Wis. Admin. Code Department of Safety and Professional Services SPS 321.25
Unless designed through structural analysis, wood frame walls shall comply with the following requirements.
Note: See ch. SPS 325 Appendix A for acceptable nailing schedule.
Note: See s. SPS 321.10 for requirements on treating wood for decay and termite resistance.
Note: 20 gauge is approximately 0.036 inch.
Note: A sill plate can be made of multiple pieces to achieve the full width.
Note: Under ACI 318 Section 7.7, the minimum cover for a 5/8-inch-diameter or smaller bolt is 1 1/2 inches.
Table 321.25-A
SIZE, HEIGHT AND SPACING OF WOOD STUDSa,c
Bearing and Exterior Nonbearing Walls | Interior Nonbearing Walls | ||||||
Nominal Stud Size (inches) | Maximum Laterally Unsupported Stud Heighta (feet) | Maximum Spacing When Supporting Roof and Ceiling Only (inches) | Maximum Spacing When Supporting One Floor, Roof and Ceiling (inches) | Maximum Spacing When Supporting Two Floors, Roof and Ceiling (inches) | Maximum Spacing When Supporting One Floor Only (inches) | Maximum Laterally Unsupported Stud Heighta (feet) | Maximum Spacing (inches) |
2 x 3b | - | - | - | - | - | 10 | 16 |
2 x 4 | 10 | 24 | 16 | - | 24 | 14 | 24 |
3 x 4 | 10 | 24 | 24 | 16 | 24 | 14 | 24 |
2 x 5 | 10 | 24 | 24 | - | 24 | 16 | 24 |
2 x 6 | 12d | 24 | 24 | 16 | 24 | 20 | 24 |
aListed heights are distances between points of lateral support placed perpendicular to the plane of the wall. Increases in unsupported height are permitted where justified by analysis. Studs shall be stud grade or better, except that utility grade may be used when spaced not more than 16 inches on center, supports no more than a roof and ceiling and does not exceed 8 feet in height for exterior walls or 10 feet in height for interior nonload-bearing walls.
bMay not be used in exterior walls.
cAll spacing dimensions are to the center of the studs.
dUse of stud heights that range from over 10 feet to 12 feet for bearing and exterior nonbearing walls is prohibited unless supported by structural analysis. The allowable deflection may not exceed whichever of the following are applicable:
Interior walls and partitions - span height/180.
Exterior walls with plaster or stucco finish - span height/360.
Exterior walls with other brittle finishes - span height/240.
Exterior walls with flexible finishes - span height/120.
Exterior walls with interior gypsum wallboard finish - span height/180.
Any manufacturer-specified limits for any included windows or doors.
Note: A 3-story frame house with walls constructed of 2 x 4 standard grade studs would require a 12-inch stud spacing on the lowest level, a 24-inch stud spacing on the intermediate level, and a 24-inch stud spacing on the upper level.
Table 321.25-B
ALLOWABLE SPANS (FEET) FOR HEADERS SUPPORTING ROOF/CEILING ASSEMBLIES*
Header Members | ||||||||||
House Width (feet) | Two 2 x 4s | Two 2 x 6s | Two 2 x 8s | Two 2 x 10s | Two 2 x 12s | |||||
Zone 2/Zone 1 | Zone 2/Zone 1 | Zone 2/Zone 1 | Zone2/Zone 1 | Zone 2/Zone 1 | ||||||
24 | 2.5 | 2.5 | 4 | 4 | 5 | 5 | 7 | 6 | 9 | 8 |
26 | 2.5 | 2 | 4 | 3 | 5 | 5 | 7 | 6 | 8 | 7 |
28 | 2.5 | 2 | 4 | 3 | 5 | 4 | 6 | 6 | 8 | 7 |
30 | 2.5 | 2 | 4 | 3 | 5 | 4 | 6 | 6 | 8 | 7 |
32 | 2 | 2 | 3 | 3 | 5 | 4 | 6 | 5 | 7 | 7 |
Table 321.25-C
ALLOWABLE SPANS (FEET) FOR HEADERS SUPPORTING ONE FLOOR*
Header Members | |||||
