# Table 502.3.3(1) Building Width



## Francis Vineyard (Feb 7, 2012)

Actually three questions in reference for load bearing wall; according to footnote h how do you use the building width instead of the roof width supported to interpolate?

Why are the 2x12 columns under 24 ft. blank?

Know that overhangs limit to 4 ft. for braced wall offsets; I didn't find the WFCM - 01 (don't have the 08) helpful unless designed. With a header frame in the opening to support the roof above would allow the overhang to be extended?

*502.3.3 Floor cantilevers.*

Floor cantilever spans shall not exceed the nominal depth of the wood floor joist. Floor cantilevers constructed in accordance with Table R502.3.3(1) shall be permitted when supporting a light-frame bearing wall and roof only. Floor cantilevers supporting an exterior balcony are permitted to be constructed in accordance with Table R502.3.3(2).

*TABLE R502.3.3(1) CANTILEVER SPANS FOR FLOOR JOISTS SUPPORTING LIGHT-FRAME EXTERIOR BEARING WALL AND ROOF ONLY **a, b, c, f, g, h** (Floor Live Load £ 40 psf, Roof Live Load £ 20 psf)*


*Member & Spacing*

*Maximum Cantilever Span (Uplift Force at Backspan Support in Lbs.)**d, e*



*Ground Snow Load*

*£** 20 psf*

*30 psf*

*50 psf*

*70 psf*

*Roof Width*

*Roof Width*

*Roof Width*

*Roof Width*

*24 ft.*

*32 ft.*

*40 ft.*

*24 ft.*

*32 ft.*

*40 ft.*

*24 ft.*

*32 ft.*

*40 ft.*

*24 ft.*

*32 ft.*

*40 ft.*

2 ´ 8 @ 12²

20²

(177)

15²

(227)

—

18²

(209)

—

—

—

—

—

—

—

—

2 ´ 10 @ 16²

29²

(228)

21²

(297)

16²

(364)

26²

(271)

18²

(354)

—

20²

(375)

—

—

—

—

—

2 ´ 10 @ 12²

36²

(166)

26²

(219)

20²

(270)

34²

(198)

22²

(263)

16²

(324)

26²

(277)

—

—

19²

(356)

—

—

2 ´ 12 @ 16²

—

32²

(287)

25²

(356)

36²

(263)

29²

(345)

21²

(428)

29²

(367)

20²

(484)

—

23²

(471)

—

—

2 ´ 12 @ 12²

—

42²

(209)

31²

(263)

—

37²

(253)

27²

(317)

36²

(271)

27²

(358)

17²

(447)

31²

(348)

19²

(462)

—

2 ´ 12 @ 8²

—

48²

(136)

45²

(169)

—

48²

(164)

38²

(206)

—

40²

(233)

26²

(294)

36²

(230)

29²

(304)

18²

(379)



For SI: 1 inch = 25.4 mm, 1 pound per square foot = 0.0479 kN/m2.

a. Tabulated values are for clear-span roof supported solely by exterior bearing walls.

b. Spans are based on No. 2 Grade lumber of Douglas fir-larch, hem-fir, southern pine, and spruce-pine-fir for repetitive (3 or more) members.

c. Ratio of backspan to cantilever span shall be at least 3:1.

d. Connections capable of resisting the indicated uplift force shall be provided at the backspan support.

e. Uplift force is for a backspan to cantilever span ratio of 3:1. Tabulated uplift values are permitted to be reduced by multiplying by a factor equal to 3 divided by the actual backspan ratio provided (3/backspan ratio).

f. See Section R301.2.2.2.2, item 1, for additional limitations on cantilevered floor joists for detached one- and two-family dwellings in Seismic Design Categories D1 and D2 and townhouses in Seismic Design Categories C, D1, and D2.

g. A full-depth rim joist shall be provided at the cantilevered end of the joists. Solid blocking shall be provided at the cantilever support.

h. Linear interpolation shall be permitted for building widths and ground snow loads other than shown.

Francis


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## Yankee (Feb 8, 2012)

My understanding is that the roof width and the building width are the same thing.


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## Paul Sweet (Feb 8, 2012)

1. I'd use the building width of the upper (larger) floor.

2. I'd guess that the blanks indicate the overhang calculated over 48" or less than the joist depth.

3. This is beyond the prescriptive design.  Engineering would be required.


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