Unless designed through structural analysis, wood frame floors shall comply with the following requirements:
Note: See ch. SPS 325 Appendix A for design information.
Note: Section SPS 321.18(1) (d) requires the floor joists to also be fastened to the sill plate.
Note: A sill plate can be made of multiple pieces to achieve the full width.
Note: A saddle supports the beam on the bottom and allows for the through-connection of fasteners into the side of the beam.
Note: The tributary length is usually half the span of the joist or rafter.
TABLE 321.22-A1
MINIMUM SIZES FOR BEAMS AND GIRDERS OF STEEL OR WOOD
Column Spacing | One Floor Only | Roof/Ceiling and One Floor | Roof/Ceiling+ One Floor/Ceiling + One Floor | |||||||
Wood Beams1 (in., nominal) | A 36 Steel Beams2 | Wood Beams1,3 Zone 2 | (in., nominal) Zone 1 | Zone 2 | A 36 Steel Beams2 Zone 1 | Wood Beams Zone 2 | 1,3 (in., nominal) Zone 1 | Zone2 | A 36 Steel Beams2 Zone 1 | |
24 ft. wide house: | ||||||||||
8 ft. | 8x8 | - | 8x10 | 10x10 | - | - | 8x12 | 10x12 | - | - |
6x12 | 6x12 | - | - | 6x14 | 8x14 | - | - | |||
10 ft. | 8x10 | - | 8x12 | 10x12 | M 10x9 | M 10x9 | 10x14 | 10x14 | M 12x11.8 | M 12x11.8 |
6x14 | 8x14 | W 6x12 | W 8x10 | 8x16 | 8x16 | W 8x15 | W 8x15 | |||
12 ft. | 8x12 | - | 12x12 | 10x14 | W 12x10 | M 12x11.8 | 14x14 | 14x14 | W 12x16 | W 12x16 |
10x14 | 8x16 | W 10x11.5 | W 8x15 | 10x16 | 12x16 | W10x17 | W 8x21 | |||
15 ft. | 12x12 | - | - | - | W 12x16 | W 12x16 | - | - | W 12x22 | W 14x22 |
- | - | W 10x17 | W 6x25 | - | - | W 8x28 | W 8x31 | |||
26 ft. wide house: | ||||||||||
8 ft. | 6x10 | - | 10x10 | 10x10 | - | - | 10x12 | 10x12 | - | - |
6x12 | 8x12 | - | - | 8x14 | 8x14 | - | - | |||
10 ft. | 10x10 | - | 10x12 | 10x12 | M 10x9 | M 12x10 | 10x14 | 12x14 | M 12x11.8 | W 12x14 |
8x14 | 8x14 | W 8x10 | W 8x13 | 8x16 | 8x16 | W 8x15 | W 8x17 | |||
12 ft. | 8x12 | - | 10x14 | 10x14 | M 12x11.8 | M 12x11.8 | 14x14 | 12x16 | W 12x16 | W 10x19 |
8x16 | 8x16 | W 8x15 | W 6x20 | 12x16 | 10x18 | W 8x21 | W 8x24 | |||
15 ft. | 10x14 | - | - | - | W 12x16 | W 10x19 | - | - | W 14x22 | W 14x22 |
- | - | W 8x21 | W 8x24 | - | - | W 8x31 | W 8x35 | |||
28 ft. wide house: | ||||||||||
8 ft. | 6x10 | - | 10x10 | 8x12 | - | - | 10x12 | 10x12 | - | - |
8x12 | 4x16 | - | - | 8x14 | 8x14 | - | - | |||
10 ft. | 10x10 | M 10x7.5 | 10x12 | 12x12 | M 12x10 | W 10x12 | 12x14 | 12x14 | W 12x14 | W 12x14 |
W 6x9 | 8x14 | 8x14 | W 8x13 | W 8x13 | 8x16 | 10x16 | W 8x17 | W 10x15 | ||
12 ft. | 10x12 | M 10x9 | 10x14 | 12x14 | M 12x11.8 | W 12x14 | 12x16 | 12x16 | W 10x19 | M 14x18 |
W 6x12 | 8x16 | 10x16 | W 8x15 | W 8x18 | 10x18 | 10x18 | W 8x24 | W 8x24 | ||
