My research has shown that fence posts should be dug to a depth of at least 1/3 of the height of the post—for a six foot fence, the post depth would be 3 feet.

I purchased a 6 foot vinyl privacy fence from Lowe's, and the manufacturer's recommended post was a 5"x5"x8' post, an entire foot short of what I would have expected. Indeed, Lowe's doesn't even appear to sell a 9 foot fence post (without routed holes). Should I return the 8 foot posts and find something longer? Or is there some way to approximate a longer post (e.g. concrete+rebar going deeper or something?)?

  • My soil is extremely rocky (on a mountain in Utah County), but otherwise loamy.
  • It's not usually windy, 40 mph sustained winds with 60 mph gusts would be the strongest wind you might see in a year. Most of the length of the fence will separate my house and the neighbors, about 20 feet away from either house, which I'm hoping should should act as a windbreak.
  • The frost line here is 36 inches
  • I'm planning on using concrete to set the posts.
  • 1/3 of 6 is 2 1/3 of 8 is 2.666 actual panel height is 5.6. 8 footers will be fine. Or use 10 foot posts and cut off excess after panel is placed
    – Kris
    Jun 12, 2018 at 20:08
  • 1
    For a 6' tall fence, 2' buried is one 3rd of the height above ground, resulting in an 8' post. But this is the minimum recommended post length.
    – brhans
    Jun 12, 2018 at 20:08
  • 1
    Wind is one concern but frozen ground is a more serious concern. You want the post below the freeze depth.
    – RoboKaren
    Jun 12, 2018 at 20:13
  • With a frost line that deep if use the 10 foot post and cut to fit panel height
    – Kris
    Jun 12, 2018 at 22:40

1 Answer 1


I'm about to put some of these in myself. I believe the manufacturer's instructions answer this question in Step 2c, shown below. Note that the post does not extend the entire depth of the hole, but the hole is back-filled with concrete to a 30-inch depth before placing the post. That way, the concrete holding the post extends past the frost line, even though the post itself does not.

Post hole design

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.