Sec. 8-1.17. Amendments: Chapter 18 Soils and Foundations.
   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:
   Refer to Tile 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.
   Sections 1804.2, 1804.3, 1804.4, 1804.5, 108.6 and 1804.7 are hereby deleted.
   Section 1807.1.4 "Permanent Wood Foundation Systems" is amended by adding the following sentence to read as follows:
   Permanent wood foundation systems shall not be used for structures assigned to Seismic Design Category D, E or F.
   Section 1807.1.6 "Prescriptive Design of Concrete and Masonry Walls" is amended by adding the following sentence to read as follows:
   Prescriptive design of foundation walls shall not be used for structures assigned to Seismic Design Category D, E or F.
   Section 1808.6 "Design for Expansive Soil" is amended by adding the following exception:
   3. Foundations for buildings and structures with shallow foundations may be designed in accordance with Section 1809 as amended herein.
   Section 1808.7 "Foundations on or adjacent to slopes" is amended to read as follows.
   1808.7 Foundations on or adjacent to 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 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 to his/her satisfaction that, because of special design or unique circumstances, no hazard or failure could reasonably be expected.
   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 1808.7.1 is amended by deleting the last sentence in that section.
   Section 1808.7.3 "Pools" is amended by adding the following phrase to the end of the first sentence:
   but not less than five (5') feet.
   Table 1808.8.1 (2a) is amended to read specified compressive strength 3,000 psi
   Section 1809 "Shallow Foundations" is amended as follows:
   Amend Section 1809.1 "General" by adding the following:
   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 1809.2 "Supporting soils" is amended to read as follows:
   Shallow foundations shall be constructed on soil that provides adequate support as approved by the Building Official.
   Section 1809.3 "Stepped footings" is amended by adding the following:
   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 by adding the following:
   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:
   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
 
 
 
Expansion Index
Foundations for slab and Raised Floor Systems
Concrete Slabs 3 1/2’ Minimum Thickness 4” over 51 E1
 
 
Premoistening of Soils under footings, piers and slabs
 
 
Restrictions on piers under raised floors
Number of Stories
Stem Thickness
Footing Width
Footing Thickness
All perimeter footings
Interior footings for slab & raised floors b
Reinforcement for continuous foundations
Reinforcement c
Total thickness of Sand
Depth Below Natural Surface of Ground and Finish Grace
0-20 Very low (non- expansive)
1
2
3
6”
8”
10”
12”
15”
18”
6”
7”
8”
12”
18”
24”
12”
18”
24”
1-#4 top and bottom
#4 @ 48”
or
#3 @36”
2”
Moistening ground recommended prior to placing concrete
Piers allowed for single floor loads only
21-50 Low
1
2
3
6”
8”
10”
12”
15”
18”
6”
7”
8”
15”
18”
24”
12”
18”
24”
1-#4 top and bottom
2”
3% over optimum moisture required to a depth of 18” below lowest adjacent grade. Testing required
Piers allowed for single floor loads only
51-90 Medium
1
2
3
6”
8”
10”
12”
12”
15”
6”
8”
8”
21”
21”
24”
12”
18”
24”
1-#4 top and bottom
   Footnote e
#3 @24” each way
4”
3% over optimum moisture required to a depth of 18” below lowest adjacent grade. Testing required.
Piers not allowed
91-130 High
1
2
3
6”
8”
10”
12”
12”
15”
8”
8”
8”
27”
27”
27”
12”
18”
24”
2-#4 top and bottom
   Footnote e
#3 @24” each way
6”
3% over optimum moisture required to a depth of 24” below lowest adjacent grade. Testing required.
Piers not allowed
Above 130 Very high
Special Design by registered design professional d
 
