Virginia publishes no frost depth of its own; the state code expressly leaves the frost line depth to each locality, so a builder in Roanoke or Winchester gets the number from the local building department, which fills in the frost line row of Table R301.2(1) for that jurisdiction.
Virginia leaves the frost line depth to the local building department, which is where the number for an address comes from.
103.4 Use of certain provisions of referenced codes. The following provisions of the IBC and of other indicated codes or standards are to be considered valid provisions of this code. Where any such provisions have been modified by the state amendments to the IBC, then the modified provisions apply. ... 3. Section R301.2 of the IRC authorizing localities to determine climatic and geographic design criteria.2021 Virginia Construction Code (13VAC5-63 Part I), Virginia Department of Housing and Community Development, 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 Virginia 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. Roanoke is the coldest of the 3 cities on the record in Virginia.
77degree days
average freezing index a winter
Roanoke-Blacksburg Rgnl AP
| City | State | Freezing index | Once a century | Nights below freezing |
|---|---|---|---|---|
| Roanoke | Virginia | 77 | 256 | 83 |
| Richmond | Virginia | 62 | 210 | 80 |
| Norfolk | Virginia | 31 | 108 | 48 |
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 Virginia marked at 57 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 Virginia: soil, drainage, snow cover and local amendments all move the figure, and the building department issuing the permit is the office whose number binds.
Virginia code read September 22, 2026 from 2021 Virginia Construction Code (13VAC5-63 Part I), Virginia Department of Housing and Community Development. 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.