The provisions of this chapter shall control the design and construction of the foundation and foundation spaces for all buildings. In addition to the provisions of this chapter, the design and construction of foundations in areas prone to flooding as established by Table R301.2(1) shall meet the provisions of Section R322. Wood foundations shall be designed and installed in accordance with AF&PA PWF.
Exception: The provisions of this chapter shall be permitted to be used for wood foundations only in the following situations:
1. In buildings that have no more than two floors and a roof.
2. When interior basement and foundation walls are constructed at intervals not exceeding 50 feet (15 240 mm).
Wood foundations in Seismic Design Category D0, D1 or D2 shall be designed in accordance with accepted engineering practice.
Surface drainage shall be diverted to a storm sewer conveyance or other approved point of collection that does not create a hazard. Lots shall be graded to drain surface water away from foundation walls. The grade shall fall a minimum of 6 inches (152 mm)within the first 10 feet (3048 mm).
Exception: Where lot lines, walls, slopes or other physical barriers prohibit 6 inches (152 mm) of fall within 10 feet (3048 mm), drains or swales shall be constructed to ensure drainage away from the structure. Impervious surfaces within 10 feet (3048 mm) of the building foundation shall be sloped a minimum of 2 percent away from the building.
In lieu of a complete geotechnical evaluation, the load-bearing values in Table R401.4.1 shall be assumed.
TABLE R401.4.1
PRESUMPTIVE LOAD-BEARING VALUES OF
FOUNDATION MATERIALSa
| CLASS OF MATERIAL | LOAD-BEARING PRESSURE |
| Crystalline bedrock | 12,000 |
| Sedimentary and foliated rock | 4,000 |
| Sandy gravel and/or gravel (GW and GP) | 3,000 |
| Sand, silty sand, clayey sand, silty gravel and clayey gravel (SW, SP, SM, SC, GM and GC) | 2,000 |
| Clay, sandy clay, silty clay, clayey silt, silt and sandy silt (CL, ML, MH and CH) | 1,500b |
For SI: 1 pound per square foot = 0.0479 kPa.
a. When soil tests are required by Section R401.4, the allowable bearing capacities of the soil shall be part of the recommendations.
b. Where the building official determines that in-place soils with an allowable bearing capacity of less than 1,500 psf are likely to be present at the site, the allowable bearing capacity shall be determined by a soils investigation.
Concrete shall have a minimum specified compressive strength of f 'c , as shown in Table R402.2. Concrete subject to moderate or severe weathering as indicated in Table R301.2(1) shall be air entrained as specified in Table R402.2. The maximum weight of fly ash, other pozzolans, silica fume, slag or blended cements that is included in concrete mixtures for garage floor slabs and for exterior porches, carport slabs and steps that will be exposed to deicing chemicals shall not exceed the percentages of the total weight of cementitious materials specified in Section 4.2.3 of ACI 318. Materials used to produce concrete and testing thereof shall comply with the applicable standards listed in Chapter 3 of ACI 318 or ACI 332.
TABLE R402.2
MINIMUM SPECIFIED COMPRESSIVE STRENGTH OF CONCRETE
| TYPE OR LOCATION OF CONCRETE CONSTRUCTION | MINIMUM SPECIFIED COMPRESSIVE STRENGTHa (f 'c) | ||
| Weathering Potentialb | |||
| Negligible | Moderate | Severe | |
| Basement walls, foundations and other concrete not exposed to the weather | 2,500 | 2,500 | 2,500c |
| Basement slabs and interior slabs on grade, except garage floor slabs | 2,500 | 2,500 | 2,500c |
| Basement walls, foundation walls, exterior walls and other vertical concrete work exposed to the weather | 2,500 | 3,000d | 3,000d |
| Porches, carport slabs and steps exposed to the weather, and garage floor slabs | 2,500 | 3,000d, e, f | 3,500d, e, f |
For SI: 1 pound per square inch = 6.895 kPa.
a. Strength at 28 days psi.
b. See Table R301.2(1) for weathering potential.
c. Concrete in these locations that may be subject to freezing and thawing during construction shall be air-entrained concrete in accordance with Footnote d.
d. Concrete shall be air-entrained. Total air content (percent by volume of concrete) shall be not less than 5 percent or more than 7 percent.
e. See Section R402.2 for maximum cementitious materials content.
f. For garage floors with a steel troweled finish, reduction of the total air content (percent by volume of concrete) to not less than 3 percent is permitted if the specified compressive strength of the concrete is increased to not less than 4,000 psi.
Materials used to produce precast concrete foundations shall meet the following requirements.
1. All concrete used in the manufacture of precast concrete foundations shall have a minimum compressive strength of 5,000 psi (34 470 kPa) at 28 days. Concrete exposed to a freezing and thawing environment shall be air entrained with a minimum total air content of 5 percent.
2. Structural reinforcing steel shall meet the requirements of ASTM A 615, A 706 or A 996. The minimum yield strength of reinforcing steel shall be 40,000 psi (Grade 40) (276 MPa). Steel reinforcement for precast concrete foundation walls shall have a minimum concrete cover of 3/4 inch (19.1 mm).
3. Panel-to-panel connections shall be made with Grade II steel fasteners.
4. The use of nonstructural fibers shall conform to ASTM C 1116.
5. Grout used for bedding precast foundations placed upon concrete footings shall meet ASTM C 1107.
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 which 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.
TABLE R403.1
MINIMUM WIDTH OF CONCRETE,
PRECAST OR MASONRY FOOTINGS
(inches)a
| LOAD-BEARING VALUE OF SOIL (psf) | ||||
| 1,500 | 2,000 | 3,000 | ≥ 4,000 | |
| Conventional light-frame construction | ||||
| 1-story | 12 | 12 | 12 | 12 |
| 2-story | 15 | 12 | 12 | 12 |
| 3-story | 23 | 17 | 12 | 12 |
| 4-inch brick veneer over light frame or 8-inch hollow concrete masonry | ||||
| 1-story | 12 | 12 | 12 | 12 |
| 2-story | 21 | 16 | 12 | 12 |
| 3-story | 32 | 24 | 16 | 12 |
| 8-inch solid or fully grouted masonry | ||||
| 1-story | 16 | 12 | 12 | 12 |
| 2-story | 29 | 21 | 14 | 12 |
| 3-story | 42 | 32 | 21 | 16 |
For SI: 1 inch = 25.4 mm, 1 pound per square foot = 0.0479 kPa.
a. Where minimum footing width is 12 inches, use of a single wythe of solid or fully grouted 12-inch nominal concrete masonry units is permitted.
Minimum sizes for concrete and masonry footings shall be as set forth in Table R403.1 and Figure R403.1(1). The footing width, W, shall be based on the load-bearing value of the soil in accordance with Table R401.4.1. Spread footings shall be at least 6 inches (152 mm) in thickness, T. Footing projections, P, shall be at least 2 inches (51 mm) and shall not exceed the thickness of the footing. 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. 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).
For SI: 1 inch = 25.4 mm.
FIGURE R403.1(1)
CONCRETE AND MASONRY FOUNDATION DETAILS
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mil = 0.0254 mm.
FIGURE R403.1(2)
PERMANENT WOOD FOUNDATION BASEMENT WALL SECTION
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
Concrete footings located in Seismic Design Categories D0, D1 and D2, as established in Table R301.2(1), shall have minimum reinforcement. Bottom reinforcement shall be located a minimum of 3 inches (76 mm) clear from the bottom of the footing.
In Seismic Design Categories D0, D1 and D2 where a construction joint is created between a concrete footing and a stem wall, a minimum of one No. 4 bar shall be installed at not more than 4 feet (1219 mm) on center. The vertical bar shall extend to 3 inches (76 mm) clear of the bottom of the footing, have a standard hook and extend a minimum of 14 inches (357 mm) into the stem wall.
In Seismic Design Categories D0, D1 and D2 where a grouted masonry stem wall is supported on a concrete footing and stem wall, a minimum of one No. 4 bar shall be installed at not more than 4 feet (1219 mm) on center. The vertical bar shall extend to 3 inches (76 mm) clear of the bottom of the footing and have a standard hook.
In Seismic Design Categories D0, D1 and D2 masonry stem walls without solid grout and vertical reinforcing are not permitted.
Exception: In detached one- and two-family dwellings which are three stories or less in height and constructed with stud bearing walls, plain concrete footings without longitudinal reinforcement supporting walls and isolated plain concrete footings supporting columns or pedestals are permitted.
Slabs on ground with turned down footings shall have a minimum of one No. 4 bar at the top and the bottom of the footing.
Exception: For slabs-on-ground cast monolithically with the footing, locating one No. 5 bar or two No. 4 bars in the middle third of the footing depth shall be permitted as an alternative to placement at the footing top and bottom.
Where the slab is not cast monolithically with the footing, No. 3 or larger vertical dowels with standard hooks on each end shall be provided in accordance with Figure R403.1.3.2. Standard hooks shall comply with Section R611.5.4.5.
For SI: 1 inch = 25.4 mm.
FIGURE R403.1.3.2
DOWELS FOR SLABS-ON-GROUND WITH TURNED-DOWN FOOTINGS
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.(1);
2. Constructing in accordance with Section R403.3;
3. Constructing in accordance with ASCE 32; or
4. Erected on solid rock.
Exceptions:
1. Protection of freestanding accessory structures with an area of 600 square feet (56 m2) or less, of light-frame construction, with an eave height of 10 feet (3048 mm) or less shall not be required.
2. Protection of freestanding accessory structures with an area of 400 square feet (37 m2) or less, of other than light-frame construction, with an eave height of 10 feet (3048 mm) or less shall not be required.
3. Decks not supported by a dwelling need not be provided with footings that extend below the frost line.
Footings shall not bear on frozen soil unless the frozen condition is permanent.
Sill plates and walls supported directly on continuous foundations 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 anchor bolts spaced a maximum of 6 feet (1829 mm) on center. Bolts shall be at least 1/2 inch (12.7 mm) in diameter and shall extend a minimum of 7 inches (178 mm) into concrete or grouted cells of concrete masonry units. A nut and washer shall be tightened on each anchor bolt. There shall be a minimum of 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 R317 and R318. Cold-formed steel framing systems shall be fastened to wood sill plates or anchored directly to the foundation as required in Section R505.3.1 or R603.3.1.
Exceptions:
1. Foundation anchorage, spaced as required to provide equivalent anchorage to 1/2-inch-diameter (12.7 mm) anchor bolts.
2. Walls 24 inches (610 mm) total length or shorter connecting offset braced wall panels shall be anchored to the foundation with a minimum of 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 Figure R602.10.4.4(1).
3. 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 Figure R602.10.4.4(1).
0, D1 and D2. In addition to the requirements of Section R403.1.6, the following requirements shall apply to wood light-frame structures in Seismic Design Categories D0, D1 and D2 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 when 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 when 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).
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 one unit vertical in one 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.
For SI: 1 foot = 304.8 mm.
FIGURE R403.1.7.1
FOUNDATION CLEARANCE FROM SLOPES
Foundation and floor slabs for buildings located on expansive soils shall be designed in accordance with Section 1805.8 of the International Building Code.
Exception: Slab-on-ground and other foundation systems which have performed adequately in soil conditions similar to those encountered at the building site are permitted subject to the approval of the building official.
Soils meeting all four of the following provisions shall be considered 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 D 4318.
2. More than 10 percent of the soil particles pass a No. 200 sieve (75 mm), determined in accordance with ASTM D 422.
3. More than 10 percent of the soil particles are less than 5 micrometers in size, determined in accordance with ASTM D 422.
4. Expansion Index greater than 20, determined in accordance with ASTM D 4829.
For buildings where the monthly mean temperature of the building is maintained at a minimum of 64°F (18°C), footings are not required to extend below the frost line when 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 C 578.
Foundations that adjoin frost protected shallow foundations shall be protected from frost in accordance with Section R403.1.4.
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.
