Home / Frost line depth
Frost data
Frost line depth by state
The short answer
The frost line is the depth your building code assumes the ground can freeze to, and footings and water lines have to sit below it. 13 states publish a single statewide figure, running from 0 in in Florida to 42 to 60 in in Minnesota. The other 37 adopt a model code and leave the number to whichever city or county issues the permit, so for those we list the figures real jurisdictions publish rather than inventing a state average. Every row below carries its source.
The weather.gov map is a different number
Searching for a frost depth map usually lands on the National Weather Service product, which reports how deep the ground is frozen at the moment. That figure moves through the winter and is close to zero in October. The code frost line does not move: it is the design depth your jurisdiction adopted, set to sit below the deepest frost a hard winter is expected to reach. Build to the code figure and read the NWS map for conditions. NOAA National Weather Service, North Central River Forecast Center frost depth map.
- Under 12 in
- 12 to 23 in
- 24 to 35 in
- 36 to 47 in
- 48 in and deeper
- No statewide figure
Small states, left unlabelled on the map: Connecticut, Delaware, Hawaii, Maryland, Massachusetts, New Hampshire, New Jersey, Rhode Island, Vermont.
By ZIP code
Frost depth and freeze dates for your ZIP
The state figure, the burial minimum it implies, and the freeze record at your nearest NOAA station.
Enter a ZIP code
All 50 states
Code frost depth by state
The figure, the basis, and the source. Linked states have a page of their own.
| State | Code frost depth | Basis | Where it comes from |
|---|---|---|---|
| Alabama | set locally | local jurisdiction (varies)City of Mobile, AL 12 in; Mobile County, AL (unincorporated) 12 in | City of Mobile, Ordinance Adopting the 2021 IRC (Table R301.2) |
| Alaska | set locally | local jurisdiction (varies)Municipality of Anchorage, AK 42 in | Municipality of Anchorage, Chapter 23.85 local amendments to t… |
| Arizona | set locally | local jurisdiction (varies)City of Phoenix, AZ 0 in; City of Flagstaff, AZ 30 in | City of Phoenix 2018 IRC Amendments (Table R301.2(1)) |
| Arkansas | set locally | local jurisdiction (varies)City of Little Rock, AR 12 in | City of Little Rock Codes & Design Criteria |
| California | set locally | local jurisdiction (varies)Truckee/Tahoe area, Placer County (5,001,7,000 ft) 18 in; Truckee/Tahoe area, Placer County (7,001,8,000 ft) 24 in | California Building Standards Commission (Dept. of General Ser… |
| Colorado | set locally | local jurisdiction (varies)City and County of Denver 36 in; Colorado Springs / El Paso County (Pikes Peak Regional Building Dept.) 30 in | 2022 Denver Building & Fire Code (official), frost protection … |
| Connecticut | 42 in | state code amendment | 2022 Connecticut State Building Code (w/ Errata #1), Amd 1809.… |
| Delaware | set locally | local jurisdiction (varies)New Castle County (unamended IRC baseline) 12 in; Sussex County, DE 24 in | New Castle County Dept. of Land Use, Single-Family Dwelling Pl… |
| Florida | 0 in | state code amendment | 2023 Florida Building Code, Residential, 8th Ed., Ch. 4 Founda… |
| Georgia | set locally | local jurisdiction (varies)Macon-Bibb County, GA 18 in; City of Sandy Springs, GA 12 in | 2018 IRC with Georgia Amendments, Ch. 3, Table R301.2(1) footn… |
| Hawaii | set locally | local jurisdiction (varies) | Hawaii State Building Code Council, Hawaii State Residential C… |
| Idaho | set locally | local jurisdiction (varies)City of Boise (local IBC/IRC amendment, eff. 2021) 24 in; Kootenai County (local IBC/IRC amendment) 24 in | Idaho Administrative Code IDAPA 24.39.30, Rules of Building Sa… |
| Illinois | set locally | local jurisdiction (varies)City of Chicago 42 in; Village of Flossmoor 42 in; City of Peoria, IL 36 in | City of Chicago Dept. of Buildings, Porch Design & Constructio… |
| Indiana | 24 to 36 in | state code amendmentWayne County, IN 30 in; Wells, White and Whitley Counties, IN 36 in | Indiana Administrative Code 675 IAC 14-4.4-5, Table R301.2(1),… |
