Section R403 — FOOTINGS

All exterior walls shall be supported on continuous solid or fully grouted masonry or concrete footings, crushed stone footings, wood foundations, or other approved structural systems that shall be of sufficient design to accommodate all loads according to Section R301 and to transmit the resulting loads to the soil within the limitations as determined from the character of the soil. Footings shall be supported on undisturbed natural soils or engineered fill. Concrete footing shall be designed and constructed in accordance with the provisions of Section R403 or in accordance with ACI 332.

be of sufficient design to accommodate all loads according to Section R301 and to transmit the resulting loads to the soil within the limitations as determined from the character of the soil. Footings shall be supported on undisturbed natural soils or engineered fill. Concrete footing shall be designed and constructed in accordance with the provisions of Section R403 or in accordance with ACI 332.

TABLE R403.1(1)—MINIMUM WIDTH AND THICKNESS FOR
CONCRETE FOOTINGS FOR LIGHT-FRAME CONSTRUCTION (inches)a, b, c, d

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FOUNDATIONS

TABLE R403.1(1)—MINIMUM WIDTH AND THICKNESS FOR
CONCRETE FOOTINGS FOR LIGHT-FRAME CONSTRUCTION (inches)a, b, c, d—continued

For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 47.9 N/m2.
a. Linear interpolation of footing width is permitted between the soil bearing pressures in the table. Extrapolation is not permitted.
b. The table is based on the following conditions and loads: building width, 32 feet; wall height, 9 feet; basement wall height, 8 feet; dead loads, 15 psf roof and ceiling assembly,
10 psf floor assembly, 12 psf wall assembly; live loads, roof and ground snow loads as listed, 40 psf first floor, 30 psf second and third floors. Footing sizes are calculated
assuming a clear span roof/ceiling assembly and an interior bearing wall or beam at each floor.
c. Where the building width perpendicular to the wall footing is greater than 32 feet, the footing width shall be increased by 2 inches and footing depth shall be increased by 1
inch for every 4 feet of increase in building width.
d. Where the building width perpendicular to the wall footing is less than 32 feet, a 2-inch decrease in footing width and 1-inch decrease in footing depth is permitted for every 4
feet of decrease in building width provided that the minimum width is 12 inches and minimum depth is 6 inches.
SLAB
ON GRADE
BASEMENT
CRAWL
SPACE

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FOUNDATIONS

TABLE R403.1(2)—MINIMUM WIDTH AND THICKNESS FOR CONCRETE FOOTINGS FOR
LIGHT-FRAME CONSTRUCTION WITH BRICK VENEER OR LATH AND PLASTER (inches)a, b, c, d

For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 47.9 N/m2.
a. Linear interpolation of footing width is permitted between the soil bearing pressures in the table. Extrapolation is not permitted.
b. The table is based on the following conditions and loads: building width, 32 feet; wall height, 9 feet; basement wall height, 8 feet; dead loads, 15 psf roof and ceiling assembly,
10 psf floor assembly, 12 psf wall assembly; live loads, roof and ground snow loads as listed, 40 psf first floor, 30 psf second and third floors. Footing sizes are calculated
assuming a clear span roof/ceiling assembly and an interior bearing wall or beam at each floor.
c. Where the building width perpendicular to the wall footing is greater than 32 feet, the footing width shall be increased by 2 inches and footing depth shall be increased by 1
inch for every 4 feet of increase in building width.
d. Where the building width perpendicular to the wall footing is less than 32 feet, a 2-inch decrease in footing width and 1-inch decrease in footing depth is permitted for every 4
feet of decrease in building width provided that the minimum width is 12 inches and minimum depth is 6 inches.
SLAB
ON GRADE
BASEMENT
CRAWL
SPACE

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FOUNDATIONS

TABLE R403.1(3)—MINIMUM WIDTH AND THICKNESS FOR CONCRETE FOOTINGS WITH
CAST-IN-PLACE CONCRETE OR PARTIALLY GROUTED MASONRY WALL CONSTRUCTION (inches)a, b, c, d

