Setting fence posts

[Brian G]

Which method is better for setting 4 X 4 posts, concrete or tamping loose soil? I was taught that wood posts should not be encased in concrete since the post tends to rot quicker.

[fordrules]

Setting them in concrete will make them more solid. Another thing to consider is to soak the posts in old motor oil. We have fence posts on the farm that are over 40 years old and are still in perfect condition.

[Medic]

Either way is fine as long as the post are treated and rated for ground contact. Personally I do not use concrete. I will dig the hole about 4 inches deeper than I want to set the post and add gravel or small rock to the bottom of the hole for drainage. Set the post in and add a few more inches of rock, then add soil while tamping well. Sometimes I will toss in a couple of big rocks while filling up for extra side to side strength (one down lower in the hole and one up higher on the other side depending on wich direction the tension will come from). Have you ever noticed posts that lean wether they are in concrete or not? Its because the posts are not set deep enough. Some people think that if you use concrete the post will be more solid, this is not quite true. The post need to be set below the frost line with either method. If I want to have a 6 ft high post I will buy a 10 ft post and dig my hole 3-4 ft depending on what the post is used for. Gate post will be closer to 4 ft. and simple fence post closer to 3 ft. cut off the unwanted height with a chain saw.

[Wgoodrich]

I have seen some "dead man posts" being corners of a tight fence being set in concrete trying to make a bigger wad to resist movement from plumb. Better method is to install to treated post the corner being a much thicker post to hold the fence at the corner then a second post placed about 6' away in line with the fence with a brace post from the line post just above the grass to the corner post just below the top of the fence using a #9 wire with a turnbuckle to pull the two posts together tightly against the diagnal brace post. Do this both directions using the same corner post and you created a corner dead man post without need of concrete. The posts need to be to a depth exceeding your frost line in your area.

Line posts are normal treated 4x4 or locust or other redwood posts resistant to rot set below the frost line without concrete. The rock under the post is added protection from rot and not a bad idea.

Good Luck

Wg

[CraigFL]

I think some of the worry about concrete is that the post may be "encased" which means that there is concrete not only on the sides but on the bottom too. This doesn't allow good drainage out the bottom.
I prefer putting some gravel in the bottom and then using concrete for the sides. I find this better because the concrete fills the sides to the undisturbed, compacted dirt. If you set without concrete, you must make sure the side fill is packed very solid to keep the post from moving.