Skip to main content
Loading…
This section is included in your selections.

The provisions of CBC Chapter 16 and Section 1608 and CRC Sections R301.2 and R301.2.3 are hereby amended to include the following additional requirements for roof snow load design. The unincorporated area of Sierra County shall be divided into zones, established by climatic and geographic analysis, to determine applicable snow loads for a parcel of property and the zone within which a parcel is located. The location within a zone combined with the elevation of the parcel of property shall be the basis for determining the roof snow load design requirements for any construction project. A cartographic representation of the zones shall be maintained in the office of the County Building Official. The zones hereby established are described as follows:

A. Zone I. All of the area encompassed within the following:

T. 22 N., R. 9 E.; T. 22 N., R. 10 E.; T. 21 N., R. 9 E.;

T. 21 N., R. 10 E.; T. 20 N., R. 9 E., M.D.B.&M., excepting those portions lying outside Sierra County.

B. Zone II. All of the area encompassed within the following:

T. 22 N., R. 11 E.; T. 21 N., R. 11 E.; T. 21 N., R. 12 E.;

T. 21 N., R. 13 E.; T. 20 N., R. 8 E.; T. 20 N., R. 10 E.;

T. 20 N., R. 11 E.; T. 20 N., R. 12 E.; T. 20 N., R. 13 E.;

T. 19 N., R. 8 E.; T. 19 N., R. 9 E.; T. 19 N., R. 10 E.;

T. 19 N., R. 11 E.; T. 19 N., R. 12 E.; T. 19 N., R. 13 E.;

T. 18 N., R. 8 E.; T. 18 N., R. 9 E.; T. 18 N., R. 10 E,;

T. 18 N., R. 11 E.; T. 18 N., R. 13 E.; M.D.B.&M., excepting those portions lying outside Sierra County.

C. Zone III. All of the area encompassed within the following:

T. 21 N., R. 14 E.; T. 20 N., R. 14 E.; T. 20 N., R. 15 E.;

T. 19 N., R. 14 E.; T. 18 N., R. 14 E.; M.D.B.&M., excepting those portions lying outside Sierra County.

D. Zone IV. All of the area encompassed within the following:

T. 20 N., R. 16 E.; T. 19 N., R. 15 E.; T. 19 N., R. 16 E.;

T. 18 N., R. 15 E.; T. 18 N., R. 16 E.; M.D.B.&M., excepting those portions lying outside Sierra County, and Sections 4, 5, 6, 7, 8, 9, 16, 17, 18, 19, 20, 21, 28, 29, 30, 31, 32, 33, T. 20 N., R. 17 E., M.D.B.&M.; and Sections 4, 5, 6, 7, 8, 9, 16, 17, 18, 19, 20, 21, 28, 29, 30, 31, 32, 33, T. 19 N., R. 17 E., M.D.B.&M.; and Sections 4, 5, 6, T. 18 N., R. 17 E., M.D.B.&M., excepting those portions lying outside Sierra County.

E. Zone V. All of the area encompassed within the following:

T. 21 N., R. 15. E.; T. 21 N., R. 16 E.; T. 21 N., R. 17 E.;

T. 21 N., R. 18 E.; T. 20 N., R. 18 E.; T. 19 N., R. 18 E.;

T. 18 N., R. 18 E.; M.D.B.&M., excepting those portions lying outside Sierra County; and Sections 1, 2, 3, 10, 11, 12, 13, 14, 15, 22, 23, 24, 25, 26, 27, 34, 35, and 36, T. 20 N., R. 17 E., M.D.B.&M.; and Sections 1, 2, 3, 10, 11, 12, 13, 14, 15, 22, 23, 24, 25, 26, 27, 34, 35, and 36, T. 19 N., R. 17 E., M.D.B.&M.; and Sections 1, 2, 3, T. 18 N., R. 17 E., M.D.B.&M., excepting those portions lying outside Sierra County.

F. Snow roof load design requirements cross referenced by elevation and proximity to the established zones are as follows:

Elevation Range

Snow Load Design Requirements (Lbs./Sq. Ft.)