a   Slabs for masonry fireplaces shall be reinforced with No. 4 deformed bars at twenty-four (24”) inches on center both ways.
b   Interior footings on soils in the zero (0) index to twenty (20) index range of expansiveness need not be continuous.
c   All slab reinforcement shall be positioned above the center of the slab.
d   All foundations on soils that fall into an expansive index in excess of one hundred-thirty (130) shall have a special design by a foundation engineer registered as a soil or civil engineer in California, and such design shall not be less than the minimum standards specified in Table 1809.7(1) for soils with an expansion index between ninety-one (91) and one hundred thirty (130).
e   Exterior footing to slab L shaped dowel bars #3 bars @ 24” o.c., 12” into footings, 36” into slab required.
   Section 1809.8 "Plain concrete footings" is amended by adding the following:
   Plain concrete footings shall not be utilized in structures assigned to Seismic Design Category D, E or F.
   Section 1809.12 "Timber footings" is amended by adding the following sentence:
   Timber footings shall not be utilized in structures assigned to Seismic Design Category D, E or F.
   Sections 1809.14, 1809.15, 1809.16, 1809.17 and 1805.18 are added to read as follows:
   1809.14 Slabs.
   1809.14.1 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.
   1809.14.2 Moisture membrane.
   An approved moisture membrane with a minimum thickness of six (6) mils shall be installed in an approved manner under all interior concrete slabs, including residential garage slabs.
   1809.14.3 Loose fill.
   Loose fill shall be compacted in an approved manner and to the satisfaction of the Building Official or shall be removed and replaced with coarse sand or gravel.
   1809.14.4 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.
   1805.14.5 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.
   1809.14.6 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.
   1809.14.7 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.
   1809.14.8 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.
   1809.15 Drainage.
   1809.15.1  Drainage around Building Foundations.
   Finish grades around structures and buildings shall conform to the grading provisions of the City and shall slope downward away from the building or structure footing/foundation to lower areas or drainage swales. Unless otherwise approved by the Building Official, the minimum gradients of such slopes shall not be less than five (5%) percent for the first ten (10') feet. The minimum longitudinal gradient of swales shall be sufficient to dispose of all water and shall not be less than one (1%) percent. A non-erosive drainage device may be required by the Building Official when he/she determines it is reasonably necessary to protect a structure or slopes.
   Exception:
   Where the property line is less than ten (10') feet from the structure, a longitudinal swale may be located one-half (1/2) the distance to the property line.
   1809.15.2 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.
   1809.15.3 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.
   1809.15.4 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.
   1809.16 Adjacent Loads.
   Where footings are placed at varying elevations, the effect of adjacent loads shall be included in the footing/foundation design.
   1809.17 Exceptions:
   The foregoing provisions of Section 1809 Shallow Foundations may be waived by the Building Official for the following structures:
   1.   Minor buildings or structures;
   2.   Type V buildings except where expansive soils or materials of highly different bearing capacities are present; and,
   3.   Agricultural buildings under two thousand (2,000) square feet in the area.
   1809.18 Repair and Replacement of Existing Foundations and Slabs.
   Repair and replacement of existing footings/foundations and slabs may be limited to the area of proposed new construction provided that the following conditions are met:
   1.   The proposed repair and/or replacement of the existing footing/foundation and/or slab is predicated on a soils report by a licensed civil, structural, soils or geotechnical engineer.
   2.   All aspects of the new construction regarding footings/foundations and slabs shall meet or exceed the requirements contained in Section 1-8.17 of the Thousand Oaks Municipal Code.
   3.   The footing/foundation and/or slab repair may be limited to a designated area of the residence.
   4.   The footing/foundation and/or slab repair need not address the overall footing/foundation and/or slab distress when the overall cost of the permanent repair and upgrade of the complete footing/foundation and/or slab repair causes an unbearable hardship due to economic conditions.
   Section 1810.3.2.4 is amended by adding the following sentence:
   Timber deep foundation elements shall not be used in structures assigned to Seismic Design Category D, E or F.
(§ 2, Ord. 1669-NA, eff. January 10, 2020)