Indiana

Statewide summary — confirm with your building department before designing

AUDIT 2026-08-12 (physical design data pass). Indiana publishes a binding county-by-county climatic table and you should look your county up in it rather than rely on any single figure here. Section 5 of 675 IAC 14-4.4, the 2020 Indiana Residential Code, deletes IRC Table R301.2(1) and its footnotes outright and substitutes a table with one row for each of the 92 Indiana counties, giving wind speed, seismic design category, ground snow load in psf, foundation depth in inches, winter design temperature, decay and termite probability, weathering, ice shield underlayment, air freezing index and mean annual temperature. All 92 rows were extracted from the published final rule and then spot-checked against a rendered image of the table page to guard against column misalignment in the text layer. Ground snow load ranges from 20 to 30 psf and nothing else appears in that column. Thirty psf applies in 16 northern counties: DeKalb, Elkhart, Fulton, Jasper, Kosciusko, LaGrange, Lake, LaPorte, Marshall, Newton, Noble, Porter, Pulaski, St. Joseph, Starke and Steuben. The other 76 counties, including Marion, Allen, Vanderburgh and Tippecanoe, are 20 psf. These are ground loads, so labelled in the table header. The stored 20 psf is correct for the great majority of the state and for Indianapolis, but it understates the northern tier by half again. Note that Indiana assigns a flat 30 psf to the lake-effect counties rather than declaring them a case-study area, which contradicts the earlier note on this row suggesting that the South Bend belt falls in an ASCE case-study zone with no mapped value; Indiana simply legislates a number there, and that number governs. Wind speed corrected from 105 to 115 mph. The state table assigns 115 mph to every one of the 92 counties without exception, so this is a uniform state-adopted ultimate design wind speed and there is nothing to interpolate. Seismic design category is retained at C, but two official sources disagree and both are recorded here. Indiana own adopted table assigns A to 47 counties, B to 31 and C to 14, and section 6 of the same rule replaces the text of R301.2.2.1 to say that buildings shall be assigned a seismic design category in accordance with Table R301.2(1). The 14 C counties are Daviess, Dubois, Gibson, Greene, Knox, Martin, Monroe, Perry, Pike, Posey, Spencer, Sullivan, Vanderburgh and Warrick, all in the southwest on the Wabash Valley and New Madrid systems. Marion County, containing Indianapolis, is B under the state table. The earlier audit on this row derived D for Evansville and D0 for Posey County from the USGS ASCE 7-16 design maps at Site Class D; those computed values are higher than anything Indiana adopts, because Indiana caps its table at C. The state table is used here because it is the legally operative assignment for residential work in Indiana, and C is retained as the row value because it is the highest category the state assigns anywhere. A designer in the southwest should still run a site-specific determination, which the rule permits under footnote b and R301.2.2.1.1. Frost depth 36 inches is retained but is a maximum rather than a statewide figure. Indiana calls this column Foundation and defines it in footnote c as the minimum depth in inches from finish grade to the bottom of the footing. It takes exactly three values: 36 inches across the northern counties, 30 inches across a central band including Marion, and 24 inches across the southern counties. The stored 36 protects the north and over-digs the south by a foot. Other state-published values from the same table, none of which were previously confirmed: weathering is Severe in all 92 counties; decay probability is slight to moderate and termite probability moderate to heavy in all 92; ice shield underlayment is required in the northern counties and not in the south; winter design temperature is 1 degree F in the northern counties, 2 degrees in the central band and 9 degrees in the south, so the winter design temperature on this row is a state-published figure after all rather than unverified ASHRAE data, and should be reconciled against that column. Retrieval caveat: the Indiana Administrative Code at iar.iga.in.gov is a JavaScript application that serves no document text to a plain fetch, and the Department of Homeland Security copy of the final rule has been removed from in.gov. The rule text used here is the Indiana Register published final rule for LSA Document #19-330(F), retrieved from an Indiana county government host, clarkcounty.in.gov, and carrying the Commission own Title 675 header. The Commission rules page independently confirms that 675 IAC 14 rule 4.4, the 2020 Indiana Residential Code, is the current residential code and that the current Indiana Building Code is still the 2014 edition at 675 IAC 13-2.6. PRIOR AUDIT NOTE (retained; its statement that no value other than seismic category was changed is superseded by the wind speed correction above, and its ground snow and seismic figures are superseded by the state table described above): Seismic design category corrected from A to C by audit. Indianapolis, the state dominant metropolitan area, is not SDC A under any reading: at Site Class D and Risk Category II under ASCE 7-16 it computes to C, and to B on short-period spectral response alone. Southern Indiana is higher, with Terre Haute and Bloomington at C, Evansville at D and Mount Vernon in Posey County at D0 on the Wabash Valley and New Madrid fault systems. Only the far north, Fort Wayne, South Bend and Gary, bands to A or B. C is published as the value governing the largest metropolitan area and the southern half of the state; a site-specific determination is required and southwestern Indiana should be checked individually. No other value on this row was changed. Wind speed 105 mph is the ASCE 7-16 interior base contour for ultimate design wind speed at Risk Category II; Indiana site values interpolate to roughly 106 to 108 mph, so 110 mph is the conservative reading. Ground snow load 20 psf matches Indianapolis and Fort Wayne under ASCE 7-16; Evansville is 15 psf, Gary is 25 psf, and the lake-effect belt around South Bend falls in an ASCE case-study area where no mapped value applies and a site-specific study is required. Frost depth 36 inches is set locally in Indiana and was not verified against any government source. The winter design temperature is ASHRAE data, is not published by any Indiana authority, and is unverified.