House Width (feet) | Two 2 x 4s | Two 2 x 6s | Two 2 x 8s | Two 2 x 10s | Two 2 x 12s |
24 | 2.5 | 4 | 5 | 6 | 8 |
26 | 2.5 | 3 | 5 | 6 | 8 |
28 | 2 | 3 | 5 | 6 | 7 |
30 | 2 | 3 | 4 | 6 | 7 |
32 | 2 | 3 | 4 | 5 | 7 |
Table 321.25-D
ALLOWABLE SPANS (FEET) FOR HEADERS SUPPORTING ONE FLOOR AND ROOF/CEILING ASSEMBLY*
Header Members | ||||||||||
House Width (feet) | Two 2 x 4s | Two 2 x 6s | Two 2 x 8s | Two 2 x 10s | Two 2 x 12s | |||||
Zone 2/Zone 1 | Zone 2/Zone 1 | Zone 2/Zone 1 | Zone2/Zone 1 | Zone 2/Zone 1 | ||||||
24 | 1.5 | 1.5 | 3 | 2.5 | 4 | 3 | 5 | 4 | 6 | 5 |
26 | 1.5 | 1.5 | 2.5 | 2.5 | 3 | 3 | 4 | 4 | 5 | 5 |
28 | 1.5 | 1.5 | 2.5 | 2.5 | 3 | 3 | 4 | 4 | 5 | 5 |
30 | 1.5 | 1.5 | 2.5 | 2.5 | 3 | 3 | 4 | 4 | 5 | 5 |
32 | 1.5 | 1.5 | 2.5 | 2 | 3 | 3 | 4 | 4 | 5 | 5 |
*These tables are based on wood with a fiber bending stress of 1,000 psi. For other species with different fiber bending stresses, multiply the span by the square root of the ratio of the actual bending stress to 1,000 psi. Example: From Table 321.25-B, the allowable roof/ceiling span for a 28-foot wide house in zone 2, using two 2 x 8 header members with a 1400 psi bending stress, is 5 feet x [SQUARE ROOT] 71400/1000 = 5.9 feet.
Table 321.25-E
COLUMNS MADE OF STEEL PIPE STOCK1,2
Column Diameter (inches) | Wall Thickness (inches) | Weight/ft (pounds) | Height (feet) | Allowable Load (pounds) |
3 | 0.216 | 7.58 | 8 | 34,000 |
10 | 28,000 | |||
12 | 22,000 | |||
3.5 | 0.226 | 9.11 | 8 | 44,000 |
10 | 38,000 | |||
12 | 32,000 | |||
4 | 0.237 | 10.79 | 8 | 54,000 |
10 | 49,000 | |||
12 | 43,000 | |||
5 | 0.258 | 14.62 | 8 | 78,000 |
10 | 73,000 | |||
12 | 68,000 | |||
6 | 0.280 | 18.97 | 8 | 106,000 |
10 | 101,000 | |||
12 | 95,000 |
1This Table is based on a yield strength or Fy of 36,000 psi.
2This table is for columns made solely of steel pipe stock. The addition of any adjustment mechanism or other feature will alter the load-carrying capacity of the column.
Table 321.25-F
WOOD COLUMNS
Wood Nominal Size (inches) | Cross Section Area (inches) | Height (feet) | Allowable Load (pounds) |
4 x 4 | 12.25 | 8 | 4,900 |
10 | 3,100 | ||
12 | 2,150 | ||
4 x 6 | 19.25 | 8 | 7,700 |
10 | 4,900 | ||
12 | 3,400 | ||
6 x 6 | 30.25 | 8 | 30,000 |
10 | 18,900 | ||
12 | 13,300 |
Note: This Table is based on a modulus of elasticity or E of 1,000,000 psi and a fiber bending strength or Fb of 1,000 psi.
Note: Acceptable engineering wall bracing practices include any of the following:
Note: For a walk-out basement where some of the walls are concrete and other walls or portions thereof are wood-framed, the Department considers a minimum 8-inch-nominal-thickness poured-in-place concrete basement wall as being equivalent in lateral load and shear resistance to any of the allowable wood-framed wall bracing materials. To determine the required bracing for a walk-out basement, first draw a rectangle around the entire floor plan and projections as if all of the walls are wood-framed. Determine the required bracing amounts per the chosen bracing material and method and then locate the bracing to meet the requirements of Figure 321.25-C. Any required braced wall panel locations that occur on a wall or portion of a wall that is actually of poured-in-place concrete construction is considered equivalent, and that amount of bracing will count towards the minimum required amount and will not need to be provided in another location on that rectangle side.
