Frost Line Depth by State
How deep footings must go to stay below the frost, state by state, taken from each state's building code. 10 states and Washington, DC set a depth for the whole state, by zone or by county, and Florida's code says frost depth doesn't apply. The other 39 states leave it to each city or county; we list official city values where we could verify them.
Quick answer
Footings must reach at least 12 inches below undisturbed ground and below your local frost line. Code frost depths run from 30 inches in Washington, DC and southern New Jersey to 48 inches in Massachusetts and Wisconsin, and 60 inches in northern Minnesota. Most states let each city or county set it, so check with your building department.
Frost depth by state
| State | Minimum footing depth for frost | Source |
|---|---|---|
| Alabama | Set by each city or county | Your city or county building department |
| Alaska | Set by each city or county Examples: Anchorage 42" | Your city or county building department |
| Arizona | Set by each city or county Examples: Phoenix 0" | Your city or county building department |
| Arkansas | Set by each city or county | Your city or county building department |
| California | Set by each city or county | Your city or county building department |
| Colorado | Set by each city or county Examples: Denver 36" | Your city or county building department |
| Connecticut | 42" (3 ft 6 in) | 2022 Connecticut State Building Code (2021 IRC portion), Table R301.2 (Climatic and Geographic Design Criteria) |
| Delaware | Set by each city or county | Your city or county building department |
| District of Columbia | 30" (2 ft 6 in) | 2017 District of Columbia Residential Code (12-C DCMR), UpCodes copy, Table R301.2(1) |
| Florida | No frost depth ("NA"); 12" minimum footing depth | Florida Building Code, Residential, 8th Ed. (2023), UpCodes copy, Table R301.2(1); R403.1.4 |
| Georgia | Set by each city or county Examples: Fayette County 5" | Your city or county building department |
| Hawaii | Set by each city or county | Your city or county building department |
| Idaho | Set by each city or county | Your city or county building department |
| Illinois | Set by each city or county | Your city or county building department |
| Indiana | 24", 30", 36" by county | Indiana Residential Code 2020 (675 IAC 14-4.4), UpCodes copy, Table R301.2(1) "Foundation" column, footnote c |
| Iowa | Set by each city or county | Your city or county building department |
| Kansas | Set by each city or county | Your city or county building department |
| Kentucky | 24" (2 ft) in most counties; 27–33" in 19 counties | 2018 Kentucky Residential Code (based on 2015 IRC), UpCodes copy, R403.1.4 and Table R403.1.4 "Minimum Frost Protection Depth for Kentucky" |
| Louisiana | Set by each city or county | Your city or county building department |
| Maine | Set by each city or county | Your city or county building department |
| Maryland | Set by each city or county Examples: Baltimore City 30", Prince George's County 30" | Your city or county building department |
| Massachusetts | 48" (4 ft) | Massachusetts Residential Code, 10th ed. (780 CMR 51.00), UpCodes copy, Table R301.2(1) |
| Michigan | 42" (3 ft 6 in) | Michigan Residential Code (Mich. Admin. Code R 408.30516, eff. 8/29/2025; R 408.30522), Table R301.2(1); R403.1.4 |
| Minnesota | 42", 60" by zone | Minnesota Rules 1303.1600 (Minnesota Provisions of the State Building Code), 1303.1600 subp. 1 |
| Mississippi | Set by each city or county | Your city or county building department |
| Missouri | Set by each city or county Examples: Kansas City 36" | Your city or county building department |
| Montana | Set by each city or county Examples: Billings 42" | Your city or county building department |
| Nebraska | Set by each city or county Examples: Omaha 42" | Your city or county building department |
| Nevada | Set by each city or county | Your city or county building department |
| New Hampshire | Set by each city or county | Your city or county building department |
| New Jersey | 30", 36" by zone | N.J.A.C. 5:23 UCC One- & Two-Family Dwelling Subcode 2024 (IRC/NJ), UpCodes copy, Table R301.2(1) and footnote |
| New Mexico | Set by each city or county | Your city or county building department |
| New York | Set by each city or county Examples: Syracuse 42" | Your city or county building department |
| North Carolina | Set by each city or county | Your city or county building department |
| North Dakota | Set by each city or county Examples: Fargo 54" | Your city or county building department |
| Ohio | Set by each city or county Examples: Columbus 32" | Your city or county building department |
| Oklahoma | Set by each city or county | Your city or county building department |
| Oregon | 12", 18", 24" by county | 2023 Oregon Residential Specialty Code (ORSC), UpCodes copy, Table R301.2 and footnote e |
| Pennsylvania | Set by each city or county Examples: Philadelphia 30" | Your city or county building department |
| Rhode Island | 40" (3 ft 4 in) | Rhode Island State Building Code SBC-2 Residential 2021 (UpCodes copy), Table R301.2(1) and notes |
| South Carolina | Set by each city or county | Your city or county building department |
| South Dakota | Set by each city or county Examples: Sioux Falls 42" | Your city or county building department |
| Tennessee | Set by each city or county Examples: Nashville-Davidson County 12" | Your city or county building department |
| Texas | Set by each city or county Examples: Austin 12", Dallas 6", Fort Worth 6", San Antonio 0" | Your city or county building department |
| Utah | Set by each city or county | Your city or county building department |
| Vermont | Set by each city or county | Your city or county building department |
| Virginia | Set by each city or county | Your city or county building department |
| Washington | Set by each city or county Examples: Seattle 12", Spokane 24" | Your city or county building department |
| West Virginia | Set by each city or county Examples: Elkins 24" | Your city or county building department |
| Wisconsin | 48" (4 ft), or deeper if frost goes deeper | Wisconsin Uniform Dwelling Code, Wis. Admin. Code SPS 321.16, SPS 321.16(1)(a) |
| Wyoming | Set by each city or county | Your city or county building department |
Values are the minimum depth from finished grade to the bottom of the footing, as written in each code. Cities can require more, and codes change when a state or city adopts a new edition, so confirm with the building department before you dig.