15 ft. | 10x14 | M 12x10 | - | - | W 10x19 | M 14x18 | - | - | W 14x22 | W 14x26 |
W 8x13 | - | - | W 8x24 | W 8x24 | - | - | W 8x35 | W 8x35 | ||
30 ft. wide house: | ||||||||||
8 ft. | 8x10 | - | 10x10 | 8x12 | - | - | 10x12 | 12x12 | - | - |
8x12 | 6x14 | - | - | 8x14 | 8x14 | - | - | |||
10 ft. | 10x10 | M 10x7.5 | 10x12 | 12x12 | M 12x10 | M 12x10 | 12x14 | 12x14 | W 12x14 | W 12x14 |
W 6x9 | 8x14 | 10x14 | W 8x13 | W 8x13 | 10x16 | 10x16 | W 10x15 | W 10x15 | ||
12 ft. | 10x12 | M 10x9 | 12x14 | 12x14 | W 12x14 | W 12x14 | 12x16 | 14x16 | M 14x18 | M 14x18 |
W 6x12 | 8x16 | 10x16 | W 8x18 | W 8x18 | 10x18 | 12x18 | W 8x24 | W 8x24 | ||
15 ft. | 12x14 | M 12x11.8 | - | - | M 14x18 | W 10x21 | - | - | W 14x26 | W 14x26 |
W 8x15 | - | - | W 8x24 | W 8x28 | - | - | W 8x35 | W 10x33 | ||
32 ft. wide house: | ||||||||||
8 ft. | 8x10 | - | 8x12 | 8x12 | - | - | 12x12 | 12x12 | - | - |
6x14 | 6x14 | - | - | 8x14 | 10x14 | - | - | |||
10 ft. | 10x10 | M 10x7.5 | 12x12 | 12x12 | W 10x12 | W 10x12 | 12x14 | 14x14 | W 12x14 | W 12x16 |
W 6x9 | 8x14 | 10x14 | W 8x13 | W 6x16 | 10x16 | 10x16 | W 10x15 | W 10x17 | ||
12 ft. | 10x12 | M 10x9 | 12x14 | 14x14 | W 12x14 | W 12x14 | 14x16 | 14x16 | M 14x18 | W 12x22 |
W 6x12 | 10x16 | 10x16 | W 10x15 | W 10x17 | 12x18 | 12x18 | W 8x24 | W 8x28 | ||
15 ft. | 12x14 | M 12x11.8 | - | - | M 14x18 | W 12x22 | - | - | W 14x26 | W 14x26 |
W 8x15 | - | - | W 8x24 | W 8x28 | - | - | W 10x33 | W 10x33 |
1This table is based upon wood with a fiber bending stress of 1,000 psi. Two acceptable wood beam selections are listed for each loading condition.
2Two acceptable steel beam selections are listed for each loading condition. The first entry is the most economical selection based upon beam weight.
3Wood main beams or girders may be built up from nominal 2-inch members. The 2-inch members shall be laid on edge and fastened together with a double row of common nails not less than 31/2-inches in length. Nails shall be spaced not more than 18 inches apart in each row with the end nails placed 4 inches to 6 inches from the end of each piece. Where built-up beams are employed over a single span, the length of each individual piece used to fabricate the beam shall equal the length of the beam.
TABLE 321.22-A2
MINIMUM SIZES FOR BUILT-UP WOOD BEAMS IN BASEMENTS AND CRAWL SPACES SUPPORTING ONE FLOOR ONLY
HOUSE WIDTH | Fb=800 psi | Fb=1000 psi | Fb=1200 psi | Fb=1400 psi | ||||
Col. Spacing ft-in | Beam size | Col. Spacing ft-in | Beam size | Col. Spacing ft-in | Beam size | Col. Spacing ft-in | Beam size | |
16 ft. | 7-8 | 3-2x8 | 8-7 | 3-2x8 | 9-4 | 3-2x8 | 10-2 | 3-2x8 |
8-11 | 4-2x8 | 9-11 | 4-2x8 | 10-11 | 4-2x8 | 11-10 | 4-2x8 | |
