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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 (10-1)

Wp shall be as defined in Section 2332. The value of Cp need not exceed the values set forth in Table No. 1-C.*

B. Height to Thickness Limitations. Unreinforced masonry wall height to thickness ratios shall not exceed the ratios set forth in Table 1-D.* If a wall height to thickness ratio exceeds the specified limits, the wall shall be laterally supported by bracing members complying with subsection (C)(1) or (C)(2). Bracing systems shall be designed in accordance with subsection A. The wall thickness may include the thickness of plaster, stucco or concrete that is determined by the architect or engineer to be bonded to the full height of the wall between wall anchors.

C. Bracing Methods.

1. 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 the unsupported height of the wall nor ten feet. Deflection of such bracing members at design loads, shall not exceed one-tenth of the wall thickness.

2. Wall Bracing. The wall height may be measured to bracing elements other than a floor or roof. Horizontal spacing of the bracing elements and wall anchors shall not exceed six feet on center nor six 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.

D. Wall Anchorage.

1. Anchor Locations. Unreinforced masonry walls shall be anchored at the roof and floor levels in order to resist the forces specified in this section.

2. Tension Anchor Requirements. Tension anchors shall have a maximum spacing of six feet or six times the wall thickness, whichever is less, and shall comply with the requirements set forth in Table No. 1-B.* Tension anchors used to resist required forces may be assumed to develop the allowable values listed in Table No. 1-B.* Tension anchors shall be secured to the rafters or joists to transfer the required forces into the roof or floor sheathing.

3. New Tension Anchors. New tension anchors installed to meet the requirements of this section shall be combination tension and shear bolts, and shall be secured to the roof or floor framing to develop tension and shear forces into the diaphragm.

4. Minimum Wall Anchorage Forces. New or existing tension anchors shall anchor masonry walls to each floor or roof with a capacity to resist a minimum tension force determined by Formula (10-1) or two hundred pounds per linear foot whichever is greater, acting normal to the wall at the level of the floor or roof. In addition, new combination tension and shear bolts shall be connected to the framing to resist a shear force of two hundred pounds per foot acting parallel to the wall at the level of the floor or roof.

Exception: where the roof or floor sheathing consist only of one inch nominal thickness single board sheathing, new combination tension and shear bolts may be connected to the framing to resist a shear force of one hundred pounds per foot acting parallel to the wall.

The city building official may approve an analysis by the architect or engineer that demonstrates that the required shear capacity is less than required by this section.

5. Anchors at Corners. New combination tension and shear bolts at the roof and floor levels, if required by this section, shall be provided within two feet horizontally from the inside of the corners of the walls.

E. Parapets. Parapets and exterior wall appendages not capable of resisting the forces specified in this section shall be removed, stabilized or braced to ensure 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 (10-1) 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.

F. 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 for pointing shall be inspected by the architect or engineer or their representative.

G. Masonry Veneer.

1. Veneer shall be anchored to the structure of the building with approved anchor ties conforming to the required design capacity specified in the building code and placed at a maximum spacing of twenty-four inches with a maximum supported area of two square feet.

a. Exception:

1. Existing masonry veneer anchor ties may be acceptable provided the ties are in sound condition and conform to the following minimum size, maximum spacing and material requirements:

Existing masonry veneer anchor ties shall be corrugated galvanized iron strips not less than one inch in width, eight inches in length and one-sixteenth inch in thickness and shall be located and laid in every alternate course in the vertical height of the wall at a spacing not to exceed seventeen inches on center horizontally. As an alternate, such ties may be laid in every fourth course vertically at a spacing not to exceed nine inches on center horizontally.

2. Masonry veneer, no portion of which six feet is above grade need not be anchored.

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

a. The architect or engineer shall determine the location and spacing of the ties.

b. The veneer shall be removed from not less than four locations designated by the architect or engineer for the architect or engineer’s evaluation.

c. The architect or engineer shall report to the city building official the veneer anchor tie locations and spacings, their evaluation of the condition and effectiveness of the veneer anchor ties, and their recommendations whether or not the existing veneer anchor ties need to be supplemented with new veneer anchor ties.

3. Unreinforced masonry walls which carry no loads other than their own weight may be considered as veneer if they are adequately anchored to new supporting elements. (Ord. 3552 § 1, 1993)

* Editor’s Note: The tables referred to herein may be found in Section 15.40.080.