The other day somebody wiped out my mailbox. It's a typical plastic mailbox, that mounts onto a 4×4 post.
The old post snapped off right at ground level. Instead of trying to dig it out, I've dug a new hole nearby. After talking with a neighbor, it turns out this type of thing happens a lot (lots of crazy/drunk drivers in the area, I guess). My original plan was to simply stick the post in the ground, and back fill with dirt.
Post in dirt
I also considered using concrete.
Post in concrete
According to the Federal Highway Administration
Do not embed the post in
concrete unless the mailbox support design is shown to be NCHRP 350 compliant when so installed.
So putting the post in concrete is out.
After the neighbors comment, I'm trying to think of ways to make the inevitable next repair easier. My first though was to fill the hole entirely with concrete, embed threaded rod in the top, and then use a bracket to attach the 4×4 post to the concrete.
Post on concrete
I'd likely use a bracket similar to this one from Lowes.
I'm worried that if another car comes along, the impact could actually bend or break the threaded rod, making it difficult to install a new post. So instead of saving myself time, I'd find myself digging another hole anyway.
Is it worth the extra time and money to install the mailbox using the post bracket, or should I just stick the post in the ground? Are there other common solutions that I haven't thought of?
After reading the USPS mailbox guidelines, I'm now thinking maybe I should build this a bit lighter duty. I'm now considering installing a post in the hole flush with the ground, then using a bracket to attach the above ground portion of the post.
Post in dirt with breakaway
I'd likely use a bracket similar to this one from Lowes
This way if somebody hits the mailbox again, hopefully the in ground portion will be undamaged.
Best Answer
Years ago, growing up on a rural farm in the midwest, my father solved the drunk driver mail box problem. He did this after drivers and snowplows took out the mail box several times.
He placed the mail box on a long arm that was cantilevered over a swivel post 10 to 12 feet off the side of the roadway. The design of the swivel post was such that the mail box arm would self return to the normal position if the snow plow would go by and gently push the box out of the way. On the other hand if a driver came by and made a direct hit on the box it would swing 90 degrees and latch into that position till one came to release the catch and let it return to normal position.
The "return to normal" mechanism worked by having springs pull down hard on the swivel part which was mounted against a V-groove seat on the post.