For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 47.9 N/m2.
a. Linear interpolation of footing width is permitted between the soil bearing pressures in the table. Extrapolation is not permitted.
b. The table is based on the following conditions and loads: building width, 32 feet; wall height, 9 feet; basement wall height, 8 feet; dead loads, 15 psf roof and ceiling assembly,
10 psf floor assembly, 12 psf wall assembly; live loads, roof and ground snow loads as listed, 40 psf first floor, 30 psf second and third floors. Footing sizes are calculated
assuming a clear span roof/ceiling assembly and an interior bearing wall or beam at each floor.
c. Where the building width perpendicular to the wall footing is greater than 32 feet, the footing width shall be increased by 2 inches and footing depth shall be increased by 1
inch for every 4 feet of increase in building width.
d. Where the building width perpendicular to the wall footing is less than 32 feet, a 2-inch decrease in footing width and 1-inch decrease in footing depth is permitted for every 4
feet of decrease in building width provided that the minimum width is 12 inches and minimum depth is 6 inches.
SLAB
ON GRADE
BASEMENT
CRAWL
SPACE

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FOUNDATIONS

FIGURE R403.1(1)—PLAIN CONCRETE FOOTINGS WITH MASONRY AND CONCRETE STEM WALLS IN SEISMIC DESIGN CATEGORIES A, B AND C [a, b, c, d, e, f]

For SI: 1 inch = 25.4 mm. W = Width of footing, T = Thickness of footing and P = Projection per Section R403.1.1.

NOTES:

a. See Section R404.3 for sill requirements. b. See Section R403.1.6 for sill attachment.

c. See Section R506.3.3 for vapor barrier requirements. d. See Section R403.1 for base.

e. See Figure R403.1.3 for additional footing requirements for structures in Seismic Design Categories D 0, D 1 and D 2 and townhouses in Seismic Design Category C. f. See Section R408 for under-floor ventilation and access requirements.

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FOUNDATIONS

FIGURE R403.1(2)—PERMANENT WOOD FOUNDATION BASEMENT WALL SECTION

PRESSURE-PRESERVATIVE TREATED

FLASHING

FIELD-APPLIED 2 � 6 IN. TOP PLATE

2 � 6 IN. TOP PLATE

MIN. 3.5-IN. CONCRETE SLAB WITH s

VAPOR BARRIER AND OPTIONAL

1-IN. SCREED BOARD

2 � 6 IN. STUD INSULATED

AS APPROPRIATE AND WARM SIDE

VAPOR BARRIER

FINISH GRADE SLOPE [1] / 2 IN. PER FOOT, MIN. 6 FT. FROM WALL

PRESSURE-PRESERVATIVETREATED PLYWOOD (SEE TABLE R404.2.3)

6 MIL POLYETHYLENE FILM

6 MIL POLYETHYLENE FILM ON CRUSHED STONE OR GRAVEL BACKFILL

PRESSURE-PRESERVATIVE TREATED 2 � 6 IN. BOTTOM

STONE FILL UNDER FLOOR (SEE SECTION R403.2)

6 IN.

For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mil = 0.0254 mm.

FIGURE R403.1(3)—PERMANENT WOOD FOUNDATION CRAWL SPACE SECTION

PRESSURE-PRESERVATIVE TREATED

6 MIL POLYETHYLENE FILM

6 IN.

6 IN. GRAVEL OR CRUSHED STONE (SEE SECTION R403.2)

For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mil = 0.0254 mm.

FINISH GRADE SLOPE [1] / 2 IN. PER FOOT, MIN. 6 FT. FROM WALL

16 IN.

PRESSURE-PRESERVATIVE TREATED 2 � 6 IN. STUD WALL

PRESSURE-PRESERVATIVE TREATED PLYWOOD (SEE TABLE R404.2.3)

PRESSURE-PRESERVATIVE TREATED 2 � 6 IN. BOTTOM PLATE

PRESSURE-PRESERVATIVE TREATED 2 � 8 IN. FOOTING PLATE

BELOW FROST LINE

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�

FOUNDATIONS

R403.1.1 Minimum size. The minimum width, W, and thickness, T, for concrete footings shall be in accordance with Tables R403.1(1) through R403.1(3) and Figure R403.1(1) or R403.1.3, as applicable, but not less than 12 inches (305 mm) in width and 6 inches (152 mm) in depth. The footing width shall be based on the load-bearing value of the soil in accordance with Table R401.4.1(1). Footing projections, P, shall be not less than 2 inches (51 mm) and shall not exceed the thickness of the footing. Footing thickness and projection for fireplaces shall be in accordance with Section R1001.2. The size of footings supporting piers and columns shall be based on the tributary load and allowable soil pressure in accordance with Table R401.4.1(1). Footings for wood foundations shall be in accordance with the details set forth in Section R403.2, and Figures R403.1(2) and R403.1(3). Footings for precast foundations shall be in accordance with the details set forth in Section R403.4, Table R403.4, and Figures R403.4(1) and R403.4(2). Crushed stone footings for cast-in-place concrete foundations shall be in accordance with Section R403.5.

