Home / Frost line depth / Maine
Frost data
Frost line depth in Maine
The short answer
Maine publishes no single statewide frost depth. Maine has no statewide frost figure in code, but the municipalities enforcing the state building code design to five feet, and its winters justify it. 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 Maine works out to a minimum of 12 inches. Source: City of Bangor, Maine, Building Codes.
Maine’s statewide code, MUBEC, does not publish a frost-depth table, and it excludes the model code’s plumbing chapters entirely, so neither the footing figure nor the water-line rule comes from the state document. What the enforcing municipalities publish is consistent: Bangor and Brewer both design to 60 inches.
Five feet puts Maine alongside northern Minnesota at the deep end of the country, and it is worth understanding as a plumbing fact rather than a construction one. A service line five feet down is effectively immune to the frost front. The pipes that fail in a Maine winter are the ones in unheated cellars, crawl spaces and camps left unheated between visits.
The seasonal-property pattern is particular to northern New England and worth naming. A house drained properly in October has no freeze exposure at all; a house left on a low thermostat with a failed furnace can lose its entire supply system in a night.
By jurisdiction
What Maine jurisdictions publish
With no statewide figure, these are the depths real building departments have published.
| Jurisdiction | Frost depth | Source |
|---|---|---|
| Bangor, ME | 60 in | City of Bangor, Maine, Building Codes (MUBEC base climate data) |
| Brewer, ME | 60 in | City of Brewer, Maine, Codes (MUBEC) |
These are the jurisdictions whose published figure we could read and verify, so it isn’t a complete list of Maine building departments. Yours may differ, and yours is the one that governs your permit.
The weather behind the number
When it freezes in Maine
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 |
|---|---|---|---|---|---|
| BRUNSWICK NAS | October 10 | October 23 | November 17 | May 2 | 72 |
| CARIBOU MUNI AP | October 1 | October 12 | November 7 | May 7 | 105 |
| FRYEBURG E SLOPES AP | September 25 | October 4 | November 1 | May 17 | 93 |
| GREENVILLE MAINE FORESTRY SVC | October 9 | October 22 | November 12 | May 7 | 98 |
| HOULTON INTL AP | September 18 | October 1 | October 29 | May 27 | 106 |
| OLD TOWN 2 W | September 28 | October 11 | November 9 | May 13 | 88 |
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 82 Maine stations with published normals, the median first 32°F night falls around October 2 and the median station records 93 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 CLAYTON LAKE, where the median first freeze is September 13, to WOODLAND at October 26.
The median Maine station reaches its first freeze on 2 October and records about 93 nights a year below 20°F and 175 below freezing, the longest freezing season of any state on these pages except Minnesota. Clayton Lake in the north woods reaches its median first freeze on 13 September; Woodland, near the New Brunswick border, on 26 October. Even the late end of Maine’s range is earlier than the median in most of the country.
Water lines
Burial depth for a water service line in Maine
Maine's MUBEC residential adoption excludes the IRC plumbing chapters, so the IRC P2603.5.1 baseline does not directly govern; municipalities enforcing MUBEC design to a 5-foot (60-inch) frost depth, meaning water services are buried well below the 12-inch federal-baseline minimum in practice.
Under the model rule that Maine 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 12 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
Maine frost line questions
How deep is the frost line in Maine?
Maine publishes no statewide code figure, and the municipalities enforcing the state building code design to 60 inches. Bangor and Brewer both state five feet. Because MUBEC leaves the number out, the figure that governs your project is the one your code enforcement officer applies.
How should I protect the plumbing in a Maine camp or seasonal house?
Draining is the only reliable answer for a property that will be unheated. Shut the main, open the lowest faucets until the system runs dry, drain the water heater, and add antifreeze to the traps. Leaving the heat on low works only as long as the heat actually stays on, and a furnace failure in January in a house nobody is visiting is how whole supply systems are lost.
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 Maine frost figure was researched against the body that publishes it, and it’s recorded with a confidence note of “local jurisdiction, deep” 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.
- City of Bangor, Maine, Building Codes The Maine frost depth figure and basis.
- City of Brewer, Maine, Codes (MUBEC) The Maine frost depth figure and basis.
- Maine DPS / Office of State Fire Marshal, MUBEC Standards and Amendments (eff. 4/7/2025) The Maine 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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