A new Section 1803.8 is added to read as follows:
1803.8 Additional Tests and Reports.
The Building Official may require further tests where the type and class of soil is in question. The Building Official may require an engineering geotechnical or geologic report, submitted by a State certified engineering geologist, on all sites as a condition precedent to the permit issuance to construct a building or structure.
Section 1804.1 “Excavation near foundations” is hereby amended to read as follows:
1804.1 Excavation Near Foundations
Excavation for any purpose shall not reduce vertical or lateral support for any foundation or adjacent foundation without first underpinning or protecting the foundation against detrimental lateral or vertical movement, or both, in accordance with Section 1803.5.7.
Refer to Title 8 Section 8-1.24 and Title 7, Chapter 3 of the Thousand Oaks Municipal Code for grading regulations administered by the Public Works Department, and for requirements governing excavation, grading, and earthwork construction, including fills and embankments.
Section 1807.1.4 “Permanent Wood Foundation Systems” is amended by to read as follows:
1807.1.4 Permanent Wood Foundation Systems.
[OSHPD 1R, 2 & 5] Not permitted by OSHPD. Permanent wood foundation systems shall not be used for structures assigned to Seismic Design Category D, E or F. Permanent wood foundation systems shall be designed and installed in accordance with AWC PWF. Lumber and plywood shall be preservative treated in accordance with AWPA U1 (Commodity Specification A, Special Requirement 4.2) and shall be identified in accordance with Section 2303.1.9.1.
Section 1808.6 “Design for Expansive Soil” is amended, with adoption of subsections 1808.6.1 thru 1808.6.4 as published, to read as follows:
1808.6 Design for Expansive Soils.
Foundations for buildings and structures founded on expansive soils shall be designed in accordance with Section 1808.6.1 or 1808.6.2.
Exceptions: Foundation design need not comply with Section 1808.6.1 or 1808.6.2 where one of the following conditions is satisfied:
1. The soil is removed in accordance with Section 1808.6.3.
2. The building official approves stabilization of the soil in accordance with Section 1808.6.4.
3. Foundations for buildings and structures with shallow foundations may be designed in accordance with Section 1809 as amended herein.
Section 1808.7.1 “Foundations on or adjacent to slopes” is amended to read as follows.
1808.7.1 Building Clearance From Ascending Slopes
In general, buildings below slopes shall be set a sufficient distance from the slope to provide protection from slope drainage, erosion and shallow failures. Except as provided in Section 1808.7.5 and Figure 1808.7.1, the following criteria will be assumed to provide this protection. Where the existing slope is steeper than one unit vertical in one unit horizontal (100-percent slope), the toe of the slope shall be assumed to be at the intersection of a horizontal plane drawn from the top of the foundation and a plane drawn tangent to the slope at an angle of 45 degrees (0.79 rad) to the horizontal. Where a retaining wall is constructed at the toe of the slope, the height of the slope shall be measured from the top of the wall to the top of the slope.
For SI: 1 foot = 304.8m m
FIGURE 1808.7.1
FOUNDATION CLEARANCES FROM SLOPES
The footings of all structures shall be setback from the tops and toes of slopes as far as necessary for adequacy of footing/foundation support and to prevent damage as a result of water runoff or erosion of the slopes. Unless otherwise recommended in an approved soil engineering and/or engineering geology report, setbacks shall be no less than shown in Figure 1808.7.1 “Foundation Clearances from Slopes” or five (5') feet, whichever is greater. The setbacks given in that table are minimum requirements, and may be increased by the Building Official if considered necessary for safety or stability.
Exceptions:
1. Retaining walls may be used to reduce the required slope setback when approved by the Building Official.
2. Footings for freestanding garden walls may be founded on three (3') feet minimum from the face of any slope.
3. The Building Official may waive the setback requirement for any structure where it is determined because of special design or unique circumstances.
No building or structure, or portion thereof, governed by this Code shall be constructed on any slope greater than 5:1 without a finding by the Building Official that the site is safe for its intended use. The Building Official may require a geological investigation, soil engineer's report, and/or the footing/foundation to be designed by a civil or structural engineer registered as such by the State of California.
Section 1808.7.3 “Pools” is amended to read as follows:
1808.7.3 Pools.
The setback between pools regulated by this code and slopes shall be equal to one-half the building footing setback distance required by this section but not less than five (5’) feet. That portion of the pool wall within a horizontal distance of 7 feet (2134 mm) from the top of the slope shall be capable of supporting the water in the pool without soil support.
