Frost depth in Texas
Texas has two code depths: 12 inches in 24 inches — and which one applies depends on the county you build in. Add 6 inches of bearing and that becomes a dig depth of 18" / 30". The numbers below are the code values an inspector measures, not climate averages — the local building department always has the final word.
| Area / zone | Frost depth | Dig depth | Set by |
|---|---|---|---|
| Most of the state | 12" | 18" | IRC R403.1.4 minimum |
| Panhandle (Amarillo) | 24" | 30" | Local Table R301.2(1) |
Two rows, two numbers: the county you build in decides which one governs your permit. Never take the shallower value to a counter in a deeper zone.
Why Texas's number looks the way it does
Texas is one state with two winters: 12 inches across most of it, and 24 in the Panhandle, where Amarillo catches the arctic fronts sliding down the Rockies. On the Gulf coast, frost is not a design consideration at all.
From frost depth to dig depth in Texas
Footings bear on undisturbed soil below the frost line, so the hole goes 6 inches deeper than the code number. In Texas that means:
| Code frost depth | Dig depth | Shortest Sonotube |
|---|---|---|
| 12" | 18" | 4 ft tube |
| 24" | 30" | 4 ft tube |
A 4-inch gravel base at the bottom of the hole is common practice for drainage, and if you use one, add it to the tube length rather than the dig depth — the footing still has to reach the full 12–24 inches below grade.
How much concrete a footing takes in Texas
Bags of 80-lb mix per footing, for a solid pier with no post in the hole, at Texas's code depth:
| Frost depth | 10" hole | 12" hole | 16" hole | 20" hole |
|---|---|---|---|---|
| 12" (18" dig) | 2 bags | 2 bags | 4 bags | 6 bags |
| 24" (30" dig) | 3 bags | 4 bags | 6 bags | 10 bags |
The bags calculator converts any total into 80, 60, 50 or 40-pound bags, and the concrete calculator handles slab and footing volumes.
Texas frost depth FAQ
How deep is the frost line in Texas?
Texas has two code depths, and the county you build in decides which one an inspector measures: 12 inches in Most of the state, and 24 inches in Panhandle (Amarillo). These are code values, not the average depth the ground actually froze last winter.
How deep do footings have to go in Texas?
Bearing sits below the frost depth, so dig to the code depth plus 6 inches: 12 inches of frost means a 18-inch dig, and 24 inches of frost means a 30-inch dig in Texas. The extra 6 inches is the bearing layer that keeps the footing from sitting on frost-susceptible soil, and it is what IRC R403.1.4 minimum expects to see on a permit drawing.
How do I know which Texas zone my county is in?
The citation in the table above names the authority that drew the lines — IRC R403.1.4 minimum; Local Table R301.2(1). Your county or city publishes its own amendment to IRC Table R301.2(1) (or its own zone map), and that local document, not a state table, is what a permit reviewer checks. One call to the building department settles it before you rent an auger.
Plan a pour in Texas
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Last updated: 2026-11-02