Table 321.25-G
BRACING METHODSa, f
Material | Minimum Brace Material Thickness or Size | Maximum Nominal Wall Heightb | Minimum Braced Wall Panel Width or Brace Angle | Connection Criteria | |
Minimum Fasteners | Maximum Spacing | ||||
Intermittent Bracing Methods | |||||
LIBc Let-in bracing | 1x4 wood brace (or approved metal brace installed per manufacturer instructions) | 10' | 45° angle and maximum 16" o.c. stud spacingb | 2-8d common nails or 3-8d box nails (2 3/8" long x 0.113" diameter) | Per stud and top and bottom platese |
DWB Diagonal wood boards | 3/4" (1" nominal) for maximum 24" o.c. stud spacing | 10' | 48" | 2-8d box nails (2 3/8" long x 0.113" diameter) or 2 - 1 3/4" long 16-gage staples | Per stud and top and bottom platese |
WSP Wood structural panel | 3/8" for maximum 16"o.c. stud spacing; 7/16" for maximum 24" o.c. stud spacing | 10' | 48" | 6d common nail or 8d box nail (2 3/8" long x 0.113" diameter); or 7/16"- or 1/2"-crown 16-gage staples, 1 1/4" long | 6" edges, 12" field (nails) 3" edges, 6" field (staples) |
SFB Structural fiber-board sheathing | 1/2" for maximum 16" o.c. stud spacing | 10' | 48" | 1 1/2" long x 0.120" diameter galvanized roofing nails or 1"-crown 16-gage staples, 1 1/4" long | 3" edges, 6" field |
GB Gypsum board (installed on both sides of wall) | 1/2" for maximum 24" o.c. stud spacing | 10' | 96" | 5d cooler nails, or #6 screws | 7" edges, 7" field (including top and bottom plates) |
Continuous Sheathed Bracing Methods | |||||
CS-WSPd Continuous sheathed WSP | 3/8" for maximum 16"o.c. stud spacing; 7/16" for maximum 24" o.c. stud spacing | 12' | Refer to Table 321.25-H | Same as WSP | Same as WSP |
CS-SFBd Continuous sheathed SFB | 1/2" for maximum 16" o.c. stud spacing | Same as SFB | Same as SFB | ||
Narrow Panel Bracing | |||||
PF Portal frame | 7/16" | 12' | Refer to Figure 321.25-A | Refer to Figure 321.25-A | Refer to Figure 321.25-A |
aThe interior side of all exterior walls shall be sheathed with minimum 1/2-inch gypsum wallboard unless otherwise permitted to be excluded by this subsection. All edges of panel-type wall bracing, except horizontal joints in GB bracing, shall be attached to framing or blocking.
bThe actual measured wall height shall include stud height and thickness of top and bottom plates. The actual wall height shall be permitted to exceed the listed nominal values by not more than 41/2 inches. Tabulated bracing amounts in s. SPS 321.25(8) (c) are based on a 10-foot nominal wall height for all bracing methods and shall be permitted to be adjusted to other nominal wall heights not exceeding 12 feet in accordance with footnotes to Table 321.25-I or Table 321.25-J.
cLIB is not permitted for walls supporting a roof and two floors. Two LIB braces installed at a 60° angle from horizontal shall be permitted to be substituted for each 45°angle LIB brace.
dBracing with CS-WSP and CS-SFB shall have sheathing installed on all sheathable surfaces above, below, and between wall openings.
dShall be attached to the top and bottom plates and any intermediate studs, in one continuous length.
eEach braced panel may contain no more than one hole, having a maximum dimension of no more than ten percent of the least dimension of the panel, and confined to the middle three-fourths of the panel.
