Alameda Municipal Code § 13-63 Requirements

a. General. Unreinforced masonry bearing wall buildings subject to this article shall undergo structural alterations necessary to comply with the minimum requirements set forth in this article within the time limits set forth in Table 13-63.5A. As an alternate, said buildings may be demolished if all necessary permits for demolition have been obtained, including a Certificate of Approval from the Historical Advisory Board, if applicable.

EXCEPTION: Buildings which have undergone earthquake hazard reduction work which is deemed by the building official to be equivalent to the requirements set forth in this article need have no additional work performed.

b. Change In Use. After the effective date of this article the time limits set forth in Table No. 13-63.5A shall not apply to any building which will undergo a change of use or occupancy which will result in the building being classified as a Group A Occupancy having an occupant load of one hundred (100) 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 article.

c. Wall Bracing.

1. General. Where the wall height to thickness ratio exceeds those allowed in Table 13-63.5C the wall must be laterally supported by vertical bracing members or by reducing the wall height by bracing.

2. Vertical Bracing Members. Vertical bracing members shall be attached to floor and roof construction for their design loads independent of required wall anchors. Horizontal spacing of vertical bracing members shall not exceed one-half (½) the unsupported height of the wall nor ten (10′) feet. Deflection of such bracing members at design loads, shall not exceed one-tenth of the wall thickness.

3. Wall Bracing. The wall height may be reduced by bracing elements connected to a floor or roof. Horizontal spacing of the bracing elements and wall anchors shall be as required by design and shall not exceed six (6′) feet on center nor six (6) times the wall thickness, whichever is less. Bracing elements shall be detailed to minimize the horizontal displacement of the wall by the vertical displacement of the floor or roof.

(Ord. No. 2573 N.S. § 1)

a. Wall Anchorage.

1. General. Wall anchors shall be installed in unreinforced masonry walls at each roof and floor level as required by this article and shall be designed to resist the lateral forces specified by this article. Existing rod anchors, tension anchors, combination tension and shear anchors, or embedment bolts, which comply with the material requirements of this article may be used as wall anchors.

Wall anchors shall be adequately secured to rafters or joists in order to transfer the required forces into the roof or floor sheathing.

2. Wall Anchor Spacing. The spacing for wall anchors shall not exceed six (6) times the wall thickness and in no case shall exceed six (6′) feet.

Wall anchors may not be installed closer than twelve (12″) inches to the top of any unreinforced masonry wall. If a reinforced concrete beam is provided at the top of the wall, anchors may be installed to within six (6″) inches of the top of the wall.

3. Anchors at Corners. At the roof and floor levels, combination tension and shear anchors shall be provided within two (2′) feet horizontally from the inside of the corners of the walls.

4. Minimum Wall Anchorage Force. Anchorage of masonry walls to each floor or roof shall resist a minimum force determined by Formula (10-1) or two hundred (200) pounds per linear foot, whichever is greater, acting normal to the wall at the level of the floor or roof.

b. Parapet Bracing. Parapets and exterior wall appendages not capable of resisting the forces specified 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 wall anchors shall not exceed one and one-half (1 ½) times the thickness of the parapet wall. If the parapet height exceeds this maximum height, a bracing system designed for the force determined by Formula (10-1) shall be installed to support the parapet. Parapet corrective work shall be performed in conjunction with the installation of tension roof anchors.

c. Veneer.

1. Unreinforced masonry walls which carry no design loads other than their own weight may be considered as veneer if they are adequately anchored to new supporting elements.

2. Veneer shall be anchored with approved anchor ties, conforming to the required design capacity specified in this Code and placed at a maximum spacing of twenty-four (24″) inches with a maximum supported area of two (2) 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 (1″x 8″ x 1/16 ″) or equal and shall be located in every alternate course in the height of the wall at a spacing not to exceed eighteen (18″) inches on centers horizontally. As an alternate, such ties may be laid in every fourth course vertically at a spacing not to exceed nine (9″) inches on centers horizontally.

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

(a) An approved testing laboratory shall verify the location and spacing of the ties and shall submit a report to the Building Official 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 (4)) for inspection by the Building Official.

