CHAPTER 4

FOUNDATIONS

SECTION R401GENERAL

R401.1 Application. The provisions of this chapter shallcontrol the design and construction of the foundation andfoundation spaces for all buildings. In addition to the provi­sions of this chapter, the design and construction of founda ­tions in flood hazard areas as es tablished by Tab le R301.2(1)shall meet the provisions of Section R322. Wood foundationsshall be designed and install ed in accordan ce with AF&PAPWF.

Exception: The provisions of this chapter shall be permit­ted to be used for wood foundations only in the followingsituations:

1. In buildings that have no more than two floors and aroof.

2. When interior basement and foundation walls areconstructed at intervals not exceeding 50 feet (15240 mm) .

Wood foundations in Seism ic Design Category Do. D, orDzshall be designed in accordance with acce pted engineeringpractice.

R401.2 Requirements. Foundation construction shall becapable of accom modating all loads according to SectionR301 and of transmlttlng the resulting loads to the supportingso il. Fill soils that support footings and foundation s hall bedesigned, installed and tested in accordance with acce ptedengineering practice. Grave l III1 used as footings for woodand precast concrete foundations shall comply with SectionR403.

R401.3 Drainage. Surface dra inage shall be divert ed to astorm sewer conveyance or other approved point of collec­tion that does not create a hazard. Lots shall be graded todrain surface water away from foundation walls. The gradeshall fall a minimum of 6 inches (152 mill) within the first 10feet (3048 mm).

Exception: Where lot lilies. walls, s lopes or other physicalbarr iers prohibit 6 inches (152 mm) of fall within 10 feet(3048 mill). dra ins or swales shall be constructed to ensuredrainage away from the structure. Impervious surfaceswithin 10 feet (3048 mm) of the building foundation shallbe sloped a minimum of 2 percent away from the building.

R401A Soil tests. Where qua ntifiab le data created byaccepted soi l scien ce methodologies Indica te expans ive, COIll ­

presslble , shifting or other questionable soil charact eristics-are likely to be present, the building otttctal shall determinewhether to require a soil test to determ ine the soil's character­istlcs at a particular localion . This test shall be done by anapproved agency using an approved method.

R401.4.1 Geotechnical evaluation. In lieu of a completegeotechnical evaluation, the load-bearing values in TableR401.4.l shall be assum ed.

2012 INTERNATIONAL RESIDENTIAL CODE-

TABLE R401.4.1PRESUMPTIVE LOAD·BEARING VALUES OF

FOUNDATION MATERIALS'

LOAD·BEARINGCLASS OF MATERIAL PRESSURE

(pounds per square foot)

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 graveland clayey gravel (SW, SP , SM, SC , GM 2.000and GC)

Clay . sandy clay, silty clay, clayey sil t, silt1.500"and sandy silt (CL, ML, MH and CH)

For 5 1: t pound per square roo t = 0.0479 kPa.a. When so li tests arc required by Sec tion R40 1A. the allowable bearing

capaclties or the soli shall be pari or the recommendations.b. Wherl' Ihe building offlclnl determines that In-place se lls wlth an

allowable hearing capachy or less than 1.500 psf are likely 10 be present atthe sue, the allowab le bearing capacity shall he determined by a solislnvcsttgatlon .

R401.4.2 Compressible or shifting oil. Instead of acomplete geotechnical evaluation, when top or subsoilsare compressib le or shifting. they shall be removed 10 adepth and width sufficient to assur e stab le moisture con­tent in each active zone and shall not be used as fill or sta­bilized within each active zone by chemical, dewatering orpresaturation.

SECTION R402MATERIALS

R402.1 Wood foundations. Wood found ation systems shallbe designed and installed in accordance with the provision sof this code.

R402 .1.1 Fasteners. Fasteners used below grade to attac hplywoo d to the exterior side of exterior basement or crawl-pace wall s tuds, or fasteners used in knee wall construc­

tion, sha ll be of Type 304 or 3I6 stainless s teel. Fastenersused above grade to attach plywood and all lumber-to­lumber fasteners except those used in knee wall construc­tion sha ll be of Type 304 or 31G stainless steel, s iliconbronz e. copper. hot-dipped galvanized (Zinc coated) steelnails, or hot-tumbled galvanized (Zinc coated) steel nails.Electro-galvanized steel nails and galvanized (zinc coated)s teel stap les sha ll not be permitted.