Table 321.25-Ha, b
MINIMUM WIDTHS OF CS-WSP AND CS-SFB BRACED WALL PANELS
Maximum Opening Height Adjacent to Braced Wall Panel | Minimum Width of Full-Height Braced Wall Panel (inches) | |||
8' Tall Wall | 9' Tall Wall | 10' Tall Wall | 12' Tall Wall | |
5'- 4" | 24 | 27 | 30 | 36 |
6'- 8" | 32 | 30 | 30 | 36 |
8' | 48 | 41 | 38 | 36 |
9' | - | 54 | 46 | 41 |
10' | - | - | 60 | 48 |
12' | - | - | - | 72 |
aSheathing shall extend from the top of the top plate to the bottom of the bottom plate and may be multiple sheets. All joints shall be blocked.
bInterpolation is permitted.
Figure 321.25-A
METHOD PF - PORTAL FRAME BRACE CONSTRUCTION
Note: Steel headers are permitted if designed by structural analysis.
Note: As shown in the above cross-section, 1/2-inch gypsum wallboard is not required on the interior side of the wall.
FIGURE 321.25-B
DEFINING BUILDING SIDES AND LENGTHS WITH ONE OR MORE CIRCUMSCRIBED RECTANGLESa,b,c
TABLE 321.25-I
REQUIRED NUMBER OF INTERMITTENT BRACED WALL PANELS ON WALLS PARALLEL TO EACH RECTANGLE SIDE AT EACH FLOOR LEVELa,b,c,d,e,f, h, j
Wall Supporting: | Required Number of Brace Panels on a Building Side | |||
Length of Perpendicular Side (feet)g | ||||
<=25 | <=50 | <=75 | ||
Roof and ceiling only | 1i | 2 | 3 | |
One floor, roof and ceiling | 2 | 4 | 6 | |
Two floors, roof and ceiling | 3 | 6 | 9 | |
aInterpolation is permitted. Extrapolation to buildings larger than addressed in this table is prohibited.
bThis table applies to wind exposure category B. For wind exposure category C or D, multiply the number of braced wall panels required by 1.3 or 1.6, respectively.
Wind exposure category B is comprised of urban and suburban areas, wooded areas, or other terrain with numerous closely spaced obstructions having the size of single-family dwellings or larger. Exposure B shall be assumed unless the site meets the definition of another type exposure.
Wind exposure category C is comprised of flat, open country and grasslands with scattered obstructions, including surface undulations or other irregularities, having heights generally less than 30 feet extending more than 1,500 feet from the building site in any quadrant. This exposure also applies to any building located within Exposure B type terrain where the building is directly adjacent to open areas of Exposure C type terrain in any quadrant for a distance of more than 600 feet.
Wind exposure category D is comprised of flat, unobstructed areas exposed to wind flowing over open water for a distance of at least 1 mile. This exposure applies only to those buildings and other structures exposed to the wind coming from over the water. Exposure D extends inland from the shoreline a distance of 1,500 feet or 10 times the height of the building or structure, whichever is greater.
cTabulated values are based on a nominal wall height of 10 feet. For nominal wall heights other than 10 feet and not more than 12 feet, multiply the required number of brace panels by the following factors: 0.9 for 8 feet, 0.95 for 9 feet, 1.15 for 11 feet, or 1.3 for 12 feet.
dTabulated values are based on a roof with a top-of-wall-to-ridge height of 10 feet. For top-of-wall-to-ridge heights other than 10 feet, multiply the required number of brace panels by the following factors for each floor level support condition:
Roof only - 0.7 for 5 feet, 1.3 for 15 feet, or 1.6 for 20 feet
Roof + 1 Floor - 0.85 for 5 feet, 1.15 for 15 feet, or 1.3 for 20 feet
Roof + 2 Floors - 0.9 for 5 feet or 1.1 for 15 feet.
eWhere minimum 1/2-inch gypsum wallboard is not included on the interior side of the wall, multiply the number of braced wall panels by 1.7 for LIB bracing or 1.4 for all other bracing methods, except this increase is not required for the portal frame method.
fAdjustments in footnotes b to e apply cumulatively. Fractions of panels shall be rounded to the nearest one-half braced wall panel.
gPerpendicular sides to the front and rear sides are the left and right sides. Perpendicular sides to the left and right sides are the front and rear sides. See Figure 321.25-B.
hThe following braced wall panel conditions shall be permitted to be counted as one-half a braced wall panel toward meeting the required number of panels:
iThis value of less than 2 serves only as the beginning value for calculation purposes. The resulting value shall be 2 or greater, to be consistent with subd. 2.
jAny floor, habitable or otherwise, that is contained wholly within the roof rafters or roof trusses is exempt from being considered a floor for purposes of determining wall bracing if the top-of-wall-to-ridge height does not exceed 20 feet and if no opening in the roof exceeds 48 inches in height.