R403.1.2 Continuous footing in Seismic Design Categories D 0 , D 1 and D 2 . Exterior walls and required interior braced wall panels of buildings located in Seismic Design Categories D 0, D 1 and D 2 shall be supported by continuous solid or fully grouted masonry or concrete footings in accordance with Table R403.1.2. Other footing materials or systems shall be designed in accordance with accepted engineering practice.

TABLE R403.1.2—CONTINUOUS FOOTING REQUIREMENTS IN SEISMIC DESIGN CATEGORIES D, D AND D
0 1 2

For SI: 1 foot = 304.8 mm.
R = Continuous solid or fully grouted masonry or concrete footings in accordance with Section R403.1.3.4 required.
NR = Continuous footings not required.
a. Buildings shall be permitted to have interior braced wall panels supported on continuous foundations at intervals not exceeding 50 feet, provided that the following condi-
tions are all met:
1. The height of cripple walls does not exceed 4 feet.
2. First-floor braced wall panels are supported on doubled floor joists, continuous blocking or floor beams.
3. The distance between bracing lines does not exceed twice the building width measured parallel to the braced wall line.

R403.1.3 Footing and stem wall reinforcing in Seismic Design Categories D 0 , D 1 and D 2 . Concrete footings located in Seismic Design Categories D 0, D 1 and D 2, as established in Table R301.2, shall have minimum reinforcement in accordance with this section and Figure R403.1.3. Reinforcement shall be installed with support and cover in accordance with Section R403.1.3.5.

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FOUNDATIONS

FIGURE R403.1.3—REINFORCED CONCRETE FOOTINGS AND MASONRY AND CONCRETE STEM WALLS IN SDC D 0 , D 1 AND D 2a, b, c, d, e, f

W = Width of footing, T = Thickness of footing and P = Projection per Section R403.1.1.

NOTES:

a. See Section R404.3 for sill requirements. b. See Section R403.1.6 for sill attachment.

c. See Section R506.3.3 for vapor barrier requirements. d. See Section R403.1 for base.

e. See Section R408 for under-floor ventilation and access requirements. f. See Section R403.1.3.5 for reinforcement requirements.

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FOUNDATIONS

R403.1.3.1 Concrete stem walls with concrete footings. In Seismic Design Categories D 0, D 1 and D 2 where a construction joint is created between a concrete footing and a concrete stem wall, not fewer than one No. 4 vertical bar shall be installed at not more than 4 feet (1219 mm) on center. The vertical bar shall have a standard hook and extend to the bottom of the footing and shall have support and cover as specified in Section R403.1.3.5.3 and extend not less than 14 inches (357 mm) into the stem wall. Standard hooks shall comply with Section R608.5.4.5. Not fewer than one No. 4 horizontal bar shall be installed within 12 inches (305 mm) of the top of the stem wall and one No. 4 horizontal bar shall be located 3 to 4 inches (76 mm to 102 mm) from the bottom of the footing.

R403.1.3.2 Masonry stem walls with concrete footings. In Seismic Design Categories D 0, D 1 and D 2 where a masonry stem wall is supported on a concrete footing, not fewer than one No. 4 vertical bar shall be installed at not more than 4 feet (1219 mm) on center. The vertical bar shall have a standard hook and extend to the bottom of the footing and shall have support and cover as specified in Section R403.1.3.5.3 and extend not less than 14 inches (357 mm) into the stem wall. Standard hooks shall comply with Section R608.5.4.5. Not fewer than one No. 4 horizontal bar shall be installed within 12 inches (305 mm) of the top of the wall and one No. 4 horizontal bar shall be located 3 to 4 inches (76 mm to 102 mm) from the bottom of the footing. Masonry stem walls shall be solid grouted.

R403.1.3.3 Slabs-on-ground with turned-down footings. In Seismic Design Categories D 0, D 1 and D 2, slabs-on-ground cast monolithically with turned-down footings shall have not fewer than one No. 4 bar at the top and the bottom of the footing or one No. 5 bar or two No. 4 bars in the middle third of the footing depth.

Where the slab is not cast monolithically with the footing, No. 3 or larger vertical dowels with standard hooks on each end shall be installed at not more than 4 feet (1219 mm) on center in accordance with Figure R403.1.3, Detail 2. Standard hooks shall comply with Section R608.5.4.5.

R403.1.3.4 Interior bearing and braced wall panel footings in Seismic Design Categories D 0 , D 1 and D 2 . In Seismic Design Categories D 0, D 1 and D 2, interior footings supporting bearing walls or braced wall panels, and cast monolithically with a slab on grade, shall extend to a depth of not less than 12 inches (305 mm) below the top of the slab.