County and zone tables
Five states set the depth by county or by zone. Open a state for its full list.
Indiana: county list
| County | Frost depth |
|---|---|
| Adams County | 36" |
| Allen County | 36" |
| Bartholomew County | 24" |
| Benton County | 36" |
| Blackford County | 30" |
| Boone County | 30" |
| Brown County | 24" |
| Carroll County | 36" |
| Cass County | 36" |
| Clark County | 24" |
| Clay County | 24" |
| Clinton County | 30" |
| Crawford County | 24" |
| Daviess County | 24" |
| Dearborn County | 24" |
| Decatur County | 24" |
| DeKalb County | 36" |
| Delaware County | 30" |
| Dubois County | 24" |
| Elkhart County | 36" |
| Fayette County | 30" |
| Floyd County | 24" |
| Fountain County | 30" |
| Franklin County | 24" |
| Fulton County | 36" |
| Gibson County | 24" |
| Grant County | 30" |
| Greene County | 24" |
| Hamilton County | 30" |
| Hancock County | 30" |
| Harrison County | 24" |
| Hendricks County | 30" |
| Henry County | 30" |
| Howard County | 30" |
| Huntington County | 36" |
| Jackson County | 24" |
| Jasper County | 36" |
| Jay County | 30" |
| Jefferson County | 24" |
| Jennings County | 24" |
| Johnson County | 30" |
| Knox County | 24" |
| Kosciusko County | 36" |
| LaGrange County | 36" |
| Lake County | 36" |
| LaPorte County | 36" |
| Lawrence County | 24" |
| Madison County | 30" |
| Marion County | 30" |
| Marshall County | 36" |
| Martin County | 24" |
| Miami County | 36" |
| Monroe County | 24" |
| Montgomery County | 30" |
| Morgan County | 30" |
| Newton County | 36" |
| Noble County | 36" |
| Ohio County | 24" |
| Orange County | 24" |
| Owen County | 24" |
| Parke County | 30" |
| Perry County | 24" |
| Pike County | 24" |
| Porter County | 36" |
| Posey County | 24" |
| Pulaski County | 36" |
| Putnam County | 30" |
| Randolph County | 30" |
| Ripley County | 24" |
| Rush County | 30" |
| St. Joseph County | 36" |
| Scott County | 24" |
| Shelby County | 30" |
| Spencer County | 24" |
| Starke County | 36" |
| Steuben County | 36" |
| Sullivan County | 24" |
| Switzerland County | 24" |
| Tippecanoe County | 30" |
| Tipton County | 30" |
| Union County | 30" |
| Vanderburgh County | 24" |
| Vermillion County | 30" |
| Vigo County | 24" |
| Wabash County | 36" |
| Warren County | 30" |
| Warrick County | 24" |
| Washington County | 24" |
| Wayne County | 30" |
| Wells County | 36" |
| White County | 36" |
| Whitley County | 36" |
Kentucky: county list
| County | Frost depth |
|---|---|
| Bell County | 27" |
| Boone County | 30" |
| Breathitt County | 30" |
| Campbell County | 30" |
| Clay County | 27" |
| Floyd County | 33" |
| Harlan County | 30" |
| Johnson County | 30" |
| Kenton County | 30" |
| Knott County | 33" |
| Knox County | 27" |
| Lawrence County | 27" |
| Leslie County | 30" |
| Letcher County | 33" |
| Magoffin County | 30" |
| Martin County | 33" |
| Owsley County | 27" |
| Perry County | 30" |
| Pike County | 33" |
| All other Kentucky counties | 24" |
All other Kentucky counties: 24".
