Section 321.18. Foundations.

 

(1)   General.

(a) Design. Foundation walls shall be designed and constructed to support the vertical loads of the dwelling, lateral soil pressure, and other loads without exceeding the allowable stresses of the materials of which the foundations are constructed.

(b) Lateral support at base. Lateral support such as floor slabs or framing shall be provided at the base of foundation walls.

(c) Lateral support at top. Lateral support shall be provided at the top of the foundation walls by one of the following:

2. Structural analysis. A system designed through structural analysis.

3. Anchor bolts.

a. Structural steel anchor bolts, at least 1/2 inch in diameter, embedded at least 7 inches into the concrete or grouted masonry with a maximum spacing of 72 inches and located within 18 inches of wall corners.

b. A properly sized nut and washer shall be tightened on each bolt to the plate or sill.

c. When vertical-reinforcing steel is provided in masonry construction, as required under sub. (3) , the location requirements under subd. 3. a. shall be modified as necessary so anchor bolts are placed in the same core as the reinforcement without exceeding the limits of subd. 3. a.

d. Alternate foundation anchorage, designed and spaced in accordance with structural analysis and as required to provide equivalent anchorage to the requirements of subd. 3. a. , is allowable.

4. Other mechanical fasteners.

a. Mechanical fasteners used in accordance with the manufacturer's testing and listing.

b. When vertical-reinforcing steel is provided in masonry construction, as required under sub. (3) , the location requirements under subd. 4. a. shall be modified as necessary so the fasteners are placed in the same core as the reinforcement without exceeding the limits of subd. 4. a.

(d) Floor framing .

1. Floor framing shall be fastened to the sill plate by one of the following methods:

a. Mechanical fasteners used in accordance with the manufacturer's testing and listing.

b. In accordance with structural analysis.

c. In accordance with the fastener table printed in ch. SPS 325 Appendix A .

2.

a. Where the floor framing is parallel to the foundation wall, solid blocking or bridging shall be installed in at least the first adjacent joist space at a spacing of no more than 32 inches on center.

b. Blocking and bridging shall be the same depth as the joist.

c. Fastening of the blocking or bridging shall be in accordance with structural analysis or the fastener schedule in Table 321.02-2.

(e) Soil lateral load. Unless designed through structural analysis, soil lateral loads shall be determined from Table 321.18-A. - See PDF for table

(2)   Concrete foundation walls.

(a) General structural requirements. Except as provided in par. (b) , unless designed through structural analysis, the minimum thickness of concrete foundation walls shall be determined from Table 321.18-B, but in no case shall the thickness of the foundation wall be less than the thickness of the wall it supports.

(b) Equalized loading. A 6-inch nominal wall thickness may be used provided the fill on one side of the wall is within 12 inches vertically of the fill on the other side of the wall.

(3)   Masonry foundation walls.

(a) Dampproofing.

1. Except as allowed under subd. 3. , masonry block foundation walls shall be coated with a layer of minimum 3 / 8 -inch thick type M or S portland cement mortar parging on the exterior of the wall from footing to finished grade.

2. Masonry foundation walls shall be damp-proofed by applying to the exterior surface of the portland cement parging from footing to finished grade, a continuous coating of one of the following:

a. A bituminous coating applied in accordance with the manufacturer's instructions.

b. Acrylic-modified cement applied at a minimum rate of 3 pounds per square yard.

c. A layer of minimum 1 / 8 -inch thick structural surface bonding material labeled as complying with ASTM C887.

d. A waterproofing treatment applied in accordance with the manufacturer's instructions.

3.

a. Parging of masonry block foundation walls is not required where a dampproofing material is sufficiently flexible to be listed or designed for direct application to masonry block.

b. Parging of masonry block foundation walls is not required where a layer of minimum ¼ -inch thick structural surface bonding material labeled as complying with ASTM C887 is used for dampproofing.

(b) Structural requirements. Unless designed through structural analysis, the masonry foundation walls shall be constructed in accordance with ACI 530.1 and the following requirements:

1. The minimum thickness of unreinforced masonry foundation walls shall be determined by Table 321.18-C, but in no case shall the thickness be less than the thickness of the wall it supports.

