{"data":{"id":"us-nyc/n.y.c.-admin.-code-bc-1809","jurisdiction":"us-nyc","citation":"N.Y.C. Admin. Code § BC 1809","heading":"Section BC 1809: Shallow Foundations","body":"1809.1 General.\n\nShallow foundations shall be designed and constructed in accordance with Sections 1809.1 through 1809.6. Shallow foundations shall be constructed on suitable bearing materials established in accordance with the requirements of Sections 1804 and 1806.\n\n1809.2 Stepped footings.\n\nThe 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 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).\n\n1809.3 Depth of footings.\n\nThe minimum depth of shallow foundations below the undisturbed ground surface shall be 12 inches (304.8 mm). Where applicable, the depth of shallow foundations shall also conform to Section 1809.3.1.\n\n1809.3.1 Frost protection.\n\nExcept where otherwise protected from frost, shallow foundations, pile caps, and other permanent supports of buildings and structures shall be protected from frost by one or more of the following methods:\n\n1. Extending a minimum of 4 feet (1220 mm) below the lowest adjacent permanent exposed grade;\n\nException: Grade beams shall be embedded a minimum of 18 inches (457.2 mm) below the lowest adjacent permanent exposed grade.\n\n2. Constructing in accordance with ASCE 32; or\n\n3. Erecting on solid rock.\n\nException: Free-standing buildings meeting all of the following conditions shall not be required to be frost protected:\n\n1. Classified in Structural Occupancy Category I (see Table 1604.5);\n\n2. Area of 400 square feet (37.1 m\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t2\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t) or less; and\n\n3. Eave height of 10 feet (3048 mm) or less.\n\n1809.3.2 Foundations on frozen soil.\n\nShallow foundations shall not bear on frozen soil.\n\nException: Temporary structures may bear on frozen soil if the soil is maintained in a frozen condition throughout the service life of the temporary structures being supported. The method of maintaining the soil in a frozen condition shall be approved by the commissioner.\n\n1809.4 Shallow foundations at different levels.\n\nWhere shallow foundations are supported at different levels, or are at different levels from the shallow foundations of adjacent structures, the influence of the pressures under the higher foundation on the stability of the lower foundations shall be considered in the design. The design shall consider the requirements for lateral support of the material supporting the higher foundation, the additional load imposed on the lower foundations, and assessment of the effects of dragdown on deep foundations supporting adjacent buildings or compression of soils supporting adjacent buildings.\n\n1809.5 Shallow foundations.\n\nShallow foundations shall be designed and constructed in accordance with Sections 1809.5.1 through 1809.5.8.\n\n1809.5.1 Design.\n\nShallow foundations shall be designed so that the allowable bearing capacity of the soil is not exceeded, and that differential settlements are within the allowable limits for the structure. The minimum width of shallow foundations shall be 18 inches (457.2 mm).\n\n1809.5.1.1 Design loads.\n\nShallow foundations shall be designed for the most unfavorable effects due to the combinations of loads specified in Section 1605.3. The dead load shall include the weight of shallow foundations and overlying fill. Reduced live loads, as specified in Section 1607.11, are permitted to be used in the design of shallow foundations.\n\n1809.5.1.2 Vibratory loads.\n\nWhere machinery operations or other vibrations are transmitted through the shallow foundations, consideration shall be given in the shallow foundation design to prevent detrimental disturbances of the soil.\n\n1809.5.1.3 Shifting or moving soils.\n\nWhen the possibility of shifting or moving soil exists, the short and long term impact of such soils shall be considered in the design of shallow foundations.\n\n1809.5.2 Concrete shallow foundations.\n\nThe design, materials and construction of concrete shallow foundations shall comply with Sections 1809.5.2.1 through 1809.5.2.5 and the provisions of Chapter 19.\n\n1809.5.2.1 Concrete strength.\n\nConcrete in shallow foundations shall have a specified compressive strength (f'\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\tc\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t) of not less than 2,500 pounds per square inch (psi) (17.24 MPa) at 28 days.\n\n1809.5.2.2 Footing seismic ties.\n\nWhere a structure is assigned to Seismic Design Category D in accordance with Section 1613, individual spread footings founded on soil defined in Section 1613.3.2 as Site Class E or F shall be interconnected by ties. Ties shall be capable of carrying, in tension or compression, a force equal to the product of the larger footing load times the seismic coefficient SDS divided by 10 unless it is demonstrated that equivalent restraint is provided by reinforced concrete beams within slabs on grade or reinforced concrete slabs on grade.\n\n1809.5.2.3 Plain concrete footings.\n\nThe thickness of plain concrete footings supporting walls of other than light-frame construction shall not be less than 8 inches (203.2 mm) where placed on soil.\n\nException: For plain concrete footings supporting Group R-3 occupancies, the thickness is permitted to be 6 inches (152.4 mm), provided that the footing does not extend beyond a distance greater than the thickness of the footing on either side of the supported wall.\n\n1809.5.2.4 Placement of concrete.\n\nConcrete shallow foundations shall not be placed through water unless a tremie or other method approved by the commissioner is used. Where placed under or in the presence of water, the concrete shall be deposited by approved means to ensure minimum segregation of the mix and negligible turbulence of the water.\n\n1809.5.2.5 Protection of concrete.