R1I02.1.2 Wood treatment. All lumber and plywood shallbe pressure-preservative treated and dried after treatmentin accordance wit h AWP A U1 (Commod tty SpecificationA, Use Category 48 and Section 5.2). and shall bear thelabel of all acc redited agency. Where lumber and/or ply­wood is cut or drill ed after treatm ent, the treated surface

73

FOUNDATIONS

shall be field treated with copper naphthenate, the concen­tration of which shall contain a minimum of 2 percent cop­per metal, by repeated brushing, dipping or soaking untilthe wood absorbs no more preservative.

R402.2 Concrete. Concrete shall have a minimum specifiedcompressive strength of f' c' as shown in Table R402.2 . Con­crete subject to moderate or severe weathering as indicated inTable R301.2(1) shall be air entrained as specified in TableR402 .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 ofcementitious materials specified in Section 4.2.3 of ACI 318.Materials used to produce concrete and testing thereof shallcomply with the applicable standards listed in Chapter 3 ofACI 318 or ACI 332.

R402.3 Precast concrete. Precast concrete foundations shallbe designed in accordance with Section R404.5 and shall beinstalled in accordance with the provisions of this code andthe manufacturer's installation instructions.

R402.3.1 Precast concrete foundation materials. Mate ­rials used to produce precast concrete foundations shallmeet the following requirements.

I. 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 totalair 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 be40,000 psi (Grade 40) (276 MPa) . Steel reinforce­ment for precast concrete foundation walls shall

have a minimum concrete cover of 3/ 4 inch (19.1mm) .

3. Panel-to-panel connections shall be made withGrade II s teel faste ners.

4. The use of nonstructural fibers shall conform toASTM C 1116.

5. Grout used for bedd ing precast foundations placedupon concrete footings shall meet ASTM C 1107.

SECTION R403FOOTINGS

R403.1 General. All exterior walls shall be supported oncontinuous solid or fully grouted masonry or concrete foot­ings. crushed sto ne footings . woo d foundations. or otherappro ved structural syste ms which shall be of sufficientdesign to accommodate all loads according to Section R301and to transmi t the resulting loads to the soil within the limi­tations as determined from the character of the soil. Footingsshall be supported on undisturbed natural soils or engineeredfill. Concrete footing shall be designed and constructed inaccordance with the provisions of Section R403 or in accor­dance with ACI 332.

R403.1.1 Minimum size. Minimum sizes for concrete andmasonry footings shall be as set forth in Table R403.1 andFigure R403.1(1). The footing wid th. W. shall be based onthe load-bearing value of the soil in accordance with TableR401.4 .1. Spread footings shall be at least 6 inches (152mm) in thicknes s. T. Footing projections. P, shall be atleast 2 inches (51 mm) and shall not exceed the thicknessof the footing. The size of footings supporting piers andcolumns shall be based on the tributary load and allowabl esoil pressure in accordance with Table R401.4.1. Footingsfor wood foundations shall be in accordance with thedetails set forth in Section R403.2, and Figures R403.1 (2)and R403.1(3).

TABLE R402.2MINIMUM SPECIFIED COMPRESSIVE STRENGTH OF CONCRETE

MINIMUM SPECIFIED COMPRESSIVE STRENGTH' If:>TYPE OR LOCATION OF CONCRETE CONSTRUCTION Weathering Potential"

Negligible Moderate Severe

Basement walls, foundations and other concrete not exposed to the weather 2,500 2,500 2,500·

Basement slabs and interiorslabs on grade, except garage floor slabs 2,500 2,500 2.500·

Basement walls, foundation walls, exteriorwalls and other verticalconcrete 2,500 3,000d 3.00Qdwork exposed to the weather

Porches. carport slabsand steps exposed to the weather, and garage floor 2,500 3,000d,c,r 3,500d,c,rslabs

