which

shall demonstrate that the building meets the minimum requirements of this chapter, or

2. A structural analysis and plans by a civil or structural engineer or architect licensed by the state of

California for proposed structural alterations necessary to make the building comply with the minimum

requirements of this chapter; or

3. Plans for the demolition of the building.

After plans are submitted and approved by the building o\cial; the owner shall obtain a building permit;

commence and complete the required construction or demolition within the time limits set forth in Table No.

17.34.110.

(Ord. 1882 NCS §1, 1992.)

A. Existing Materials. All existing materials utilized as part of the lateral force resisting system shall be in sound

condition or shall be removed and replaced with new materials.

B. Existing Unreinforced Masonry.

1. General. Unreinforced masonry parapets that exceed the maximum height in Section 17.34.100(C) shall

be tested as speciZed in this subsection. Masonry that does not meet or exceed the minimum standards

established by this chapter shall be removed and replaced by new materials or shall have its structural

functions replaced by new materials and anchored to supporting elements.

2. Lay-up of parapets. The facing and backing shall be bonded so that not less than four percent of the wall

surface of each face is composed of solid headers extending not less than four inches into the backing. The

distance between adjacent full-length headers shall not exceed twenty-four inches either vertically or

horizontally. In walls in which a single header does not extend through the wall; headers from opposite sides

shall overlap at least four inches; or headers from opposite sides shall be covered with another header

course overlapping the header below at least four inches. Wythes of walls not bonded as described above

shall be considered as veneer. The veneer wythe shall not be included in the e]ective thickness used in

calculating the height to thickness ratio of the wall unless it is bonded and anchored to the backing in a

manner acceptable to the building o\cial.

3. Mortar.

a. Tests. The quality of mortar in unreinforced masonry wall shall be determined by performing in-

place shear tests in accordance with UBC Standard 24-40. Alternate methods of testing may be approved

by the building o\cial.

b. Location of tests. Shear tests shall be taken at locations representative of the mortar conditions

throughout the entire building. The exact test location shall be determined at the building site by the

engineer or architect in responsible charge of the structural design work. An accurate record of such

tests and their location in the building shall be recorded and these results shall be submitted to the

building o\cial for approval as part of the structural analysis.

c. Number of tests. The minimum number of tests per wall or line of wall elements providing a common

line of resistance to lateral forces shall be as follows: Two tests per wall with a minimum total number of

eight tests or one test per one thousand Zve hundred square feet of wall area; whichever results in the

greater number of tests.

d. Minimum quality mortar.

(1) Mortar shear test values; vto; shall be obtained for each in-place shear test in accordance with

the following equation:

vto = vtest - PD+L/AW

WHERE:

Vto = Mortar shear test value; in psi.

vtest = Shear stress at incipient cracking
for each in-place test per UBC

Standard No. 24-7.

PD+L = Actual dead plus live load in place
at the time of testing, in pounds.

AW = Area of the wall supporting PD+L

at each in-place shear test.

(2) Individual unreinforced masonry walls with vto less than 30 psi shall be pointed prior to

retesting.

(3) The mortar shear strength; vto; is the value in psi that is exceeded by eighty percent of all of the
mortar shear test values, vto.

(4) Unreinforced masonry with mortar shear strength; vto; less than 30 psi shall be removed or

pointed and retested or treated as veneer.

e. Pointing. All deteriorated mortar joints in unreinforced masonry walls shall be pointed according to

UBC Standard No. 24-42. Nothing shall prevent pointing with mortar of all masonry wall joints before the

tests are made.

(Ord. 1882 NCS §1, 1992.)

A. Pointing. Special inspection shall be provided during preparation and mortar pointing.

B. Shear Tests. In-place shear tests shall comply with Section 17.34.070 B. and UBC Standard 24.41.

C. Existing Floor Level Wall Anchors. If existing rod anchors are to be utilized as all or part of the required wall

anchorage system at the [oor level; not less than Zve percent of such existing rod anchors shall be tested by an

approved testing laboratory. The minimum number of anchors tested shall be four per [oor; with two tests at

walls with joists parallel to the wall but not less than ten percent of the total number of existing tension anchors at

each level. The test apparatus shall be supported on the masonry wall at a minimum distance of the wall thickness

from the anchor tested. The rod anchor shall be given a preload of three hundred pounds prior to establishing a

datum for recording elongation. The tension test load reported shall be recorded at one-eighth inch relative

movement of the anchor and the adjacent masonry surface. Results of all tests shall be reported. The report shall

include the test results as related to the wall thickness and joint orientation. Ends of existing anchors shall be

secured into the wood framing by an approved method.