(Ord. No. 2573 N.S. § 1)

a. General. The owner of each building within the scope of this Chapter shall cause a structural analysis of the building to be made by a civil or structural engineer or architect licensed by the State of California. If the building does not meet the minimum earthquake standards specified in this Chapter, the owner shall either cause it to be structurally altered to conform to such standards; or shall initiate proceedings for demolition of the building.

b. Submittal of Analyses. Within seven hundred thirty (730) days after the service of the order, specified in this article the owner shall comply with the requirements set forth in this subsection by submitting to the Building Official either of the following:

1. A structural analysis and supporting test data which shall demonstrate that the building meets the minimum requirements of this article;

2. A structural analysis, supporting test data and plans for proposed structural alterations necessary to make the building comply with the minimum requirements of this article; or

3. An application for the demolition of the building.

c. Certification of Analysis. The Building Official shall review the structural analysis submitted and determine whether all requirements of this article are satisfied. Once it is determined, the analysis is acceptable, a Certification stating that said analysis conforms with the requirements of this article shall be prepared by the Building Official.

A copy of this Certification along with copies of the Structural Analysis and plans showing proposed structural alterations will be required in order to obtain a building permit for this work.

d. Detailed Design Requirements.

1. 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 = CpWp .....(10-1)

Where:

Wp = weight of an element or component

Cp = as set forth in Table No. 1446 B

2. Height to Thickness Limitations. Unreinforced masonry wall height to thickness ratios shall not exceed the ratios set forth in Table No. 13-63.5C. If a wall height to thickness ratio exceeds the specified limits, the wall shall be laterally supported by bracing members designed in accordance with this article.

(Ord. No. 2573 N.S. § 1)

a. Existing Materials. All existing materials utilized as part of the load carrying system of the building shall be in sound condition or shall be removed and replaced with new materials.

b. Existing Unreinforced Masonry Bearing Wall.

1. General. Unreinforced masonry walls shall be tested as specified in this subsection. Masonry that does not meet or exceed the minimum standards established by this article 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 Walls. The facing and backing shall be bonded so that not less than four (4%) percent of the wall surface of each face is composed of solid headers extending not less than four (4″) inches into the backing. The distance between adjacent full-length headers shall not exceed twenty-four (24″) inches either vertically or horizontal. In walls in which a single header does not extend through the wall, headers from opposite sides shall overlap at least four (4″) inches, or headers from opposite sides shall be covered with another header course overlapping the header below at least four (4″) inches. Wythes of walls not bonded as described above shall be considered as veneer. The veneer wythe shall not be included in the effective 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 Official.

3. Mortar Joints. The quality of mortar in unreinforced masonry walls shall be determined by performing in-place shear tests in accordance with this section. Alternate methods of testing may be approved by the Building Official.

All deteriorated mortar shall be removed and the joints shall be pointed with new mortar as required by this section.

(a) Mortar Test 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 Official for approval as part of the structural analysis.

(b) 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 (2) tests per wall with a minimum total number of eight (8) tests or one (1) test per one thousand five hundred (1,500) square feet of wall area, whichever results in the greater number of tests.

(c) Test Procedure. 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 first crack or movement of the test brick by the nominal gross area of the sum of the two (2) bed joints.

(d) Minimum Quality Standards.

(1) Mortar shear test values, V to , shall be obtained for each in place shear test in accordance with the following equation:

V to = V test — P D+L /A w .....(10-2)

Where:

V to = Mortar shear test value, in psi.

V test = Shear stress at incipient cracking for each in-place test.

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

A w = Area of the wall supporting P D+L at each in-place shear test.

(2) The mortar shear strength, V, is the value in psi that is exceeded by eighty (80%) percent of all the mortar shear test values, V to.

(3) Unreinforced masonry with mortar shear strength, V, less than thirty (30) psi shall be removed or pointed and retested or the wall shall be treated as veneer.

(e) Pointing. All preparation and pointing shall be done under continuous inspection by a Special Inspector certified to inspect masonry or concrete. At the conclusion of the project, the Special Inspector shall submit a written report to the Building Official.

