Texas adopts the International Residential Code as a municipal residential building code and publishes no statewide frost depth number, so the depth that governs comes from the city that issues your permit, and outside city limits the chapter does not reach at all.
Texas leaves the frost line depth to the local building department, which is where the number for an address comes from.
(c) Subject to Subsection (e), a municipality may establish procedures: (1) to adopt local amendments to the International Residential Code that may add, modify, or remove requirements set by the code; and (2) for the administration and enforcement of the International Residential Code.Local Government Code Chapter 214, Municipal Regulation of Housing and Other Structures, Texas Statutes, Texas 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 Texas does publish is below, and it is worth having in hand first.
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. Amarillo is the coldest of the 3 cities on the record in Texas.
98degree days
average freezing index a winter
Amarillo Rick Husband Intl AP
| City | State | Freezing index | Once a century | Nights below freezing |
|---|---|---|---|---|
| Amarillo | Texas | 98 | 321 | 108 |
| Lubbock | Texas | 53 | 176 | 87 |
| Dallas-Fort Worth | Texas | 23 | 107 | 35 |
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 Texas marked at 58 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 Texas: soil, drainage, snow cover and local amendments all move the figure, and the building department issuing the permit is the office whose number binds.
Texas code read September 22, 2026 from Local Government Code Chapter 214, Municipal Regulation of Housing and Other Structures, Texas Statutes, Texas 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.