Louisiana adopts the 2021 International Residential Code statewide but publishes no frost line depth of its own, so the number comes from the parish or municipal building department; the state's one frost related amendment is a water service pipe buried at least 12 inches deep and 6 inches below whatever the local frost line is.
Louisiana leaves the frost line depth to the local building department, which is where the number for an address comes from.
In accordance with the requirements set forth in R.S.40:1730.28, effective February 1, 2018 the following is hereby adopted as an amendment to the Louisiana state Uniform Construction Code.Louisiana Administrative Code, Title 17, Construction, Louisiana Office of the State Register, Division of Administration, read September 23, 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 Louisiana 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. Louisiana writes one of them out.
Louisiana amends the residential code's freezing section so a water service pipe is buried at least 12 inches deep and at least 6 inches below the frost line, with the frost line itself left to the parish or municipality.
In localities having a winter design temperature of 32°F (0°C) or lower as shown in Table R301.2(1) of this code, a water pipe and/or sanitary traps shall not be installed outside of a building, in exterior walls, in attics or crawl spaces, or in any other place subjected to freezing temperature unless adequate provision is made to protect it from freezing by insulation or heat or both. 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.Louisiana Administrative Code, Title 17, Construction, Section 107, International Residential Code, amendment to Section P2603.5, Freezing, read September 23, 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. Shreveport is the coldest of the 3 cities on the record in Louisiana.
13degree days
average freezing index a winter
Shreveport Rgnl AP
| City | State | Freezing index | Once a century | Nights below freezing |
|---|---|---|---|---|
| Shreveport | Louisiana | 13 | 69 | 33 |
| Baton Rouge | Louisiana | 5 | 31 | 20 |
| New Orleans | Louisiana | 0 | 5 | 2 |
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 Louisiana marked at 6 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 North Carolina at 12 inches, Massachusetts at 4 feet and Connecticut at 42 inches. That is a reading of other states’ codes rather than a depth for an address in Louisiana: soil, drainage, snow cover and local amendments all move the figure, and the building department issuing the permit is the office whose number binds.
Louisiana code read September 23, 2026 from Louisiana Administrative Code, Title 17, Construction, Louisiana Office of the State Register, Division of Administration. 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.