Page 321 - 2018_IRC

WALL CONSTRUCTION

TABLE R608.7(1C)—continued
UNREDUCED LENGTH, UR, OF SOLID WALL REQUIRED IN EACH
EXTERIOR SIDEWALL FOR WIND PARALLEL TO RIDGE a, c, d, e, f, g
UNREDUCED LENGTH, UR, OF SOLID WALL REQUIRED IN SIDEWALLS FOR WIND PARALLEL TO RIDGE (feet)
Basic Wind Speed Exposure (mph)
SIDEWALL ENDWALL ROOF 115B 120B 130B 140B 150B 160B
LENGTH LENGTH SLOPE
(feet) (feet) — — 110C 119C 127C 136C Minimum b
— — — 110D 117D 125D
First story of two story
< 1:12 3.03 3.30 3.88 4.49 5.16 5.87 2.52
5:12 3.24 3.52 4.14 4.80 5.51 6.26 2.70
15
7:12 3.33 3.62 4.25 4.93 5.66 6.44 2.79
12:12 3.58 3.90 4.58 5.31 6.10 6.94 3.01
< 1:12 5.50 5.99 7.03 8.16 9.36 10.65 5.14
5:12 6.21 6.76 7.93 9.20 10.56 12.01 5.86
30
7:12 6.52 7.10 8.34 9.67 11.10 12.63 6.19
12:12 7.41 8.06 9.46 10.97 12.60 14.33 7.10
< 30
< 1:12 8.00 8.71 10.22 11.85 13.61 15.48 7.85
5:12 9.52 10.37 12.17 14.11 16.20 18.43 9.48
45
7:12 10.21 11.12 13.05 15.14 17.38 19.77 10.21
12:12 12.13 13.20 15.50 17.97 20.63 23.47 12.25
< 1:12 10.56 11.50 13.50 15.65 17.97 20.44 10.65
5:12 13.24 14.41 16.91 19.62 22.52 25.62 13.54
60
7:12 14.45 15.73 18.46 21.41 24.58 27.97 14.85
12:12 17.80 19.38 22.75 26.38 30.29 34.46 18.48
< 1:12 8.39 9.14 10.72 12.44 14.28 16.25 7.85
5:12 9.97 10.86 12.74 14.78 16.97 19.30 9.48
45
7:12 10.69 11.64 13.66 15.84 18.19 20.69 10.21
12:12 12.67 13.80 16.19 18.78 21.56 24.53 12.25
60
< 1:12 11.37 12.38 14.53 16.85 19.35 22.01 10.65
5:12 14.18 15.44 18.12 21.02 24.13 27.45 13.54
60
7:12 15.46 16.83 19.75 22.91 26.29 29.92 14.85
12:12 18.98 20.66 24.25 28.13 32.29 36.74 18.48
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mile per hour = 0.447 m/s, 1 pound-force per linear foot = 0.146 kN/m, 1 pound per square foot = 47.88 Pa.
a. Tabulated lengths were derived by calculating design wind pressures in accordance with Figure 28.4-1 of ASCE 7 for a building with a mean roof height of 35
feet, topographic factor, K , equal to 1.0, and Risk Category II. The design pressures were used to calculate forces to be resisted by solid wall segments in each
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sidewall. The forces to be resisted by each wall line were then divided by the default design strength of 840 pounds per linear foot of length to determine the
unreduced length, UR, of solid wall length required in each sidewall. The actual mean roof height of the building shall not exceed the least horizontal
dimension of the building.
b. Tabulated lengths in the “minimum” column are based on the requirement of Section 28.4.4 of ASCE 7 that the main windforce-resisting system be designed
for a minimum pressure of 16 psf multiplied by the wall area of the building and 8 psf multiplied by the roof area of the building projected onto a vertical
plane normal to the assumed wind direction. Tabulated lengths in shaded cells are less than the “minimum” value. Where the minimum controls, it is
permitted to be reduced in accordance with Notes c, d and e. See Section R608.7.1.1.
c. For buildings with a mean roof height of less than 35 feet, tabulated lengths are permitted to be reduced by multiplying by the appropriate factor, R 1 , from
Table R608.7(2). The reduced length shall be not less than the “minimum” value shown in the table.
d. Tabulated lengths for “one story or top story of two story” are based on a floor-to-ceiling height of 10 feet. Tabulated lengths for “first story of two story” are
based on floor-to-ceiling heights of 10 feet each for the first and second story. For floor-to-ceiling heights less than assumed, use the lengths in this table or
Table R608.7(1A) or (1B), or multiply the value in the table by the reduction factor, R , from Table R608.7(3).
2
e. Tabulated lengths are based on the default design shear strength of 840 pounds per linear foot of solid wall segment. The tabulated lengths are permitted to be
reduced by multiplying by the applicable reduction factor for design strength, R , from Table R608.7(4).
3
f. The reduction factors, R 1 , R 2 and R 3 , in Tables R608.7(2), R608.7(3), and R608.7(4), respectively, are permitted to be compounded, subject to the limitations
of Note b. However, the minimum number and minimum length of solid walls segments in each wall line shall comply with Sections R608.7.1 and
R608.7.2.1, respectively.
g. For intermediate values of sidewall length, endwall length, roof slope and basic wind speed, use the next higher value, or determine by interpolation.

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