Materials
How deep should fence posts be set?
Below the local frost line, in a concrete footing sized for the post and the load it carries. In southeastern Pennsylvania that means a substantially deeper hole than most do-it-yourself installations use. Posts set too shallow will heave with freeze-thaw cycles and the fence will begin to lean within a few seasons regardless of what material is above grade.
Corner posts, end posts and gate posts carry far more load than line posts, because the tension of the runs terminating on them is transferred into the ground. They should be set deeper, sized larger, and — on long ranch or paddock runs — braced.
Drainage matters as much as depth. A footing that traps water against the post accelerates rot at grade on wood and worsens heave in any material. Footings should be shaped to shed water rather than hold it.
This is where the money should go on a fence. Post setting is invisible once the fence is up and it is the single largest determinant of how long the fence stands straight.