| Iowa | set locally | local jurisdiction (varies)City of Des Moines, IA 42 in; Johnson County, IA 42 in | City of Des Moines, Construction Codes (Design Criteria / Loca… |
| Kansas | set locally | local jurisdiction (varies)City of Manhattan, KS 34 in; Johnson County, KS 36 in | City of Manhattan, KS, Climate & Geographic Design Criteria |
| Kentucky | 24 to 33 in | state code amendmentMartin, Pike, Knott, Letcher, Floyd Counties, KY 33 in; All other Kentucky counties (default) 24 in | 2018 Kentucky Residential Code, 2nd Edition (Kentucky Dept. of… |
| Louisiana | 12 in | state code amendment | LSUCCC, Uniform Construction Codes and Amendments (eff. 01-01-… |
| Maine | set locally | local jurisdiction (varies)Bangor, ME 60 in; Brewer, ME 60 in | City of Bangor, Maine, Building Codes |
| Maryland | set locally | local jurisdiction (varies)Montgomery County, MD 30 in; Baltimore County, MD 30 in | Montgomery County MD, guidelines for building residential deck… |
| Massachusetts | 48 in | state code amendment | 780 CMR 51.00 Massachusetts Residential Code, Ch. 3 Building P… |
| Michigan | 42 in | state code amendment | Michigan LARA, 2021 Michigan Residential Code, Rule 516 (R 408… |
| Minnesota | 42 to 60 in | state code amendmentZone I (33 northern counties incl. St. Louis, Itasca, Beltrami, Cook, Koochiching) 60 in; Zone II (48 central/southern counties incl. Hennepin, Ramsey, Anoka, Washington, Winona) 42 in | Minnesota Rule 1303.1600, Footing Depth for Frost Protection (… |
| Mississippi | set locally | local jurisdiction (varies) | jurisdiction sources only, listed above |
| Missouri | set locally | local jurisdiction (varies)Springfield, MO (city ordinance) 24 in; Missouri, north of Hwy 36 (state agency reference map) 25 in; Missouri, south of I-44 (state agency reference map) 12 in | Missouri Public Service Commission, 2016 State of Missouri Fro… |
| Montana | 36 to 48 in | state code amendment | Montana Dept. of Labor & Industry, Building Codes Bureau, Buil… |
| Nebraska | set locally | local jurisdiction (varies)City of Lincoln / Lancaster County, NE 36 in | Lincoln Municipal Code §20.12.140, Table R301.2 Amended (Clima… |
| Nevada | set locally | local jurisdiction (varies)Washoe County / Reno, NV 24 in; Clark County / Las Vegas Valley, NV (elevations below 1,600 ft) 12 in | Washoe County Building Division, Construction Design Requireme… |
| New Hampshire | set locally | local jurisdiction (varies)City of Manchester, NH 48 in | City of Manchester, NH, Locally adopted Building Code / Table … |
| New Jersey | set locally | local jurisdiction (varies) | N.J.A.C. 19:6-2.3, Depth of Foundations (NJ UCC Building Subco… |
| New Mexico | set locally | state code amendmentStatewide (2021 NM Residential Code, 14.7.3.12 NMAC §R403.1.4) 12 in; City of Albuquerque, NM 16 in; City of Farmington, NM 24 in | New Mexico Regulation & Licensing Dept., Construction Industri… |
| New York | set locally | local jurisdiction (varies)Town of Smithtown, Suffolk County, NY 36 in; Town of Pittsford, Monroe County, NY 42 in; Town of Enfield, Tompkins County, NY 42 in | NYS Dept. of State, Division of Building Standards and Codes, … |
| North Carolina | set locally | local jurisdiction (varies) | NC Office of State Fire Marshal, 2018 NC Plumbing Code Amendme… |
| North Dakota | set locally | local jurisdiction (varies)City of Fargo, ND 52 in; City of Bismarck, ND 48 in | North Dakota Department of Commerce / State Building Code Book… |
| Ohio | set locally | local jurisdiction (varies)City of Toledo, OH 36 in; Lucas County, OH 36 in; City of Stow, OH (Summit County) 36 in; City of Dayton, OH 32 in | Ohio Administrative Code 4101:8-3-01, Table 301.2(1) Climatic … |
| Oklahoma | set locally | local jurisdiction (varies)City of The Village, OK (Oklahoma County) 18 in | Oklahoma Uniform Building Code Commission (OUBCC) |
| Oregon | 12 to 24 in | state code amendmentMultnomah County (below 2,500 ft elevation) 18 in; Baker County 24 in; Benton, Clackamas, Lane Counties (Willamette Valley) 12 in | 2023 Oregon Residential Specialty Code, Summary of Amendments,… |
