Title 16 - Buildings and Construction

16.110 Residential Code for One- & Two-Family Dwellings

16.110.R301.2(1)

Table No. R301.2(1) of Section 301 of the International Residential Code for One- and Two-Family Dwellings is hereby amended to read as follows:

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

Region

Windborne

Debris

Zone

Weatheringa Frost line depthb Termitec
20 PSF 115 No No No A Severe 36”

Moderate 

to Heavy

6° F Yes

09/14/1977, 

08/03/2009

1500 or

Less

54.8° F
 Manual J Design Criteria       
 Elevation  Latitude

 Winter

heating

 Summer

cooling

 Altitude

correction

factor

 Indoor

design

temp

 Design

temp 

Cooling

 Heating temp

difference

 1096 ft  39  10° F 10° F  0.97 Heating 72° F   75° F  62° F

 Cooling temp

difference

 Wind

velocity

heating

Wind

velocity

cooling 

Coincident

wet bulb 

 Daily range

 Wind

humidity

Summer

humidity 

 
18° F  15 MPH  7.5 MPH  76° F   M  -

46@ 50%

RH 

 

 

For SI: 1 pound per square foot = 0.0479 kPa, 1 mile per hour = 0.447 m/s.

Where weathering requires a higher strength concrete or grade of masonry than necessary to satisfy the structural requirements of this code, the frost line depth strength required for weathering shall govern.

The weathering column shall be filled in with the weathering index, “negligible,” “moderate” or “severe” for concrete as determined from Figure R301.2(4). The grade of masonry units shall be determined from ASTM C34, C55, C62, C73, C90, C129, C145, C216 OR C652.

Where the frost line depth requires deeper footings than indicated in Figure R403.1(1), the frost line depth strength required for weathering shall govern. The jurisdiction shall fill in the frost line depth column with the minimum depth of footing below finish grade.

The 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.

The jurisdiction shall fill in this part of the table with the wind speed from the basic wind speed map [Figure R301.2(5)A]. Wind exposure category shall be determined on a site-specific basis in accordance with Section R301.2.1.4.

The outdoor design dry-bulb temperature shall be selected from the columns of 971/2-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. [Also see Figure R301.2(1).]

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

The 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.

In accordance with Section sR905.1.2, 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.”

The 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 percent) value on the National Climatic Data Center data table “Air Freezing Index-USA Method (Base 32oF).”

The 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 32oF).”

In 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.

In accordance with Figure R301.2(5)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 specific requirements. Otherwise, the jurisdiction shall indicate “NO” in this part of the table.

In accordance with Section R301.2.1.2 the jurisdiction shall indicate the wind-borne debris wind zone(s). Otherwise, the jurisdiction shall indicate “NO” in this part of the table.

The jurisdiction shall fill in these sections of the table to establish the design criteria using Table 1a or 1b from ACCA Manual J or established criteria determined by the jurisdiction.

The jurisdiction shall fill in this section of the table using the Ground Snow Loads in Figure R301.2(6).

 

 

(History: Ord. BC-3286 §51, 2020; Ord. BC-2936 §33, 2012; BC-2635 §55, 2007; BC-2459 §38, 2004; BC-2237 §2, 2001; Source or prior law: 16.05.120; BC-2013 §20, 97)

Effective on: 1/1/1901