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PART 300  Amendments to the International Residential Code.
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30.52F.300 Table R 301.2(1) - amended.
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IRC Table R 301.2(1) is amended to read:

Table R301.2(1) Climatic and Geographic Design Criteria

Minimum Roof Snow Load (PSF)

Wind Design

Seismic Design Categoryf

Subject to Damage From

Winter Design Tempe

Ice Barrier Underlayment Requiredh

Flood Hazardsg

Air Freezing Indexi

Mean Annual Tempj

Speedd (MPH)

Topographic Effectsk

Special wind regionl

Windborne debris zonem

Weatheringa

Frost line depthb

Termitec

25

May increase depending on site location

110

NO

NO

NO

D/D2

Moderate

18 inches

Moderate

26° F

NO

12/23/71

9/16/05

175

50.5° F

aWeathering may require a higher strength concrete or grade of masonry than necessary to satisfy the structural requirements of the residential code. The weathering column shall be filled in with the weathering index (i.e., "negligible," "moderate" or "severe") for concrete as determined from the Weathering Probability Map [Figure R.301.2(3)]. The grade of masonry units shall be determined from ASTM C 34, C 55, C 62, C 73, C 90, C 129, C 145, C 216 or C 652.

bThe frost line depth may require deeper footings than indicated in Figure R403.1(1). The jurisdiction shall fill in the frost line depth column with the minimum depth of footing below finish grade.

cThe jurisdiction shall fill in this part of the table to indicate the need for protection depending on whether there has been a history of local subterranean termite damage.

dThe jurisdiction shall fill in this part of the table with the wind speed from the basic wind speed map [Figure R301.2(4)]. Wind exposure category shall be determined on a site-specific basis in accordance with section R301.2.1.4.

eThe outdoor design dry-bulb temperature shall be selected from the columns of 97 1/2-percent values for winter from Appendix D of the International Plumbing Code. Deviations from the Appendix D temperatures shall be permitted to reflect local climates or local weather experience as determined by the building official.

fThe jurisdiction shall fill in this part of the table with the seismic design category determined from section R301.2.2.1.

gThe jurisdiction shall fill in this part of the table with (a) the date of the jurisdiction’s entry into the National Flood Insurance Program (date of adoption of the first code or ordinance for management of flood hazard areas), (b) the date(s) of the Flood Insurance Study, and (c) the date(s) of the currently effective FIRM and FBFM, or other flood hazard map adopted by the county, as may be amended.

hIn accordance with 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, where there has been a history of local damage from the effects of ice damming, the jurisdiction shall fill in this part of the table with "YES." Otherwise, the jurisdiction shall fill in this part of the table with "NO."

iThe jurisdiction shall fill in this part of the table with the 100-year return period air freezing index (BF-days) from Figure R403.3.(2) or from the 100-year (99%) value on the National Climatic Data Center data table "Air Freezing Index - USA Method (Base 32 o Fahrenheit)" at www.ncdc.noaa.gov/fpsf.html.

jThe jurisdiction shall fill in this part of the table with the mean annual temperature from the National Climatic Data Center data table "Air Freezing Index-USA Method (Base 32° Fahrenheit)" at www.ncdc.noaa.gov/fpsf.html.

kIn accordance with section R301.2.1.5, where there is local historical data documenting structural damage to buildings due to topographic wind speed-up effects, the jurisdiction shall fill in this part of the table with "YES." Otherwise, the jurisdiction shall indicate "NO" in this part of the table.

lIn accordance with Figure R301.2(4)A, where there is local historical data documenting unusual wind conditions, the jurisdiction shall fill in this part of the table with "YES" and identify any special requirements. Otherwise, the jurisdiction shall indicate "NO" in this part of the table.

mIn accordance with section R301.2.1.2.1, the jurisdiction shall indicate the windborne debris wind zone(s). Otherwise, the jurisdiction shall indicate "NO" in this part of the table.

Note to footnote d: Minimum 110 mph ultimate design wind speed to be used for buildings designed according to the International Building Code.

Note to footnote k: Topographical effects shall be included for buildings designed according to the International Building Code.

(Added by Amended Ord. 07-084, Sept. 5, 2007, Eff date Sept. 21, 2007; Amended by Amended Ord. 11-031, Aug. 3, 2011, Eff date Aug. 18, 2011; Amended by Amended Ord. 14-057, Aug. 27, 2014, Eff date Sept. 13, 2014; Amended by Ord. 17-057, Oct. 18, 2017, Eff date Nov. 9, 2017).

(Ord. 17-057 , 2017; Amended Ord. 14-057 , 2014; Amended Ord. 11-031 , 2011; Amended Ord. 07-084 , 2007.)
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