How to Build and Install a Mailbox

person in shirt and tie opening a mailbox with the flag up and mail sticking out
  • 4 hours
  • Intermediate
  • 75-150
What You'll Need
1 sheet of plywood
Two 4x4x8 pressure-treated lumber
four 2x4x8 pressure-treated lumber
4x4 post and mounting hardware
Power drill and bits
2" bolt and nut with washers
Arched cabinet pull
Window/door caulk
Magnetic catch
Composite shim
2 small hinges
Cup hook
Quick-setting concrete mix
Table saw
Tape measure
Wood glue and wood screws and wood putty
Medium and fine grit sandpaper
Two clamps

Like garage doors, mailboxes are generally valued for its function rather than its form. Occasionally, you’ll find homeowners who've taken the mailbox to the next level, showcasing their creativity and quirkiness without sacrificing function. Take on this weekend project and challenge your neighbors to do the same, because we know they’re always looking to keep up with your DIY successes.

Before you begin, check the rules and regulations of your area to ensure the mailbox and its position on the curb is acceptable for USPS delivery. They are pretty specific to ensure access for your postal carrier. For example, a height of 41”-45” from the ground to the level of the incoming mail area, with a two to six inch clearance for incoming mail is the standard.

The post on which it's mounted should only be 27” high from sidewalk to bottom of the box, which changes to 31” high when installing an in-ground mailbox, with another 12” below ground for additional stability. Evaluate the USPS required specs before deciding on the type of mailbox for your installation.

mailbox on a grassy country road

Build the Mailbox

Step 1 - Decide on Design

You can purchase ready made mailboxes from home improvement stores, but that doesn’t mean you have to use it as-is. Bust out the paints and find inspiration. Or get crafty with patterned duct tape. For this project we’ve chosen to illustrate a basic house shaped mailbox you can customize to your liking with different paints and finishes.

Step 2 - Cut the Parts

These five parts will form the base, sides, and roof. Cut the lumber to these dimensions.

2 – 1″ x 12″ x 19″

1 – 1″ x 8″ x 19″

2 – 1″ x 8″ x 21″

Rip the long edge of the 1” x 12” x 19” at a 45 degree angle. This will be at each side of the top of the box slanted to the outside to support the roof.

Step 3 - Attach a Base

Place a line of glue along the long edges of the base (this is the single 1″ x 8″ x 19″ you cut out.) Lay the base on a support to raise it ¾”. Clamp the two sides onto the base. This gives you a three-sided structure with clearance at the bottom where you’ll attach it to the mounting post.

Pre-drill holes and attach wood screws through the sides into the base you just glued together.

Step 4 - Fit the Roof

Approximate the fit of the two remaining boards, and you’ll see one side is longer by about ¾”. Cut the extra width off the lower board. Glue roofline and attach with wood screws as you did with the sides.

Step 5 - Cut out Front and Back

Don’t attach the roof just yet. Lay it on top of the structure, then place on its end so you can trace the peak from the inside onto a remaining 1” x 8” piece of wood.

Cut out and fit both pieces into the structure, clamping them in place. Pre-drill and attach only the BACK side with glue and wood screws.

Step 6 - Attach the Roof

Center the roof on top of the structure. Mark where the wall meets the roof on one side, and do the same on the other. Draw a line connecting the marks on each end. This line marks where you can drill to attach the roof to the box. Pre-drill and attach with three wood screws along each side.

Step 7 - Caulk, Fill and Sand

Seal seams with caulk and use putty to fill screw holes. Once dry, sand smooth the box.

Step 8 - Fit the Door

For ease of maneuvering, attach a cup hook to the outside of the door to use as a handle. Dry fit the door, sanding down sides to help it fit it loosely and make it easy to open. Attach with two hinges at the inner edge of the bottom of the mailbox and the bottom edge of the door.

Step 9 - Install Flag

Cut off 1 ½” from fatter end of wood shim. Drill hole through paint scraper and shim for the bolt, and a pilot hole into right side of the box. To ensure the flag can raise and lower properly, thread parts in this order: washer, paint scraper, washer, shim, mailbox wall, nut. Tighten nut only until it is secure, but can be raised and lowered easily.

Step 10 - Attach Hardware

Mount magnetic catch 1 ¾” from opening. Attach metal plate where it will strike the catch when door is closed.

Close door, remove cup hook, and attach drawer pull to outside of door, centering it properly.

Mount and Install the Mailbox

When installing your mailbox in the ground, call 811 before you begin digging to check for underground lines that might be damaged when you dig.

hand leveling a cement block for a mailbox post

Step 1 - Dig a Hole

Dig 12” hole with post hole digger, keeping in mind the distance from the road required by the USPS. Fill with 6” of gravel to provide drainage.

A hole must be dug deep enough to hold the mailbox securely in the ground, whether it's being set in quick set cement or just in soil. In areas where there is a lot of freezing and thawing in the winter, a mailbox post set in cement is the best choice.

Step 2 - Prep the Foundation

Prepare concrete mix according to manufacturer’s instructions.

Step 3 - Insert the Post

Most lumber companies and home improvement centers have pre-cut posts, that allow for the part that must be buried in dirt or cement. This will save you cutting time and buying extra tools, if you don't already own them.Set the post and pour concrete, tamping to remove air pockets, and checking that it’s plumb before the concrete dries. Slope concrete away from base to allow water to run off without pooling, or if you’d rather conceal the concrete, pour it shy a few inches from the top so you can backfill with soil once it has set.

Step 4 - Affix a Bracket

Use a standard 4” x 4” bracket to attach the mailbox to the top of the post. Check your work, ensuring the mailbox is level on its mounting.

Step 5 - Paint

Paint to protect the work you’ve just done. This is where you can showcase your creativity and style! You've shaped it like a house, but does that mean you must paint it to look like a house?

Step 6 - Add Number

Attach house numbers or paint them at least 1” high so they are clearly visible.

Step 7 - Share Your Work

Ok, this is optional, but we’d love to see how you did. Share your accomplishments with the world on our projects pages!