FIGURE R403.3(1)
INSULATION PLACEMENT FOR FROST PROTECTED FOOTINGS IN HEATED BUILDINGS
TABLE R403.3(1)
MINIMUM FOOTING DEPTH AND INSULATION REQUIREMENTS FOR FROST-PROTECTED FOOTINGS IN HEATED BUILDINGSa
| AIR FREEZING INDEX (°F-days)b | MINIMUM | VERTICAL INSULATION | HORIZONTAL INSULATION R-VALUEc, e | HORIZONTAL INSULATION DIMENSIONS | |||
| Along walls | At corners | A | B | C | |||
| 1,500 or less | 12 | 4.5 | Not required | Not required | Not required | Not required | Not required |
| 2,000 | 14 | 5.6 | Not required | Not required | Not required | Not required | Not required |
| 2,500 | 16 | 6.7 | 1.7 | 4.9 | 12 | 24 | 40 |
| 3,000 | 16 | 7.8 | 6.5 | 8.6 | 12 | 24 | 40 |
| 3,500 | 16 | 9.0 | 8.0 | 11.2 | 24 | 30 | 60 |
| 4,000 | 16 | 10.1 | 10.5 | 13.1 | 24 | 36 | 60 |
a. Insulation requirements are for protection against frost damage in heated buildings. Greater values may 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—2.4R per inch; Type IV extruded polystyrene— 4.5R per inch; Type VI extruded polystyrene—4.5R per inch; Type IX expanded polystyrene—3.2R per inch; Type X extruded polystyrene—4.5R per inch.
d. Vertical insulation shall be expanded polystyrene insulation or extruded polystyrene insulation.
For SI: C = [(F) -32]/1.8.
Note: The air-freezing index is defined as cumulative degree days below 32F. It is used as a measure of the combined magnitude and duration of air temperature below freezing. The index was computed over a 12-month period (July-June) for each of the 3,044 stations used in the above analysis. Date from the 1951-80 period were fitted to a Weibull probability distribution to produce an estimate of the 100-year return period.
FIGURE R403.3(2)
AIR-FREEZING INDEX
AN ESTIMATE OF THE 100-YEAR RETURN PERIOD
TABLE R403.3(2)
AIR-FREEZING INDEX FOR U.S. LOCATIONS BY COUNTY
| STATE | AIR-FREEZING INDEX | |||||
| 1500 or less | 2000 | 2500 | 3000 | 3500 | 4000 | |
| Alabama | All counties | — | — | — | — | — |
| Alaska | Ketchikan Gateway, | — | Aleutians West | — | — | All counties not listed |
| Arizona | All counties | — | — | — | — | — |
| Arkansas | All counties | — | — | — | — | — |
| California | All counties not listed | Nevada, Sierra | — | — | — | — |
| Colorado | All counties not listed | Archuleta, Custer, | Clear Creek, | Alamosa, Grand, | Chaffee, Gunnison, Lake, Saguache | Hinsdale, |
| Connecticut | All counties not listed | Hartford, | — | — | — | — |
| Delaware | All counties | — | — | — | — | — |
| District of Columbia | All counties | — | — | — | — | — |
| Florida | All counties | — | — | — | — | — |
| Georgia | All counties | — | — | — | — | — |
| Hawaii | All counties | — | — | — | — | — |
| Idaho | All counties not listed | Adams, Bannock, | Bingham, | Bear Lake, | Clark | — |
| Illinois | All counties not listed | Boone, Bureau, Cook, | Carroll, Ogle, Stephenson, Winnebago | — | — | — |
| Indiana | All counties not listed | Allen, Benton, Cass, Fountain, Fulton, Howard, Jasper, Kosciusko, | — | — | — | — |
(continued)
TABLE R403.3(2)—continued
AIR-FREEZING INDEX FOR U.S. LOCATIONS BY COUNTY
| STATE | AIR-FREEZING INDEX | |||||
| 1500 or less | 2000 | 2500 | 3000 | 3500 | 4000 | |
| Iowa | Appanoose, Davis, | All counties not listed | Allamakee, Black Hawk, Boone, Bremer, Buchanan, Buena Vista, Butler, Calhoun, Cerro Gordo, Cherokee, Chickasaw, Clay, Clayton, Delaware, Dubuque, Fayette, Floyd, Franklin, Grundy, Hamilton, Hancock, Hardin, Humboldt, Ida, Jackson, Jasper, Jones, Linn, Marshall, | Dickinson, Emmet, Howard, Kossuth, Lyon, Mitchell, O’Brien, Osceola, Winneshiek | — | — |
| Kansas | All counties | — | — | — | — | — |
| Kentucky | All counties | — | — | — | — | — |
| Louisiana | All counties | — | — | — | — | — |
| Maine | York | Knox, Lincoln, Sagadahoc | Androscoggin, Cumberland, Hancock, Kennebec, Waldo, Washington | Aroostook, Franklin, Oxford, Penobscot, Piscataquis, Somerset | — | — |
| Maryland | All counties | — | — | — | — | — |
| Massachusetts | All counties not listed | Berkshire, Franklin, Hampden, Worcester | — | — | — | — |
| Michigan | Berrien, Branch, Cass, Kalamazoo, Macomb, Ottawa, | All counties not listed | Alger, Charlevoix, Cheboygan, Chippewa, Crawford, Delta, Emmet, Iosco, Kalkaska, Lake, Luce, Mackinac, Menominee, Missaukee, Montmorency, Ogemaw, Osceola, Otsego, Roscommon, Schoolcraft, Wexford | Baraga, Dickinson, Iron, Keweenaw, Marquette | Gogebic, Houghton, Ontonagon | — |
| Minnesota | — | — | Houston, Winona | All counties not listed | Aitkin, | Becker, Beltrami, Cass, Clay, Clearwater, Grant, Hubbard, Kittson, Koochiching, Lake of the Woods, Mahnomen, Marshall, Norman, St Louis, Traverse, Wilkin |
| Mississippi | All counties | — | — | — | — | — |
| Missouri | All counties not listed | Atchison, Mercer, Nodaway, Putnam | — | — | — | — |
(continued)
TABLE R403.3(2)—continued
AIR-FREEZING INDEX FOR U.S. LOCATIONS BY COUNTY
| STATE | AIR-FREEZING INDEX | |||||
| 1500 or less | 2000 | 2500 | 3000 | 3500 | 4000 | |
| Montana | Mineral | Broadwater, Golden Valley, Granite, Lake, Lincoln, Missoula, Ravalli, Sanders, | Big Horn, Carbon, Jefferson, Judith Basin, Lewis and Clark, Meagher, Musselshell, Powder River, Powell, Silver Bow, Stillwater, Westland | Carter, Cascade, Deer Lodge, Falcon, Fergus, Flathead, Gallanting, Glacier, Madison, Park, Petroleum, Ponder, Rosebud, Teton, Treasure, Yellowstone | Beaverhead, Blaine, Chouteau, Custer, Dawson, Garfield, Liberty, McCone, Prairie, Toole, Wibaux | Daniels, Hill, Phillips, Richland, Roosevelt, Sheridan, Valley |
| Nebraska | Adams, Banner, Chase, Cheyenne, Clay, Deuel, Dundy, Fillmore, Franklin, Frontier, Furnas, Gage, Garden, Gosper, Harlan, Hayes, Hitchcock, Jefferson, Kimball, Morrill, Nemaha, Nuckolls, Pawnee, Perkins, Phelps, Red Willow, Richardson, Saline, Scotts Bluff, Seward, Thayer, Webster | All counties not listed | Boyd, Burt, Cedar, Cuming, Dakota, Dixon, Dodge, Knox, Thurston | — | — | — |
| Nevada | All counties not listed | Elko, Eureka, Nye, Washoe, White Pine | — | — | — | — |
| New Hampshire | — | All counties not listed | — | — | — | Carroll, Coos, Grafton |
| New Jersey | All counties | — | — | — | — | — |
| New Mexico | All counties not listed | Rio Arriba | Colfax, Mora, Taos | — | — | — |
| New York | Albany, Bronx, Cayuga, Columbia, Cortland, Dutchess, Genessee, Kings, Livingston, Monroe, Nassau, New York, Niagara, Onondaga, Ontario, Orange, Orleans, Putnam, Queens, Richmond, Rockland, Seneca, Suffolk, Wayne, Westchester, Yates | All counties not listed | Clinton, Essex, Franklin, Hamilton, Herkimer, Jefferson, Lewis, St. Lawrence, Warren | — | — | — |
| North Carolina | All counties | — | — | — | — | — |
| North Dakota | — | — | — | Billings, Bowman | Adams, Dickey, Golden Valley, Hettinger, LaMoure, Oliver, Ransom, Sargent, Sioux, Slope, Stark | All counties not listed |
| Ohio | All counties not listed | Ashland, Crawford, Defiance, Holmes, Huron, Knox, Licking, Morrow, Paulding, Putnam, Richland, Seneca, Williams | — | — | — | — |
(continued)
TABLE R403.3(2)—continued
AIR-FREEZING INDEX FOR U.S. LOCATIONS BY COUNTY
| STATE | AIR-FREEZING INDEX | |||||
| 1500 or less | 2000 | 2500 | 3000 | 3500 | 4000 | |
| Oklahoma | All counties | — | — | — | — | — |
| Oregon | All counties not listed | Baker, Crook, Grant, Harney | — | — | — | — |
| Pennsylvania | All counties not listed | Berks, Blair, Bradford, Cambria, Cameron, Centre, Clarion, Clearfield, Clinton, Crawford, Elk, Forest, Huntingdon, Indiana, Jefferson, Lackawanna, Lycoming, McKean, Pike, Potter, Susquehanna, Tioga, Venango, Warren, Wayne, Wyoming | — | — | — | — |
| Rhode Island | All counties | — | — | — | — | — |
| South Carolina | All counties | — | — | — | — | — |
| South Dakota | — | Bennett, Custer, Fall River, Lawrence, Mellette, Shannon, Todd, Tripp | Bon Homme, Charles Mix, Davison, Douglas, Gregory, Jackson, Jones, Lyman | All counties not listed | Beadle, Brookings, Brown, Campbell, Codington, Corson, Day, Deuel, Edmunds, Faulk, Grant, Hamlin, Kingsbury, Marshall, McPherson, Perkins, Roberts, Spink, Walworth | — |
| Tennessee | All counties | — | — | — | — | — |
| Texas | All counties | — | — | — | — | — |
| Utah | All counties not listed | Box Elder, Morgan, Weber | Garfield, Salt Lake, Summit | Carbon, Daggett, Duchesne, Rich, Sanpete, Uintah, Wasatch | — | — |
| Vermont | — | Bennington, Grand Isle, Rutland, Windham | Addison, Chittenden, Franklin, Orange, Washington, Windsor | Caledonia, Essex, Lamoille, Orleans | — | — |
| Virginia | All counties | — | — | — | — | — |
| Washington | All counties not listed | Chelan, Douglas, Ferry, Okanogan | — | — | — | — |
| West Virginia | All counties | — | — | — | — | — |
| Wisconsin | — | Kenosha, Kewaunee, Racine, Sheboygan, Walworth | All counties not listed | Ashland, Barron, Burnett, Chippewa, Clark, Dunn, Eau Claire, Florence, Forest, Iron, Jackson, | Bayfield, Douglas, Lincoln, Oneida, Sawyer, Washburn | — |
| Wyoming | Goshen, Platte | Converse, Crook, Laramie, Niobrara | Campbell, Carbon, Hot Springs, Johnson, Natrona, Sheridan, Uinta, Weston | Albany, Big Horn, Park, Washakie | Fremont, Teton | Lincoln, Sublette, Sweetwater |
For SI: 1 inch = 25.4 mm.
a. See Table R403.3(1) for required dimensions and R-values for vertical and horizontal insulation.
FIGURE R403.3(3)
INSULATION PLACEMENT FOR FROST-PROTECTED FOOTINGS ADJACENT TO UNHEATED SLAB-ON-GROUND STRUCTURE
Where a frost protected shallow foundation abuts a structure that has a monthly mean temperature maintained at a minimum of 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.
FIGURE R403.3(4)
INSULATION PLACEMENT FOR FROST-PROTECTED FOOTINGS ADJACENT TO HEATED STRUCTURE
Clean crushed stone shall be free from organic, clayey or silty soils. Crushed stone shall be angular in nature and meet ASTM C 33, 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 a maximum of 8-inch lifts. Crushed stone footings shall be limited to Seismic Design Categories A, B and C.