D. Testing of Bolts. One-fourth of new embedded bolts in unreinforced masonry walls shall be tested by a special

inspector using a torque calibrated wrench to the following minimum torques:

1/2" diameter bolts or dowels= 40 foot-lbs

5/8" diameter bolts or dowels = 50 foot-lbs

3/4" diameter bolts or dowels = 60 foot-lbs

No bolts exceeding three-quarter inches diameter shall be used. Nuts shall be installed over malleable iron or cut

plate washers when bearing on wood and heavy cut washers when bearing on steel.

(Ord. 1882 NCS §1, 1992.)

A. Tension Anchors. Allowable values for tension anchors are given in Table No. 17-A. A one-third increase is not

allowed for values listed in this table.

B. Other Materials. Allowable values not speciZed in this chapter shall be as speciZed elsewhere in this code.

(Ord. 1882 NCS §1, 1992.)

A. Lateral Force on Elements of Structures and Nonstructural Components. Parts or portions of structures;

nonstructural components and their anchorage to the main structural system shall be designed for lateral forces

in accordance with the following formula:

Fp = Cp Wp ...................... (100-1)

Wp shall be as deZned in Section 2312(c) of the UBC. The value of Cp need not exceed the values set forth in

Table No. 17-B.

B. Wall Anchorage.

1. Anchor locations. Unreinforced masonry walls shall be anchored at the roof and [oor levels in order to

resist the forces speciZed in this section.

2. Wall anchor requirements. Wall anchors shall be tension bolts through the wall having a maximum

spacing of six feet or six times the wall thickness; whichever is less. Alternate anchors shall be combination

tension and shear bolts complying with the requirements set forth in Table No. 17A. Tension bolts used to

resist required forces may be assumed to develop the allowable values listed in Table No. 17-A. If access to

the exterior face of a masonry wall is prevented by proximity of an existing building or when the appearance

of through the wall tension anchors will a]ect the architectural appearance of the building; embedded bolts

conforming to Table No. 17-A may be used. Wall anchors shall be secured to the rafters or joists to transfer

the required forces into roof or [oor sheathing.

3. Minimum wall anchorage force. Anchorage of masonry walls to each [oor or roof shall resist a minimum

force determined by Formula (100-1) or two hundred pounds per linear foot; whichever is greater; acting

normal to the wall at the level of the [oor or roof. Existing wall anchors installed under previous permits must

meet or must be upgraded to meet the requirements of this chapter.

4. Anchors at corners. At the roof and [oor levels, combination tension and shear anchors shall be provided

within two feet horizontally from the inside of the corners of the walls.

C. Parapets. Parapets and exterior wall appendages not capable of resisting the forces speciZed in this section

shall be removed; stabilized or braced to insure that the parapets and appendages remain in their original

position.

The maximum height of an unbraced unreinforced masonry parapet above the level of tension anchors shall not

exceed one and one-half times the thickness of the parapet wall. If the required parapet height exceeds this

maximum height; a bracing system designed for the force determined by formula (100-1) shall be installed to

support the parapet. Parapet corrective work shall be performed in conjunction with the installation of tension

roof anchors.

The minimum height of a parapet above the wall anchor shall be twelve inches.

Exception: If a reinforced concrete beam is provided at the top of the wall; the minimum height above the wall

anchor may be six inches.

D. Veneer.

1. Unreinforced concrete beam is provided at the top of the wall; the minimum height above the wall

anchor may be six inches.

2. Veneer shall be anchored with approved anchor ties; conforming to the required design capacity

speciZed in this code and placed at a maximum spacing of 24 inches with a maximum supported area of two

square feet.

Exception: Existing veneer anchor ties may be acceptable provided the ties are in good condition and conform

to the following minimum size; maximum spacing and material requirements.

