Alaska publishes no frost depth of its own and has no statewide residential building code, because the state fire code reaches only buildings with four or more dwelling units, so the footing depth and the water line cover for a house are set by the borough or city building department where the house stands, or by the designer where no local code applies.
Alaska leaves the frost line depth to the local building department, which is where the number for an address comes from.
The Department of Public Safety shall adopt regulations for the purpose of protecting life and property from fire and explosion by establishing minimum standards for (1) fire detection and suppression equipment; (2) fire and life safety criteria in commercial, industrial, business, institutional, or other public buildings, and buildings used for residential purposes containing four or more dwelling units;Alaska Statutes, AS 18.70.080 Regulations, Alaska State Legislature, read September 22, 2026. Read it at the source
That makes the building department issuing the permit the office with the number, and it is a short call: the counter gives the depth for the address, and the same call settles whether a deck footing or a slab edge needs a footing inspection before the concrete goes in. What Alaska does publish is below, and it is worth having in hand first.
A frost line depth turns into two separate requirements in most codes: how far a footing has to bear below grade, and how far a buried water service has to sit below the same line. Alaska writes one of them out.
Alaska adopts the 2018 Uniform Plumbing Code as the statewide minimum plumbing standard and does not amend its water service burial section, so the required cover is set relative to the local frost depth, a number the state itself does not publish. State plumbing inspection reaches communities of 2,500 people and above.
The codes set out in this section are adopted in accordance with AS 18.60.705 as the minimum plumbing standards to be followed throughout the state. The Department of Labor and Workforce Development adopts the following codes by reference that are published by the International Association of Plumbing and Mechanical Officials (IAPMO): (1) Uniform Plumbing Code, 2018 edition, sections 101.0 – 103.2, 103.3.1 – 103.4, 105.0 – 105.2.2, and 105.3 – 106.6 of chapter 1, chapters 2 – 10, chapter 11 excluding the requirements of section 1101.5, chapters 12 – 17, and appendices A – LPlumbing Code Statutes and Regulations, April 2020, 8 AAC 63.010 Minimum plumbing standards, Alaska Department of Labor and Workforce Development, read September 22, 2026. Read it at the source
The air freezing index is the quantity the frost provisions of the model codes are written on: add up how far each day’s mean temperature fell below freezing over a winter, in degree days, and take the deepest run the winter managed. It measures how much cold the ground had to absorb, which is why it is the honest way to set one place beside another. Fairbanks is the coldest of the 3 cities on the record in Alaska.
5,310degree days
average freezing index a winter
Fairbanks Intl AP
| City | State | Freezing index | Once a century | Nights below freezing |
|---|---|---|---|---|
| Fairbanks | Alaska | 5,310 | 7,689 | 222 |
| Anchorage | Alaska | 1,902 | 3,754 | 190 |
| Juneau | Alaska | 552 | 1,717 | 134 |
Computed from NOAA National Centers for Environmental Information, Global Historical Climatology Network daily temperature records for each station, from 1951 onward. These are measurements of winter, not depths.
Only a handful of states answer with one number for the whole state, and they are the only codes that can be set beside each other directly. Ranked by the freezing index at their own reference cities, with Alaska marked at 2,588 degree days for comparison against what those codes settled on:
Left to right, the mildest winters to the hardest. The figure on the right is what that state wrote into its code.
The nearest by winter are Wisconsin at 4 feet, Vermont at 5 feet and Michigan at 42 inches. That is a reading of other states’ codes rather than a depth for an address in Alaska: soil, drainage, snow cover and local amendments all move the figure, and the building department issuing the permit is the office whose number binds.
Alaska code read September 22, 2026 from Alaska Statutes, AS 18.70.080 Regulations, Alaska State Legislature. Codes are amended and a local amendment can be deeper than the state figure, so the building department issuing the permit has the number that binds. Every state is on the frost line depth hub.