R403.1.3.5 Reinforcement. Footing and stem wall reinforcement shall comply with Sections R403.1.3.5.1 through R403.1.3.5.4.

R403.1.3.5.1 Steel reinforcement. Steel reinforcement shall comply with the requirements of ASTM A615, A706M or A996M. ASTM A996M bars produced from rail steel shall be Type R. The minimum yield strength of reinforcing steel shall be 40,000 psi (Grade 40) (276 MPa).

R403.1.3.5.2 Location of reinforcement in wall. The center of vertical reinforcement in stem walls shall be located at the centerline of the wall. Horizontal and vertical reinforcement shall be located in footings and stem walls to provide the minimum cover required by Section R403.1.3.5.3.

R403.1.3.5.3 Support and cover. Reinforcement shall be secured in the proper location in the forms with tie wire or other bar support system to prevent displacement during the concrete placement operation. Steel reinforcement in concrete cast against the earth shall have a minimum cover of 3 inches (75 mm). Minimum cover for reinforcement in concrete cast in removable forms that will be exposed to the earth or weather shall be 1 [1] / 2 inches (38 mm) for No. 5 bars and smaller, and 2 inches (50 mm) for No. 6 bars and larger. For concrete cast in removable forms that will not be exposed to the earth or weather, and for concrete cast in stay-in-place forms, minimum cover shall be [3] / 4 inch (19 mm).

R403.1.3.5.4 Lap splices. Vertical and horizontal reinforcement shall be the longest lengths practical. Where splices are necessary in reinforcement, the length of lap splice shall be in accordance with Table R608.5.4(1) and Figure R608.5.4(1). The maximum gap between noncontact parallel bars at a lap splice shall not exceed the smaller of one-fifth the required lap length and 6 inches (152 mm) [see Figure R608.5.4(1)].

R403.1.3.6 Isolated concrete footings. In detached one- and two-family dwellings that are three stories or less in height and constructed with stud bearing walls, isolated plain concrete footings supporting columns or pedestals are permitted.

R403.1.4 Minimum depth. Exterior footings shall be placed not less than 12 inches (305 mm) below the undisturbed ground surface. Where applicable, the depth of footings shall also conform to Section R403.1.4.1. Deck footings shall be in accordance with Section R507.3.

R403.1.4.1 Frost protection. Except where otherwise protected from frost, foundation walls, piers and other permanent supports of buildings and structures shall be protected from frost by one or more of the following methods:

1. Extended below the frost line specified in Table R301.2.

2. Constructed in accordance with Section R403.3.

3. Constructed in accordance with ASCE 32.

4. Erected on solid rock.

Footings shall not bear on frozen soil unless the frozen condition is permanent.

Exceptions:

1. Protection of free-standing accessory structures with an area of 600 square feet (56 m [2] ) or less, of light-frame construction, with an eave height of 10 feet (3048 mm) or less shall not be required.
2. Protection of free-standing accessory structures with an area of 400 square feet (37 m [2] ) or less, of other than lightframe construction, with an eave height of 10 feet (3048 mm) or less shall not be required.

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FOUNDATIONS

R403.1.5 Slope. The top surface of footings shall be level. The bottom surface of footings shall not have a slope exceeding 1 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 footings or where the slope of the bottom surface of the footings will exceed 1 unit vertical in 10 units horizontal (10percent slope).

R403.1.6 Foundation anchorage. Wood sill plates and wood walls supported directly on continuous foundations shall be anchored to the foundation in accordance with this section.

Cold-formed steel framing shall be anchored directly to the foundation or fastened to wood sill plates in accordance with Section R505.3.1 or R603.3.1, as applicable. Wood sill plates supporting cold-formed steel framing shall be anchored to the foundation in accordance with this section.

Wood sole plates at all exterior walls on monolithic slabs, wood sole plates of braced wall panels at building interiors on monolithic slabs and all wood sill plates shall be anchored to the foundation with minimum [1] / 2 -inch-diameter (12.7 mm) anchor bolts spaced not greater than 6 feet (1829 mm) on center or approved anchors or anchor straps spaced as required to provide equivalent anchorage to [1] / 2 -inch-diameter (12.7 mm) anchor bolts. Bolts shall extend not less than 7 inches (178 mm) into concrete or grouted cells of concrete masonry units. The bolts shall be located in the middle third of the width of the plate. A nut and washer shall be tightened on each anchor bolt. There shall be not fewer than two bolts per plate section with one bolt located not more than 12 inches (305 mm) or less than seven bolt diameters from each end of the plate section. Interior bearing wall sole plates on monolithic slab foundation that are not part of a braced wall panel shall be positively anchored with approved fasteners. Sill plates and sole plates shall be protected against decay and termites where required by Sections R304 and R305. Anchor bolts shall be permitted to be located while concrete is still plastic and before it has set. Where anchor bolts resist placement or the consolidation of concrete around anchor bolts is impeded, the concrete shall be vibrated to ensure full contact between the anchor bolts and concrete.