Table 321.25-J
REQUIRED LENGTH OF CONTINUOUS BRACING ON WALLS PARALLEL TO EACH RECTANGLE SIDE AT EACH FLOOR LEVEL a,b,c,d,e,g,h, j
Top-of-Wall-to-Ridge Height (feet) | Wall Supporting: | Total Required Length (feet) of Full-Height Bracing on Any Side of Rectangle | ||||||||
Length of Perpendicular Side (feet)f | ||||||||||
10 | 20 | 30 | 40 | 50 | 60 | 70 | 80 | |||
Roof and ceiling only | 2.0 i | 3.5 i | 5.0 | 6.0 | 7.5 | 9.0 | 10.5 | 12.0 | ||
10 | One floor, roof and ceiling | 3.5 i | 6.5 | 9.0 | 12.0 | 14.5 | 17.0 | 19.8 | 22.6 | |
Two floors, roof and ceiling | 5.0 | 9.5 | 13.5 | 17.5 | 21.5 | 25.5 | 29.2 | 33.4 | ||
Roof and ceiling only | 2.6 i | 4.6 | 6.5 | 7.8 | 9.8 | 11.7 | 13.7 | 15.7 | ||
15 | One floor, roof and ceiling | 4.0 | 7.5 | 10.4 | 13.8 | 16.7 | 19.6 | 22.9 | 26.2 | |
Two floors, roof and ceiling | 5.5 | 10.5 | 14.9 | 19.3 | 23.7 | 27.5 | 32.1 | 36.7 | ||
Roof and ceiling only | 2.9 i | 5.2 | 7.3 | 8.8 | 11.1 | 13.2 | 15.4 | 17.6 | ||
20 | One floor, roof and ceiling | 4.5 | 8.5 | 11.8 | 15.6 | 18.9 | 22.1 | 25.8 | 29.5 | |
Two floors, roof and ceiling | 6.2 | 11.9 | 16.8 | 21.8 | 27.3 | 31.1 | 36.3 | 41.5 | ||
aInterpolation is permitted. Extrapolation to buildings larger than addressed in this table is prohibited.
bThis table applies to wind exposure category B. For wind exposure category C or D, multiply the required length of wall bracing by 1.3 or 1.6, respectively. Wind exposure categories are as defined in Table 321.25-I footnote b.
cTabulated values are based on a nominal wall height of 10 feet. For nominal wall heights other than 10 feet, multiply the required length of bracing by the following factors: 0.90 for 8 feet, 0.95 for 9 feet, 1.05 for 11 feet, or 1.10 for 12 feet.
dWhere minimum 1/2-inch gypsum wallboard interior finish is not provided, the required bracing amount for the affected rectangle side shall be multiplied by 1.4, except this increase is not required for the portal frame method.
eAdjustments in footnotes b to d apply cumulatively.
fPerpendicular sides to the front and rear sides are the left and right sides. Perpendicular sides to the left and right sides are the front and rear sides. See Figure 321.25-B.
gContinuous sheathing shall be applied to all surfaces of the wall, including areas between brace panels and above and below wall openings.
hWhen used on a wall line with continuous sheathing, each portal frame panel is counted for its actual length in contributing toward the length of continuous sheathing used on other portions of the same wall line, such as the building side at a given story level.
iAny value of less than 4.0 in this table serves only as the beginning value for calculation purposes. The resulting value shall be 4.0 or greater, to be consistent with Table 321.25-H and subd.2.
jAny floor, habitable or otherwise, that is contained wholly within the roof rafters or roof trusses is exempt from being considered a floor for purposes of determining wall bracing if the top-of-wall-to-ridge height does not exceed 20 feet and if no opening in the roof exceeds 48 inches in height.
Figure 321.25-C
LOCATION OF BRACED WALL PANELS ALONG A BUILDING SIDEa
Wis. Admin. Code Department of Safety and Professional Services SPS 321.25