How deep for 4x4 posts in concrete?

[rschissler]

I have an elderly neighbor that wants me to help her install a couple of wood 4x4 posts in her garden.  The purpose of the posts are to hold up some string lights, and they would be about 6 feet above ground.  Everything I read says posts need to be buried at least two feet deep.  For this application, don't you think one foot would be deep enough, with concrete added to the hole?

[MT Woodworker]

8 footers 2 feet deep
I used the quick Crete you put in the hole then add water
Worked great for a couple support posts I put in last year

[aquaticjim]

I have an elderly neighbor that wants me to help her install a couple of wood 4x4 posts in her garden.  The purpose of the posts are to hold up some string lights, and they would be about 6 feet above ground.  Everything I read says posts need to be buried at least two feet deep.  For this application, don't you think one foot would be deep enough, with concrete added to the hole?

How heavy are her string lights?  A 4x4 with no concrete should hold up lights.

[R Clark]

Two feet, in my opinion.  

Just putting them in the ground will likely result in a "leaning" post over time.  You can use gravel or concrete around the posts to make them stay in place.

  - Gravel:  I have put a lot of posts in the ground over the years here at our acreage, and I almost always put gravel under and around the posts when I sink them in the ground.  That allows me to remove the post easily if a change is warranted.  I pack it as I add it.  Even with the gravel though, the post can begin leaning over time and may need to be straightened and the gravel packed again.  If the two posts are connected to each other, the leaning can be controlled, reduced, eliminated.

  - Concrete:  If a post is standing alone with no other support, and a straight appearance is important, then concrete is likely the best bet.  However, if it needs to be removed later, I think it's a lot harder to get out of the ground.

[EatenByLimestone]

Depends on the ground!   If clay, 2 feet in the ground, 160lbs of concrete, and itll still heave!

[joe1086]

One foot deep definitely is not enough....

[MT Woodworker]

+ 1
2 feet deep and I prefer concrete

[K. L. McReynolds]

Frost line depth. In my area(Kansas City) that is 32".

[John Mihich]

I would go 2'.  If it's in a cold area you will have heaving due to frost.  I have some that I put in the garden to have plants grow up.  They ate about 1' deep and each spring I have to adjust them a bit.  I really don't care if they are vertical but it just looks better.

[Pirate]

Most fences Ive seen with 4 x 4 posts are put in with no concrete. I put gravel in bottom of hole, and put roofing tar on post from 4" above ground to bottom of post. Ive heard epoxy resin works good also.
Worked as a fence installer years ago in NJ, and we didn't use concrete.