9-11 | 3-2x10 | 11-1 | 3-2x10 | 12-1 | 3-2x10 | 13-1 | 3-2x10 | |
11-4 | 4-2x10 | 12-8 | 4-2x10 | 13-1 | 4-2x10 | 15-0 | 4-2x10 | |
12-0 | 3-2x12 | 13-5 | 3-2x12 | 14-8 | 3-2x12 | 15-10 | 3-2x12 | |
13-10 | 4-2x12 | 15-7 | 4-2x12 | 17-0 | 4-2x12 | 18-4 | 4-2x12 | |
20 ft. | 6-11 | 3-2x8 | 7-8 | 3-2x8 | 8-5 | 3-2x8 | 9-1 | 3-2x8 |
7-11 | 4-2x8 | 8-11 | 4-2x8 | 9-9 | 4-2x8 | 10-7 | 4-2x8 | |
8-10 | 3-2x10 | 9-11 | 3-2x10 | 10-10 | 3-2x10 | 11-8 | 3-2x10 | |
10-2 | 4-2x10 | 11-4 | 4-2x10 | 12-6 | 4-2x10 | 13-6 | 4-2x10 | |
10-9 | 3-2x12 | 12-0 | 3-2x12 | 13-2 | 3-2x12 | 14-3 | 3-2x12 | |
11-5 | 4-2x12 | 13-11 | 4-2x12 | 15-2 | 4-2x12 | 16-5 | 4-2x12 | |
24 ft. | 6-3 | 3-2x8 | 7-1 | 3-2x8 | 7-8 | 3-2x8 | 8-4 | 3-2x8 |
7-3 | 4-2x8 | 8-2 | 4-2x8 | 8-11 | 4-2x8 | 9-8 | 4-2x8 | |
8-1 | 3-2x10 | 9-0 | 3-2x10 | 9-11 | 3-2x10 | 10-8 | 3-2x10 | |
9-4 | 4-2x10 | 10-4 | 4-2x10 | 11-5 | 4-2x10 | 12-4 | 4-2x10 | |
9-9 | 3-2x12 | 10-11 | 3-2x12 | 12-0 | 3-2x12 | 12-11 | 3-2x12 | |
11-3 | 4-2x12 | 12-7 | 4-2x12 | 13-11 | 4-2x12 | 15-0 | 4-2x12 | |
28 ft. | 5-10 | 3-2x8 | 6-6 | 3-2x8 | 7-2 | 3-2x8 | 7-8 | 3-2x8 |
6-8 | 4-2x8 | 7-6 | 4-2x8 | 8-3 | 4-2x8 | 8-11 | 4-2x8 | |
7-5 | 3-2x10 | 8-4 | 3-2x10 | 9-1 | 3-2x10 | 9-11 | 3-2x10 | |
8-7 | 4-2x10 | 9-8 | 4-2x10 | 10-6 | 4-2x10 | 11-4 | 4-2x10 | |
9-0 | 3-2x12 | 10-1 | 3-2x12 | 11-1 | 3-2x12 | 10-11 | 3-2x12 | |
10-5 | 4-2x12 | 11-8 | 4-2x12 | 12-10 | 4-2x12 | 13-10 | 4-2x12 | |
32 ft. | 5-4 | 3-2x8 | 6-1 | 3-2x8 | 6-8 | 3-2x8 | 7-3 | 3-2x8 |
6-3 | 4-2x8 | 7-1 | 4-2x8 | 7-8 | 4-2x8 | 8-4 | 4-2x8 | |
7-0 | 3-2x10 | 7-9 | 3-2x10 | 8-7 | 3-2x10 | 9-2 | 3-2x10 | |
8-1 | 4-2x10 | 8-11 | 4-2x10 | 9-10 | 4-2x10 | 10-8 | 4-2x10 | |
8-5 | 3-2x12 | 9-6 | 3-2x12 | 10-4 | 3-2x12 | 11-1 | 3-2x12 | |
9-9 | 4-2x12 | 11-0 | 4-2x12 | 12-0 | 4-2x12 | 12-11 | 4-2x12 | |
36 ft. | 5-1 | 3-2x8 | 5-9 | 3-2x8 | 6-3 | 3-2x8 | 6-9 | 3-2x8 |
5-11 | 4-2x8 | 6-7 | 4-2x8 | 6-9 | 4-2x8 | 7-10 | 4-2x8 | |
6-6 | 3-2x10 | 7-4 | 3-2x10 | 8-1 | 3-2x10 | 8-8 | 3-2x10 | |
7-6 | 4-2x10 | 8-6 | 4-2x10 | 9-4 | 4-2x10 | 10-0 | 4-2x10 | |
7-11 | 3-2x12 | 8-11 | 3-2x12 | 9-9 | 3-2x12 | 10-7 | 3-2x12 | |
9-2 | 4-2x12 | 10-4 | 4-2x12 | 11-4 | 4-2x12 | 12-4 | 4-2x12 |
1This table provides maximum allowable spans in feet and inches for main beams or girders which are built-up from nominal 2-inch members.
2Fiber bending stress for various species and grades of wood is given in Appendix A321.
3The 2-inch members shall be laid on edge and fastened together with a double row of common nails not less than 31/2-inches in length. Nails shall be spaced not more than 18 inches apart in each row with the end nails placed 4 inches to 6 inches from the end of each piece.