Table 1808.8.1 is amended to read as follows:
TABLE 1808.8.1
MINIMUM SPECIFIED COMPRESSIVE STRENGTH f'c OF CONCRETE OR GROUT
FOUNDATION ELEMENT OR CONDITION | SPECIFIED COMPRESSIVE STRENGTH, f'c |
FOUNDATION ELEMENT OR CONDITION | SPECIFIED COMPRESSIVE STRENGTH, f'c |
1. Foundations for structures assigned to Seismic Design Category A, B or C. [OSHPD 1R, 2 & 5] Not permitted by OSHPD. | 2,500 psi |
2a. Foundations for Group R or U occupancies of light-frame construction, two stories or less in height, assigned to Seismic Design Category D, E or F. [OSHPD 1R, 2 & 5] Not permitted by OSHPD. | 3,000 psi |
2b. Foundations for other structures assigned to Seismic Design Category D, E or F | 3,000 psi |
3. Precast nonprestressed driven piles | 4,000 psi |
4. Socketed drilled shafts | 4,000 psi |
5. Micropiles | 4,000 psi |
6. Precast prestressed driven piles | 5,000 psi |
For SI: 1 pound per square inch = 0.00689 MPa.
Section 1809.1 “General” is amended as to read as follows:
Shallow foundations shall be designed and constructed in accordance with Sections 1809.2 through 1809.13. All footing/foundation and/or slab designs shall be predicated upon a soil analysis. Said design shall not be less than those minimum requirements set forth in Table 1809.7(1) for each soil expansion range.
Post-tensioned slab design, when recommended by the soils engineer, may be used in lieu of the requirements when approved by the Building Official.
In areas where the soil is determined to be of an expansive range index over twenty (20), the soil under the footings and slabs shall be pre-saturated in accordance with Table 1809.7(1).
Section 1809.3 “Stepped Footings” is amended to read as follows:
1809.3 Stepped Footings.
The top surface of footings shall be level. The bottom surface of footings shall be permitted to have a slope not exceeding 1 unit vertical in 10 units horizontal (10-percent slope). Footings shall be stepped where it is necessary to change the elevation of the top surface of the footing or where the surface of the ground slopes more than 1 unit vertical in 10 units horizontal (10-percent slope).
[OSHPD 1R, 2 & 5] Individual steps in continuous footings shall not exceed 18 inches (457 mm) in height and the slope of a series of such steps shall not exceed 1 unit vertical to 2 units horizontal (50-percent slope) unless otherwise recommended by a geotechnical report. The steps shall be detailed on the drawings. The local effects due to the discontinuity of the steps shall be considered in the design of the foundation.
For structures assigned to Seismic Design Category D, E or F, the stepped requirement footing/foundation wall shall also apply to the top surface of grade beams, and supporting walls. Footings shall be reinforced with four (4) one-half (1/2”) inch diameter minimum deformed reinforcing bars. Two reinforcement bars shall be placed at the top and bottom of the footings in accordance with Figure 1809.1
Section 1809.4 “Depth and width of footings” is amended to read as follows:
1809.4 Depth and Width of Footings.
The minimum depth of footings below the undisturbed ground surface shall be 12 inches (305 mm). Where applicable, the requirements of Section 1809.5 shall be satisfied. The minimum width of footings shall be 12 inches (305 mm).
Footings for buildings and structures on expansive soils shall have a depth and width not less than the minimum requirements set forth in Table 1809.7 (1).
Section 1809.7 “Prescriptive footings for light-frame construction” is amended to read as follows:
1809.7 Prescriptive Footings for Light-Frame Construction.
[OSHPD 1R, 2 & 5] Not permitted by OSHPD. When a specific design is not provided, concrete or masonry-unit footings supporting walls of light-frame construction shall be permitted to be designed in accordance with Table 1809.7(1).
Table No. 1809.7 is hereby deleted and all Code references to Table 1809.7 shall now refer to Table 1809.7(1).
A new Table No. 1809.7(1) entitled “MINIMUM FOOTING AND SLAB REQUIREMENTS” is hereby added as follows:
Table 1809.7(1)
MINIMUM FOOTING AND SLAB REQUIREMENTS a
Section 1809.8 “Plain concrete footings” is amended, deletes exception and is to read as follows:
1809.8 Plain Concrete Footings
[OSHPD 1R, 2 & 5] Not permitted by OSHPD. Plain concrete footings shall not be utilized in structures assigned to Seismic Design Category D, E or F. The edge thickness of plain concrete footings supporting walls of other than light-frame construction shall be not less than 8 inches (203 mm) where placed on soil or rock.