TABLE R403.4
MINIMUM DEPTH OF CRUSHED STONE FOOTINGS (D), (inches)
| LOAD BEARING VALUE OF SOIL (psf) | |||||||||||||||||
| 1500 | 2000 | 3000 | 4000 | ||||||||||||||
| MH, CH, CL, ML | SC, GC, SM, GM, SP, SW | GP, GW | |||||||||||||||
| Wall width (inches) | Wall width (inches) | Wall width (inches) | Wall width (inches) | ||||||||||||||
| 6 | 8 | 10 | 12 | 6 | 8 | 10 | 12 | 6 | 8 | 10 | 12 | 6 | 8 | 10 | 12 | ||
| Conventional light-frame construction | |||||||||||||||||
| 1-story | 1100 plf | 6 | 4 | 4 | 4 | 6 | 4 | 4 | 4 | 6 | 4 | 4 | 4 | 6 | 4 | 4 | 4 |
| 2-story | 1800 plf | 8 | 6 | 4 | 4 | 6 | 4 | 4 | 4 | 6 | 4 | 4 | 4 | 6 | 4 | 4 | 4 |
| 3-story | 2000 plf | 16 | 14 | 12 | 10 | 10 | 8 | 6 | 6 | 6 | 4 | 4 | 4 | 6 | 4 | 4 | 4 |
| 4-inch brick veneer over light-frame or 8-inch hollow concrete masonry | |||||||||||||||||
| 1-story | 1500 plf | 6 | 4 | 4 | 4 | 6 | 4 | 4 | 4 | 6 | 4 | 4 | 4 | 6 | 4 | 4 | 4 |
| 2-story | 2700 plf | 14 | 12 | 10 | 8 | 10 | 8 | 6 | 4 | 6 | 4 | 4 | 4 | 6 | 4 | 4 | 4 |
| 3-story | 4000 plf | 22 | 22 | 20 | 18 | 16 | 14 | 12 | 10 | 10 | 8 | 6 | 4 | 6 | 4 | 4 | 4 |
| 8-inch solid or fully grouted masonry | |||||||||||||||||
| 1-story | 2000 plf | 10 | 8 | 6 | 4 | 6 | 4 | 4 | 4 | 6 | 4 | 4 | 4 | 6 | 4 | 4 | 4 |
| 2-story | 3600 plf | 20 | 18 | 16 | 16 | 14 | 12 | 10 | 8 | 8 | 6 | 4 | 4 | 6 | 4 | 4 | 4 |
| 3-story | 5300 plf | 32 | 30 | 28 | 26 | 22 | 22 | 20 | 18 | 14 | 12 | 10 | 8 | 10 | 8 | 6 | 4 |
For SI: 1 inch = 25.4 mm, 1 pound per square inch = 6.89 kPa.
FIGURE R403.4(1)
BASEMENT OR CRAWL SPACE WITH PRECAST
FOUNDATION WALL BEARING ON CRUSHED STONE
FIGURE R403.4(2)
BASEMENT OR CRAWL SPACE WITH PRECAST
FOUNDATION WALL ON SPREAD FOOTING
Masonry foundation walls shall be designed and constructed in accordance with the provisions of this section or in accordance with the provisions of ACI530/ASCE 5/TMS 402 or NCMA TR68-A. When ACI530/ASCE 5/TMS 402, NCMA TR68-A or the provisions of this section are used to design masonry foundation walls, project drawings, typical details and specifications are not required to bear the seal of the architect or engineer responsible for design, unless otherwise required by the state law of the jurisdiction having authority.
TABLE R404.1.1(1)
PLAIN MASONRY FOUNDATION WALLS
| MAXIMUM WALL HEIGHT | MAXIMUM | PLAIN MASONRYa MINIMUM NOMINAL WALL THICKNESS (inches) | ||
| Soil classesb | ||||
| GW, GP, SW | GM, GC, SM, | SC, MH, ML-CL | ||
| 5 | 4 5 | 6 solidd or 8 6 solidd or 8 | 6 solidd or 8 8 | 6 solidd or 8 10 |
| 6 | 4 5 6 | 6 solidd or 8 6 solidd or 8 8 | 6 solidd or 8 8 10 | 6 solidd or 8 10 12 |
| 7 | 4 5 6 7 | 6 solidd or 8 6 solidd or 8 10 12 | 8 10 12 10 solidd | 8 10 10 solidd 12 solidd |
| 8 | 4 5 6 7 8 | 6 solidd or 8 6 solidd or 8 10 12 10 solidd | 6 solidd or 8 10 12 12 solidd 12 solidd | 8 12 12 solidd Footnote e Footnote e |
| 9 | 4 5 6 7 8 9 | 6 solidd or 8 8 10 12 12 solidd Footnote e | 6 solidd or 8 10 12 12 solidd Footnote e Footnote e | 8 12 12 solidd Footnote e Footnote e Footnote e |
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square inch = 6.895 Pa.
a. Mortar shall be Type M or S and masonry shall be laid in running bond. Ungrouted hollow masonry units are permitted except where otherwise indicated.
b. Soil classes are in accordance with the Unified Soil Classification System. Refer to Table R405.1.
c. Unbalanced backfill height is the difference in height between the exterior finish ground level and the lower of the top of the concrete footing that supports the foundation wall or the interior finish ground level. Where an interior concrete slab-on-grade is provided and is in contact with the interior surface of the foundation wall, measurement of the unbalanced backfill height from the exterior finish ground level to the top of the interior concrete slab is permitted.
d. Solid grouted hollow units or solid masonry units.
e. Wall construction shall be in accordance with either Table R404.1.1(2), Table R404.1.1(3), Table R404.1.1(4), or a design shall be provided.
TABLE R404.1.1(2)
8-INCH MASONRY FOUNDATION WALLS WITH REINFORCING
WHERE d > 5 INCHESa, c
| WALL HEIGHT | HEIGHT OF | MINIMUM VERTICAL REINFORCEMENT AND SPACING (INCHES)b, c | ||
| Soil classes and lateral soil loadd (psf per foot below grade) | ||||
| GW, GP, SW and SP soils | GM, GC, SM, SM-SC and ML soils | SC, ML-CL and inorganic CL soils | ||
| 6 feet 8 inches | 4 feet (or less) | #4 at 48 | #4 at 48 | #4 at 48 |
| 7 feet 4 inches | 4 feet (or less) | #4 at 48 | #4 at 48 | #4 at 48 |
| 8 feet | 4 feet (or less) | #4 at 48 | #4 at 48 | #4 at 48 |
| 8 feet 8 inches | 4 feet (or less) | #4 at 48 | #4 at 48 | #4 at 48 |
| 9 feet 4 inches | 4 feet (or less) | #4 at 48 | #4 at 48 | #4 at 48 |
| 10 feet | 4 feet (or less) | #4 at 48 | #4 at 48 | #4 at 48 |
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot per foot = 0.157 kPa/mm.
a. Mortar shall be Type M or S and masonry shall be laid in running bond.
b. Alternative reinforcing bar sizes and spacings having an equivalent cross-sectional area of reinforcement per lineal foot of wall shall be permitted provided the spacing of the reinforcement does not exceed 72 inches.
c. Vertical reinforcement shall be Grade 60 minimum. The distance, d, from the face of the soil side of the wall to the center of vertical reinforcement shall be at least 5 inches.
d. Soil classes are in accordance with the Unified Soil Classification System and design lateral soil loads are for moist conditions without hydrostatic pressure. Refer to Table R405.1.
e. Unbalanced backfill height is the difference in height between the exterior finish ground level and the lower of the top of the concrete footing that supports the foundation wall or the interior finish ground level. Where an interior concrete slab-on-grade is provided and is in contact with the interior surface of the foundation wall, measurement of the unbalanced backfill height from the exterior finish ground level to the top of the interior concrete slab is permitted.
TABLE R404.1.1(3)
10-INCH FOUNDATION WALLS WITH REINFORCING
WHERE d > 6.75 INCHESa, c
| WALL HEIGHT | HEIGHT OF | MINIMUM VERTICAL REINFORCEMENT AND SPACING (INCHES)b, c | ||
| Soil classes and later soil loadd (psf per foot below grade) | ||||
| GW, GP, SW and SP soils | GM, GC, SM, SM-SC and ML soils | SC, ML-CL and inorganic CL soils | ||
| 6 feet 8 inches | 4 feet (or less) | #4 at 56 | #4 at 56 | #4 at 56 |
| 7 feet 4 inches | 4 feet (or less) | #4 at 56 | #4 at 56 | #4 at 56 |
| 8 feet | 4 feet (or less) | #4 at 56 | #4 at 56 | #4 at 56 |
| 8 feet 8 inches | 4 feet (or less) | #4 at 56 | #4 at 56 | #4 at 56 |
| 9 feet 4 inches | 4 feet (or less) | #4 at 56 | #4 at 56 | #4 at 56 |
| 10 feet | 4 feet (or less) | #4 at 56 | #4 at 56 | #4 at 56 |
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot per foot = 0.157 kPa/mm.
a. Mortar shall be Type M or S and masonry shall be laid in running bond.
b. Alternative reinforcing bar sizes and spacings having an equivalent cross-sectional area of reinforcement per lineal foot of wall shall be permitted provided the spacing of the reinforcement does not exceed 72 inches.
c. Vertical reinforcement shall be Grade 60 minimum. The distance, d, from the face of the soil side of the wall to the center of vertical reinforcement shall be at least 6.75 inches.
d. Soil classes are in accordance with the Unified Soil Classification System and design lateral soil loads are for moist conditions without hydrostatic pressure. Refer to Table R405.1.
e. Unbalanced backfill height is the difference in height between the exterior finish ground level and the lower of the top of the concrete footing that supports the foundation wall or the interior finish ground level. Where an interior concrete slab-on-grade is provided and is in contact with the interior surface of the foundation wall, measurement of the unbalanced backfill height from the exterior finish ground level to the top of the interior concrete slab is permitted.
TABLE R404.1.1(4)
12-INCH MASONRY FOUNDATION WALLS WITH REINFORCING
WHERE d > 8.75 INCHESa, c
| WALL HEIGHT | HEIGHT OF | MINIMUM VERTICAL REINFORCEMENT AND SPACING (INCHES)b, c | ||
| Soil classes and lateral soil loadd (psf per foot below grade) | ||||
| GW, GP, SW and SP soils | GM, GC, SM, SM-SC and ML soils | SC, ML-CL and inorganic CL soils | ||
| 6 feet 8 inches | 4 feet (or less) | #4 at 72 | #4 at 72 | #4 at 72 |
| 7 feet 4 inches | 4 feet (or less) | #4 at 72 | #4 at 72 | #4 at 72 |
| 8 feet | 4 feet (or less) | #4 at 72 | #4 at 72 | #4 at 72 |
| 8 feet 8 inches | 4 feet (or less) | #4 at 72 | #4 at 72 | #4 at 72 |
| 9 feet 4 inches | 4 feet (or less) | #4 at 72 | #4 at 72 | #4 at 72 |
| 10 feet | 4 feet (or less) | #4 at 72 | #4 at 72 | #4 at 72 |
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot per foot = 0.157 kPa/mm.
a. Mortar shall be Type M or S and masonry shall be laid in running bond.
b. Alternative reinforcing bar sizes and spacings having an equivalent cross-sectional area of reinforcement per lineal foot of wall shall be permitted provided the spacing of the reinforcement does not exceed 72 inches.
c. Vertical reinforcement shall be Grade 60 minimum. The distance, d, from the face of the soil side of the wall to the center of vertical reinforcement shall be at least 8.75 inches.
d. Soil classes are in accordance with the Unified Soil Classification System and design lateral soil loads are for moist conditions without hydrostatic pressure. Refer to Table R405.1.
e. Unbalanced backfill height is the difference in height between the exterior finish ground level and the lower of the top of the concrete footing that supports the foundation wall or the interior finish ground levels. Where an interior concrete slab-on-grade is provided and in contact with the interior surface of the foundation wall, measurement of the unbalanced backfill height is permitted to be measured from the exterior finish ground level to the top of the interior concrete slab is permitted.
