Mailbox Post Repair

How to Repair a Mailbox Arm Post on Your Own

By Mark J. Donovan

Last weekend my mailbox post was damaged by a pickup truck that backed up into it when it was snow plowing the driveway across the street. The mailbox and the horizontal 4×4 pressure treated arm were knocked right of the vertical post. The pressure treated 4×4 wooden arm that extended outward from the post broke off at the lap joint area where it connected into the vertical post. So I found myself having to repair the mailbox post this weekend.

To repair my mailbox post I cut a new piece of pressure treated 4×4 lumber to the same length as the original mailbox post arm.

In my case the arm was 25 inches in length from tip to tip. However I had to make 45 degree tapered cuts to match the original mailbox post arm. I used a miter saw to do this.

After cutting the basic length and shape of the mailbox arm post, I then needed to put a lap joint notch in it. To do this I first measured 4.75 inches in from one of the outer edge tips and made a pencil mark. I then measured from that mark 3.5 inches back towards the tip and made another mark. The 3.5 inches is the width of the 4×4 lumber.

I then used a square to make two straight lines where I placed the marks. I then rotated the 4×4 lumber on its side 90 degrees and measured down 1.75 inches at both mark edges.

Next I drew a straight light connecting the two marks.

Then I drew lines down from the original marks to the straight line. Afterwards I rotated the 4×4 lumber back to its original position.

Next, using a skill saw with the blade set to 1.75 inches in depth I made a series of cuts in between the original two lines. I made make sure that I made very square cuts on the two lines.

After making approximately a dozen cuts I used a hammer to tap out the small sections of remaining wood. Then I used a hammer and chisel to clean out the lap joint.

With the mailbox arm post fabricated I then went out to the mailbox post and removed the mailbox and then the broken mailbox arm post from the vertical mailbox post.

I then slid the new mailbox arm post into position at the lap joint interconnect. Then I secured it in place using 2-1/2 inch galvanized deck screws.

With the horizontal arm attached I then used the original 45 degree 4×4 cut brace to attach between the vertical and horizontal 4×4 lumber sections.

Again, I used 2-1/2 inch galvanized deck screws to connect it to the horizontal and vertical 4×4 mailbox post sections.

Mail Box Post Repair

I then reattached the mailbox mounting board to the horizontal mailbox arm post using 1-1/2 inch galvanized deck screws.

Finally, I placed the mailbox back onto the mounting board and secured it to the mounting board with 1-1/2 galvanized deck screws.

And with that, my mailbox was back in business and looking as good as new.

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