\n\nNo shallow foundation shall be placed on frozen soils unless the soils are maintained in frozen condition throughout the service life of the structure being supported. No foundation shall be placed in freezing weather unless provision is made to maintain the underlying soil free of frost. Concrete shallow foundations 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.\n\n1809.5.3 Masonry-unit footings.\n\nThe design, materials and construction of masonry-unit footings shall comply with the provisions of Chapter 21.\n\n1809.5.4 Steel grillage footings.\n\nGrillage footings of structural steel elements shall be separated with approved steel spacers and be entirely encased in concrete with at least 6 inches (152.4 mm) on the bottom and at least 4 inches (101.6 mm) at all other points. The spaces between the elements shall be completely filled with concrete or cement grout.\n\n1809.5.5 Timber footings.\n\nRefer to Chapter 23.\n\n1809.5.6 Wood foundations.\n\nRefer to Chapter 23.\n\n1809.5.7 Pier foundations.\n\nThe design, materials, and construction of pier foundations shall conform to the requirements of Sections 1809.5.2, 1809.5.3, and 1809.5.7.1 through 1809.5.7.6.\n\nException: Piers shall be load tested as a deep foundation in accordance with the applicable portions of Section 1810 when the bearing stratum is not physically available for inspection during construction as required by Chapter 17.\n\n1809.5.7.1 Dimensions and height.\n\nThe minimum horizontal dimension of piers shall be 2 feet (609.6 mm), and the height shall not exceed 12 times the least horizontal dimension.\n\n1809.5.7.2 Concrete design.\n\nWhere adequate lateral support is furnished by the surrounding materials defined in Section 1810.7 of this code, piers may be constructed of plain or reinforced concrete and the requirements of ACI 318 shall apply.\n\nException: Where adequate lateral support is not provided, and the ratio of unsupported height to least horizontal dimension does not exceed three, piers of plain concrete shall be designed and constructed as pedestals in accordance with ACI 318. Where the unsupported height to least horizontal dimension exceeds three, piers shall be constructed of reinforced concrete, and shall conform to the requirements for columns in ACI 318.\n\n1809.5.7.3 Reinforcement placement.\n\nReinforcement shall be tied and placed as a unit in the pier prior to placement of concrete.\n\nException: Steel dowels embedded 5 feet (1524 mm) or less in the pier may be placed individually. Reinforcement is permitted to be wet set and the concrete cover that is otherwise required to measure a minimum of 2 1/2 inches (63.5 mm) may be reduced to 2 inches (50.8 mm) for Groups R-3 and U occupancies not exceeding two stories of light-frame construction, provided the construction method is approved by the commissioner.\n\n1809.5.7.4 Concrete placement.\n\nConcrete shall be placed in such a manner as to ensure the exclusion of any foreign matter and to fill the full lateral dimensions of each pier. Concrete shall not be placed through water except where a tremie or other approved method is used. When depositing concrete from the top of the pier, the concrete shall not be chuted directly into the pier but shall be poured in a rapid and continuous operation through a funnel hopper centered at the top of the pier.\n\n1809.5.7.5 Steel shell.\n\nWhere concrete piers are entirely encased within a circular steel shell, and the area of the shell steel is considered reinforcing steel, the steel shall be protected under the conditions specified in Section 1810.2.12. Horizontal joints in the shell shall be spliced to comply with Section 1810.2.11.\n\n1809.5.7.6 Dewatering.\n\nWhere piers are carried to depths below the groundwater level, the piers shall be constructed by a method that will provide accurate preparation and inspection of the subgrade in dry conditions.\n\n1809.5.8 Foundation walls.\n\nConcrete and masonry foundation walls shall be designed in accordance with Chapter 19 or 21, respectively.\n\n1809.5.8.1 Foundation wall thickness.\n\nThe minimum thickness of concrete and masonry foundation walls shall comply with Section 1809.5.8.1.1.\n\n1809.5.8.1.1 Thickness based on walls supported.\n\nThe thickness of foundation walls shall not be less than the thickness of the wall supported, except that foundation walls of at least 8 inch (203.2 mm) nominal width are permitted to support brick-veneered frame walls and 10 inch wide (254 mm) cavity walls.\n\n1809.5.8.2 Foundation wall drainage.\n\nFoundation walls shall be designed to support the weight of the full hydrostatic pressure of undrained backfill unless a drainage system is installed in accordance with Sections 1805.4.2 and 1805.4.3.\n\n1809.6 Seismic requirements.\n\nFor structures assigned to Seismic Design Category C or D, provisions of ACI 318 18.13, as modified by Section 1908 of this code, shall apply when not in conflict with the provisions of Section 1809 of this code. Concrete shall have a specified compressive strength of not less than 3,000 psi (20.68 MPa) at 28 days.\n\nExceptions:\n\n1. Group R or U occupancies of light-framed construction and two stories or fewer in height are permitted to use concrete with a specified compressive strength of not less than 2,500 psi (17.2 MPa) at 28 days.\n\n2. One and two-family dwellings not more than three stories in height are not required to comply with the provisions of ACI 318, Section 18.11, as modified by Section 1908 of this code.","path":["New York City Administrative Code","Title 28","Chapter 7: New York City Building Code"],"source_url":"https://files.amlegal.com/pdffiles/NewYorkCity/Admin/XML.zip","current_through":"Local Law 2026/135 (enacted August 31, 2026)","vintage":"","retrieved_at":"2026-09-06T02:48:57Z","sha256":"5073705d16fa9fc7965214eb180d639b6388bc04d4137b8a755ffa5f5351d411","source_id":"us-nyc","stale":false,"prev":"us-nyc/n.y.c.-admin.-code-bc-1808","next":"us-nyc/n.y.c.-admin.-code-bc-1810"},"notice":"GroundRules: Original legal text. Not legal advice."}