· by Michael Blair, Nashville's Handyman Service
A mailbox post usually goes the same way: a mower clips it, a car backs into it, or the bottom of the wood softens until the box leans toward the street. It is one of the small jobs on our general repairs list, and it is easy to do twice if the new one goes in at the wrong height, on the wrong kind of post, or into a spot where a cable runs. Here are the numbers the Postal Service uses, the post it recommends, and the call Tennessee law requires before any digging.
How high and how far back does a mailbox go?
The bottom of the box, or the point where mail goes in, should sit 41 to 45 inches above the road surface, and the box should stand 6 to 8 inches back from the curb. Those are the figures on the U.S. Postal Service’s mailbox installation page, which also asks that the carrier always have a clear path to the box. Where there is no raised curb, the Postal Service says to ask the local postmaster where the box should go.
The same page asks for the house or apartment number on the box, and the full street address if the box stands on a different street from the house. A store-bought box with the Postmaster General’s seal already meets the Postal Service’s size and construction standards; a homemade or custom box has to meet them too, and the page says to show the local postmaster the plans or the box for approval.
What kind of post should hold the mailbox?
A 4x4 wooden post or a 2-inch-diameter standard steel or aluminum pipe, which is what the Postal Service passes along from the Federal Highway Administration. The idea behind it is that the best support is steady in everyday use but bends or falls away if a car hits it.
That rules out the sturdy-looking options. The Postal Service names heavy metal pipe, concrete posts and farm equipment such as a milk can filled with concrete as supports to avoid, because they do not give. It also says to bury the post no more than 24 inches deep. A brick or stone column is a masonry project and a different job from the one described here.
Do I need to call 811 for a mailbox post?
Yes. The Tennessee 811 FAQ says the state’s Underground Utility Damage Prevention Act, TCA 65-31-101, requires anyone who digs, hand digging included, to give Tennessee 811 at least three working days’ notice, and that the rule covers homeowners as well as contractors. A normal request needs those three working days; a ticket can be placed up to ten working days ahead if the schedule allows.
Tennessee 811 does not mark anything itself. It passes the request to its member utilities, which mark their own lines, and the FAQ points out that not every underground line belongs to a utility, so privately owned lines may not be marked. The service is free. If you hire someone to set the post, the FAQ is clear that the ticket has to be in that company’s name, because a ticket issued to the homeowner does not cover a contractor digging on the property. When we replace a post, we call in our own ticket and wait for the marks.
Resetting the old post or replacing it
A post that leans but is solid can sometimes be straightened and firmed up where it stands. One that is soft or broken at the ground line, or one that was never the right kind of support, gets replaced. Either way, the box comes off first, the post goes in plumb and no deeper than 24 inches, and the box goes back on at 41 to 45 inches above the road with the house number showing.
It is the kind of item that fits well on a longer list, which is the idea behind our post on small jobs worth doing now. We do this work in Hendersonville, Nashville and across Middle Tennessee. Send us the list, mailbox included, and we will price the visit in writing.
Sources
- U.S. Postal Service, Mailboxes: placement and installation — 41 to 45 inches from the road surface to the bottom of the box or point of mail entry; 6 to 8 inches back from the curb; ask the postmaster with no raised curb; house number on the box; Postmaster General’s seal; FHWA-recommended 4x4 wood or 2-inch steel or aluminum pipe; avoid heavy metal pipe, concrete posts, concrete-filled milk cans; bury no more than 24 inches.
- Tennessee 811, Frequently Asked Questions — TCA 65-31-101 requires anyone who digs, hand digging included, to give at least three working days’ notice; applies to homeowners; up to ten working days by postdating; Tennessee 811 does not mark lines; private lines may not be marked; a contractor needs a ticket in its own name; free service.
FAQ
Replacing a Leaning Mailbox Post: Height and Depth — questions
How high should a mailbox be from the road?
The Postal Service asks for 41 to 45 inches from the road surface to the bottom of the box or the point where mail goes in. The box should also stand 6 to 8 inches back from the curb, and where there is no raised curb the local postmaster says where it goes.
How deep should a mailbox post be buried?
No more than 24 inches, according to the Postal Service’s installation guidance. The post itself should be a 4x4 of wood or a 2-inch steel or aluminum pipe, which stays steady in daily use but gives way if a car hits it. Dig only after the Tennessee 811 ticket has cleared.
Why does my mailbox post keep leaning?
Usually because the wood has softened where it meets the ground, or because the post took a hit from a mower, a trash truck or a car and loosened in its hole. A post that was never set plumb leans from the start. A solid post can be reset; a rotted one needs replacing.
Does a mailbox need the house number on it?
Yes. The Postal Service asks for the house or apartment number on the mailbox, and the full street address when the box stands on a different street from the house. Reflective or high-contrast numbers on both sides of the box are easier to read from the road in either direction.
How long does Tennessee 811 take to mark the lines?
Plan on at least three working days. Tennessee 811 says a normal locate request needs three working days’ notice, and you can give up to ten working days by postdating the ticket. It does not mark lines itself; it notifies its member utilities, and privately owned lines may not be marked at all.