The old mortar should be cut out, by means of a toothing chisel or a special painter's grinder, to a uniform depth of three-fourth (¾″) inches, 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 specification. The tuck-pointing mortar should be prehydrated to reduce excessive shrinkage. The proper prehydration 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 (1) to one and one-half (1 ½) 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 prehydrated 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 one-fourth (¼″) inch. Each layer should become "thumbprint hard" before applying the next layer. The joints should be tooled to match the original profile after the last layer of mortar is "thumbprint hard".

c. Existing Rod Anchors.

1. General. If existing rod anchors are to be utilized as all or part of the required wall anchorage system, they shall be required to be tested by an approved testing laboratory.

2. Testing of Existing Rod Anchors.

(a) Number of Tests. At least ten (10%) percent of the total number of existing rod anchors shall be tested.

At least four (4) anchors shall be tested at each floor level and roof level.

At each level, at least two (2) tests shall be performed at walls with joints framing into wall and at least two (2) tests shall be performed at walls with joints framing parallel to the wall.

3. Test Procedure. 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 (300) pounds prior to establishing a datum for recording elongation. The tension test load reported shall be recorded at one-eighth (⅛″) 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 joist orientation. Ends of existing anchors shall be secured into the wood framing by an approved method.

4. Allowable Design Values. The allowable design value for existing rod anchors shall be equal to forty (40%) percent of the average test value for anchors having the same wall thickness and joist orientation.

No stress increase in allowable design values is allowed when considering wind or earthquake forces.

d. Embedment Bolts.

1. General. Impact tools shall not be used for drilling holes or tightening anchor bolts and nuts. Any drilling for anchors shall be done with a rotary drill.

Embedment bolts shall be installed at an angle of twenty-two and one-half (22 1/2°) degrees to the horizontal. Bolts shall be centered in two and one-half (2 1/2″) inches diameter holes with dry-pack or non-shrink grout around circumference of bolts.

2. Testing. One-fourth (¼) of new embedment bolts in unreinforced masonry walls shall be tested using a torque calibrated wrench to the following minimum torques:

½″ diameter bolts or dowels = 40 foot-lbs.

⅝″ diameter bolts or dowels = 50 foot-lbs.

¾″ diameter bolts or dowels = 60 foot-lbs.

3. No bolts exceeding three-fourths (¾″) 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. Washers shall be at least two and one-half (2 ½″) inches in diameter.

e. Tension Anchors.

1. General. No tension anchor less than one-half (½″) inch in diameter shall be allowed.

Anchors shall extend entirely through masonry walls and shall be secured with a bearing plate on far side of wall. Each bearing plate shall have a bearing area of at least thirty (30) square inches.

Impact tools shall not be used for drilling holes or tightening anchor bolts and nuts. Any drilling for anchors shall be done with a rotary drill.

2. Allowable Design Value. The allowable design value for tension anchors is as follows:

2 wythe wall = 900 lbs. per bolt

3 wythe wall = 1800 lbs. per bolt

No stress increase in allowable design value is allowed when considering wind or earthquake forces.

f. Combination Tension and Shear Anchors.

1. General. Combination tension and shear anchors are tension anchors centered in a two and one-half inch by eight inch (2 ½″ x 8″) minimum depth hole with dry-pack or non-shrink grout around the circumference of bolt.

2. Allowable Design Values. The allowable design values for combination tension and shear anchors are the same as for tension anchors.

(Ord. 2573 N.S. § 1)

For Time Limits and Technical Specifications see Table Nos. 13-63.5A, 13-63.5B, and 13-63.5C.

Table No. 13-63.5A Time Limits for Compliance

1 Measured from the date of the order.

2 Measured from the date of building permit issuance.

The Building Official may allow the time limit for obtaining a building permit to be extended a maximum of two (2) additional years on a case by case basis, considering various factors of economic impact on the property owners and the seriousness of the existing structural hazard as shown by the required engineering analysis.

Table No. 13-63.5B Horizontal Force Factor "Cp" for Parts or Portions of Buildings or Other Structures

Table No. 13-63.5C Allowable Value of Height-Thickness Ratio of Unreinforced Masonry Walls With Minimum Quality Mortar 1

1 Minimum quality mortar shall be determined by laboratory testing in accordance with this article.

(Ord. No. 2573 N.S. § 1)