Chapter 18.06
AMENDMENTS TO CHAPTER 18, SOILS AND FOUNDATIONS, OF THE CALIFORNIA BUILDING CODE
Sections:
18.06.005 Chapter 18 Is Amended.
18.06.006 Section 1805.1 Is Amended.
18.06.010 Section 1807.1.4 Is Amended.
18.06.013 Section 1807.1.6 Is Amended.
18.06.015 Section 1807.2 Is Amended.
18.06.020 Section 1807.3.1 Is Amended.
18.06.030 Section 1808.7.2 Is Amended.
18.06.040 Section 1809.3 Is Amended.
18.06.050 Section 1809.4 Is Amended.
18.06.060 Section 1809.7 and Table 1809.7 Are Amended.
18.06.070 Section 1809.12 Is Amended.
18.06.080 Section 1810.3.2.4 Is Amended.
18.06.005 Chapter 18 Is Amended.
The following sections of Chapter 18 of the California Building Code, as adopted by Chapter 18.01 hereof, are added, deleted, or amended as follows. (Ord. 22-10 § 2, 12/13/22)
18.06.006 Section 1805.1 Is Amended.
Section 1805.1 is amended to read as follows:
1805.1 General. Walls or portions thereof that retain earth and enclose interior spaces and floors below grade shall be waterproofed and dampproofed in accordance with this section, with the exception of those spaces containing groups other than residential and institutional where such omission is not detrimental to the building or occupancy. Ventilation for crawl spaces shall comply with Section 1202.5. Walls retaining 8 feet of soil or more shall have a waterproofing membrane installed in accordance with Section 1805.3.2. Where the geotechnical engineer determines that a waterproofing membrane is not required to protect against corrosion of reinforcing steel, a waterproofing membrane shall not be required.
(Ord. 22-10 § 2, 12/13/22)
18.06.010 Section 1807.1.4 Is Amended.
Section 1807.1.4 is amended to read as follows:
1807.1.4 Permanent wood foundation systems. Permanent wood foundation systems shall not be permitted.
(Ord. 22-10 § 2, 12/13/22)
18.06.013 Section 1807.1.6 Is Amended.
Section 1807.1.6 is amended to read as follows:
1807.1.6 Prescriptive design of concrete and masonry foundation walls. Concrete and masonry foundation walls that are laterally supported at the top and bottom shall be permitted to be designed and constructed in accordance with this section. Prescriptive design of foundation walls shall not be used for structures assigned to Seismic Design Category D, E or F.
(Ord. 22-10 § 2, 12/13/22)
18.06.015 Section 1807.2 Is Amended.
Section 1807.2 is amended to read as follows:
1807.2 Retaining walls. Retaining walls shall be designed in accordance with Section 1807.2.1 through 1807.2.4. Retaining walls assigned to Seismic Design Category D, E or F shall not be constructed of wood.
(Ord. 22-10 § 2, 12/13/22)
18.06.020 Section 1807.3.1 Is Amended.
Section 1807.3.1 is amended to read as follows:
1807.3.1 Limitations. The design procedures outlined in this section are subject to the following limitations:
1. The frictional resistance for structural walls and slabs on silts and clays shall be limited to one-half of the normal force imposed on the soils by the weight of the fooling or slab.
2. Posts embedded in earth shall not be used to provide lateral support for structural or nonstructural materials such as plaster, masonry or concrete unless bracing is provided that develops the limited deflection required.
Wood poles shall be treated in accordance with AWPA U1 for sawn timber posts (Commodity Specification A, Use Category 4B) and for round timber posts (Commodity Specification B, Use Category 4B). Wood poles and posts embedded in direct contact with soil shall not be used for structures assigned to Seismic Design Category D, E or F.
Exception: Wood poles and posts embedded in direct contact with soil may be used to support non- habitable, non-occupiable structures such as fences when approved by the Building Official.
(Ord. 22-10 § 2, 12/13/22)
18.06.030 Section 1808.7.2 Is Amended.
Section 1808.7.2 is amended to read as follows:
1808.7.2 Foundation setback from descending slope surface. Foundations on or adjacent to slope surfaces shall be founded in firm material with an embedment and set back from the slope surface sufficient to provide vertical and lateral support for the foundation without detrimental settlement. Except as provided for in Section 1808.7.5 and Figure 1808.7.1, the following setback is deemed adequate to meet the criteria. Where the slope is steeper than 1 unit vertical in 1 unit horizontal (100-percent slope), the required setback shall be measured from an imaginary plane 45 degrees (0.79 rad) to the horizontal, projected upward from the toe of the slope. The setback shall be that determined using Figure 1808.7.1 or 5 feet, whichever is larger.
(Ord. 22-10 § 2, 12/13/22)
18.06.040 Section 1809.3 Is Amended.
Section 1809.3 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 one 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 one unit vertical in 10 units horizontal (10-percent slope).
For structures assigned to Seismic Design Category D, E or F, the stepping requirement shall also apply to the top surface of grade beams supporting walls. Footings shall be reinforced with a minimum of four #4 steel reinforcing bars. Two bars shall be place at the top and bottom of the footings as shown in Figure 1809.3.
Figure 1809.3
(Ord. 22-10 § 2, 12/13/22)
18.06.050 Section 1809.4 Is Amended.
Section 1809.4 is amended to read as follows:
1809.4 Depth and width of footings. Where a geotechnical report is not provided and the presence of expansive soils is unknown, the minimum depth of footings shall be 24 inches (610 mm) for exterior walls and 18 inches (458 mm) for interior bearing walls. Such footings shall be reinforced with a minimum of two #4 rebar at the top and two #4 rebar at the bottom.
Exception: The minimum footing depth for unoccupied group U structures or patio structures associated with an R-3 occupancy shall be 12 inches (305 mm).
Otherwise, 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 also be satisfied. The minimum width of footings shall be 12 inches (305 mm).
(Ord. 22-10 § 2, 12/13/22)
18.06.060 Section 1809.7 and Table 1809.7 Are Amended.
Section 1809.7 and Table 1809.7 are amended to read as follows:
1809.7 Prescriptive footings for light-frame construction. Where 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. Prescriptive footings in Table 1809.7 shall not exceed two stories above grade plane for structures assigned to Seismic Design Category D, E or F.
|
NUMBER OF FLOORS SUPPORTED BY THE FOOTING |
WIDTH OF FOOTING (inches) |
THICKNESS OF FOOTING (inches) |
|---|---|---|
|
1 |
12 |
8 |
|
2 |
15 |
8 |
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.
a. Depth of footings shall be in accordance with Section 1809.4.
b. The ground under the floor shall be permitted to be excavated to the elevation of the top of the footing.
c. See Section 1905 for additional requirements for concrete footings of structures assigned to Seismic Design Category C, D, E or F.
d. For thickness of foundation walls, see Section 1807.1.6.
e. Footings shall be permitted to support a roof addition to the stipulated number of floors. Footings supporting roof only shall be as required for supporting one floor.
(Ord. 22-10 § 2, 12/13/22)
18.06.070 Section 1809.12 Is Amended.
Section 1809.12 is amended to read as follows:
1809.12 Timber footings. Timber footings shall not be permitted.
(Ord. 22-10 § 2, 12/13/22)
18.06.080 Section 1810.3.2.4 Is Amended.
Section 1810.3.2.4 is amended to read as follows:
1810.3.2.4 Timber. Timber deep foundation elements shall not be permitted.
(Ord. 22-10 § 2, 12/13/22)