Washington Administrative Code › Title 51 - Enterprise Services, Department of (Building Code Council) › Chapter 51-51 - State Building Code adoption and amendment of the 2021 edition of the International Residential Code › Section 51-51-0403 - Section R403-Footings

Current through Register Vol. 24-14, July 15, 2024
R403.1.1
Minimum
			 size.
The minimum width, W, and thickness, T, for concrete footings
			 shall be in accordance with Tables R403.1(1) through R403.1(3) and Figure
			 R403.1(1) or R403.1.3, as applicable, but not less than 12 inches (305 mm) in
			 width and 6 inches (152 mm) in depth. The footing width shall be based on the
			 load-bearing value of the soil in accordance with Table R401.4.1. Footing
			 projections, P, shall be not less than 2 inches (51 mm) and shall not exceed
			 the thickness of the footing. Footing thickness and projection for fireplaces
			 shall be in accordance with Section R1001. The size of footings supporting
			 piers and columns shall be based on the tributary load and allowable soil
			 pressure in accordance with Table R401.4.1. Footings for wood foundations shall
			 be in accordance with the details set forth in Section R403.2, and Figures
			 R403.1(2) and R403.1(3). Footings for precast foundation shall be in accordance
			 with the details set forth in Section R403.4, Table R403.4, and Figures
			 R403.4(1) and R403.4(2).
EXCEPTION:
Light-frame construction shall be permitted to have
						  minimum footing size in accordance with Figures R403.1.1(1) through R403.1.1(4)
						  in lieu of that determined by Table R403.1(1).
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				to view image
Notes:
a The minimum footing size is based
				on the following assumptions: Material weights per Section R301.2.2.2.1 and
				soil density = 120 pcf. Wood-framed walls = 10 foot; crawlspace stem wall = 6
				inches * 36 inches; basement wall = 8 inches *120 inches. Total load (TL) equal
				to the maximum of three load combinations: LC1=D+L, LC2=D+S and
				LC3=D=0.75(L+S), where D=dead load, L=live load, S=snow load. TL=max (LC1, LC2,
				LC3).
b Use tributary span of floor and
				roof. Figure may be used to size exterior and interior footings.
c Add 4 feet to tributary floor span
				for each wood-framed wall above first level (i.e., 4 feet for 2-story, 8 feet
				for 3-story).
d Multiply floor span by 1.25 for
				interior footings supporting continuous joists.
e Multiply footing width by (1500
				psf/capacity) for soil capacity other than 1500 psf. See Section R403.1.1 for
				thickness.
f Dashed line may be used for
				interior footing size only.
g Use footing size indicated on line
				above the span combination used.
h For span combinations above the
				upper line, a design professional is required.
i Interpolation between footing
				sizes is allowed. Extrapolation is not allowed.
Click
				to view image
Notes:
a The minimum footing size is based
				on the following assumptions: Material weights per Section R301.2.2.2.1 and
				soil density = 120 pcf. Wood-framed walls = 10 foot; crawlspace stem wall = 6
				inches *36 inches; basement wall = 8 inches *120 inches. Total load (TL) equal
				to the maximum of three load combinations: LC1=D+L, LC2=D+S and
				LC3=D=0.75(L+S), where D=dead load, L=live load, S=snow load. TL=max (LC1, LC2,
				LC3).
b Use tributary span of floor and
				roof. Figure may be used to size exterior and interior footings.
c Add 4 feet to tributary floor span
				for each wood-framed wall above first level (i.e., 4 feet for 2-story, 8 feet
				for 3-story).
d Multiply floor span by 1.25 for
				interior footings supporting continuous joists.
e Multiply footing width by (1500
				psf/capacity) for soil capacity other than 1500 psf. See Section R403.1.1 for
				thickness.
f Dashed line may be used for
				interior footing size only.
g Use footing size indicated on line
				above the span combination used.
h For span combinations above the
				upper line, a design professional is required.
i Interpolation between footing
				sizes is allowed. Extrapolation is not allowed.
Click
				to view image
Notes:
a The minimum footing size is based
				on the following assumptions: Material weights per Section R301.2.2.2.1 and
				soil density = 120 pcf. Wood-framed walls = 10 foot; crawlspace stem wall = 6
				inches *36 inches; basement wall = 8 inches *120 inches. Total load (TL) equal
				to the maximum of three load combinations: LC1=D+L, LC2=D+S and
				LC3=D=0.75(L+S), where D=dead load, L=live load, S=snow load. TL=max (LC1, LC2,
				LC3).
b Use tributary span of floor and
				roof. Figure may be used to size exterior and interior footings.
c Add 4 feet to tributary floor span
				for each wood-framed wall above first level (i.e., 4 feet for 2-story, 8 feet
				for 3-story).
d Multiply floor span by 1.25 for
				interior footings supporting continuous joists.
e Multiply footing width by (1500
				psf/capacity) for soil capacity other than 1500 psf. See Section R403.1.1 for
				thickness.
f Dashed line may be used for
				interior footing size only.
g Use footing size indicated on line
				above the span combination used.
h For span combinations above the
				upper line, a design professional is required.
i Interpolation between footing
				sizes is allowed. Extrapolation is not allowed.
Click
				to view image
Notes:
a The minimum footing size is based
				on the following assumptions: Material weights per Section R301.2.2.2.1 and
				soil density = 120 pcf. Wood-framed walls = 10 foot; crawlspace stem wall = 6
				inches *36 inches; basement wall = 8 inches *120 inches. Total load (TL) equal
				to the maximum of three load combinations: LC1=D+L, LC2=D+S and
				LC3=D=0.75(L+S), where D=dead load, L=live load, S=snow load. TL=max (LC1, LC2,
				LC3).
b Use tributary span of floor and
				roof. Figure may be used to size exterior and interior footings.
c Add 4 feet to tributary floor span
				for each wood-framed wall above first level (i.e., 4 feet for 2-story, 8 feet
				for 3-story).
d Multiply floor span by 1.25 for
				interior footings supporting continuous joists.
e Multiply footing width by (1500
				psf/capacity) for soil capacity other than 1500 psf. See Section R403.1.1 for
				thickness.
f Dashed line may be used for
				interior footing size only.
g Use footing size indicated on line
				above the span combination used.
h For span combinations above the
				upper line, a design professional is required.
i Interpolation between footing
				sizes is allowed. Extrapolation is not allowed.
Statutory Authority:
				  RCW
				    19.27.031 and
				  chapters
				  19.27 and
				  34.05 RCW. 13-04-068, §
				  51-51-0403, filed 2/1/13, effective 7/1/13. Statutory Authority:
				  Chapter
				  19.27 RCW. 10-24-061,
				  § 51-51-0403, filed 11/29/10, effective 7/1/11. Statutory Authority:
				  RCW
				    19.27.031 and
				  19.27.074. 10-03-098, §
				  51-51-0403, filed 1/20/10, effective 7/1/10. Statutory Authority:
				  RCW
				    19.27.190,
				  19.27.020, and
				  chapters
				  19.27 and
				  34.05 RCW. 08-01-103, §
				  51-51-0403, filed 12/18/07, effective 4/1/08. Statutory Authority:
				  RCW
				    19.27.074,
				  19.27.020, and
				  chapters
				  19.27 and
				  34.05 RCW. 07-01-090, §
				  51-51-0403, filed 12/19/06, effective
				  7/1/07.