Garden bench 4x4's. How deep (in concrete)?

[r0GuE]

Garden bench 4x4\'s. How deep (in concrete)?

I'm building an L shaped bench on pressure treated 4x4's buried in holes filled with concrete. I will then use cedar 2x2's to make the top. I'm not sure how deep I need to go (or how wide of a hole as well) to make sure it is stable. I am thinking 18". Sound resonable for a bench?

There will be no back on the bench, so the forces on it should largely be straight down. But there will be some cantelever effect from the fact that the bench face will be 19" wide. So half that is 9.5". minus the 2 that will be dirctly in the post, gives a 7.5" hang.

I thought I'd post for a quick sanitty check. Thanks all!!

 

[MikePA]

Re: Garden bench 4x4\'s. How deep (in concrete)?

I always thought they had to go beneath the frost line, which would be 3 feet, to prevent heaving in the winter?

Plus, I would not use concrete since it attracts moisture. I'd just tamp them in with either the dirt dug out of the hole or some limestone that packs well (1/2 inch down to fines).