Concrete foundation walls that support light-frame walls shall be designed and constructed in accordance with the provisions of this section, ACI 318, ACI 332 or PCA 100. Concrete foundation walls that support above-grade concrete walls that are within the applicability limits of Section R611.2 shall be designed and constructed in accordance with the provisions of this section, ACI 318, ACI 332 or PCA 100. Concrete foundation walls that support above-grade concrete walls that are not within the applicability limits of Section R611.2 shall be designed and constructed in accordance with the provisions of ACI 318, ACI 332 or PCA 100. When ACI 318, ACI 332, PCA 100 or the provisions of this section are used to design concrete foundation walls, project drawings, typical details and specifications are not required to bear the seal of the architect or engineer responsible for design, unless otherwise required by the state law of the jurisdiction having authority.
TABLE R404.1.2(1)
MINIMUM HORIZONTAL REINFORCEMENT FOR CONCRETE BASEMENT WALLSa, b
| MAXIMUM UNSUPPORTED HEIGHT OF BASEMENT WALL | LOCATION OF HORIZONTAL REINFORCEMENT |
| ≤ 8 | One No. 4 bar within 12 inches of the top of the wall story and one No. 4 bar near mid-height of the wall story |
| > 8 | One No. 4 bar within 12 inches of the top of the wall story and one No. 4 bar near third points in the wall story |
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square inch = 6.895 kPa.
a. Horizontal reinforcement requirements are for reinforcing bars with a minimum yield strength of 40,000 psi and concrete with a minimum concrete compressive strength 2,500 psi.
b. See Section R404.1.2.2 for minimum reinforcement required for foundation walls supporting above-grade concrete walls.
TABLE R404.1.2(2)
MINIMUM VERTICAL REINFORCEMENT FOR 6-INCH NOMINAL FLAT CONCRETE BASEMENT WALLSb, c, d, e, g, h, i, j
| MAXIMUM UNSUPPORTED | MAXIMUM UNBALANCED | MINIMUM VERTICAL REINFORCEMENT—BAR SIZE AND SPACING (inches) | ||
| Soil classesa and design lateral soil (psf per foot of depth) | ||||
| GW, GP, SW, SP | GM, GC, SM, SM-SC and ML | SC, ML-CL and inorganic CL | ||
| 8 | 4 | NR | NR | NR |
| 5 | NR | 6 @ 39 | 6 @ 48 | |
| 6 | 5 @ 39 | 6 @ 48 | 6 @ 35 | |
| 7 | 6 @ 48 | 6 @ 34 | 6 @ 25 | |
| 8 | 6 @ 39 | 6 @ 25 | 6 @ 18 | |
| 9 | 4 | NR | NR | NR |
| 5 | NR | 5 @ 37 | 6 @ 48 | |
| 6 | 5 @ 36 | 6 @ 44 | 6 @ 32 | |
| 7 | 6 @ 47 | 6 @ 30 | 6 @ 22 | |
| 8 | 6 @ 34 | 6 @ 22 | 6 @ 16 | |
| 9 | 6 @ 27 | 6 @ 17 | DR | |
| 10 | 4 | NR | NR | NR |
| 5 | NR | 5 @ 35 | 6 @ 48 | |
| 6 | 6 @ 48 | 6 @ 41 | 6 @ 30 | |
| 7 | 6 @ 43 | 6 @ 28 | 6 @ 20 | |
| 8 | 6 @ 31 | 6 @ 20 | DR | |
| 9 | 6 @ 24 | 6 @ 15 | DR | |
| 10 | 6 @ 19 | DR | DR | |
For SI:1 foot = 304.8 mm; 1 inch = 25.4 mm; 1 pound per square foot per foot = 0.1571 kPa2/m, 1 pound per square inch = 6.895 kPa.
a. Soil classes are in accordance with the Unified Soil Classification System. Refer to Table R405.1.
b. Table values are based on reinforcing bars with a minimum yield strength of 60,000 psi concrete with a minimum specified compressive strength of 2,500 psi and vertical reinforcement being located at the centerline of the wall. See Section R404.1.2.3.7.2.
c. Vertical reinforcement with a yield strength of less than 60,000 psi and/or bars of a different size than specified in the table are permitted in accordance with Section R404.1.2.3.7.6 and Table R404.1.2(9).
d. Deflection criterion is L/240, where L is the height of the basement wall in inches.
e. Interpolation is not permitted.
f. Where walls will retain 4 feet or more of unbalanced backfill, they shall be laterally supported at the top and bottom before backfilling.
g. NR indicates no vertical wall reinforcement is required, except for 6-inch nominal walls formed with stay-in-place forming systems in which case vertical reinforcement shall be No. 4@48 inches on center.
h. See Section R404.1.2.2 for minimum reinforcement required for basement walls supporting above-grade concrete walls.
i. See Table R611.3 for tolerance from nominal thickness permitted for flat walls.
j. DR means design is required in accordance with the applicable building code, or where there is no code, in accordance with ACI 318.
TABLE R404.1.2(3)
MINIMUM VERTICAL REINFORCEMENT FOR 8-INCH (203 mm) NOMINAL FLAT CONCRETE BASEMENT WALLSb, c, d, e, f, h, i
| MAXIMUM UNSUPPORTED | MAXIMUM UNBALANCED | MINIMUM VERTICAL REINFORCEMENT—BAR SIZE AND SPACING (inches) | ||
| Soil classesa and design lateral soil (psf per foot of depth) | ||||
| GW, GP, SW, SP | GM, GC, SM, SM-SC and ML | SC, ML-CL and inorganic CL | ||
| 8 | 4 | NR | NR | NR |
| 5 | NR | NR | NR | |
| 6 | NR | NR | 6 @ 37 | |
| 7 | NR | 6 @ 36 | 6 @ 35 | |
| 8 | 6 @ 41 | 6 @ 35 | 6 @ 26 | |
| 9 | 4 | NR | NR | NR |
| 5 | NR | NR | NR | |
| 6 | NR | NR | 6 @ 35 | |
| 7 | NR | 6 @ 35 | 6 @ 32 | |
| 8 | 6 @ 36 | 6 @ 32 | 6 @ 23 | |
| 9 | 6 @ 35 | 6 @ 25 | 6 @ 18 | |
| 10 | 4 | NR | NR | NR |
| 5 | NR | NR | NR | |
| 6 | NR | NR | 6 @ 35 | |
| 7 | NR | 6 @ 35 | 6 @ 29 | |
| 8 | 6 @ 35 | 6 @ 29 | 6 @ 21 | |
| 9 | 6 @ 34 | 6 @ 22 | 6 @ 16 | |
| 10 | 6 @ 27 | 6 @ 17 | 6 @ 13 | |
For SI:1 foot = 304.8 mm; 1 inch = 25.4 mm; 1 pound per square foot per foot = 0.1571 kPa2/m, 1 pound per square inch = 6.895 kPa.
a. Soil classes are in accordance with the Unified Soil Classification System. Refer to Table R405.1.
b. Table values are based on reinforcing bars with a minimum yield strength of 60,000 psi (420 MPa), concrete with a minimum specified compressive strength of 2,500 psi and vertical reinforcement being located at the centerline of the wall. See Section R404.1.2.3.7.2.
c. Vertical reinforcement with a yield strength of less than 60,000 psi and/or bars of a different size than specified in the table are permitted in accordance with Section R404.1.2.3.7.6 and Table R404.1.2(9).
d. NR indicates no vertical reinforcement is required.
e. Deflection criterion is L/240, where L is the height of the basement wall in inches.
f. Interpolation is not permitted.
g. Where walls will retain 4 feet or more of unbalanced backfill, they shall be laterally supported at the top and bottom before backfilling.
h. See Section R404.1.2.2 for minimum reinforcement required for basement walls supporting above-grade concrete walls.
i. See Table R611.3 for tolerance from nominal thickness permitted for flat walls.
TABLE R404.1.2(4)
MINIMUM VERTICAL REINFORCEMENT FOR 10-INCH NOMINAL FLAT CONCRETE BASEMENT WALLSb, c, d, e, f, h, i
| MAXIMUM UNSUPPORTED | MAXIMUM UNBALANCED | MINIMUM VERTICAL REINFORCEMENT—BAR SIZE AND SPACING (inches) | ||
| Soil classesa and design lateral soil (psf per foot of depth) | ||||
| GW, GP, SW, SP | GM, GC, SM, SM-SC and ML | SC, ML-CL and inorganic CL | ||
| 8 | 4 | NR | NR | NR |
| 5 | NR | NR | NR | |
| 6 | NR | NR | NR | |
| 7 | NR | NR | NR | |
| 8 | 6 @ 48 | 6 @ 35 | 6 @ 28 | |
| 9 | 4 | NR | NR | NR |
| 5 | NR | NR | NR | |
| 6 | NR | NR | NR | |
| 7 | NR | NR | 6 @ 31 | |
| 8 | NR | 6 @ 31 | 6 @ 28 | |
| 9 | 6 @ 37 | 6 @ 28 | 6 @ 24 | |
| 10 | 4 | NR | NR | NR |
| 5 | NR | NR | NR | |
| 6 | NR | NR | NR | |
| 7 | NR | NR | 6 @ 28 | |
| 8 | NR | 6 @ 28 | 6 @ 28 | |
| 9 | 6 @ 33 | 6 @ 28 | 6 @ 21 | |
| 10 | 6 @ 28 | 6 @ 23 | 6 @ 17 | |
For SI:1 foot = 304.8 mm; 1 inch = 25.4 mm; 1 pound per square foot per foot = 0.1571 kPa2/m, 1 pound per square inch = 6.895 kPa.
a. Soil classes are in accordance with the Unified Soil Classification System. Refer to Table R405.1.
b. Table values are based on reinforcing bars with a minimum yield strength of 60,000 psi concrete with a minimum specified compressive strength of 2,500 psi and vertical reinforcement being located at the centerline of the wall. See Section R404.1.2.3.7.2.
c. Vertical reinforcement with a yield strength of less than 60,000 psi and/or bars of a different size than specified in the table are permitted in accordance with Section R404.1.2.3.7.6 and Table R404.1.2(9).
d. NR indicates no vertical reinforcement is required.
e. Deflection criterion is L/240, where L is the height of the basement wall in inches.
f. Interpolation is not permitted.
g. Where walls will retain 4 feet or more of unbalanced backfill, they shall be laterally supported at the top and bottom before backfilling.
h. See Section R404.1.2.2 for minimum reinforcement required for basement walls supporting above-grade concrete walls.
i. See Table R611.3 for tolerance from nominal thickness permitted for flat walls.
