Section 1809.7 of Chapter 18 of the California Building Code is amended to read:
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.
TABLE 1809.7
Prescriptive Footings Supporting Walls of Light-Frame Constructionabcd
Number of Floors Supported by the Footinge |
Thickness of Foundation Wall (inches) | Width of Footing (inches) | Thickness of Footing (inches) | Depth of Foundation Below Natural Surface of Ground or Finish Grade (inches) |
1 & 2 | 8 | 15 | 8 | 20 |
3 | 8 | 18 | 8 | 30 |
Group U Occupancies | 8 | 12 | 8 | 12 |
ADU Conversionsf | 8 | 12 | 8 | 12 |
a. Ground under the floor shall be permitted to be excavated to elevation of footing.
b. Interior stud-bearing walls shall be permitted to be supported by isolated footings. Footing width and length shall be twice the width shown in this table, and footings shall be spaced not more than 6 feet on center.
c. See Section 1905 for additional requirements for concrete footings of structures assigned to Seismic Design Category C, D, E or F.
d. All foundations as required in the above Table shall be continuous and have a minimum of three #4 bars of reinforcing steel, except for one story, detached accessory buildings of Group U occupancy where two bars are required.
e. Footings shall be permitted to support a roof in addition to the stipulated number of floors. Footings supporting roof only shall be as required for supporting one floor.
f. If existing detached accessory building is being converted to an Accessory Dwelling Unit (ADU) and the existing foundation is being utilized, then a designer, architect or engineer shall provide a letter that the existing foundation complies with the conditions above and is deemed structurally sound.
(Ord. 5564 § 1 (part), 2022)