Exceptions:

1. Walls 24 inches (610 mm) total length or shorter connecting offset braced wall panels shall be anchored to the foundation with not fewer than one anchor bolt located in the center third of the plate section and shall be attached to adjacent braced wall panels at corners as shown in Item 9 of Table R602.3(1).
2. Connection of walls 12 inches (305 mm) total length or shorter connecting offset braced wall panels to the foundation without anchor bolts shall be permitted. The wall shall be attached to adjacent braced wall panels at corners as shown in Item 9 of Table R602.3(1).

third of the plate section and shall be attached to adjacent braced wall panels at corners as shown in Item 9 of Table R602.3(1). 2. Connection of walls 12 inches (305 mm) total length or shorter connecting offset braced wall panels to the foundation without anchor bolts shall be permitted. The wall shall be attached to adjacent braced wall panels at corners as shown in Item 9 of Table R602.3(1).

R403.1.6.1 Foundation anchorage in Seismic Design Categories C, D 0 , D 1 and D 2 . In addition to the requirements of Section R403.1.6, the following requirements shall apply to wood light-frame structures in Seismic Design Categories D 0, D 1 and D 2 and wood light-frame townhouses in Seismic Design Category C.

1. Plate washers conforming to Section R602.11.1 shall be provided for all anchor bolts over the full length of required braced wall lines except where approved anchor straps are used. Properly sized cut washers shall be permitted for anchor bolts in wall lines not containing braced wall panels.
2. Interior braced wall plates shall have anchor bolts spaced at not more than 6 feet (1829 mm) on center and located within 12 inches (305 mm) of the ends of each plate section where supported on a continuous foundation.
3. Interior bearing wall sole plates shall have anchor bolts spaced at not more than 6 feet (1829 mm) on center and located within 12 inches (305 mm) of the ends of each plate section where supported on a continuous foundation.
4. The maximum anchor bolt spacing shall be 4 feet (1219 mm) for buildings over two stories in height.
5. Stepped cripple walls shall conform to Section R602.11.2.
6. Where continuous wood foundations in accordance with Section R404.2 are used, the force transfer shall have a capacity equal to or greater than the connections required by Section R602.11.1 or the braced wall panel shall be connected to the wood foundations in accordance with the braced wall panel-to-floor fastening requirements of Table R602.3(1).

R403.1.7 Footings on or adjacent to slopes. The placement of buildings and structures on or adjacent to slopes steeper than 1 unit vertical in 3 units horizontal (33.3-percent slope) shall conform to Sections R403.1.7.1 through R403.1.7.4.

R403.1.7.1 Building clearances from ascending slopes. In general, buildings below slopes shall be set a sufficient distance from the slope to provide protection from slope drainage, erosion and shallow failures. Except as provided in Section R403.1.7.4 and Figure R403.1.7.1, the following criteria will be assumed to provide this protection. Where the existing slope is steeper than 1 unit vertical in 1 unit horizontal (100-percent slope), the toe of the slope shall be assumed to be at the intersection of a horizontal plane drawn from the top of the foundation and a plane drawn tangent to the slope at an angle of 45 degrees (0.79 rad) to the horizontal. Where a retaining wall is constructed at the toe of the slope, the height of the slope shall be measured from the top of the wall to the top of the slope.

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FOUNDATIONS

For SI: 1 foot = 304.8 mm.

FIGURE R403.1.7.1—FOUNDATION CLEARANCE FROM SLOPES

FACE OF

AT LEAST THE SMALLER OF H/2 AND 15 FEET

R403.1.7.2 Footing setback from descending slope surfaces. Footings on or adjacent to slope surfaces shall be founded in material with an embedment and setback from the slope surface sufficient to provide vertical and lateral support for the footing without detrimental settlement. Except as provided for in Section R403.1.7.4 and Figure R403.1.7.1, 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.

R403.1.7.3 Foundation elevation. On graded sites, the top of any exterior foundation shall extend above the elevation of the street gutter at point of discharge or the inlet of an approved drainage device not less than 12 inches (305 mm) plus 2 percent. Alternate elevations are permitted subject to the approval of the building official, provided that it can be demonstrated that required drainage to the point of discharge and away from the structure is provided at all locations on the site.

