Height and setback rules.
Get these two numbers right and everything else is straightforward.
- Height: the bottom of the mailbox — where mail goes in — should sit 41 to 45 inches above the surface of the road.
- Setback: the front face of the box should sit 6 to 8 inches back from the front face of the curb.
Measure from the road, not from your lawn or sidewalk. Yards slope, and a box that measures perfectly from the grass can end up too low for a carrier reaching out of a vehicle window. Also make sure the door swings clear and nothing — a shrub, a decorative rock, a parked trailer — blocks the approach.
If you are replacing an existing box on an existing post, mark the old height before you pull it. It was probably already approved.
What you need.
Included in the quoted price
- New mailbox and post
- Post hole digger or shovel
- Fast-setting concrete (one to two bags)
- Level and tape measure
- Drill, driver, and exterior screws
Quoted separately
- Digging bar for caliche
- Gravel for the bottom of the hole
- Exterior paint or stain for a wood post
- House numbers and adhesive
Post-mount install.
1. Call 811 first. It is free, and irrigation and low-voltage lines run shallower than you would guess in East Valley yards. Do not skip this to save two days.
2. Dig the hole. Roughly 24 inches deep and 10 to 12 inches wide. In caliche, soak the spot with a hose for an hour first, dig what you can, then soak again. Water is the only thing that makes caliche cooperate.
3. Add a few inches of gravel at the bottom so the base of a wood post is not sitting in trapped water during monsoon season.
4. Set the post and check plumb on two adjacent faces with your level. Have someone hold it, or brace it with scrap wood.
5. Pour in fast-setting concrete dry, add water per the bag, and re-check plumb immediately. You have a few minutes to nudge it. Crown the top of the concrete slightly so water runs away from the post.
6. Wait, then mount the box. Give the concrete at least a few hours — a full day is better before you hang anything heavy. Then attach the mounting board and box, confirm your 41–45 inch height, and add house numbers.
Wall-mount install.
A wall-mount box next to the front door is simpler, but the anchor matters. On stucco over wood framing, find the studs and drive exterior screws into them. On block or stucco with no stud where you need it, drill with a masonry bit and use sleeve anchors or plastic anchors rated for the weight.
Never rely on drywall anchors on an exterior wall, and seal each screw penetration with a dab of exterior caulk. A mailbox full of mail plus a monsoon gust puts real load on four small fasteners.
HOA and cluster boxes.
In most Gilbert and Chandler HOA neighborhoods you cannot just pick a mailbox you like. The community specifies the model, the post, the color, and often the numbering style. Check your CC&Rs or email the management company before you buy anything — swapping in the wrong style is a violation letter and a second purchase.
Newer neighborhoods frequently use USPS-owned cluster box units at the curb. Those are postal property: if the lock is broken or your compartment key is lost, that is a call to the post office, not to a handyman. What we can help with there is the pedestal, the pad, and anything decorative around it.
FAQ.
How high should a mailbox be mounted?
USPS asks for the bottom of the mailbox — the incoming mail slot — to sit 41 to 45 inches above the road surface, and the face of the box set back 6 to 8 inches from the front face of the curb.
How deep should a mailbox post be buried?
About 24 inches deep for a 4x4 wood post, with the hole roughly 10 to 12 inches wide. Deeper than that and USPS regulations discourage it, since a post should give way rather than act like a barrier in a collision.
Do I need concrete for a mailbox post?
It is the most durable option, and in Arizona's dry, rocky soil it keeps the post from loosening. Fast-setting concrete poured dry into the hole and then watered works fine and firms up in about half an hour.
How do you dig a mailbox hole in caliche?
Soak the spot with a hose for an hour, dig what you can, then soak again. Caliche softens with water and fights every dry swing of a shovel. A digging bar or a rented one-man auger saves a lot of frustration.
Can I replace my own mailbox in an HOA neighborhood?
Usually only with an approved style. Most Gilbert and Chandler HOAs specify the box and post model, color, and numbering, and many newer neighborhoods use USPS cluster boxes that only the post office can service.
How much does mailbox installation cost?
As a standalone visit it is a small job, so it is best bundled with other items on your list. Ask us for a flat price on the whole list — travel and setup happen once either way.
Would rather not fight caliche on a Saturday? See general repairs in Gilbert, AZ