15.30.200 - Structural weaknesses.

A.

Structural weaknesses shall include the following:

1.

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

2.

Perimeter foundation constructed of wood posts supported by isolated footings.

3.

Perimeter foundation that is not continuous.

Exception: existing porches, storage rooms, and similar spaces that do not contain fuel-burning appliances.

4.

Perimeter foundation constructed of unreinforced concrete or assembled masonry.

5.

Sill plates not connected to the foundation in accordance with this chapter.

6.

Cripple walls not braced in accordance with this chapter.

B.

A separate permit for strengthening structural weaknesses set forth in Sections 15.30.200(A)(1) through (A)(4) (inclusive) shall be required as a condition of issuance of a permit for strengthening structural weaknesses set forth in Sections 15.30.200(A) (5) and (A)(6).

(Ord. 12812 § 1 (part), 2007)

15.30.210 - Seismic strengthening—General.

A.

Scope.

1.

Residential buildings may be seismically strengthened by newly installed construction and alteration of existing construction. Alternate prescriptive and non-prescriptive designs shall be equivalent to or exceed the performance levels of this chapter and be approved by the Building Official.

2.

Alternative prescriptive designs with provisions for voluntary seismic retrofitting of wood-framed cripple walls have been developed by a committee representing the East Bay, Peninsula, and Monterey Bay Chapters of the International Code Council (ICC) with additional committee representation by other governmental organizations. Alternative prescriptive designs include those that were approved by the three chapters of ICC, the Association of Bay Area Governments (ABAG), the California Building Officials (CALBO), the Structural Engineers Association of Northern California, and the Earthquake Engineering Research Institute of Northern California in October 2004, with later amendments, and are considered equivalent to this chapter.

B.

Wood Materials.

1.

Wood materials that are part of the seismic strengthening system shall be free of defects which substantially reduce the structural capacity of the member. Wood material that is infested with or damaged by fungus or insects shall be replaced with new material that provides an equivalent original dimension and structural capacity of the existing member. Newly installed material in contact with concrete or masonry shall be approved preservative treated wood or foundation-grade redwood in accordance with the Oakland Building Construction Code.

2.

Fasteners, anchors, washers, plates, connectors, and similar metal attachments shall be corrosion resistant metal and shall not be detrimentally affected by wood preservative coatings or impregnations in accordance with the Oakland Building Construction Code. Installed fasteners shall not split wood members.

(Ord. 12812 § 1 (part), 2007)

15.30.220 - Seismic strengthening—Quality control.

A.

Permits, Inspections, and Fees.

Applications, fees, permits, and inspection approvals shall be required for seismic strengthening and shall be in accordance with the Oakland Building Construction Code and the Master Fee Schedule.

B.

Special Inspection.

Special inspection for a prescriptive design shall not be required, unless otherwise determined to be necessary by the Building Official. Special inspection for a non-prescriptive design shall be in accordance with the Oakland Building Construction Code and the requirements of the registered design professional in responsible charge of the work.

C.

Structural Observation.

Structural observation shall not be required for a prescriptive design. Structural observation for a non-prescriptive design shall be in accordance with the Oakland Building Construction Code.

(Ord. 12812 § 1 (part), 2007)

15.30.230 - Prescriptive design—Framing.

A.

Floor Joists—End Bearing.

End bearing of floor joists shall be restrained by a continuous rim joist (two-inch nominal thickness), or tightly-fitting, full-depth, lumber blocking (two-inch nominal thickness) or exterior grade structural wood panel sheathing (one-inch minimum thickness). Bottom edge fasteners for rim joists and perimeter edge fasteners for blocking and sheathing shall be either 8d common angled ("toe") nails spaced apart four inches or equivalent supplemental connectors. Foundation blocking or sheathing shall be installed between alternate floor joists. Cripple wall blocking or sheathing shall be installed between each floor joist, except for obstructions (piping, underfloor ventilation and access, conduits, ducts, etc.). The perimeter of supplemental blocking shall be fastened to adjoining members.

B.

Floor Joists—Parallel Span.

Floor joists that are parallel to a perimeter foundation shall have a parallel rim joist fully supported by the foundation sill plate or cripple wall top plate. Bottom edge fasteners for rim joists shall be either 8d angled ("toe") nails spaced apart four inches or equivalent supplemental connectors.

(Ord. 12812 § 1 (part), 2007)

15.30.240 - Prescriptive design—Foundations.

A.

Construction.

Foundations shall be constructed in accordance with the Oakland Building Construction Code. Soil investigations or geotechnical studies shall not be required unless the building has structural distress from soil movement.

B.

Analysis.

1.

Foundations with structural weaknesses set forth in Sections 15.30.200(A)(1) and 15.30.200(A) (2) shall be replaced with a continuous perimeter foundation.

2.