TABLE R404.1.2(5)
MINIMUM VERTICAL WALL REINFORCEMENT FOR 6-INCH WAFFLE-GRID BASEMENT WALLSb, c, d, e, g, h, i
| MAXIMUM UNSUPPORTED | MAXIMUM UNBALANCED | MINIMUM VERTICAL REINFORCEMENT—BAR SIZE AND SPACING (inches) | ||
| Soil classesa and design lateral soil (psf per foot of depth) | ||||
| GW, GP, SW, SP | GM, GC, SM, SM-SC and ML | SC, ML-CL and inorganic CL | ||
| 8 | 4 | 4 @ 48 | 4 @ 46 | 6 @ 39 |
| 5 | 4 @ 45 | 5 @ 46 | 6 @ 47 | |
| 6 | 5 @ 45 | 6 @ 40 | DR | |
| 7 | 6 @ 44 | DR | DR | |
| 8 | 6 @ 32 | DR | DR | |
| 9 | 4 | 4 @ 48 | 4 @ 46 | 4 @ 37 |
| 5 | 4 @ 42 | 5 @ 43 | 6 @ 44 | |
| 6 | 5 @ 41 | 6 @ 37 | DR | |
| 7 | 6 @ 39 | DR | DR | |
| > 8 | DRi | DR | DR | |
| 10 | 4 | 4 @ 48 | 4 @ 46 | 4 @ 35 |
| 5 | 4 @ 40 | 5 @ 40 | 6 @ 41 | |
| 6 | 5 @ 38 | 6 @ 34 | DR | |
| 7 | 6 @ 36 | DR | DR | |
| > 8 | DR | DR | DR | |
For SI: 1 foot = 304.8 mm; 1 inch = 25.4 mm; 1 pound per square foot per foot = 0.1571 kPa2/m, 1 pound per square inch = 6.895 kPa.
a. Soil classes are in accordance with the Unified Soil Classification System. Refer to Table R405.1.
b. Table values are based on reinforcing bars with a minimum yield strength of 60,000 psi concrete with a minimum specified compressive strength of 2,500 psi and vertical reinforcement being located at the centerline of the wall. See Section R404.1.2.3.7.2.
c. Maximum spacings shown are the values calculated for the specified bar size. Where the bar used is Grade 60 and the size specified in the table, the actual spacing in the wall shall not exceed a whole-number multiple of 12 inches (i.e., 12, 24, 36 and 48) that is less than or equal to the tabulated spacing. Vertical reinforcement with a yield strength of less than 60,000 psi and/or bars of a different size than specified in the table are permitted in accordance with Section R404.1.2.3.7.6 and Table R404.1.2(9).
d. Deflection criterion is L/240, where L is the height of the basement wall in inches.
e. Interpolation is not permitted.
f. Where walls will retain 4 feet or more of unbalanced backfill, they shall be laterally supported at the top and bottom before backfilling.
g. See Section R404.1.2.2 for minimum reinforcement required for basement walls supporting above-grade concrete walls.
h. See Table R611.3 for thicknesses and dimensions of waffle-grid walls.
i. DR means design is required in accordance with the applicable building code, or where there is no code, in accordance with ACI 318.
3. Exterior wall covering. Stay-in-place forms constructed of rigid foam plastics shall be protected from sunlight and physical damage by the application of an approved exterior wall covering complying with this code. Exterior surfaces of other stay-in-place forming systems shall be protected in accordance with this code.
4. Termite hazards. In areas where hazard of termite damage is very heavy in accordance with Figure R301.2(6), foam plastic insulation shall be permitted below grade on foundation walls in accordance with one of the following conditions:
4.1. Where in addition to the requirements in Section R318.1, an approved method of protecting the foam plastic and structure from subterranean termite damage is provided.
4.2. The structural members of walls, floors, ceilings and roofs are entirely of noncombustible materials or pressure-preservative-treated wood.
TABLE R404.1.2(6)
MINIMUM VERTICAL REINFORCEMENT FOR 8-INCH WAFFLE-GRID BASEMENT WALLSb, c, d, e, f, h, i, j
| MAXIMUM UNSUPPORTED | MAXIMUM UNBALANCED | MINIMUM VERTICAL REINFORCEMENT—BAR SIZE AND SPACING (inches) | ||
| Soil classesa and design lateral soil (psf per foot of depth) | ||||
| GW, GP, SW, SP | GM, GC, SM, SM-SC and ML | SC, ML-CL and inorganic CL | ||
| 8 | 4 | NR | NR | NR |
| 5 | NR | 5 @ 48 | 5 @ 46 | |
| 6 | 5 @ 48 | 5 @ 43 | 6 @ 45 | |
| 7 | 5 @ 46 | 6 @ 43 | 6 @ 31 | |
| 8 | 6 @ 48 | 6 @ 32 | 6 @ 23 | |
| 9 | 4 | NR | NR | NR |
| 5 | NR | 5 @ 47 | 5 @ 46 | |
| 6 | 5 @ 46 | 5 @ 39 | 6 @ 41 | |
| 7 | 5 @ 42 | 6 @ 38 | 6 @ 28 | |
| 8 | 6 @ 44 | 6 @ 28 | 6 @ 20 | |
| 9 | 6 @ 34 | 6 @ 21 | DR | |
| 10 | 4 | NR | NR | NR |
| 5 | NR | 5 @ 46 | 5 @ 44 | |
| 6 | 5 @ 46 | 5 @ 37 | 6 @ 38 | |
| 7 | 5 @ 38 | 6 @ 35 | 6 @ 25 | |
| 8 | 6 @ 39 | 6 @ 25 | DR | |
| 9 | 6 @ 30 | DR | DR | |
| 10 | 6 @ 24 | DR | DR | |
For SI: 1 foot = 304.8 mm; 1 inch = 25.4 mm; 1 pound per square foot per foot = 0.1571 kPa2/m, 1 pound per square inch = 6.895 kPa.
a. Soil classes are in accordance with the Unified Soil Classification System. Refer to Table R405.1.
b. Table values are based on reinforcing bars with a minimum yield strength of 60,000 psi concrete with a minimum specified compressive strength of 2,500 psi and vertical reinforcement being located at the centerline of the wall. See Section R404.1.2.3.7.2.
c. Maximum spacings shown are the values calculated for the specified bar size. Where the bar used is Grade 60 (420 MPa) and the size specified in the table, the actual spacing in the wall shall not exceed a whole-number multiple of 12 inches (i.e., 12, 24, 36 and 48) that is less than or equal to the tabulated spacing. Vertical reinforcement with a yield strength of less than 60,000 psi and/or bars of a different size than specified in the table are permitted in accordance with Section R404.1.2.3.7.6 and Table R404.1.2(9).
d. NR indicates no vertical reinforcement is required.
e. Deflection criterion is L/240, where L is the height of the basement wall in inches.
f. Interpolation shall not be permitted.
g. Where walls will retain 4 feet or more of unbalanced backfill, they shall be laterally supported at the top and bottom before backfilling.
h. See Section R404.1.2.2 for minimum reinforcement required for basement walls supporting above-grade concrete walls.
i. See Table R611.3 for thicknesses and dimensions of waffle-grid walls.
j. DR means design is required in accordance with the applicable building code, or where there is no code, in accordance with ACI 318.
TABLE R404.1.2(7)
MINIMUM VERTICAL REINFORCEMENT FOR 6-INCH (152 mm) SCREEN-GRID BASEMENT WALLSb, c, d, e, g, h, i,
| MAXIMUM UNSUPPORTED | MAXIMUM UNBALANCED | MINIMUM VERTICAL REINFORCEMENT—BAR SIZE AND SPACING (inches) | ||
| Soil classesa and design lateral soil (psf per foot of depth) | ||||
| GW, GP, SW, SP | GM, GC, SM, SM-SC and ML | SC, ML-CL and inorganic CL | ||
| 8 | 4 | 4 @ 48 | 4 @ 48 | 5 @ 43 |
| 5 | 4 @ 48 | 5 @ 48 | 5 @ 37 | |
| 6 | 5 @ 48 | 6 @ 45 | 6 @ 32 | |
| 7 | 6 @ 48 | DR | DR | |
| 8 | 6 @ 36 | DR | DR | |
| 9 | 4 | 4 @ 48 | 4 @ 48 | 4 @ 41 |
| 5 | 4 @ 48 | 5 @ 48 | 6 @ 48 | |
| 6 | 5 @ 45 | 6 @ 41 | DR | |
| 7 | 6 @ 43 | DR | DR | |
| > 8 | DR | DR | DR | |
| 10 | 4 | 4 @ 48 | 4 @ 48 | 4 @ 39 |
| 5 | 4 @ 44 | 5 @ 44 | 6 @ 46 | |
| 6 | 5 @ 42 | 6 @ 38 | DR | |
| 7 | 6 @ 40 | DR | DR | |
| > 8 | DR | DR | DR | |
For SI: 1 foot = 304.8 mm; 1 inch = 25.4 mm; 1 pound per square foot per foot = 0.1571 kPa2/m, 1 pound per square inch = 6.895 kPa.
a. Soil classes are in accordance with the Unified Soil Classification System. Refer to Table R405.1.
b. Table values are based on reinforcing bars with a minimum yield strength of 60,000 psi (420 MPa), concrete with a minimum specified compressive strength of 2,500 psi and vertical reinforcement being located at the centerline of the wall. See Section R404.1.2.3.7.2.
c. Maximum spacings shown are the values calculated for the specified bar size. Where the bar used is Grade 60 and the size specified in the table, the actual spacing in the wall shall not exceed a whole-number multiple of 12 inches (i.e., 12, 24, 36 and 48) that is less than or equal to the tabulated spacing. Vertical reinforcement with a yield strength of less than 60,000 psi and/or bars of a different size than specified in the table are permitted in accordance with Section R404.1.2.3.7.6 and Table R404.1.2(9).
d. Deflection criterion is L/240, where L is the height of the basement wall in inches.
e. Interpolation is not permitted.
f. Where walls will retain 4 feet or more of unbalanced backfill, they shall be laterally supported at the top and bottom before backfilling.
g. See Sections R404.1.2.2 for minimum reinforcement required for basement walls supporting above-grade concrete walls.
h. See Table R611.3 for thicknesses and dimensions of screen-grid walls.
i. DR means design is required in accordance with the applicable building code, or where there is no code, in accordance with ACI 318.
TABLE R404.1.2(8)
MINIMUM VERTICAL REINFORCEMENT FOR 6-, 8-, 10-INCH AND 12-INCH NOMINAL FLAT BASEMENT WALLSb, c, d, e, f, h, i, k, n
| MAXIMUM | MAXIMUM UNBALANCED | MINIMUM VERTICAL REINFORCEMENT—BAR SIZE AND SPACING (inches) | |||||||||||
| Soil classesa and design lateral soil (psf per foot of depth) | |||||||||||||
| GW, GP, SW, SP | GM, GC, SM, SM-SC and ML | SC, ML-CL and inorganic CL | |||||||||||
| Minimum nominal wall thickness (inches) | |||||||||||||
| 6 | 8 | 10 | 12 | 6 | 8 | 10 | 12 | 6 | 8 | 10 | 12 | ||
| 5 | 4 | NR | NR | NR | NR | NR | NR | NR | NR | NR | NR | NR | NR |
| 5 | NR | NR | NR | NR | NR | NR | NR | NR | NR | NR | NR | NR | |
| 6 | 4 | NR | NR | NR | NR | NR | NR | NR | NR | NR | NR | NR | NR |
| 5 | NR | NR | NR | NR | NR | NRl | NR | NR | 4 @ 35 | NRl | NR | NR | |
| 6 | NR | NR | NR | NR | 5 @ 48 | NR | NR | NR | 5 @ 36 | NR | NR | NR | |
| 7 | 4 | NR | NR | NR | NR | NR | NR | NR | NR | NR | NR | NR | NR |
| 5 | NR | NR | NR | NR | NR | NR | NR | NR | 5 @ 47 | NR | NR | NR | |
| 6 | NR | NR | NR | NR | 5 @ 42 | NR | NR | NR | 6 @ 43 | 5 @ 48 | NRl | NR | |
| 7 | 5 @ 46 | NR | NR | NR | 6 @ 42 | 5 @ 46 | NRl | NR | 6 @ 34 | 6 @ 48 | NR | NR | |
| 8 | 4 | NR | NR | NR | NR | NR | NR | NR | NR | NR | NR | NR | NR |
| 5 | NR | NR | NR | NR | 4 @ 38 | NRl | NR | NR | 5 @ 43 | NR | NR | NR | |
| 6 | 4 @ 37 | NRl | NR | NR | 5 @ 37 | NR | NR | NR | 6 @ 37 | 5 @ 43 | NRl | NR | |
| 7 | 5 @ 40 | NR | NR | NR | 6 @ 37 | 5 @ 41 | NRl | NR | 6 @ 34 | 6 @ 43 | NR | NR | |
| 8 | 6 @ 43 | 5 @ 47 | NRl | NR | 6 @ 34 | 6 @ 43 | NR | NR | 6 @ 27 | 6 @ 32 | 6 @ 44 | NR | |
| 9 | 4 | NR | NR | NR | NR | NR | NR | NR | NR | NR | NR | NR | NR |
| 5 | NR | NR | NR | NR | 4 @ 35 | NRl | NR | NR | 5 @ 40 | NR | NR | NR | |
| 6 | 4 @ 34 | NRl | NR | NR | 6 @ 48 | NR | NR | NR | 6 @ 36 | 6 @ 39 | NRl | NR | |
| 7 | 5 @ 36 | NR | NR | NR | 6 @ 34 | 5 @ 37 | NR | NR | 6 @ 33 | 6 @ 38 | 5 @ 37 | NRl | |
| 8 | 6 @ 38 | 5 @ 41 | NRl | NR | 6 @ 33 | 6 @ 38 | 5 @ 37 | NRl | 6 @ 24 | 6 @ 29 | 6 @ 39 | 4 @ 48m | |
| 9 | 6 @ 34 | 6 @ 46 | NR | NR | 6 @ 26 | 6 @ 30 | 6 @ 41 | NR | 6 @ 19 | 6 @ 23 | 6 @ 30 | 6 @ 39 | |
| 10 | 4 | NR | NR | NR | NR | NR | NR | NR | NR | NR | NR | NR | NR |
| 5 | NR | NR | NR | NR | 4 @ 33 | NRl | NR | NR | 5 @ 38 | NR | NR | NR | |
| 6 | 5 @ 48 | NRl | NR | NR | 6 @ 45 | NR | NR | NR | 6 @ 34 | 5 @ 37 | NR | NR | |
| 7 | 6 @ 47 | NR | NR | NR | 6 @ 34 | 6 @ 48 | NR | NR | 6 @ 30 | 6 @ 35 | 6 @ 48 | NRl | |
| 8 | 6 @ 34 | 5 @ 38 | NR | NR | 6 @ 30 | 6 @ 34 | 6 @ 47 | NRl | 6 @ 22 | 6 @ 26 | 6 @ 35 | 6 @ 45m | |
| 9 | 6 @ 34 | 6 @ 41 | 4 @ 48 | NRl | 6 @ 23 | 6 @ 27 | 6 @ 35 | 4 @ 48m | DR | 6 @ 22 | 6 @ 27 | 6 @ 34 | |
| 10 | 6 @ 28 | 6 @ 33 | 6 @ 45 | NR | DRj | 6 @ 23 | 6 @ 29 | 6 @ 38 | DR | 6 @ 22 | 6 @ 22 | 6 @ 28 | |
For SI: 1 foot = 304.8 mm; 1 inch = 25.4 mm; 1 pound per square foot per foot = 0.1571 kPa2/m, 1 pound per square inch = 6.895 kPa.
