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Frost data
Frost line depth in Kentucky
The short answer
Kentucky publishes a code frost depth of 24 to 33 in. Kentucky is one of the states that does publish a table, and it is short: 24 inches for most of the state, 33 inches for five counties in the eastern coalfield. Footings have to bear below that depth, and a water service line has to sit at least six inches below it and at least twelve inches down, which in Kentucky works out to a minimum of 39 inches. Source: 2018 Kentucky Residential Code, 2nd Edition (Kentucky Dept. of Housing, Buildings and Construction), Table R301.2(1) and Table R403.1.4.
The 2018 Kentucky Residential Code carries a frost-depth table with two entries. Martin, Pike, Knott, Letcher and Floyd counties, in the Appalachian southeast, get 33 inches. Every other Kentucky county gets 24. Publishing an actual table rather than a blank cell puts Kentucky in a minority of states, and it makes the answer here unusually easy to give.
Twenty-four inches is a modest excavation and it maps to a modest winter: the median Kentucky station sees about 28 nights a year below 20°F, less than half the Iowa figure. The five-county exception is elevation again, the same effect that makes Utah and Colorado uneven.
Kentucky has not amended the water service burial rule, so the model-code language applies and the frost table sets the floor: a service line goes below 24 inches in most of the state and below 33 in the five listed counties.
By jurisdiction
What Kentucky jurisdictions publish
Local figures that sit alongside the state number, each from the jurisdiction that publishes it.
| Jurisdiction | Frost depth | Source |
|---|---|---|
| Martin, Pike, Knott, Letcher, Floyd Counties, KY | 33 in | 2018 Kentucky Residential Code, Table R403.1.4 |
| All other Kentucky counties (default) | 24 in | 2018 Kentucky Residential Code, Table R403.1.4 |
These are the jurisdictions whose published figure we could read and verify, so it isn’t a complete list of Kentucky building departments. Yours may differ, and yours is the one that governs your permit.
The weather behind the number
When it freezes in Kentucky
NOAA 1991 to 2020 normals at representative stations across the state.
| Station | First 32°F | First 28°F | First 20°F | Last 32°F | Nights below 20°F |
|---|---|---|---|---|---|
| BOWLING GREEN 21 NNE | October 31 | November 11 | December 4 | April 4 | 21 |
| JACKSON | November 1 | November 12 | December 7 | April 6 | 20 |
| LEXINGTON BLUEGRASS AP | October 28 | November 6 | November 30 | April 13 | 26 |
| LOUISVILLE BOWMAN FLD | November 3 | November 13 | December 8 | April 3 | 20 |
| PADUCAH | October 28 | November 7 | December 2 | April 5 | 21 |
| VERSAILLES 3 NNW | October 28 | November 6 | November 30 | April 12 | 27 |
Dates are the median: half of years cross that threshold earlier, half later. “no normal” means NOAA publishes none for that station, which at a warm station means it does not reliably get that cold. Source: NOAA NCEI U.S. Climate Normals, 1991-2020, retrieved 2026-09-09.
Across all 97 Kentucky stations with published normals, the median first 32°F night falls around October 25 and the median station records 28 nights a year below 20°F, which is the coldest threshold NOAA counts and a decent proxy for a hard freeze rather than a light frost. The state’s spread runs from SHELBYVILLE 1 E, where the median first freeze is October 10, to LOUISVILLE MCALPINE at November 9.
Kentucky’s median station reaches its first freeze around 25 October and its first 20°F night near the end of November, which leaves a comfortable month between the two for winterizing. Shelbyville, just east of Louisville, is the earliest station in the state at 10 October, and the Louisville McAlpine lock station on the Ohio River is the latest at 9 November. A month of spread across a state this size is modest, which is part of why a single statewide frost figure works here.
Water lines
Burial depth for a water service line in Kentucky
No confirmed Kentucky-specific statewide plumbing-code amendment to water service burial depth was found; the IRC P2603.5.1 baseline applies (below the frost line and not less than 12 inches below grade).
Under the model rule that Kentucky works from, a water service line goes 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.
which puts the floor here at 39 inches. 2021 International Residential Code, Section P2603.5 (Freezing), ICC free code viewer. Your water utility may specify more for the portion of the service it owns, and the building department that issues the permit has the final say. The national picture is on how deep water lines are buried.
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Common questions
Kentucky frost line questions
How deep is the frost line in Kentucky?
Twenty-four inches across most of the state, and 33 inches in Martin, Pike, Knott, Letcher and Floyd counties. Those figures come from the Kentucky Residential Code’s own frost-depth table, which is more than most states publish. Confirm with your building department, which can also tell you about any local amendment.
Why do five eastern Kentucky counties have a deeper requirement?
Elevation. Martin, Pike, Knott, Letcher and Floyd sit in the eastern coalfield, the highest and coldest part of the state, and the code recognises that the ground there freezes deeper than in the Bluegrass or the Jackson Purchase. It is the same reason the state’s highest weather stations record their first freeze weeks before the river valleys do.
Next
Where to go from here
The frost depth is the digging number. It won’t tell you whether your pipes are at risk this winter, and the two pages that will are at what temperature pipes freeze and when pipes freeze where you live, both with a ZIP lookup. If a pipe has already split, burst pipe repair cost covers the repair and the water damage behind it, and what to do about a frozen pipe is the page to open first.
Other state pages: Minnesota, Iowa, Michigan, Ohio, Indiana, Illinois, Virginia, Wisconsin, and all fifty in the national table.
Where these numbers come from
The Kentucky frost figure was researched against the body that publishes it, and it’s recorded with a confidence note of “state code, verified” in our source ledger. Freeze dates are NOAA normals for stations in the state, picked by a fixed rule rather than by hand: first-order stations, spread west to east. The full method is on our methodology page.
- 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.
- 2018 Kentucky Residential Code, 2nd Edition (Kentucky Dept. of Housing, Buildings and Construction), Table R301.2(1) and Table R403.1.4 The Kentucky frost depth figure and basis.
- 2021 International Residential Code, Section P2603.5 (Freezing), ICC free code viewer The water service line burial rule.
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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