For SI: I pound per square Inch = 6.895 kPa,a, Strength at 28 days psJ.b. See Table R301.2(1) for weatherIng potential.c. Concrete In these locations that may be subj ect to freezIng and thawIng during conslructlon shall be air-entrained concrete In accordance wlth Footnote d.d. Concrete shall be alr-entral ned. Total aIr content (percent by volume of concrete) shall be not less than 5 percent or more than 7 percen t.e. See Section R402,2 for maximum cementltlous materials content.f. For garage /loors wlth a steel-troweled flnlsh, reduction of the total air content (percent by volume of con crete) to not less than 3 percent Is permitted If the

spect/led compressIve strength of the concrete Is Increased to not less than 4,000 psi

74 2012 INTERNATIONAL RESIDENTIAL CODE-

FOUNDATIONS

BEARING WALL

3.5 IN. MIN.

1'/\\'-:

. '

0: I. ...'.... .:

e , '

.... 0

MONOLITHIC SLAB WITHINTEGRAL FOOTING

INTERIOR

. E.' . . ....I.. W ~I

~ ~

IjI' I'll~i!N:,:\~II//\\\\

~W ~i

3.5 IN. MIN.

CLJp

.:,': ' ".:" : ..=.' E• 0 " ': • : -

I----w ~IGROUND SUPPORT SLABWITH MASONRY WALLAND SPREAD FOOTING

BASEMENT OR CRAWL SPACEWITH MASONRY WALL ANDSPREAD FOOTING

4---W

E

~ INTERIOR

W<Wl\\W. 1I 0 -

='.." ..-

BASEMENT OR CRAWL SPACEWITH CONCRETE WALL ANDSPREAD FOOTING

BASEMENT OR CRAWL SPACEWITH FOUNDATION WALLBEARING DIRECTLY ON SOIL

ForSI: 1 Inch= 25.4mm.

FIGURE R403.1(1)CONCRETE AND MASONRY FOUNDATION DETAILS

2012 INTERNATIONAL RESIDENTIAL CODE- 75

FOUNDATIONS

R403.1.2 Continuous footing in Seismic Design Catego­ries Do. D1 and Dz. The braced wall panels at exteriorwalls of buildings located in Seismic Design CategoriesDo, D) and D, shall be supported by continuous footings.All required interior braced wall panels in buildin gs withplan dimensions greater than 50 feet (15 240 mm) shallalso be supported by continuous footings.

TABLE R403.1MINIMUM WIDTH OF CONCRETE,

PRECAST OR MASONRY FOOTINGS (inches)'

LOAD·BEARING VALUE OF SOIL (pst)1,500 2,000 3,000 ;:: 4,000

co nventtcnal uqht-rrame construction

l-story 12 12 12 12

2-story 15 12 12 12

3-story 23 17 12 12

4·inch brickveneer over lightframe or a-Inchhollowconcrete masonry

I-story 12 12 12 12

2-story 21 16 12 12

3-story 32 24 16 12

a-lnch solid or fully grouted masonry

l-story 16 12 12 12

2-story 29 21 14 12

3-story 42 32 21 16

For 51: I Inch = 25.4 mm, I poundper square foot = 0.0479 kPa.a. Where minimum footing width is 12 Inches, useof a single wythe of solid

or fully grouted 12-lnchnominal concrete masonry units Is permitted.

R403.1.3 Seismic reinforcing. Concrete footings locatedin Seismic Design Categories Do, D[ and Dz' as establishedin Table R301.2(1) , shall have minimum reinforc ement.Bottom reinforcement shall be located a minimum of 3inches (76 mrn) clear from the bottom of the footing.

In Seismic Design Categories Do, D( and D, where aconstruction joint is created between a concrete footingand a stem wall, a minimum of one No.4 bar shall be

installed at not more than 4 feet (1219 mm) on center. Thevertical bar shall extend to 3 inches (76 mm) clear of thebottom of the footing, have a standard hook and extend aminimum of 14 inches (357 mm) into the stem wall.

In Seismic Design Categories Do. D1 and D, where agrouted masonry stem wall is supported on a concretefooting and stem wall . a minimum of one No.4 bar shallbe installed at not more than 4 feet (1219 mm) on center.The vertical bar shall extend to 3 inches (76 mm) clear ofthe bottom of the footing and have a standard hook.

In Seismic Design Categories Do, D[ and D, masonrystem walls without solid grout and vertical reinforcing arenot permitted,

Exception: In detached one- and two-family dwellingsIwhich are three stories or less in height and constructedwith stud bearing walls, isolated plain concrete foot­ings, supporting columns or pedestals are permitted .