(Ft. above Sea Level)

Zone I

Zone II

Zone III

Zone IV

Zone V

2,000 – 2,500

2,501 – 3,000

50

3,001 – 3,500

180

70

3,501 – 4,000

210

100

4,001 – 4,500

230

120

4,501 – 5,000

260

150

70

5,001 – 5,500

290

180

120

70

5,501 – 6,000

310

220

170

100

90

6,001 – 6,500

340

260

210

160

110

6,501 – 7,000

370

300

260

210

130

7,001 – 7,500

390

350

300

260

150

Over 7,500

To be determined by building official.

The following design criteria are hereby adopted for roof snow loads within the unincorporated areas of Sierra County:

1. The roof snow loads are the snow loads on “flat roofs” (NOT ground snow loads). If desired or required by your engineering software, use ASCE equation 7-1 (pf = 0.7 CeC tIs pg), to determine the ground snow load where the Pf listed above is based on an exposure factor C e = 0.9, thermal factor C t = 1.1, and importance factor I = 1.0 per ASCE Standard 7-05. The flat roof snow load for each site should have these factors adjusted as appropriate.

2. Snow loads may be reduced for sloped roofs in accordance with ASCE Standard 7-05, Section 7.4 providing a minimum of eight feet of vertical eave height is provided for each 100 pounds of snow load. This minimum eave height is measured from the eave down to either grade or the first obstruction, such as a deck etc., and must be maintained for a minimum distance of 10 feet out from the eave. In areas with snow loads in excess of 100 pounds which do not have a 16-foot or greater eave height, the allowable slope reduction can be prorated (i.e., snow loads greater than 100 pounds eave height of nine feet; nine-sixteenths of the allowable reduction can be taken).

3. Snow reduction for sloped roofs shall not be used for structural members affected by valleys, dormers, slope changes, chimney chases or other areas where the snow may be restricted from sliding.

4. No roof material shall be considered “slippery” for the purposes of snow reduction for sloped roofs per ASCE Standard 7-05, Section 7.4.

5. Uncovered decks, and all similar structures, may be designed for the flat roof snow load as provided herein. Covered, but not fully enclosed decks and all similar structures shall be designed for floor loads from CBC Table 1607.1 or 50 percent of the flat roof snow load, whichever is greater.

6. The three-second gust basic wind speed for Sierra County is 85 miles per hour per ASCE Standard 7-05 Figure 6.1.

7. Roof design snow load may be reduced up to 80 percent for use in seismic calculations per CBC Section 1605.3.1.

8. Allowable soil bearing factor to be used in design without the preparation of a special soils report is 2,000 psf.

9. Frost depth shall be 18 inches below finished grade and all footings shall extend a minimum of 12 inches into undisturbed native soil. Exterior finished grade shall provide a minimum footing coverage of 18 inches.

10. Conventional light-frame construction is not permitted in Sierra County per CBC Section 2308.2.3.3.

The provisions of CBC Sections 1507.2.8.2, 1507.5.4, 1507.6.4, 1507.7.4, 1507.8.4, 1507.9.4 and CRC Sections R905.2.7.1, R905.4.3.1, R905.5.3.1, R905.6.3.1, R905.7.3.1 and R905.8.3.1 are hereby amended to require additional design and construction requirements for ice barriers. In areas where there has been a history of ice forming along the eaves causing a backup of water as designated in CRC Table R301.2(1) (or below the 6,200-foot elevation level), an ice barrier that consists of at least two layers of underlayment cemented together or a self-adhering polymer modified bitumen sheet shall be used in place of normal underlayment and extend from the lowest edges of all roof surfaces to a point at least 24 inches inside the interior wall line of the building. For areas above the 6,200-foot elevation level, a self-adhering polymer modified bitumen sheet shall be used in place of normal underlayment and extend from the lowest edges of all roof surfaces to a point at least 72 inches inside the interior wall line of the building.

A cricket or saddle-type diverter shall be installed on the ridge side of any chimney, flue or vent that is adjacent to or penetrates the roof. Crickets or saddle coverings shall be a minimum 24 gauge sheet metal or the same material as the roof covering. Plumbing vents through the barge rafter shall be approved by the building official prior to installation, provided adequate clearances are maintained from windows, vents, combustion air and exhaust vents. (Ord. 1037, eff. 3/1/12; Ord. 571, eff. 2/5/80)