R403.1.7.4 Alternate setbacks and clearances. Alternate setbacks and clearances are permitted, subject to the approval of the building official. The building official is permitted to require an investigation and recommendation of a qualified engineer to demonstrate that the intent of this section has been satisfied. Such an investigation shall include consideration of material, height of slope, slope gradient, load intensity and erosion characteristics of slope material.

R403.1.8 Foundations on expansive soils. Foundation and floor slabs for buildings located on expansive soils shall be designed in accordance with Section 1808.6 of the California Building Code .

Exception: Slab-on-ground and other foundation systems that have performed adequately in soil conditions similar to those encountered at the building site are permitted subject to the approval of the building official.

R403.1.8.1 Expansive soils classifications. Soils meeting all of the following provisions shall be considered to be expansive, except that tests to show compliance with Items 1, 2 and 3 shall not be required if the test prescribed in Item 4 is conducted:

1. Plasticity Index (PI) of 15 or greater, determined in accordance with ASTM D4318.

2. More than 10 percent of the soil particles pass a No. 200 sieve (75 μ m), determined in accordance with ASTM D422.

3. More than 10 percent of the soil particles are less than 5 micrometers in size, determined in accordance with ASTM D422.

4. Expansion Index greater than 20, determined in accordance with ASTM D4829.

Footings for wood foundations shall be in accordance with Figures R403.1(2) and R403.1(3). Gravel shall be washed and well graded. The maximum size stone shall not exceed [3] / 4 inch (19.1 mm). Gravel shall be free from organic, clayey or silty soils. Sand shall be coarse, not smaller than [1] / 16 -inch (1.6 mm) grains and shall be free from organic, clayey or silty soils. Crushed stone shall have a maximum size of [1] / 2 inch (12.7 mm).

For buildings where the monthly mean temperature of the building is maintained at not less than 64°F (18°C), footings are not required to extend below the frost line where protected from frost by insulation in accordance with Figure R403.3(1) and Table R403.3(1). Foundations protected from frost in accordance with Figure R403.3(1) and Table R403.3(1) shall not be used for unheated spaces such as porches, utility rooms, garages and carports, and shall not be attached to basements or crawl spaces that are not maintained at a minimum monthly mean temperature of 64°F (18°C).

Materials used below grade for the purpose of insulating footings against frost shall be labeled as complying with ASTM C578.

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FOUNDATIONS

FIGURE R403.3(1)—INSULATION PLACEMENT FOR FROST-PROTECTED FOOTINGS IN HEATED BUILDINGS

INSULATION DETAIL

SLAB-ON-GROUND FOUNDATION FLOOR

R403.3.3

HORIZONTAL INSULATION PLAN

For SI: 1 inch = 25.4 mm.

a. See Table R403.3(1) for required dimensions and R -values for vertical and horizontal insulation and minimum footing depth.

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FOUNDATIONS

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FOUNDATIONS

TABLE R403.3(1)—MINIMUM FOOTING DEPTH AND
INSULATION REQUIREMENTS FOR FROST-PROTECTED FOOTINGS IN HEATED BUILDINGSa

For SI: 1 inch = 25.4 mm, °C = [(°F) – 32]/1.8.
a. Insulation requirements are for protection against frost damage in heated buildings. Greater values could be required to meet energy conservation standards.
b. See Figure R403.3(2) or Table R403.3(2) for Air-Freezing Index values.
c. Insulation materials shall provide the stated minimum_R_-values under long-term exposure to moist, below-ground conditions in freezing climates. The following_R_-values
shall be used to determine insulation thicknesses required for this application: Type II expanded polystyrene (EPS)-3.2 R per inch for vertical insulation and 2.6 R per inch for
horizontal insulation; Type IX expanded polystyrene (EPS)-3.4 R per inch for vertical insulation and 2.8 R per inch for horizontal insulation; Types IV, V, VI, VII, and X extruded
polystyrene (XPS)-4.5 R per inch for vertical insulation and 4.0 R per inch for horizontal insulation.
d. Vertical insulation shall be expanded polystyrene insulation or extruded polystyrene insulation.
e. Horizontal insulation shall be expanded polystyrene insulation or extruded polystyrene insulation.