R403.1.3.1 Foundations with stemwalls. Foundationswith stem walls shall have installed a minimum of oneNo.4 bar within 12 inches (305 mm) of the top of thewall and one No. 4 bar located 3 inches (76 mm) to 4inches (102 mm) from the bottom of the footing.

R403.1.3.2 Siabs-on-ground with turned-down foot ­ings. Slabs on ground with turned down footings shallhave 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 twoNo. 4 bars in the middle third of the footing depthshall be permitted as an alternative to placement atthe footing top and bottom.

Where the slab is not cast monolithically with thefooting , No. 3 or larger vertical dowels with standardhooks on each end shall be provided in accordance withFigure R403.1.3.2. Standard hooks shall comply withSection R611.5.4 .5.

CONSTRUCTION JOINT

~_ _ NO.3 MINIMUM @ 48 IN. ONCENTER VERTICAL DOWELS

3'1, IN. MINIMUM

1I"~4l-_--I---------rr SLAB THICKNESS

". /. ,

NO. 4 MINIMUM --- -4-__Jh_HORIZONTAL BARTOP AND BOTTOM

FOOTING

31N, COVER BOTTOMAND SIDES

For 51: I Inch = 25.4 mm.

FIGURE R403.1.3 .2DOWELS FOR SLABS·ON·GROUND WITH TURNED·DOWN FOOTINGS

78 2012 INTERNATIONAL RESIDENTIAL CODE"

R403.I.4 Minimum depth. All exterior footings shall beplaced at least 12 inches (305 mm) below the undisturbedground surface. Where applicable. the depth of footingsshall also conform to Sections R403.1A.1 throughR403.1A.2.

R403.1.4.1 Frost protection. Except where otherwiseprotected from frost. foundation walls, piers and otherpermanent supports of buildings and structures shall beprotected from frost by one or more of the followingmethods:

1. Extended below the frost line specified in TableR301.2.(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 aneave height of 10 feet (3048 mm) or less shallnot 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) orless shall not be required .

3. Decks not supported by a dwelling need not beprovided with footings that extend below thefrost line.

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

R403 .I.4.2 Seismic conditions. In Seismic DesignCategories Do. D1 and D2, interior footings supportingbearing or bracing walls and cast monolithically with aslab on grade shall extend to a depth of not less than 12inches (305 mm) below the top of the slab.

R403.I.5 Slope. The top surface of footings shall be level.The bottom surface of footings shall not have a slopeexceeding one unit vertical in 10 units horizontal (10-per­cent slope). Footings shall be stepped where it is necessaryto change the elevation of the top surface of the footings orwhere the slope of the bottom surface of the footings willexceed one unit vertical in ten units horizontal (10-percentslope) .

R403.I.6 Foundation anchorage. Sill plates and wallssupported directly on continuous foundations shall beanchored to the foundation in accordance with this section.

Wood sole plates at all exterior walls on monolithicslabs, wood sole plates of braced wall panels at buildinginteriors on monolithic slabs and all wood sill plates shallbe anchored to the foundation with anchor bolts spaced amaximum of 6 feet (1829 mm) on center. Bolts shall be atleast 1/2 inch (12.7 mm) in diameter and shall extend aminimum of 7 inches (178 mm) into concrete or groutedcells of concrete masonry units. A nut and washer shall be

2012 INTERNATIONAL RESIDENTIAL CODE"

FOUNDATIONS

tightened on each anchor bolt. There shall be a minimumof two bolts per plate section with one bolt located notmore than 12 inches (305 mm) or less than seven boltdiameters from each end of the plate section. Interior bear­ing wall sole plates on monolithic slab foundation that arenot part of a braced wall panel shall be positivelyanchored with approved fasteners . Sill plates and soleplates shall be protected against decay and termites whererequired by Sections R317 and R318. Cold-formed steelframing systems shall be fastened to wood sill plates oranchored directly to the foundation as required in SectionR505.3.1 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 shorterconnecting offset braced wall panels shall beanchored to the foundation with a minimum ofone anchor bolt located in the center third of theplate section and shall be attached to adjacentbraced wall panels at corners as shown in item 8of Table R602.3(1) .