a. Soil classes are in accordance with the Unified Soil Classification System. Refer to Table R405.1.
b. Table values are based on reinforcing bars with a minimum yield strength of 60,000 psi.
c. Vertical reinforcement with a yield strength of less than 60,000 psi and/or bars of a different size than specified in the table are permitted in accordance with Section R404.1.2.3.7.6 and Table R404.1.2(9).
d. NR indicates no vertical wall reinforcement is required, except for 6-inch nominal walls formed with stay-in-place forming systems in which case vertical reinforcement shall be #4@48 inches on center.
e. Allowable deflection criterion is L/240, where L is the unsupported height of the basement wall in inches.
f. Interpolation is not permitted.
g. Where walls will retain 4 feet or more of unbalanced backfill, they shall be laterally supported at the top and bottom before backfilling.
h. Vertical reinforcement shall be located to provide a cover of 1.25 inches measured from the inside face of the wall. The center of the steel shall not vary from the specified location by more than the greater of 10 percent of the wall thickness or 3/8-inch.
i. Concrete cover for reinforcement measured from the inside face of the wall shall not be less than 3/4-inch. Concrete cover for reinforcement measured from the outside face of the wall shall not be less than 11/2 inches for No. 5 bars and smaller, and not less than 2 inches for larger bars.
j. DR means design is required in accordance with the applicable building code, or where there is no code in accordance with ACI 318.
k. Concrete shall have a specified compressive strength, f ' c , of not less than 2,500 psi at 28 days, unless a higher strength is required by footnote l or m.
l. The minimum thickness is permitted to be reduced 2 inches, provided the minimum specified compressive strength of concrete, f ' c , is 4,000 psi.
m. A plain concrete wall with a minimum nominal thickness of 12 inches is permitted, provided minimum specified compressive strength of concrete, f ' c , is 3,500 psi.
n. See Table R611.3 for tolerance from nominal thickness permitted for flat walls.
TABLE R404.1.2(9)
MINIMUM SPACING FOR ALTERNATE BAR SIZE AND/OR ALTERNATE GRADE OF STEELa, b, c
| BAR SPACING | BAR SIZE FROM APPLICABLE TABLE IN SECTION R404.1.2.2 | ||||||||||||||
| #4 | #5 | #6 | |||||||||||||
| Alternate bar size and/or alternate grade of steel desired | |||||||||||||||
| Grade 60 | Grade 40 | Grade 60 | Grade 40 | Grade 60 | Grade 40 | ||||||||||
| #5 | #6 | #4 | #5 | #6 | #4 | #6 | #4 | #5 | #6 | #4 | #5 | #4 | #5 | #6 | |
| Maximum spacing for alternate bar size and/or alternate grade of steel (inches) | |||||||||||||||
| 8 | 12 | 18 | 5 | 8 | 12 | 5 | 11 | 3 | 5 | 8 | 4 | 6 | 2 | 4 | 5 |
| 9 | 14 | 20 | 6 | 9 | 13 | 6 | 13 | 4 | 6 | 9 | 4 | 6 | 3 | 4 | 6 |
| 10 | 16 | 22 | 7 | 10 | 15 | 6 | 14 | 4 | 7 | 9 | 5 | 7 | 3 | 5 | 7 |
| 11 | 17 | 24 | 7 | 11 | 16 | 7 | 16 | 5 | 7 | 10 | 5 | 8 | 3 | 5 | 7 |
| 12 | 19 | 26 | 8 | 12 | 18 | 8 | 17 | 5 | 8 | 11 | 5 | 8 | 4 | 6 | 8 |
| 13 | 20 | 29 | 9 | 13 | 19 | 8 | 18 | 6 | 9 | 12 | 6 | 9 | 4 | 6 | 9 |
| 14 | 22 | 31 | 9 | 14 | 21 | 9 | 20 | 6 | 9 | 13 | 6 | 10 | 4 | 7 | 9 |
| 15 | 23 | 33 | 10 | 16 | 22 | 10 | 21 | 6 | 10 | 14 | 7 | 11 | 5 | 7 | 10 |
| 16 | 25 | 35 | 11 | 17 | 23 | 10 | 23 | 7 | 11 | 15 | 7 | 11 | 5 | 8 | 11 |
| 17 | 26 | 37 | 11 | 18 | 25 | 11 | 24 | 7 | 11 | 16 | 8 | 12 | 5 | 8 | 11 |
| 18 | 28 | 40 | 12 | 19 | 26 | 12 | 26 | 8 | 12 | 17 | 8 | 13 | 5 | 8 | 12 |
| 19 | 29 | 42 | 13 | 20 | 28 | 12 | 27 | 8 | 13 | 18 | 9 | 13 | 6 | 9 | 13 |
| 20 | 31 | 44 | 13 | 21 | 29 | 13 | 28 | 9 | 13 | 19 | 9 | 14 | 6 | 9 | 13 |
| 21 | 33 | 46 | 14 | 22 | 31 | 14 | 30 | 9 | 14 | 20 | 10 | 15 | 6 | 10 | 14 |
| 22 | 34 | 48 | 15 | 23 | 32 | 14 | 31 | 9 | 15 | 21 | 10 | 16 | 7 | 10 | 15 |
| 23 | 36 | 48 | 15 | 24 | 34 | 15 | 33 | 10 | 15 | 22 | 10 | 16 | 7 | 11 | 15 |
| 24 | 37 | 48 | 16 | 25 | 35 | 15 | 34 | 10 | 16 | 23 | 11 | 17 | 7 | 11 | 16 |
| 25 | 39 | 48 | 17 | 26 | 37 | 16 | 35 | 11 | 17 | 24 | 11 | 18 | 8 | 12 | 17 |
| 26 | 40 | 48 | 17 | 27 | 38 | 17 | 37 | 11 | 17 | 25 | 12 | 18 | 8 | 12 | 17 |
| 27 | 42 | 48 | 18 | 28 | 40 | 17 | 38 | 12 | 18 | 26 | 12 | 19 | 8 | 13 | 18 |
| 28 | 43 | 48 | 19 | 29 | 41 | 18 | 40 | 12 | 19 | 26 | 13 | 20 | 8 | 13 | 19 |
| 29 | 45 | 48 | 19 | 30 | 43 | 19 | 41 | 12 | 19 | 27 | 13 | 20 | 9 | 14 | 19 |
| 30 | 47 | 48 | 20 | 31 | 44 | 19 | 43 | 13 | 20 | 28 | 14 | 21 | 9 | 14 | 20 |
| 31 | 48 | 48 | 21 | 32 | 45 | 20 | 44 | 13 | 21 | 29 | 14 | 22 | 9 | 15 | 21 |
| 32 | 48 | 48 | 21 | 33 | 47 | 21 | 45 | 14 | 21 | 30 | 15 | 23 | 10 | 15 | 21 |
| 33 | 48 | 48 | 22 | 34 | 48 | 21 | 47 | 14 | 22 | 31 | 15 | 23 | 10 | 16 | 22 |
| 34 | 48 | 48 | 23 | 35 | 48 | 22 | 48 | 15 | 23 | 32 | 15 | 24 | 10 | 16 | 23 |
| 35 | 48 | 48 | 23 | 36 | 48 | 23 | 48 | 15 | 23 | 33 | 16 | 25 | 11 | 16 | 23 |
| 36 | 48 | 48 | 24 | 37 | 48 | 23 | 48 | 15 | 24 | 34 | 16 | 25 | 11 | 17 | 24 |
| 37 | 48 | 48 | 25 | 38 | 48 | 24 | 48 | 16 | 25 | 35 | 17 | 26 | 11 | 17 | 25 |
| 38 | 48 | 48 | 25 | 39 | 48 | 25 | 48 | 16 | 25 | 36 | 17 | 27 | 12 | 18 | 25 |
| 39 | 48 | 48 | 26 | 40 | 48 | 25 | 48 | 17 | 26 | 37 | 18 | 27 | 12 | 18 | 26 |
| 40 | 48 | 48 | 27 | 41 | 48 | 26 | 48 | 17 | 27 | 38 | 18 | 28 | 12 | 19 | 27 |
| 41 | 48 | 48 | 27 | 42 | 48 | 26 | 48 | 18 | 27 | 39 | 19 | 29 | 12 | 19 | 27 |
| 42 | 48 | 48 | 28 | 43 | 48 | 27 | 48 | 18 | 28 | 40 | 19 | 30 | 13 | 20 | 28 |
| 43 | 48 | 48 | 29 | 44 | 48 | 28 | 48 | 18 | 29 | 41 | 20 | 30 | 13 | 20 | 29 |
| 44 | 48 | 48 | 29 | 45 | 48 | 28 | 48 | 19 | 29 | 42 | 20 | 31 | 13 | 21 | 29 |
| 45 | 48 | 48 | 30 | 47 | 48 | 29 | 48 | 19 | 30 | 43 | 20 | 32 | 14 | 21 | 30 |
(continued)
TABLE R404.1.2(9)—continued
MINIMUM SPACING FOR ALTERNATE BAR SIZE AND/OR ALTERNATE GRADE OF STEELa, b, c
| BAR SPACING | BAR SIZE FROM APPLICABLE TABLE IN SECTION R404.1.2.2 | ||||||||||||||
| #4 | #5 | #6 | |||||||||||||
| Alternate bar size and/or alternate grade of steel desired to be used | |||||||||||||||
| Grade 60 | Grade 40 | Grade 60 | Grade 40 | Grade 60 | Grade 40 | ||||||||||
| #5 | #6 | #4 | #5 | #6 | #4 | #6 | #4 | #5 | #6 | #4 | #5 | #4 | #5 | #6 | |
| Maximum spacing for alternate bar size and/or alternate grade of steel (inches) | |||||||||||||||
| 46 | 48 | 48 | 31 | 48 | 48 | 30 | 48 | 20 | 31 | 44 | 21 | 32 | 14 | 22 | 31 |
| 47 | 48 | 48 | 31 | 48 | 48 | 30 | 48 | 20 | 31 | 44 | 21 | 33 | 14 | 22 | 31 |
| 48 | 48 | 48 | 32 | 48 | 48 | 31 | 48 | 21 | 32 | 45 | 22 | 34 | 15 | 23 | 32 |
For SI: 1 inch = 25.4 mm, 1 pound per square inch = 6.895 kPa.
a. This table is for use with tables in Section R404.1.2.2 that specify the minimum bar size and maximum spacing of vertical wall reinforcement for foundation walls and above-grade walls. Reinforcement specified in tables in Sections R404.1.2.2 is based on Grade 60 steel reinforcement.
b. Bar spacing shall not exceed 48 inches on center and shall not be less than one-half the nominal wall thickness.
c. For Grade 50 steel bars (ASTM A 996, Type R), use spacing for Grade 40 bars or interpolate between Grades 40 and 60.