| Pennsylvania | set locally | local jurisdiction (varies)City of Erie, PA 48 in; City of Allentown, PA 36 in; City of Lancaster, PA 36 in | PA Department of Labor & Industry, Uniform Construction Code (… |
| Rhode Island | 40 in | state code amendmentNew Shoreham (Block Island) â statewide code exception 30 in | Rhode Island State Building Code SBC-2 (RI One & Two Family Dw… |
| South Carolina | set locally | local jurisdiction (varies)Anderson County, SC 12 in; City of Charleston, SC 0 in; York County, SC 12 in | South Carolina 2021 Code Modifications (LLR Building Codes Cou… |
| South Dakota | set locally | local jurisdiction (varies)Hartford / Minnehaha County, SD 42 in; City of Madison, SD 42 in | City of Hartford, SD Building Handbook |
| Tennessee | set locally | local jurisdiction (varies)Knox County, TN 12 in; Nashville-Davidson County, TN (water-service cover, not footing depth) 24 in | TN Dept. of Commerce & Insurance, Div. of Fire Prevention â … |
| Texas | set locally | local jurisdiction (varies)City of Dallas, TX 6 in; City of Lubbock, TX 12 in | City of Dallas Ordinance 23-0471, amendments to the 2021 IRC, … |
| Utah | set locally | local jurisdiction (varies)St. George, UT (Washington County) 12 in; Duchesne County, UT 30 in; Greater Salt Lake Municipal Services District, UT 30 in | Utah Division of Administrative Rules â Bulletin filing for … |
| Vermont | 60 in | state code amendment | 2025 Vermont Fire & Building Safety Code (Division of Fire Saf… |
| Virginia | set locally | local jurisdiction (varies)Shenandoah County, VA 24 in; Fairfax County, VA 24 in | Virginia DHCD â Virginia Uniform Statewide Building Code (US… |
| Washington | set locally | local jurisdiction (varies)City of Spokane / Spokane County, WA (joint policy) 24 in; City of Everett, WA 18 in | WAC 51-51-0301 (WA amendments to IRC R301.2) â frost-line cr… |
| West Virginia | set locally | local jurisdiction (varies)Morgantown, WV 30 in | West Virginia State Fire Commission, 87 CSR 4 State Building C… |
| Wisconsin | 48 in | state code amendment | Wisconsin Legislature â Wis. Admin. Code SPS 321.16, "Frost … |
| Wyoming | set locally | local jurisdiction (varies)Casper / Natrona County, WY 36 in; Teton County, WY 34 in | City of Casper, WY â Engineering and Climatic Design Criteri… |
“Set locally” is the honest answer for most of the country: the state adopts a model code and leaves the frost-line cell of Table R301.2(1) for the building department that issues your permit to fill in. Where that is the case we list the figures real jurisdictions publish rather than printing a number the state does not. Confirm your own figure with your local building department before you dig or pour.
State pages: Minnesota, Iowa, Michigan, Ohio, Indiana, Illinois, Virginia, Wisconsin, Missouri, Pennsylvania, Texas, Massachusetts, Utah, Colorado, Kentucky, North Carolina, Florida, Maryland, Maine, Oklahoma.
The other depth
Frost depth is not the same as water line burial depth
Two numbers get used interchangeably and they are not the same. The frost line is a footing rule: it keeps a foundation from being lifted by soil that expands as it freezes. The burial rule is a plumbing rule: it keeps water in a service line from freezing solid and splitting the pipe.
The model code states the plumbing rule directly. Under the International Residential Code, water service pipe Water service pipe shall be installed not less than 12 inches (305 mm) deep and not less than 6 inches (152 mm) below the frost line.
(2021 International Residential Code, Section P2603.5 (Freezing), ICC free code viewer). Both clauses bind, so the minimum is the frost depth plus six inches, and the twelve-inch floor is what applies in states whose frost line is effectively zero. Several states go further again: the burial column in the table on how deep water lines are buried shows what each state’s own figure works out to, and flags the states whose plumbing code adds cover on top.