TABLE R403.3(2)—AIR-FREEZING INDEX FOR US LOCATIONS BY COUNTY

FIGURE R403.3(3)—INSULATION PLACEMENT FOR

FROST-PROTECTED FOOTINGS ADJACENT TO UNHEATED SLAB-ON-GROUND STRUCTURE

INSULATION DETAIL

FINISH GRADE OR CONCRETE

SLAB-ON-GRADE STRUCTURE

FROST-PROTECTED SHALLOW

FOUNDATION SLAB-ON-GRADE

FLOOR PER SECTION R403.3

12″ MAX.

NOMINAL 4 SCREEN AND WASHED

DRAINED PER SECTION R403.3.3

C

BEAM LINTEL OR

CANTILEVER

TO CARRY LOAD

OVER NONLOAD

CONCRETE MASONRY OR

PERMANENT WOOD

FOUNDATION GRADE BEAM

OR WALL OF ADJACENT

UNHEATED STRUCTURE

FOOTING AS REQUIRED

For SI: 1 inch = 25.4 mm.

a. See Table R403.3(1) for required dimensions and R -values for vertical and horizontal insulation.

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FOUNDATIONS

FIGURE R403.3(4)—INSULATION PLACEMENT FOR FROST-PROTECTED FOOTINGS ADJACENT TO HEATED STRUCTURE

B

C

R403.3.1 Foundations adjoining frost-protected shallow foundations. Foundations that adjoin frost-protected shallow foundations shall be protected from frost in accordance with Section R403.1.4.

R403.3.1.1 Attachment to unheated slab-on-ground structure. Vertical wall insulation and horizontal insulation of frostprotected shallow foundations that adjoin a slab-on-ground foundation that does not have a monthly mean temperature maintained at not less than 64°F (18°C) shall be in accordance with Figure R403.3(3) and Table R403.3(1). Vertical wall insulation shall extend between the frost-protected shallow foundation and the adjoining slab foundation. Required horizontal insulation shall be continuous under the adjoining slab foundation and through any foundation walls adjoining the frostprotected shallow foundation. Where insulation passes through a foundation wall, it shall be either of a type complying with this section and having bearing capacity equal to or greater than the structural loads imposed by the building, or the building shall be designed and constructed using beams, lintels, cantilevers or other means of transferring building loads such that the structural loads of the building do not bear on the insulation.

on passes through a foundation wall, it shall be either of a type complying with this section and having bearing capacity equal to or greater than the structural loads imposed by the building, or the building shall be designed and constructed using beams, lintels, cantilevers or other means of transferring building loads such that the structural loads of the building do not bear on the insulation.

R403.3.1.2 Attachment to heated structure. Where a frost-protected shallow foundation abuts a structure that has a monthly mean temperature maintained at not less than 64°F (18°C), horizontal insulation and vertical wall insulation shall not be required between the frost-protected shallow foundation and the adjoining structure. Where the frost-protected shallow foundation abuts the heated structure, the horizontal insulation and vertical wall insulation shall extend along the adjoining foundation in accordance with Figure R403.3(4) a distance of not less than Dimension A in Table R403.3(1).

Exception: Where the frost-protected shallow foundation abuts the heated structure to form an inside corner, vertical insulation extending along the adjoining foundation is not required.

R403.3.2 Protection of horizontal insulation below ground. Horizontal insulation placed less than 12 inches (305 mm) below the ground surface or that portion of horizontal insulation extending outward more than 24 inches (610 mm) from the foundation edge shall be protected against damage by use of a concrete slab or asphalt paving on the ground surface directly above the insulation or by cementitious board, plywood rated for below-ground use, or other approved materials placed below ground, directly above the top surface of the insulation.

R403.3.3 Drainage. Final grade shall be sloped in accordance with Section R401.3. In other than Group I Soils, as detailed in Table R401.4.1(2), gravel or crushed stone beneath horizontal insulation below ground shall drain to daylight or into an approved sewer system.

R403.3.4 Termite protection. The use of foam plastic in areas of “very heavy” termite infestation probability shall be in accordance with Section R305.4.

Footings for precast concrete foundations shall comply with Section R403.4.

4-20 2025 CALIFORNIA RESIDENTIAL CODE

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FOUNDATIONS

FIGURE R403.4(1)—BASEMENT OR CRAWL SPACE WITH PRECAST FOUNDATION WALL BEARING ON CRUSHED STONE

on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

FOUNDATIONS

TABLE R403.4—MINIMUM DEPTH (D) AND WIDTH (W) OF CRUSHED STONE FOOTINGSa, b (inches)

For SI: 1 inch = 25.4 mm, 1 plf = 14.6 N/m, 1 pound per square foot = 47.9 N/m2.
a. Linear interpolation of stone depth between wall widths is permitted within each Load-Bearing Value of Soil (psf).
b. Crushed stone must be consolidated in 8-inch lifts with a plate vibrator.
c. Soil classes are in accordance with the Unified Soil Classification System. Refer to Table R401.4.1(2).

