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gradient, load intensity and erosion characteristics of slope material. 1805,4 Footings, Footings shall be designed and constructed in accordance with Sections 1805.4.1 through 1805.4.6. 1805.4.1 Design. Footings shall be so designed that the. allowable bearing capacity of the soil is not exceeded, and that differential settlement is minimized. The minimum width of footings shall be 12 inches (305 mm). Footings in areas with expansive soils shall be designed in accordance with the provisions of Section 1805.8, 1805.4.1.1 Design loads, Footings shall be designed for the most unfavorable effects due to the combinations of loads specified in Section 1605.3. The dead load shall in- clude the weight of foundations, footings and overlying fi I I. Reduced Ii ve loads, as specified in Section 1607.9, are permitted to be used in designing footings. 1805.4.1.2 Vibratory loads. Where machinery opera- tions or other vibrations are transmitted through the foundation, consideration shall be given in the footing design to prevent detrimental disturbances of the soil. 1805.4.2 Concrete footings. The design, materials and con- struction of concrete footings shall comply with Sections 1805.4.2.1 through 1805.4.2.6 and the provisions of Chap- ter 19. Exception: Where a specific design is not provided, con- crete footings supporting walls of light-frame construc- tion are permitted to be designed in accordance with Table 1805.4.2. 1805,4,2.1 Concrete strength. Concrete in footings shall have a specified compressive strength if I c) of not less than 2,500 pounds per square inch (psi) (17237 kPa) at 28 days. 1805.4,2.2 Reserved, SOILS AND FOUNDATIONS 1805,4.2.3 Plain concrete footings, The edge thickness of plain concrete footings supporting walls of other than light-frame construction shall not be less than 8 i nc hes (203 nun) where placed on soil. Exception: For plain concrete footings supporting Group R-3 occupancies. the edge thickness is permit- ted to be 6 inches (152 mm), provided that the footing does not extend beyond a distance greater than the thiclcness of the footing on either side of the supported wall. 1805.4.2,4 Placement of concrete, Concrete footll1gs shall nqt be placed through water unless a tremie or otber method approved by the building official is used. Where placed under or in the presence of water, the concrete shall be deposited by approved means to ensure mi n I. mum segregation of the mix and negligible turbulence 01 the water. 1805.4.2.5 Protection of concrete. Concrete footIngs shall be protected from freezing during depositing and for a period of not less than five days thereafter. Water shall not be allowed to flow through the deposited concrete. 180~.4.2,6l4'orming of concrete, Concrete footings are perrititted to be cast against the earth where, in the opi n- ion of the building official, soil conditions do not require forming. Where forming is required, it shall be in accor- dance with Chapter 6 ofACI 318. 1805,4.3 Masonry-unit footings. The design, materials and construction of masonry-unit footings shall comply with Sections 1805.4,3.1 and 1805.4.3.2, and the prOVISions of Chapter 21. Exception: Where a specific design is not provided, ma- sonry-unit footings supporting walls of light-frame con- struction are permitted to be designed in accordance with Table 1805.4,2, 1805,4.3.1 Dimensions. Masonry-unit footings shall be .laid in Type M or S mortar complying with Section II TABLE 1805.4.2 FOOTINGS SUPPORTING WALLS OF LIGHT.FRAME CONSTRUCTION.' b, c, d I WIDTH 01" . THICKNESS OF i NUMBER OF FLOORS FOOTING FOOTING SUPPORTED BY THE FOOTING' (Inoh.l) (Inchel) I 12 6 2 15 6 I 3 18 Sf I I I II For 51 I inch = 25.4 mm, I foot = 304.8 mm. d Depth of foolings shall be in accordance with Section 1805.2. b The grou nd under the noor is permitted to be..excavated to the elevation of the top of the footing. c. Interior-stud-bearing walls are permitted to be supported by isolated footings. The footing width and length shall be twice the width shown in this table. and loot- Ings shall be spaced not more than 6 feel on center. II d For thickness of foundation walls, see SectiQn 1805.5. e. Footings are permitted 10 support a roofin addition to the stipulated number ofnoors. Footings supporting roof only shall be as required for supporting one Iloor f Plain concrete footings for Group R-3 occupancies are permitted to be 6 incites thiclc FLORIDA BUILDING CODE - BUILDING 18.5