3. Connection of walls 12 inches (305 mm) totallength or shorter connecting offset braced wallpanels to the foundation without anchor boltsshall be permitted. The wall shall be attached toadjacent braced wall panels at corners as shownin item 8 of Table R602.3(1).

R403.I.6.1 Foundation anchorage in Seismic DesignCategories C, Do. D1 and D2, In addition to therequirements of Section R403.1.6. the followingrequirements shall apply to wood light-frame structuresin Seismic Design Categories Do. D1 and D2 and woodlight-frame townhous es in Seismic Design Category C.

1. Plate washers conforming to Section R602.11.1shall be provided for all anchor bolts over the fulllength of required braced wall lines except whereapproved anchor straps are used. Properly sizedcut washers shall be permitted for anchor bolts inwall lines not containing braced wallpanels.

2. Interior braced wall plates shall have anchor boltsspaced at not more than 6 feet (1829 mm) on cen­ter and located within 12 inches (305 mm) of theends of each plate section when supported on acontinuous foundation.

3. Interior bearing wall sole plates shall have anchorbolts 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 supportedon a continuous foundation .

4. The maximum anchor bolt spacing shall be 4 feet(1219 mm) for buildings over two stories inheight.

5. Stepped cripple walls shall conform to SectionR602.11.2 .

79

FOUNDATIONS

Slump of concrete placed in stay-in-place formsshall exceed 6 inches (152 mm). Slump of concreteshall be determined in accordance with ASTM C143.

R404.1.2.3.5 Consolidation of concrete. Concreteshall be consolidated by suitable means duringplacement and shall be worked around embeddeditems and reinforcement and into corners of forms.Where stay-in-place forms are used, concrete shallbe consolidated by internal vibration,

Exception: When approved for concrete to beplaced in stay-in-place forms , self-consolidatingconcrete mixtures with slumps equal to or greaterthan 8 inches (203 mm) that are specificallydesigned for placement without internal vibrationneed not be internally Vibrated,

R404.1.2.3.6 Form materials and form ties. Formsshall be made of wood, steel, aluminum, plastic, acomposite of cement and foam insulation, a compos-

ite of cement and wood chips, or other approvedmaterial suitable for supporting and containing con­crete. Forms shall provide sufficient strength to con­tain concrete during the concrete placementoperation.

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 suitablematerial capable of resisting the forces created byfluid pressure of fresh concrete ,

R404.1.2.3.6.1 Stay-in-place forms. Stay-in­place concrete forms shall comply with this sec­tion.

1. Surface burning characteristics. The flame­spread index and smoke-developed indexof forming material, other than foam plas­tic, left exposed on the interior shall com­ply with Section R302, The surface burningcharacteristics of foam plastic used in insu-

TABLE R404.1.2(3)MINIMUM VERTICAL REINFORCEMENT FOR 8-INCH (203 mm) NOMINAL FLAT CONCRETE BASEMENT WALLSb.c.d.•.I.h.1

MINIMUM VERTICAL REINFORCEMENT·BAR SIZE AND SPACING (inches)MAXIMUM UNSUPPORTED MAXIMUM UNBALANCED

Soil classes' and design lateral soil (psf per foot of depth)WALL HEIGHT BACKFILL HEIGHTO(feet) (feet) GW, GP, SW, SP GM, GC, SM, SM-SC and ML SC, ML-CL and inorganic CL

30 45 60

4 NR NR NR5 NR NR NR

8 6 NR NR 6@37

7 NR 6@36 6@35

8 6@41 6 @35 6@ 26

4 NR NR NR5 NR NR NR6 NR NR 6@35

97 NR 6@ 35 6@ 32

8 6@36 6@32 6@23

9 6@35 6@ 25 6@ 18

4 NR NR NR5 NR NR NR6 NR NR 6@35

10 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 rnm: linch = 25.4 rnm: 1 pound per square foot per foot =0.1571 kPa2/m. 1 pound per square Inch =6.895 kPa.NR = Not required.a. Soli 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 vertlcal reinforcement being located at the centerline of the wall. See Section R404.1.2.3.7.2.c. Vertlcal 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

Sectlon R404.1.2.3.7.6 and Table R404.1.2(9).d. NR Indicates no vertlcal reinforcement is required .e. Deflection criterion Is IJ240. 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.

98 2012 INTERNATIONAL RESIDENTIAL CODE"