Just something that came up in conversation (well, because we put in a new fence last year)
When digging holes foe fence posts, does it make for a stronger post if one returns the rocks to the hole (along with dirt, of course) or is it superior to use only the dirt and discard the rocks? Is the answer the same if the post is simply sunk vs. cement added to the hole?
There should definitely be rocks! The bigger, the better.
Of course, hardened cement is a kind of rock.
I am not at all an expert, but I’m pretty sure the most important issue is that ground be compressed and compacted tightly around the fence post.
If there are large rocks mixed in with the dirt, than spaces will be left under/around the rocks, and over time as water seeps in, the ground will settle and subside into those spaces. As the ground moves, so does the fence post. So I would suggest no rocks.
Concrete, of course, contains lots of small rocks, but they are mixed in a fluid sludge which fills the post hole completely, and then dries into a strong, solid base.
One uses concrete, not cement, for post footings. Which is better than either just dirt or adding rocks, because it is a perfect fit.
Thank you, CookingWithGas, for straightening our terminology! Of course, you’re right.
I´d like to add to my previous post that not only the size, but also the shape of the rock/concrete footing is relevant. A triangle is better than a square, which is better than a circular cylinder. Better still, cut a few lengths of rebar, and drive them sideways-downwards through the wet concrete in a star formation!
There are also bags of expanding foam available that is used for post setting.
Sika 61109087 33Oz Post Backfill https://www.amazon.com/dp/B01N1Q5YNE/ref=cm_sw_r_cp_apa_i_3-iVCbAWP2V8Y
The usual advice here is to set the posts in a dry concrete mix and water it in. The hole should be 12" square and 18" deep with a layer of concrete at the bottom. A couple of half-bricks used to wedge it vertical and then some dry mix poured in followed by water and tamping down with a bit of rebar or similar. Alignment should be constantly checked and the post left at least overnight before any panels are added.
I have seen advice to wrap the buried part of a wooden post in plastic. This is a bad idea as water will run down the inside and the post will rot where it meets the ground. We tend to use concrete posts here as they will last indefinitely.
Like everything, it depends. What kind of soil, what kind of moisture and such.
I believe, that if you just bought some bags of concrete and mixed it in with the rocks and soil when putting it back in the hole is a pretty good solution. Let mother nature take her course.
Please feel free to correct me if I’m wrong.