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 degree = 0.0175 rad.
Foundation stem walls that support above-grade concrete walls shall be designed and constructed in accordance with this section.
1. Stem walls not laterally supported at top. Concrete stem walls that are not monolithic with slabs-on-ground or are not otherwise laterally supported by slabs-on-ground shall comply with this section. Where unbalanced backfill retained by the stem wall is less than or equal to 18 inches (457 mm), the stem wall and above-grade wall it supports shall be provided with vertical reinforcement in accordance with Section R611.6 and Table R611.6(1), R611.6(2) or R611.6(3) for above-grade walls. Where unbalanced backfill retained by the stem wall is greater than 18 inches (457 mm), the stem wall and above-grade wall it supports shall be provided with vertical reinforcement in accordance with Section R611.6 and Table R611.6(4).
2. Stem walls laterally supported at top. Concrete stem walls that are monolithic with slabs-on- ground or are otherwise laterally supported by slabs-on-ground shall be vertically reinforced in accordance with Section R611.6 and Table R611.6(1), R611.6(2) or R611.6(3) for above- grade walls. Where the unbalanced backfill retained by the stem wall is greater than 18 inches (457 mm), the connection between the stem wall and the slab-on-ground, and the portion of the slab-on-ground providing lateral support for the wall shall be designed in accordance with PCA 100 or in accordance with accepted engineering practice. Where the unbalanced backfill retained by the stem wall is greater than 18 inches (457 mm), the minimum nominal thickness of the wall shall be 6 inches (152 mm).
Concrete foundation stem walls that support light-frame above-grade walls shall be designed and constructed in accordance with this section.
1. Stem walls not laterally supported at top. Concrete stem walls that are not monolithic with slabs-on-ground or are not otherwise laterally supported by slabs-on-ground and retain 48 inches (1219 mm) or less of unbalanced fill, measured from the top of the wall, shall be constructed in accordance with Section R404.1.2. Foundation stem walls that retain more than 48 inches (1219 mm) of unbalanced fill, measured from the top of the wall, shall be designed in accordance with Sections R404.1.3 and R404.4.
2. Stem walls laterally supported at top. Concrete stem walls that are monolithic with slabs-on- ground or are otherwise laterally supported by slabs-on-ground shall be constructed in accordance with Section R404.1.2. Where the unbalanced backfill retained by the stem wall is greater than 48 inches (1219 mm), the connection between the stem wall and the slab-on- ground, and the portion of the slab-on-ground providing lateral support for the wall shall be designed in accordance with PCA 100 or in accordance with accepted engineering practice.
The nominal maximum size of coarse aggregate shall not exceed one-fifth the narrowest distance between sides of forms, or three-fourths the clear spacing between reinforcing bars or between a bar and the side of the form.
Exception: When approved, these limitations shall not apply where removable forms are used and workability and methods of consolidation permit concrete to be placed without honeycombs or voids.
Proportions of materials for concrete shall be established to provide workability and consistency to permit concrete to be worked readily into forms and around reinforcement under conditions of placement to be employed, without segregation or excessive bleeding. Slump of concrete placed in removable forms shall not exceed 6 inches (152 mm).
Exception: When approved, the slump is permitted to exceed 6 inches (152 mm) for concrete mixtures that are resistant to segregation, and are in accordance with the form manufacturer’s recommendations.
Slump of concrete placed in stay-in-place forms shall exceed 6 inches (152 mm). Slump of concrete shall be determined in accordance with ASTM C 143.
Concrete shall be consolidated by suitable means during placement and shall be worked around embedded items and reinforcement and into corners of forms. Where stay-in-place forms are used, concrete shall be consolidated by internal vibration.
Exception: When approved for concrete to be placed in stay-in-place forms, self-consolidating concrete mixtures with slumps equal to or greater than 8 inches (203 mm) that are specifically designed for placement without internal vibration need not be internally vibrated.
Forms shall be made of wood, steel, aluminum, plastic, a composite of cement and foam insulation, a composite of cement and wood chips, or other approved material suitable for supporting and containing concrete. Forms shall provide sufficient strength to contain concrete during the concrete placement operation.
Form ties shall be steel, solid plastic, foam plastic, a composite of cement and wood chips, a composite of cement and foam plastic, or other suitable material capable of resisting the forces created by fluid pressure of fresh concrete.
Stay-in- place concrete forms shall comply with this section.
1. Surface burning characteristics. The flame-spread index and smoke-developed index of forming material, other than foam plastic, left exposed on the interior shall comply with Section R302. The surface burning characteristics of foam plastic used in insulating concrete forms shall comply with Section R316.3.
2. Interior covering. Stay-in-place forms constructed of rigid foam plastic shall be protected on the interior of the building as required by Section R316. Where gypsum board is used to protect the foam plastic, it shall be installed with a mechanical fastening system. Use of adhesives in addition to mechanical fasteners is permitted.
Construction joints in foundation walls shall be made and located to not impair the strength of the wall. Construction joints in plain concrete walls, including walls required to have not less than No. 4 bars at 48 inches (1219 mm) on center by Sections R404.1.2.2 and R404.1.4.2, shall be located at points of lateral support, and a minimum of one No. 4 bar shall extend across the construction joint at a spacing not to exceed 24 inches (610 mm) on center. Construction joint reinforcement shall have a minimum of 12 inches (305 mm) embedment on both sides of the joint. Construction joints in reinforced concrete walls shall be located in the middle third of the span between lateral supports, or located and constructed as required for joints in plain concrete walls.
Exception: Use of vertical wall reinforcement required by this code is permitted in lieu of construction joint reinforcement provided the spacing does not exceed 24 inches (610 mm), or the combination of wall reinforcement and No.4 bars described above does not exceed 24 inches (610 mm).
Concrete or masonry foundation walls shall be designed in accordance with accepted engineering practice when either of the following conditions exists:
1. Walls are subject to hydrostatic pressure from groundwater.
2. Walls supporting more than 48 inches (1219 mm) of unbalanced backfill that do not have permanent lateral support at the top or bottom.
In addition to the requirements of Table R404.1.1(1) plain masonry foundation walls in buildings assigned to Seismic Design Category D0, D1 or D2, as established in Table R301.2(1), shall comply with the following.
1. Wall height shall not exceed 8 feet (2438 mm).
2. Unbalanced backfill height shall not exceed 4 feet (1219 mm).
3. Minimum nominal thickness for plain masonry foundation walls shall be 8 inches (203 mm).
4. Masonry stem walls shall have a minimum vertical reinforcement of one No. 3 (No. 10) bar located a maximum of 4 feet (1219 mm) on center in grouted cells. Vertical reinforcement shall be tied to the horizontal reinforcement in the footings.
Foundation walls in buildings assigned to Seismic Design Category D0, D1 or D2, as established in Table R301.2(1), supporting more than 4 feet (1219 mm) of unbalanced backfill or exceeding 8 feet (2438 mm) in height shall be constructed in accordance with Table R404.1.1(2), R404.1.1(3) or R404.1.1(4). Masonry foundation walls shall have two No. 4 (No. 13) horizontal bars located in the upper 12 inches (305 mm) of the wall.
In buildings assigned to Seismic Design Category D0, D1 or D2, as established in Table R301.2(1), concrete foundation walls that support light-frame walls shall comply with this section, and concrete foundation walls that support above-grade concrete walls shall comply with ACI 318, ACI 332 or PCA 100 (see Section R404.1.2). In addition to the horizontal reinforcement required by Table R404.1.2(1), plain concrete walls supporting light-frame walls shall comply with the following.
1. Wall height shall not exceed 8 feet (2438 mm).
2. Unbalanced backfill height shall not exceed 4 feet (1219 mm).
3. Minimum thickness for plain concrete foundation walls shall be 7.5 inches (191 mm) except that 6 inches (152 mm) is permitted where the maximum wall height is 4 feet, 6 inches (1372 mm).
Foundation walls less than 7.5 inches (191 mm) in thickness, supporting more than 4 feet (1219 mm) of unbalanced backfill or exceeding 8 feet (2438 mm) in height shall be provided with horizontal reinforcement in accordance with Table R404.1.2(1), and vertical reinforcement in accordance with Table R404.1.2(2), R404.1.2(3), R404.1.2(4), R404.1.2(5), R404.1.2(6), R404.1.2(7) or R404.1.2(8). Where Tables R404.1.2(2) through R404.1.2(8) permit plain concrete walls, not less than No. 4 (No. 13) vertical bars at a spacing not exceeding 48 inches (1219 mm) shall be provided.
The thickness of masonry or concrete foundation walls shall not be less than that required by Section R404.1.5.1 or R404.1.5.2, respectively.
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 degree = 0.0175 rad.
FIGURE R404.1.5(1)
FOUNDATION WALL CLAY MASONRY CURTAIN WALL WITH CONCRETE MASONRY PIERS
The thickness of concrete foundation walls shall be equal to or greater than the thickness of the wall in the story above. Concrete foundation walls with corbels, brackets or other projections built into the wall for support of masonry veneer or other purposes are not within the scope of the tables in this section.
Where a concrete foundation wall is reduced in thickness to provide a shelf for the support of masonry veneer, the reduced thickness shall be equal to or greater than the thickness of the wall in the story above. Vertical reinforcement for the foundation wall shall be based on Table R404.1.2(8) and located in the wall as required by Section R404.1.2.3.7.2 where that table is used. Vertical reinforcement shall be based on the thickness of the thinner portion of the wall.
Exception: Where the height of the reduced thickness portion measured to the underside of the floor assembly or sill plate above is less than or equal to 24 inches (610 mm) and the reduction in thickness does not exceed 4 inches (102 mm), the vertical reinforcement is permitted to be based on the thicker portion of the wall.
Use of pier and curtain wall foundations shall be permitted to support light-frame construction not more than two stories in height, provided the following requirements are met:
1. All load-bearing walls shall be placed on continuous concrete footings placed integrally with the exterior wall footings.
2. The minimum actual thickness of a load-bearing masonry wall shall be not less than 4 inches (102 mm) nominal or 33/8 inches (92 mm) actual thickness, and shall be bonded integrally with piers spaced in accordance with Section R606.9.
3. Piers shall be constructed in accordance with Section R606.6 and Section R606.6.1, and shall be bonded into the load-bearing masonry wall in accordance with Section R608.1.1 or Section R608.1.1.2.
4. The maximum height of a 4-inch (102 mm) load-bearing masonry foundation wall supporting wood-frame walls and floors shall not be more than 4 feet (1219 mm).
5. Anchorage shall be in accordance with Section R403.1.6, Figure R404.1.5(1), or as specified by engineered design accepted by the building official.
6. The unbalanced fill for 4-inch (102 mm) foundation walls shall not exceed 24 inches (610 mm) for solid masonry or 12 inches (305 mm) for hollow masonry.
7. In Seismic Design Categories D0, D1 and D2, prescriptive reinforcement shall be provided in the horizontal and vertical direction. Provide minimum horizontal joint reinforcement of two No.9 gage wires spaced not less than 6 inches (152 mm) or one 1/4 inch (6.4 mm) diameter wire at 10 inches (254 mm) on center vertically. Provide minimum vertical reinforcement of one No. 4 bar at 48 inches (1220 mm) on center horizontally grouted in place.
