Basic House Foundation Requirements
1809.4 Depth and width of footings.
The minimum depth of footings below the undisturbed ground surface shall be 12 inches (305 mm). The minimum width of footings shall be 12 inches.
1809.7 Prescriptive footings for light-frame construction.
TABLE 1809.7 PRESCRIPTIVE FOOTINGS SUPPORTING WALLS OF LIGHT-FRAME CONSTRUCTION a, b, c
| NUMBER OF FLOORS SUPPORTED BY THE FOOTING | WIDTH OF FOOTING (inches) | THICKNESS OF FOOTING (inches) |
| 1 | 12 | 6 |
| 2 | 15 | 6 |
| 3 | 18 | 8g |
The ground under the floor shall be permitted to be excavated to the elevation of the top of the footing.
Here you will find the complete code citation.
In order to figure out how much concrete you will need, you multiply the length of your ditch by the width and the depth using this conversion tool.
R403.1.3.1 Foundations with stem walls. Foundations with stem walls shall have installed a minimum of one No. 4 bar within 12 inches (305 mm) of the top of the wall and one No. 4 bar located 3 inches (76 mm) to 4 inches (102 mm) from the bottom of the footing.
Table R611.5.4.(1) requires Grade 60 rebar to have a lap splice as follows:
#4 Bar – Lap Splice shall be 30-inches
#5 Bar – Lap Splice shall be 38-inches
#6 Bar – Lap Splice shall be 45-inches
Preventing Decay to the Cripple Wall
2304.11.1 General
Where required by this section, protection from decay and termites shall be provided by the use of naturally durable or preservative-treated wood.
2304.11.2 Wood Used Above Ground
Wood used above ground in the locations specified in Sections 2304.11.2.1 through 2304.11.2.7, 2304.11.3 and 2304.11.5 shall be naturally durable wood or preservative-treated wood using water-borne preservatives, in accordance with AWPA U1 (Commodity Specifications A or F) for above-ground use.
2304.11.2.1 Joists, Girders and Subfloor
Where wood joists or the bottom of a wood structural floor without joists are closer than 18 inches (457 mm), or wood girders are closer than 12 inches (305 mm) to the exposed ground in crawl spaces or unexcavated areas located within the perimeter of the building foundation, the floor construction (including posts, girders, joists and subfloor) shall be of naturally durable or preservative-treated wood.
2304.11.2.2 Wood Supported by Exterior Foundation Walls
Wood framing members, including wood sheathing, that rest on exterior foundation walls and are less than 8 inches (203 mm) from exposed earth shall be of naturally durable or preservative-treated wood.
2304.11.2.3 Exterior Walls Below Grade
Wood framing members and furring strips attached directly to the interior of exterior masonry or concrete walls below grade shall be of naturally durable or preservative-treated wood.
2304.11.2.4 Sleepers and Sills
Sleepers and sills on a concrete or masonry slab that is in direct contact with earth shall be of naturally durable or preservative-treated wood.
2304.11.2.5 Girder Ends
The ends of wood girders entering exterior masonry or concrete walls shall be provided with a 1/2-inch (12.7 mm) air space on top, sides and end, unless naturally durable or preservative-treated wood is used.
2304.11.2.6 Wood Siding
Clearance between wood siding and earth on the exterior of a building shall not be less than 6 inches (152 mm) or less than 2 inches (51 mm) vertical from concrete steps, porch slabs, patio slabs and similar horizontal surfaces exposed to the weather except where siding, sheathing and wall framing are of naturally durable or preservative-treated wood.
2304.11.2.7 Posts or Columns
Posts or columns supporting permanent structures and supported by a concrete or masonry slab or footing that is in direct contact with the earth shall be of naturally durable or preservative-treated wood.
Exceptions:
- Posts or columns that are either exposed to the weather or located in basements or cellars, supported by concrete piers or metal pedestals projected at least 1 inch (25 mm) above the slab or deck and 6 inches (152 mm) above exposed earth, and are separated therefrom by an impervious moisture barrier.
- Posts or columns in enclosed crawl spaces or unexcavated areas located within the periphery of the building, supported by a concrete pier or metal pedestal at a height greater than 8 inches (203 mm) from exposed ground, and are separated therefrom by an impervious moisture barrier.