Existing veneer anchor ties shall be corrugated galvanized iron strips not less than one inch in width; eight

inches in length and one-sixteenth of an inch in thickness or equal and shall be located in every alternate

course in the height of the wall at a spacing not to exceed eighteen inches on centers horizontally. As an

alternate; such ties may be laid in every fourth course vertically at a spacing not to exceed nine inches on

centers horizontally.

3. The location and condition of existing veneer ties shall be veriZed as follows:

a. An approved testing laboratory shall verify the location and spacing of the ties and shall submit a

report to the building o\cial for approval as a part of the structural analysis.

b. The veneer in a selected area shall be removed to expose a representative sample of ties (not less

than four) for inspection by the building o\cial.

E. Mortar Joints. All deteriorated mortar joints in unreinforced masonry walls shall be pointed with Type S or N

mortar. Masonry cements shall not be used. Prior to any pointing; the wall surface must be raked and cleaned to

remove loose and deteriorated mortar. All preparation and pointing shall be done under continuous inspection by

a special inspection certiZed to inspect masonry or concrete. At the conclusion of the project; the special inspector

shall submit a written report to the building o\cial setting forth the portion of the work inspected.

(Ord. 1882 NCS §1, 1992.)

Building Groups

Building Owner Action I II III IV

Submit Plans for Review 7 yrs 12 yrs 17 yrs 22 yrs

Stabilize Parapet 10 yrs 12 yrs 12 yrs 12 yrs

Wall Anchors (roof and [oor 10 yrs 15 yrs 20 yrs 25 yrs

system)

Shear Anchors (corners) 10 yrs 15 yrs 20 yrs 25 yrs

Start construction within 180 days after building permit is issued.

Complete Construction within 10 yrs 15 yrs 20 yrs 25 yrs

Building Groupings are deZned in Petaluma Resolution No. 92-48 NCS "Establishing A List Of Unreinforced

Masonry Buildings". (Ord. 1882 NCS §1, 1992.)

TABLE NO. 17-A

ALLOWABLE VALUES FOR TENSION ANCHORS

Type of Installation 1 Allowable Values

Existing Tension Anchors for Floors: Allowable shall be 40% of the average of the tests

To be tested per Section 17.34.080(c) for anchors having same wall thickness and joist orientation.

Tension Bolts: 1800 lbs. per bolt

Bolts extending entirely through unreinforced 900 lbs. for 2 wythe walls

masonry walls secured with bearing plates on far

side of a 3 wythe minimum wall with a bearing plate

2 3

having an area of at least 30 square inches.

Combination Tension and Shear Bolts: Same as for tension bolts

Combination tension and shear bolts are tension

bolts centered in a 2-1/2 inch diameter by 8 inch

minimum depth hole with dry-pack or nonshrink

grout around the circumference of bolt.

Embedded Bolts: Same as for tension bolts

Bolts extending to the exterior wall with a 2-1/2

inch round plate under the head and drilled at an angle of 22-1/2 degrees to the horizontal. Bolts

shall be centered in 2-1/2 inch diameter holes with

dry-pack or non-shrink grout around circumference

of bolts. Bolts shall be tested per Section

17.34.080(d). (2) (3)

1 A 1/3 increase in allowable stresses is not allowed.

2 Bolts to be 1/2-inch minimum in diameter.

3 Drilling for bolts and dowels shall be done with an electric rotary drill. Impact tools shall not be used for

drilling holes or tightening anchors and shear bolt nuts.

TABLE NO. 17-B

HORIZONTAL FORCE FACTOR "Cp" FOR PARTS OR PORTIONS OF BUILDINGS OR OTHER STRUCTURES

Part or Portion of Buildings Direction of Force Value of Cp

Exterior bearing and nonbearing walls; Normal-to-[at surface 0.30

interior bearing walls and partitions;

interior non-bearing walls and partitions

over 10 feet in height.

Cantilever parapet and other cantilever Normal-to-[at surface 0.80

walls, except retaining walls.

Exterior and interior ornamentations and Any direction 1.00

appendages.

Prefabricated structural elements, other Any horizontal direction 0.30

than walls, with force applied at center of

gravity of assembly.

Connections for exterior panels or Any direction 2.00

elements.