Minnesota: zones
| Zone | Frost depth | Counties |
|---|---|---|
| Zone I (northern counties) | 60" | Aitkin, Becker, Beltrami, Carlton, Cass, Clay, Clearwater, Cook, Crow Wing, Douglas, Grant, Hubbard, Itasca, Kanabec, Kittson, Koochiching, Lake, Lake of the Woods, Mahnomen, Marshall, Mille Lacs, Morrison, Norman, Otter Tail, Pennington, Pine, Polk, Red Lake, Roseau, St. Louis, Todd, Traverse, Wadena, Wilkin |
| Zone II (southern counties) | 42" | Anoka, Benton, Big Stone, Blue Earth, Brown, Carver, Chippewa, Chisago, Cottonwood, Dakota, Dodge, Faribault, Fillmore, Freeborn, Goodhue, Hennepin, Houston, Isanti, Jackson, Kandiyohi, Lac qui Parle, Le Sueur, Lincoln, Lyon, McLeod, Martin, Meeker, Mower, Murray, Nicollet, Nobles, Olmsted, Pipestone, Pope, Ramsey, Redwood, Renville, Rice, Rock, Scott, Sibley, Sherburne, Stearns, Steele, Stevens, Swift, Wabasha, Waseca, Washington, Watonwan, Winona, Wright, Yellow Medicine |
New Jersey: zones
| Zone | Frost depth |
|---|---|
| SNJ: Monmouth and Burlington Counties and all counties to the south | 30" |
| NNJ: Mercer and Middlesex Counties and all counties to the north | 36" |
Oregon: county list
| County | Frost depth |
|---|---|
| Baker County | 24" |
| Benton County | 12" |
| Clackamas County | 12" |
| Clatsop County | 12" |
| Columbia County | 12" |
| Coos County | 12" |
| Crook County | 18" |
| Curry County | 12" |
| Deschutes County | 18" |
| Douglas County | 18" |
| Gilliam County | 24" |
| Grant County | 24" |
| Harney County | 24" |
| Hood River County | 24" |
| Jackson County | 18" |
| Jefferson County | 18" |
| Josephine County | 18" |
| Klamath County | 24" |
| Lake County | 24" |
| Lane County | 12" |
| Lincoln County | 12" |
| Linn County | 12" |
| Malheur County | 24" |
| Marion County | 12" |
| Morrow County | 24" |
| Multnomah County | 18" |
| Polk County | 12" |
| Sherman County | 24" |
| Tillamook County | 12" |
| Umatilla County | 24" |
| Union County | 24" |
| Wallowa County | 24" |
| Wasco County | 24" |
| Washington County | 12" |
| Wheeler County | 24" |
| Yamhill County | 12" |
Below 2,500 ft in Jackson, Josephine and Multnomah counties: 12".
What the code says
- 12 inches minimum, everywhere. 2021 IRC R403.1.4: "Exterior footings shall be placed not less than 12 inches (305 mm) below the undisturbed ground surface."
- Below the frost line. R403.1.4.1 requires foundations to be protected from frost by extending below the frost line in Table R301.2, by a frost-protected shallow foundation (R403.3 or ASCE 32), or by sitting on solid rock. "Footings shall not bear on frozen soil unless the frozen condition is permanent."
- Each jurisdiction fills in the number. The table's footnote reads: "The jurisdiction shall fill in the frost line depth column with the minimum depth of footing below finish grade." That's why the depth changes from state to state and often from city to city.
- Small sheds are exempt. Free-standing accessory buildings of 600 sq ft or less (light framing) or 400 sq ft or less (other construction), with eaves 10 ft high or less, don't need frost protection.
Why frost depth matters
When wet soil freezes it expands and can lift a footing a little each winter, a process called frost heave. Over a few years that cracks slabs, racks deck posts and jams doors. Setting the bottom of the footing below the deepest frost keeps it on soil that doesn't freeze. Use the depth here to size post holes with our post hole concrete calculator and plan deck footings with the deck framing planner.
Want the raw data? Download the CSV with each state's value, scope and source link. It's free to reuse under CC BY 4.0; please credit Nail the Math with a link.
Frequently asked questions
How deep do footings have to be?
The International Residential Code sets two minimums: at least 12 inches below undisturbed ground everywhere (R403.1.4), and below the frost line your local jurisdiction sets in Table R301.2 (R403.1.4.1), unless the footing is protected another way. The deeper of the two applies.
What is the frost line depth in Minnesota?
Minnesota Rule 1303.1600 sets 60 inches (5 ft) in the northern counties (Zone I) and 42 inches (3½ ft) in the southern counties, including Hennepin and Ramsey (Zone II).
Does Texas have a frost line?
Texas has no statewide value; each city sets its own. Dallas and Fort Worth list 6 inches and San Antonio 0, but the code's 12 inch minimum footing depth still applies, so footings there go at least 12 inches down.
Do deck footings have to go below the frost line?
Under the 2021 IRC, deck footings go at least 12 inches into undisturbed soil (R507.3.2), and a deck attached to a frost-protected house needs footings below the frost line, on solid rock or protected another approved way (R507.3.3). Rhode Island spells it out: decks, platforms and landings need footings 3 ft 4 in deep. Ask your building department about free-standing decks.
Why can't I find my state in the list of fixed depths?
39 of the 50 states leave the frost depth to each city or county. The building department that issues your permit lists it, usually in a handout or in its copy of Table R301.2.
Last reviewed 2026-10-23. Sources: 2021 International Residential Code; the state codes linked in the table; official city code copies. See how we calculate.