R403.4.1 Crushed stone footings. Clean crushed stone shall be free from organic, clayey or silty soils. Crushed stone shall be angular in nature and meet ASTM C33, with the maximum size stone not to exceed [1] / 2 inch (12.7 mm) and the minimum stone size not to be smaller than [1] / 16 inch (1.6 mm). Crushed stone footings for precast foundations shall be installed in accordance with Figure R403.4(1) and Table R403.4. Crushed stone footings shall be consolidated using a vibratory plate in not greater than 8-inch (203 mm) lifts. Crushed stone footings shall be limited to Seismic Design Categories A, B and C.

R403.4.2 Concrete footings. Concrete footings shall be installed in accordance with Section R403.1 and Figure R403.4(2).

Crushed stone footings in accordance with Section R403.4.1 shall be permitted for nonretaining cast-in-place concrete foundations complying with Section R404.1.3 and this section. The footing and foundation wall shall be installed in accordance with Figure R403.5(1), or Figure R403.5(2) and Table R403.5, or Figure R403.5(3). Crushed stone footings for cast-in-place concrete foundations shall be permitted for townhouses in Seismic Design Categories A and B and one- and two-family dwellings in Seismic Design Categories A, B and C.

4-22 2025 CALIFORNIA RESIDENTIAL CODE

on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

FOUNDATIONS

FIGURE R403.5(1)—CRUSHED STONE FOOTINGS FOR CAST-IN-PLACE CONCRETE FOUNDATIONS IN SEISMIC DESIGN CATEGORIES A, B, AND C AND WIND EXPOSURE CATEGORIES B, C, AND D: CAST-IN-PLACE CONCRETE FOUNDATION WALL WITH WOOD CRIPPLE WALL

MIN. CLEARANCE PER

SECTIONS R404.1.6 AND

R304.1 TYP.

TOP OF FOOTING MIN. 4 IN.

BELOW UNDISTURBED GROUND

SURFACE

12 IN. MIN. FOOTING DEPTH PER

SECTION R403.1.4

GREATER DEPTH FOR FROST

PROTECTION WHERE

APPLIABLE PER SECTION

R403.1.4.1

NOT TO SCALE

For SI: 1 inch = 25.4 mm, 1 foot = 304.5 mm.

CAST-IN-PLACE CONCRETE

FOUNDATION WALL PER TABLE

R403.5 W/ #4 HORIZONTAL REBAR @ 18" OC. MIN.

PLACE ONE #4 REBAR W/ 3" CLEAR

FROM BOTTOM AND ONE #4 REBAR

W/ 2" CLR FROM TOP

TOP OF FOOTING MIN. 4 IN.

BELOW UNDISTURBED GROUND

SURFACE

12 IN. MIN. FOOTING DEPTH PER

SECTION R403.1.4

AREA OF EXTENDED CRUSHED

STONE FOOTING DEPTH AT

WIDTH 'W' TO BELOW FROST

LINE WHERE APPLICABLE

NOT TO SCALE

For SI: 1 inch = 25.4 mm, 1 foot = 304.5 mm.

on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

FOUNDATIONS

FIGURE R403.5(3)—CRUSHED STONE FOOTINGS FOR CAST-IN-PLACE CONCRETE FOUNDATIONS IN SEISMIC DESIGN CATEGORIES A, B, AND C AND WIND EXPOSURE CATEGORIES B, C, AND D: CONCRETE SLAB-ON-GROUND WITH TURNED DOWN FOUNDATION

SILL PLATE AND ANCHORAGE

PER SECTION R403.5 ANCHORS

WITH 7" MIN. EMBEDMENT

MIN. CLEARANCE PER

SECTIONS R404.1.6 AND

R304.1 TYP.

TOP OF FOOTING MIN. 4 IN.

BELOW UNDISTURBED GROUND

SURFACE

12 IN. MIN. FOOTING DEPTH PER

SECTION R403.1.4

GREATER DEPTH FOR FROST

PROTECTION WHERE

APPLICABLE PER SECTION

R403.1.4.1

NOT TO SCALE

For SI: 1 inch = 25.4 mm, 1 foot = 304.5 mm.

TABLE R403.5—MINIMUM CAST-IN-PLACE CONCRETE FOUNDATION WALL
DIMENSIONS, REINFORCEMENT AND MAXIMUM BRACED WALL LINE SPACING