Municipal water departments often specify more than the code minimum for the portion of the line they own, so the depth of the main in the street and the depth of your service line are two more numbers that can differ. If you are locating an existing line rather than burying a new one, call 811 first and let the utility mark it.
What it means
What this means for your pipes
A deep frost line tells you two things about a house. Its water service enters below the depth that freezes, so the line under the yard is usually the safe part, and the vulnerable runs are the ones above ground in unheated space. And its winter is long enough that those runs get tested every year rather than once a decade.
The reverse holds in shallow-frost states. A house in Texas or Georgia has a service line close to the surface and pipes in unconditioned attics, which is the combination that produces a burst-pipe wave when a rare hard freeze arrives. Whichever side you are on, the two pages to read before winter are at what temperature pipes freeze and when the first freeze lands where you live. If one has already split, burst pipe repair cost covers the repair and the water damage behind it.
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Common questions
Frost line questions
How do I find the frost line depth in my area?
Ask the building department that will issue your permit, and treat anything else as a starting point. That is not a dodge; it is how the code is written. Most states adopt the International Residential Code and leave the frost-line cell of its climate table for each local jurisdiction to fill in, so the authoritative figure genuinely lives at city or county level. The table on this page gives you the 13 states that do publish a statewide number and, for the rest, the figures real jurisdictions have published, so you know roughly what to expect before you call.
What is the difference between the frost line and the frost depth on weather.gov?
They answer different questions. The National Weather Service product shows how deep the ground is frozen right now or in the days ahead, which changes through the winter. The code frost line is a fixed design figure your jurisdiction adopted, meant to sit below the deepest frost a bad winter is expected to reach. A footing or a water line is built to the code figure, not to this week’s observation. NOAA National Weather Service, North Central River Forecast Center frost depth map.
How deep do you have to dig for the frost line?
Deep enough that the bottom of the footing sits below it, which is why the published figure is a minimum rather than a target. Across the states that publish one, the range on this page runs from 0 in in Florida to 42 to 60 in in Minnesota. Water service lines follow a separate rule, covered below.
What state has the deepest frost line?
Among the states that publish a statewide figure, Minnesota is the deepest at 42 to 60 in. Deeper local figures exist in states that publish nothing statewide, which is why the table lists jurisdiction figures alongside the state ones. Depth does not track latitude cleanly either: a high-elevation interior state can require more than a coastal state further north, which is the reason to read your own jurisdiction's table rather than a map.
Do deck posts need to be below the frost line?
In most jurisdictions yes, for the same reason a house footing does: soil that freezes expands and lifts anything bearing on it, and a post that heaves takes the deck with it. The requirement and the depth both come from your local building department, and a deck permit is usually where the question gets settled. This page is about the plumbing consequence of the same number, so check the depth here and confirm it there.
Where these numbers come from
The frost depth table is compiled by hand, state by state, from the body that publishes the figure. Researched one state at a time against the body that publishes the figure: a state building-code amendment, a state administrative rule, a state DOT table, or an official municipal building department. Where a state publishes no single figure the record is null and carries the published figures of two or three real jurisdictions instead. No value is read off a contour map, averaged between neighbours, or taken from a contractor or deck-building site. Every URL is checked for HTTP 200 by scripts/etl/verify-sources.mjs. It was last compiled on 2026-09-09. Each state row links its own source; the full list with a confidence note per state is in data/frost-depth.sources.md in the site repository.
- Freeze dates and cold-night counts: NOAA NCEI U.S. Climate Normals, 1991 to 2020, annual and seasonal by station. Retrieved 2026-09-09. Field definitions are in the by-variable readme.
- ZIP code locations: U.S. Census Bureau 2023 ZIP Code Tabulation Area gazetteer, matched to the nearest station by great-circle distance.
- NOAA National Weather Service, North Central River Forecast Center frost depth map Observed and forecast frost depth, updated through the winter. Not the code frost line.
- 2021 International Residential Code, Section P2603.5 (Freezing), ICC free code viewer The water service line burial rule, quoted verbatim above.
The full method, including how we pick a station and what we do when there is not one close enough, is on our methodology page.
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