Section 1809.12 “Timber footings” is amended to read as follows:
1809.12 Timber Footings.
[OSHPD 1R, 2 & 5] Not permitted by OSHPD. Timber footings shall not be utilized in structures assigned to Seismic Design Category D, E or F. Timber footings shall be permitted for buildings of Type V construction and as otherwise approved by the building official. Such footings shall be treated in accordance with AWPA U1 (Commodity Specification A, Use Category 4B). Treated timbers are not required where placed entirely below permanent water level, or where used as capping for wood piles that project above the water level over submerged or marsh lands. The compressive stresses perpendicular to grain in untreated timber footings supported on treated piles shall not exceed 70 percent of the allowable stresses for the species and grade of timber as specified in the ANSI/AWC NDS.2022 S-66 446
Building Regulations Sec. 8-1.17
Sections 1809.15, 1809.16, and 1809.17 are added to read as follows:
1809.15 Slabs.
1809.15.1 Reinforcement.
All slabs founded on soils determined to be of an expansive index of over fifty (50) shall be doweled into foundation walls with No. 3 reinforcement steel bars minimum bent twelve (12") inches into the wall and thirty-six (36") inches minimum into the slab at twenty-four (24") inches on center maximum. Interior walls with continuous footings/foundations shall have similar floor ties. Slab floors shall be reinforced as set forth in Table 1809.7 (1). All reinforcement in slab floors shall be positioned above the center of the slab.
Exception: An alternate design, such as a floating slab that eliminates the requirement for dowels, may be submitted to the Building Official for approval.
1809.15.2 Nonresidential Structures: Perimeter grade beams.
For all nonresidential structures which have isolated footings at their perimeters to carry vertical or horizontal loads, and at private garage door openings, a perimeter grade beam eight (8") inches minimum wide and conforming to the depth and reinforcement requirements in accordance with Table 1809.7(1) shall be constructed between discontinuous footing/foundation elements.
1805.15.3 Continuous Footings.
Whenever a daylight line between the cut or natural ground and the compacted fill falls within a proposed building area, continuous footings shall be reinforced with two (2) No. 4 minimum continuous deformed steel bars, one placed at the top and one placed at the bottom. Alternate designs may be submitted to the Building Official by a geotechnical engineer that include due allowances for dissimilar footing/foundation materials.
1809.15.4 Fine Grading.
Property sites shall be graded to drain to the public way or to a disposal area approved by the Building Official and/or City Engineer.
1809.15.5 Residential Accessory Buildings.
Residential accessory buildings not attached to the main structure need not have soil tests as required above; provided, however, the slab and footing/foundation standards as set forth for soil in the zero to twenty (0-20) expansive index range in Table 1809.7(1) shall be followed.
1809.15.6 Soil Tests: Alternatives.
In lieu of the required soil tests: At the discretion of the Building Official, footings/foundations for residential one-and two-family dwellings and additions to existing residences, where the expansive qualities of the soil are unknown, may use the requirements of the ninety-one to one hundred-thirty (91-130) expansive index set forth in Table 1809.7(1); provided, however, that should there be reasonable belief by the Building Official that the soil has expansive qualities exceeding the one hundred-thirty (130) index, a special engineered design shall be submitted.
1809.16 Drainage.
1809.16.1 Roof Gutters and Downspouts.
When a building is located on expansive soil having an expansion index greater than fifty (50), gutters, downspouts, piping and/or other non-erosive devices shall be provided to collect and conduct rainwater to a street, storm drain or other approved watercourse or disposal area.
1809.16.2 Roof Waters.
Eave gutters and downspouts may be required in any location where it appears reasonably necessary to protect buildings, structures, properties, and/or slopes, or portion thereof. Concentrated roof waters from gutter downspouts may be required to be conducted by an approved non-erosive drainage device to a point five (5') feet minimum in distance from the building footings/foundations and shall connect to swale or other means of yard drainage.
1809.16.3 Planters.
The design of planters in and/or immediately adjacent to buildings shall be submitted to, and be subject to the approval of, the Building Official prior to installation. Due consideration shall be given to the means or method employed in said design to prevent intrusion of water to the soils under the footing/foundation and/or slab.
1809.17 Adjacent Loads.
Where footings are placed at varying elevations, the effect of adjacent loads shall be included in the footing/foundation design.
Section 1810.3.2.4 is amended to read as follows:
1810.3.2.4 Timber.
[OSHPD 1R, 2 & 5] Not permitted by OSHPD. Timber deep foundation elements shall not be used in structures assigned to Seismic Design Category D, E or F. Timber deep foundation elements shall be designed as piles or poles in accordance with ANSI/AWC NDS. Round timber elements shall conform to ASTM D25. Sawn timber elements shall conform to DOC PS-20.
1810.3.2.4.1 Preservative Treatment.
Timber deep foundation elements used to support permanent structures shall be treated in accordance with this section unless it is established that the tops of the untreated timber elements will be below the lowest groundwater level assumed to exist during the life of the structure. Preservative and minimum final retention shall be in accordance with AWPA U1 (Commodity Specification E, Use Category 4C) for round timber elements and AWPA U1 (Commodity Specification A, Use Category 4B) for sawn timber elements. Preservative-treated timber elements shall be subject to a quality control program administered by an approved agency. Element cutoffs shall be treated in accordance with AWPA M4.
(§ 2, Ord. 1707-NS, eff. January 1, 2023)