2. Reinforced masonry walls shall be reinforced in accordance with the requirements of Tables 321.18-D, 321.18-E or 321.18-F. Vertical reinforcement shall be provided on each side of any opening and at intervals indicated in the appropriate table. - See PDF for table - See PDF for table - See PDF for table - See PDF for table

3. Vertical reinforcement shall have a minimum yield strength of 60,000 psi.

4. Solid-grouted hollow units or cores containing vertical reinforcement shall be filled with masonry grout that complies with ASTM C 476.

5. In lieu of the reinforcement provisions of Tables 321.18-D, 321.18-E and 321.18-F, alternative reinforcing bar size and spacing having an equivalent cross-sectional area or reinforcement per linear foot of wall is permitted, provided the spacing of the reinforcement does not exceed 72 inches and reinforcing bar size does not exceed No. 11.

6. The depth below grade, wall height and reinforcement spacing may exceed the maximum values indicated in Tables 321.18-D, 321.18-E and 321.18-F only if the design is based on structural analysis.

(4)   Wood foundations. Wood foundations shall be designed and constructed in accordance with the wood-foundation standard adopted in Table 320.24-6m.

Cr. Register, November, 1979, No. 287 , eff. 6-1-80; am. (3) (intro), Register, February, 1985, No. 350 , eff. 3-1-85; cr. (2) (c) to (e), r. and recr. Tables C and D, r. (3) (a) 2., renum. (3) (a) 1. to be (a), Register, January, 1989, No. 397 , eff. 2-1-89; am. (intro.), (2) (b), (3) (b) and Table 21.18-D, cr. Table 21.18, r. (2) (c), renum. (2) (d) and (e) to be (2) (c) and (d), Register, March, 1992, No. 435 , eff. 4-1-92; renum. (1) to (3) to be (2) to (4), and am. (3) (b), (4) (intro.) and (b), Table 21.18-A, r. (intro.) and Table 21.18, cr. (1), (3) (e), Register, November, 1995, No. 479 , eff. 12-1-95; am (2), Register, January, 1999, No. 517 , eff. 2-1-99; r. and recr. (1) (b), (3), Tables 21.18-C and D, am. (2) (a), r. Table 21.18-B, renum. Table 21.18-A to be Table 21.18-B and cr. (1) (c), (d), Tables 21.18-A, E and F, Register March 2001 No. 543 , eff. 4-1-01; CR 02-077 : r. (1) (c) 1., renum. (1) (d) to be (1) (e), cr. (1) (d), am. (4) (intro.), (b) and Tables 21.18-A, C and F Register May 2003 No. 569 , eff. 8-1-03; CR 08-043 : am. (1) (d) 2. b. and Tables 21.18-C to F, cr. (2) (a) (title) and (b) (title), r. and recr. (3) (a) and (4) Register March 2009 No. 639 , eff. 4-1-09; correction in (1) (e), (2) (a), (3) (b) 1., 2., 5., 6., (4), Table 321.18-C to -F made under s. 13.92 (4) (b) 7. , Stats., Register December 2011 No. 672 ; CR 15-041 : am. (1) (c) 3. a., cr. (1) (c) 3. d., am. (1) (d) 2. c., (4) Register December 2015 No. 720 , eff. 1-1-16; CR 15-043 : am. (1) (d) 1. c. Register December 2015 No. 720 , eff. 1-1-16; correction under s. 13.92 (4) (b) 7. Register December 2015 No. 720 .

Note

Per s. SPS 321.22 (1) , sill plates are not required on foundation walls of poured concrete or on masonry walls with mortar- or grout-filled cores or on masonry walls with a solid block top course. Microsoft Windows NT 6.1.7601 Service Pack 1 The floor-framing elements required in this section are intended to provide lateral support to the top of the foundation wall. See s. SPS 321.22 (9) for further requirements relating to floor framing, including for bridging of floor framing to provide restraint against rotation or lateral displacement of the floor framing. Microsoft Windows NT 6.1.7601 Service Pack 1 See s. SPS 321.15 (1) (c) for trench footing requirements. - See PDF for table Microsoft Windows NT 6.1.7601 Service Pack 1 The ASTM C887 standard is entitled, "Standard Specification for Packaged, Dry, Combined Materials for Surface Bonding Mortar." Microsoft Windows NT 6.1.7601 Service Pack 1 The department will accept Permanent Wood Foundations Design and Construction Guide published by the Southern Forest Products Association through the Southern Pine Council, as complying with this standard. The Design and Construction Guide requires a 3.5 inch thick floor slab if a poured concrete floor slab is used. Microsoft Windows NT 6.1.7601 Service Pack 1