Frost Line
Maximum depth to which ground freezes in winter, from a few inches in the South to 5+ feet in the northern states. Footings and fence posts must bear below it, or freeze-thaw heave will lift and crack the structure. Local code sets the design depth.
Where this appears in real estimates
This term isn't trivia — it's a working variable. These tools use it directly:
- fence post depth calculator — Post hole depth and total post length from fence height and frost line.…
- concrete footing calculator — Cubic yards for strip and pad footings from length, width and depth.…
- fence calculator — Posts, rails, pickets and concrete bags for a wood fence run.…
Go deeper
- Asphalt vs Concrete Driveway — head-to-head decision guide
- Yard Drainage Fix — full project walkthrough
- Excavation in Florida — local pricing & climate
- Read the field guide on the blog — practitioner-level detail
- Related engineering article — from our licensed engineer
Reviewed: · Part of the CalculatorAsphalt Construction Glossary · Sources: see methodology & standards.