Foundations with structural weaknesses set forth in Sections 15.30.200(A)(3) and 15.30.200(A) (4) shall be either

a.

replaced with a continuous perimeter foundation, or

b.

analyzed for structural adequacy by a registered design professional for force levels determined by the formula:

V = 0.1375 W,

where V= base shear and W= tributary weight, and approved by the Building Official. Test reports to determine existing foundation material strengths, quality, and condition shall be submitted for review.

15.30.250 - Prescriptive design—Sill plates.

A.

Connection.

Sill plates shall be connected to foundations in accordance with the Oakland Building Construction Code, or as otherwise approved by the Building Official. Anchors within braced panels of cripple walls shall be spaced apart not more than thirty-two (32) inches (two-anchors minimum per continuous sill plate). Sill plates shall be drilled for fasteners used with anchor side plates before installation.

B.

Anchors.

Adhesive and expansion anchors shall be installed with a metal plate washer between the nut and the sill plate or supplemental block. Washers shall be 2-inch × 2-inch × 3/16-inch. Expansion anchors shall not be used in assembled masonry or unreinforced concrete foundations. Adhesive anchors shall be used where expansion anchors cause surface cracking of the foundation or cannot be tightened as required by the manufacturer's recommendations. Supplemental blocks for through-anchor installation, when installed, shall be two-inch nominal thickness lumber and fastened to sill plates with not less than four 10d common nails.

(Ord. 12812 § 1 (part), 2007)

15.30.260 - Prescriptive design—Supplemental connector.

Supplemental connectors that are substituted for a group of individual fasteners shall provide a structural capacity equivalent to or exceeding the combined capacity of the fasteners.

(Ord. 12812 § 1 (part), 2007)

15.30.270 - Prescriptive design—Cripple walls.

A.

Bracing.

1.

Cripple walls shall be braced with exterior grade structural wood panel sheathing not less than 15/32-inch thickness. Plywood sheathing shall be not less than five plies.

2.

Sheathing shall be fastened to cripple wall studs, top plate, and sill plate. Fasteners shall be 8d common nails spaced apart not more than four inches at sheathing edges and not more than twelve inches at intermediate supports and shall be installed not less than 3/8-inch from sheathing edges.

3.

Sheathing horizontal joints shall be continuously supported between studs by full-width and full-depth, two-inch nominal thickness lumber blocking. Sheathing vertical joints shall continuously supported by stud framing.

4.

Supplemental studs ("sistered") shall be full-depth and full-height and fastened to existing studs with 16d common nails spaced apart not more than eight inches in a vertically staggered pattern (three nails minimum).

5.

Top plates shall be lapped and fastened in accordance with the Oakland Building Construction Code or spliced with an equivalent supplemental connector installed on the sheathing face.

6.

Supplemental blocking for sheathing bottom edge-nailing shall be full-width and full-depth between studs, twice nominal thickness lumber, and fastened to sill plates with 10d common nails spaced apart not more than six inches in an alternating pattern (four nails minimum).

7.

Cutouts in sheathing and notches in top plates, sill plates, and existing studs for obstructions (piping, underfloor ventilation and access, ducts, etc.) shall be reinforced with supplemental connectors and approved by the Building Official.

B.

Bracing Distribution.

1.

Braced End-Panels.

Cripple walls shall be braced at each end of the wall line, or elsewhere along the wall line when approved by the Building Official. The horizontal length of a braced end-panel shall be not less than eight feet, measured at any point.

2.

Braced Intermediate-Panels.

Cripple walls also may be braced with intermediate-panels spaced apart evenly between braced end-panels. The horizontal length of an intermediate-panel shall be not less than four feet, measured at any point, and not less than twice the vertical height of the braced panel for buildings with tile roofing or with portland cement plaster or brick or stone veneer exterior building surfaces.

3.

Unbraced Sections.

Cripple walls may have unbraced sections between braced panels. The horizontal length of an unbraced section of wall line shall be

a.

not more than sixteen (16) feet, measured at any point, for a one-story building with wood exterior building surfaces, and

b.

not more than twelve (12) feet, measured at any point, for a one-story building with tile roofing or with portland cement plaster or brick or stone veneer exterior building surfaces, and

c.

not more than eight feet, measured at any point, for two story buildings with tile roofing or with portland cement plaster or brick or stone veneer exterior building surfaces.

C.

Ventilation.

1.

Underfloor ventilation shall not be reduced.

2.

Sheathed stud cavities shall be individually ventilated with two-inch diameter holes drilled through the bracing sheathing, and centered within the stud cavity, and located not less than one inch below the top plate, and one inch above the sill plate, and one inch above and below horizontal blocking. Cavities with stud height less than eighteen (18) inches shall have a single ventilation hole.

(Ord. 12812 § 1 (part), 2007)

15.30.280 - Prescriptive design—Deviations.

Substantive deviations from the prescriptive design requirements in this chapter shall be analyzed by a registered design professional and approved by the Building Official. Calculations, plans, and specifications shall be in accordance with the Oakland Building Construction Code.

(Ord. 12812 § 1 (part), 2007)