Backfill shall not be placed against the wall until the wall has sufficient strength and has been anchored to the floor above, or has been sufficiently braced to prevent damage by the backfill.
Exception: Bracing is not required for walls supporting less than 4 feet (1219 mm) of unbalanced backfill.
For wood foundations that are not designed and installed in accordance with AF&PA PWF, the height of backfill against a foundation wall shall not exceed 4 feet (1219 mm). When the height of fill is more than 12 inches (305 mm) above the interior grade of a crawl space or floor of a basement, the thickness of the plywood sheathing shall meet the requirements of Table R404.2.3.
TABLE R404.2.3
PLYWOOD GRADE AND THICKNESS FOR WOOD FOUNDATION CONSTRUCTION
(30 pcf equivalent-fluid weight soil pressure)
| HEIGHT OF FILL | STUD SPACING (inches) | FACE GRAIN ACROSS STUDS | FACE GRAIN PARALLEL TO STUDS | ||||
| Minimum thickness (inches) | Span rating | Minimum thickness (inches)b, c | Span rating | ||||
| 24 | 12 | B | 15/32 | 32/16 | A | 15/32 | 32/16 |
| B | 15/32c | 32/16 | |||||
| 16 | B | 15/32 | 32/16 | A | 15/32c | 32/16 | |
| B | 19/32c (4, 5 ply) | 40/20 | |||||
| 36 | 12 | B | 15/32 | 32/16 | A | 15/32 | 32/16 |
| B | 15/32c (4, 5 ply) | 32/16 | |||||
| B | 19/32 (4, 5 ply) | 40/20 | |||||
| 16 | B | 15/32c | 32/16 | A | 19/32 | 40/20 | |
| B | 23/32 | 48/24 | |||||
| 48 | 12 | B | 15/32 | 32/16 | A | 15/32c | 32/16 |
| B | 19/32c (4, 5 ply) | 40/20 | |||||
| 16 | B | 19/32 | 40/20 | A | 19/32c | 40/20 | |
| A | 23/32 | 48/24 | |||||
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per cubic foot = 0.1572 kN/m3.
a. Plywood shall be of the following minimum grades in accordance with DOC PS 1 or DOC PS 2:
1. DOC PS 1 Plywood grades marked:
1.1. Structural I C-D (Exposure 1)
1.2. C-D (Exposure 1)
2. DOC PS 2 Plywood grades marked:
2.1. Structural I Sheathing (Exposure 1)
2.2. Sheathing (Exposure 1)
3. Where a major portion of the wall is exposed above ground and a better appearance is desired, the following plywood grades marked exterior are suitable:
3.1. Structural I A-C, Structural I B-C or Structural I C-C (Plugged) in accordance with DOC PS 1
3.2. A-C Group 1, B-C Group 1, C-C (Plugged) Group 1 or MDO Group 1 in accordance with DOC PS 1
3.3. Single Floor in accordance with DOC PS 1 or DOC PS 2
b. Minimum thickness 15/32 inch, except crawl space sheathing may be 3/8 inch for face grain across studs 16 inches on center and maximum 2-foot depth of unequal fill.
c. For this fill height, thickness and grade combination, panels that are continuous over less than three spans (across less than three stud spacings) require blocking 16 inches above the bottom plate. Offset adjacent blocks and fasten through studs with two 16d corrosion-resistant nails at each end.
Precast concrete foundation wall design drawings shall be submitted to the building official and approved prior to installation. Drawings shall include, at a minimum, the information specified below:
1. Design loading as applicable;
2. Footing design and material;
3. Concentrated loads and their points of application;
4. Soil bearing capacity;
5. Maximum allowable total uniform load;
6. Seismic design category; and
7. Basic wind speed.
Drains shall be provided around all concrete or masonry foundations that retain earth and enclose habitable or usable spaces located below grade. Drainage tiles, gravel or crushed stone drains, perforated pipe or other approved systems or materials shall be installed at or below the area to be protected and shall discharge by gravity or mechanical means into an approved drainage system. Gravel or crushed stone drains shall extend at least 1 foot (305 mm) beyond the outside edge of the footing and 6 inches (152 mm) above the top of the footing and be covered with an approved filter membrane material. The top of open joints of drain tiles shall be protected with strips of building paper, and the drainage tiles or perforated pipe shall be placed on a minimum of 2 inches (51 mm) of washed gravel or crushed rock at least one sieve size larger than the tile joint opening or perforation and covered with not less than 6 inches (152 mm) of the same material.
Exception: A drainage system is not required when the foundation is installed on well-drained ground or sand-gravel mixture soils according to the Unified Soil Classification System, Group I Soils, as detailed in Table R405.1.
TABLE R405.1
PROPERTIES OF SOILS CLASSIFIED ACCORDING TO THE UNIFIED SOIL CLASSIFICATION SYSTEM
| SOIL GROUP | UNIFIED SOIL CLASSIFICATION SYSTEM SYMBOL | SOIL DESCRIPTION | DRAINAGE CHARACTERISTICSa | FROST HEAVE POTENTIAL | VOLUME CHANGE POTENTIAL EXPANSIONb |
| Group I | GW | Well-graded gravels, gravel sand mixtures, little or no fines | Good | Low | Low |
| GP | Poorly graded gravels or gravel sand mixtures, little or no fines | Good | Low | Low | |
| SW | Well-graded sands, gravelly sands, little or no fines | Good | Low | Low | |
| SP | Poorly graded sands or gravelly sands, little or no fines | Good | Low | Low | |
| GM | Silty gravels, gravel-sand-silt mixtures | Good | Medium | Low | |
| SM | Silty sand, sand-silt mixtures | Good | Medium | Low | |
| Group II | GC | Clayey gravels, gravel-sand-clay mixtures | Medium | Medium | Low |
| SC | Clayey sands, sand-clay mixture | Medium | Medium | Low | |
| ML | Inorganic silts and very fine sands, rock flour, silty or clayey fine sands or clayey silts with slight plasticity | Medium | High | Low | |
| CL | Inorganic clays of low to medium plasticity, gravelly clays, sandy clays, silty clays, lean clays | Medium | Medium | Medium to Low | |
| Group III | CH | Poor | Medium | High | |
| MH | Inorganic silts, micaceous or diatomaceous fine sandy or silty soils, elastic silts | Poor | High | High | |
| Group IV | OL | Organic silts and organic silty clays of low plasticity | Poor | Medium | Medium |
| OH | Organic clays of medium to high plasticity, organic silts | Unsatisfactory | Medium | High | |
| Pt | Peat and other highly organic soils | Unsatisfactory | Medium | High |
For SI: 1 inch = 25.4 mm.
a. The percolation rate for good drainage is over 4 inches per hour, medium drainage is 2 inches to 4 inches per hour, and poor is less than 2 inches per hour.
b. Soils with a low potential expansion typically have a plasticity index (PI) of 0 to 15, soils with a medium potential expansion have a PI of 10 to 35 and soils with a high potential expansion have a PI greater than 20.
Except where required by Section R406.2 to be waterproofed, foundation walls that retain earth and enclose interior spaces and floors below grade shall be dampproofed from the top of the footing to the finished grade. Masonry walls shall have not less than 3/8 inch (9.5 mm) portland cement parging applied to the exterior of the wall. The parging shall be dampproofed in accordance with one of the following:
1. Bituminous coating.
2. Three pounds per square yard (1.63 kg/m2) of acrylic modified cement.
3. One-eighth inch (3.2 mm) coat of surface-bonding cement complying with ASTM C 887.
4. Any material permitted for waterproofing in Section R406.2.
5. Other approved methods or materials.
Exception: Parging of unit masonry walls is not required where a material is approved for direct application to the masonry.
Concrete walls shall be dampproofed by applying any one of the above listed dampproofing materials or any one of the waterproofing materials listed in Section R406.2 to the exterior of the wall.
In areas where a high water table or other severe soil-water conditions are known to exist, exterior foundation walls that retain earth and enclose interior spaces and floors below grade shall be waterproofed from the top of the footing to the finished grade. Walls shall be waterproofed in accordance with one of the following:
1. Two-ply hot-mopped felts.
2. Fifty five pound (25 kg) roll roofing.
3. Six-mil (0.15 mm) polyvinyl chloride.
4. Six-mil (0.15 mm) polyethylene.
5. Forty-mil (1 mm) polymer-modified asphalt.
6. Sixty-mil (1.5 mm) flexible polymer cement.
7. One-eighth inch (3 mm) cement-based, fiber-reinforced, waterproof coating.
8. Sixty-mil (0.22 mm) solvent-free liquid-applied synthetic rubber.
Exception: Organic-solvent-based products such as hydrocarbons, chlorinated hydrocarbons, ketones and esters shall not be used for ICF walls with expanded polystyrene form material. Use of plastic roofing cements, acrylic coatings, latex coatings, mortars and pargings to seal ICF walls is permitted. Cold-setting asphalt or hot asphalt shall conform to type C of ASTM D 449. Hot asphalt shall be applied at a temperature of less than 200°F (93°C).
All joints in membrane waterproofing shall be lapped and sealed with an adhesive compatible with the membrane.
The columns shall be restrained to prevent lateral displacement at the bottom end. Wood columns shall not be less in nominal size than 4 inches by 4 inches (102 mm by 102 mm). Steel columns shall not be less than 3-inch-diameter (76 mm) Schedule 40 pipe manufactured in accordance with ASTM A 53 Grade B or approved equivalent.
Exception: In Seismic Design Categories A, B and C, columns no more than 48 inches (1219 mm) in height on a pier or footing are exempt from the bottom end lateral displacement requirement within under-floor areas enclosed by a continuous foundation.
The minimum net area of ventilation openings shall not be less than 1 square foot (0.0929 m2) for each 150 square feet (14 m2) of under-floor area. One ventilation opening shall be within 3 feet (915 mm) of each corner of the building. Ventilation openings shall be covered for their height and width with any of the following materials provided that the least dimension of the covering shall not exceed 1/4 inch (6.4 mm):
1. Perforated sheet metal plates not less than 0.070 inch (1.8 mm) thick.
2. Expanded sheet metal plates not less than 0.047 inch (1.2 mm) thick.
3. Cast-iron grill or grating.
4. Extruded load-bearing brick vents.
5. Hardware cloth of 0.035 inch (0.89 mm) wire or heavier.
6. Corrosion-resistant wire mesh, with the least dimension being 1/8 inch (3.2 mm) thick.
Exception: The total area of ventilation openings shall be permitted to be reduced to 1/1,500 of the under-floor area where the ground surface is covered with an approved Class I vapor retarder material and the required openings are placed to provide cross ventilation of the space. The installation of operable louvers shall not be prohibited.
Ventilation openings in under-floor spaces specified in Sections R408.1 and R408.2 shall not be required where:
1. Exposed earth is covered with a continuous Class I vapor retarder. Joints of the vapor retarder shall overlap by 6 inches (152 mm) and shall be sealed or taped. The edges of the vapor retarder shall extend at least 6 inches (152 mm) up the stem wall and shall be attached and sealed to the stem wall; and
2. One of the following is provided for the under-floor space:
2.1. Continuously operated mechanical exhaust ventilation at a rate equal to 1 cubic foot per minute (0.47 L/s) for each 50 square feet (4.7m2) of crawlspace floor area, including an air pathway to the common area (such as a duct or transfer grille), and perimeter walls insulated in accordance with Section N1102.2.9;
2.2. Conditioned air supply sized to deliver at a rate equal to 1 cubic foot per minute (0.47 L/s) for each 50 square feet (4.7 m2) of under-floor area, including a return air pathway to the common area (such as a duct or transfer grille), and perimeter walls insulated in accordance with Section N1102.2.9;
2.3. Plenum in existing structures complying with Section M1601.5, if under-floor space is used as a plenum.
For buildings located in areas prone to flooding as established in Table R301.2(1):
1. Walls enclosing the under-floor space shall be provided with flood openings in accordance with Section R322.2.2.
2. The finished ground level of the under-floor space shall be equal to or higher than the outside finished ground level on at least one side.
Exception: Under-floor spaces that meet the requirements of FEMA/FIA TB 11-1.