Braced Parapets Normal-to-[at surface 0.30

TABLE NO. 17-C

ALLOWABLE VALUE OF HEIGHT-THICKNESS RATIO OF UNREINFORCED MASONRY WALLS WITH MINIMUM QUALITY MORTAR1

Buildings with Crosswalls As All Other Buildings

DeZned by Section 17.34.040

Walls of one-story buildings 16 13

First-story walls of two-story building 16 15

Walls in top story of two-story 14 9

buildings

1 Minimum quality mortar shall be determined by laboratory testing in accordance with Section 17.34.070.

UNIFORM BUILDING CODE STANDARD NO. 24-40 IN-PLACE MASONRY SHEAR TESTS

The bed joints of the outer wythe of the masonry shall be tested in shear by laterally displacing a single brick

relative to the adjacent bricks in the same wythe. The head joint opposite the loaded end of the test brick shall be

carefully excavated and cleared. The brick adjacent to the loaded end of the test brick shall be carefully removed

by sawing or drilling and excavating to provide space for a hydraulic ram and steel loading blocks. Steel blocks, the

size of the end of the brick, shall be used on each end of the ram to distribute the load to the brick. The blocks

shall not contact the mortar joints. The load shall be applied horizontally, in the plane of the wythe, until either a

crack can be seen or slip occurs. The strength of the mortar shall be calculated by dividing the load at the Zrst

crack or movement of the test brick by the nominal gross area of the sum of the two bed joints.

UNIFORM BUILDING CODE STANDARD NO. 24-42 POINTING OF UNREINFORCED MASONRY WALLS

POINTING

The old mortar should be cut out, by means of a toothing chisel or a special painter’s grinder, to a

uniform depth of 3/4", or until sound mortar is reached. Care must be taken not to damage the brick

edges. All dust and debris must be removed from the joint by brushing, blowing air or rinsing with water.

Mortar mix shall be Type "S" or "N" proportions as called for in the construction speciZcation, The tuck-

pointing mortar should be pre-hydrated to reduce excessive shrinkage. The proper pre-hydration

process is as follows:

All dry ingredients should be thoroughly mixed. Only enough clean water should be added to the dry mix to

produce a damp, workable consistency which will retain its shape when formed into a ball. The mortar should

stand in this dampened condition for one to one and one-half hours.

The joints to be tuck-pointed should be dampened, but to ensure a good bond, the brickwork must absorb all

surface water. Add water to the pre-hydrated mortar to bring it to a workable consistency which is somewhat drier

than conventional mortar. The mortar should be packed tightly into the joints in thin layers not to exceed 1/4 inch.

Each layer should become "thumbprint hard" before applying the next layer. The joints should be tooled to match

the original proZle after the last layer of mortar is "thumbprint hard".

RELAYING OF BRICK

Replacement bricks must match the originals with respect to size, color, and texture where exposed. A

tuck-pointing tooling chisel should be used to cut out of the mortar which surrounds the a]ected units.

Power driven impact tools are not allowed. Once the units are removed, all of the old mortar shall be

carefully chiseled out and all dust and debris shall be swept out with a brush.

If used brick is to be relayed, it shall be cleaned of all old mortar. The brick surfaces in the wall shall be

dampened before new units are placed, but the masonry should absorb all surface moisture to ensure a

good bond. The appropriate surfaces of the surrounding brickwork and the replacement brick should be

buttered with mortar. The replacement brick should be centered in the opening and pressed into

position. The excess mortar should be removed with a trowel. Pointing around the replacement brick will

help to ensure full head and bed joints. When the mortar becomes "thumbprint hard", the joints shall be

tooled to match the original proZle.

(Ord. 1882 NCS §1, 1992.)

In addition to the penalties provided in this chapter, any condition caused or permitted to exist in violation of any

of the provisions of this code shall be deemed a public nuisance and may be abated by the city as such in any

manner authorized by law. (Ord. 1882 NCS §1, 1992.)

The interpretation of the building o\cial shall prevail on matters relating to the implementation of this chapter.

(Ord. 1882 NCS §1, 1992.)

This chapter shall become e]ective on the thirty-Zrst day after its passage. (Ord. 1882 NCS §1, 1992.)