4Where built-up wood beams are employed over a single span, the length of each individual piece used to fabricate the beam shall equal the length of the beam.
5Where built-up wood beams are continued over more than one span and where lengths of individual pieces are less than the total length of the complete beam, butt joints shall be located over supports or within 6 inches of the quarter points of the clear span. Where located near the quarter points, the joints in built-up beams shall be separated by at least one lamination and shall not exceed the beam width.
Note: This 4:1 ratio means bridging is required for wood-framed floors having nominal 2X10 or deeper solid-sawn-lumber joists, to provide restraint against rotation or lateral displacement.
Note: See s. SPS 321.18(1) (d) for further requirements relating to floor framing, including for bridging or blocking of floor framing to provide lateral support to the top of foundation walls.
Note: Under ACI 318 Section 7.7, the minimum cover for a 5/8-inch-diameter or smaller bolt is 1 1/2 inches.
Note: As used throughout this chapter and in the standards that the chapter incorporates by reference, the shorter side of the cross-sectional area of a wood member is the thickness of the member. The longer side of the cross-sectional area is the depth, when the longer side is vertical; and it is the width when the longer side is horizontal.
Note: Under sub. (6), wood floor joists that are perpendicular to the foundation wall can extend beyond the foundation wall by a distance of up to the depth of the joist.
Note: Subsection (1) (d) requires a full-width sill plate for floor joists over open-core masonry units.
Table 321.22-B
ALLOWABLE SPANS FOR PLYWOOD FLOOR SHEATHING CONTINUOUS OVER TWO OR MORE SPANS AND FACE GRAIN PERPENDICULAR TO SUPPORTS1
Span Rating2 | Plywood Thickness (in inches) | Maximum span3 (in inches) |
32/16 | 15/32, 1/2, 5/8 | 165 |
40/20 | 19/32, 5/8, 3/4, 7/8 | 204,5 |
48/24 | 23/32, 3/4, 7/8 | 24 |
1These values apply to C-D, C-C, and Structural I and II grades only. Spans shall be limited to values shown because of possible effect of concentrated loads.
2Span Rating appears on all panels in the construction grades listed in footnote 1.
3Plywood edges shall have approved tongue and groove joints or shall be supported with blocking, unless 1/4-inch minimum thickness underlayment or 11/2 inches of approved cellular or lightweight concrete is installed or finished floor is 25/32-inch wood strip. Allowable uniform load based on deflection of 1/360 of span is 165 pounds per square foot.
4For joists spaced 24 inches on center, plywood sheathing with Span Rating 40/20 or greater can be used for subfloors when supporting 11/2 inches lightweight concrete.
5May be 24 inches if 25/32-inch wood strip flooring is installed at right angles to joists.
Table 321.22-D
MINIMUM THICKNESS FOR PLYWOOD COMBINATION SUBFLOOR-UNDERLAYMENT. PLYWOOD CONTINUOUS OVER TWO OR MORE SPANS AND FACE GRAIN PERPENDICULAR TO SUPPORTS1,2
Plywood Grade | Plywood Species Group | Maximum Support Spacing3 | ||
16" o.c. | 20" o.c. | 24" o.c. | ||
Panel Thickness (inches) | Panel Thickness (inches) | Panel Thickness (inches) | ||
Sanded exterior type | 1 | 1/2 | 5/8 | 3/4 |
2 & 3 | 5/8 | 3/4 | 7/8 | |
4 | 3/4 | 7/8 | 1 | |
Underlayment C-C Plugged Sturd-I-Floor4 | All Groups | APA Rated Sheathing and APA Rated Sturd-I-Floor shall be installed consistent with their rating. |
1Spans shall be limited to values shown, based on possible effect of concentrated loads.
2Unsupported edges shall be tongue and groove or blocked except where 1/4-inch underlayment or 25/32-inch finish floor is used.
3Underlayment, C-C Plugged, sanded exterior type: allowable uniform load based on deflection of L/360 span for spans 24 inches or less is 125 psf; and for spans 48 inches, 65 psf.
4The department will accept subfloor underlayment panels such as Sturd-I-Floor which meet the requirements of APA manufacturing specifications for Sturd-I-Floor panels.
Table 321.22-E
MINIMUM THICKNESS OF FLOOR BOARDS
Joist Spacing (inches) | Minimum Net Thickness (inches) | |
Perpendicular to Joist | Diagonal to Joist | |
24 | 1 1/16 | 3/4 |
16 | 5/8 | 5/8 |
Wis. Admin. Code Department of Safety and Professional Services SPS 321.22