Oak Mailbox

Published Monday, September 5, 2022 by Bryan

I have always loved receiving mail. It felt like a special thing, when I was young, to cross the street, open the mailbox, and find a letter with my name on it. Even now when I'm wishing paper hadn't been wasted on pre-sorted standard junk mail, I'm just slightly tickled to have received mail anyway.

That's probably why the first curb-appeal upgrade I've made to the first home I've owned, before the laundry list of other things I could do, is to replace the old bent aluminimum mailbox with something custom and handmade.

New mailbox, installed.

The design was driven by two forces: the USPS spec for the next generation mailbox, and the ability of the material I had to fulfill that spec while meeting the demands of the weather and seasons.

A cardboard mockup, to check the spec's dimensions. Me, for scale.

I agreed with my neighbor when their first response to seeing my cardboard mockup was, "It's huge!" The bulk of mail delivery is shifting. Letters, from friendly correspondence to billing, have moved electronic. The new focus of the USPS is packages. The next-generation design is based on this trend - the standard shipping boxes that the USPS sells fit inside a box of this size.

That large size was a key component to the reason my design became an array of strips, instead of large continuous panels. The wood I wanted to use was the white oak left over from building my Adirondack chairs. Unfortunately, none of that was anywhere near wide enough to produce a continuous panel for any part of the mailbox. This was also wood I had rejected during the chair build, for having too many knots and checks in inconvenient places. Knots and cracks weren't going to work in this project either, unless I wanted to spend all of my time filling them to keep rain out.

36in. 1x4s ripped to 1/2in. widths
Floor and wall strips cut to length

Once I knew I would need to glue up smaller pieces, I started thinking about how to do that in a way that didn't look arbitrarily patchwork. I didn't want a wall to be mostly one solid piece, but then also include a couple smaller sections of other boards. Trying to figure out which section of each board could be fit into which section of each component also quickly became too much detail to manage. Then I thought about what would happen if I broke all the boards down into strips - small enough to easily exclude knots, yet large enough to not waste too much wood in saw kerfs.

Alternating overlap of wall and floor strips produces a box joint.

The decision to cut strips aligned with another detail I had been working on. I needed a strong way to join the roof, walls, and ceiling. Modern wood glue is amazing, but is strongest when paired with the right joint. Strips lent themselves to a great choice. By alternating whether a floor strip stuck out from the side, or a wall strip stuck out from the bottom, the corner naturally formed into a box joint. This interlocking knuckle should be very strong, without needing any reinforcement from screws or nails.

Ripping strips also made it easier to choose a better thickness. My boards were 3/4 inch thick to start. That would have been quite heavy, both physically and visually. I ripped the strips to 1/2 inch thick. This still feels solid, but cut the weight by a third. The 3/4 inch dimension became the width of each layer. Twenty eight layers from end to end, and one piece for each wall plus a piece for the floor in each layer comes to 84 individual pieces so far. And we haven't talked about the roof yet!

A compass jig for my trim router cuts a smooth curve along the glued roof segments.
A flush trim bit copies the curve onto neighboring layers.
Layers are added to either end, then trimmed flush. Repeat 14 times.

While the finished roof has a smooth, round shape, the pieces are not bent. Each row is, instead, a segmented arch. After the first two arches were glued together, I used a compass jig with my trim router to cut the sharp corners into a smooth arc. For each layer after that, I used a pattern bit to trace the arc into the new layer. The segments in each arch are offset from the segments in the neighboring arches, to create a staggered brick pattern. This construction has produced many more seams than full-length bent strips would have. My hope, though, is that it also reduces the seasonal movement in the roof. The grain direction of each short, straight segment crossing the grain direction of its neighboring segments seems like it should flex less during humidity changes than long, parallel, bent grain would.

Reduced wood movement is also something I hope to have gotten as a bonus of cutting the strips this way. All of my boards were plain-sawn, meaning their faces were roughly tangent to the tree's growth rings. By cutting through these faces, I exposed a quarter-sawn face - the growth rings now run from the face on the outside of the mailbox to the face on the inside. The expansion and shrinkage that wood experiences throughout the year, primarily happens along the growth rings. By putting the growth rings along my wall's shortest direction (thickness), instead of its longest direction (the mailbox's depth), I've gained only a tiny amount in thickness change in exchange for a comparatively large reduction in depth change.[1] Hopefully this means that the stress on each joint is reduced, and the seasons don't steadily work them all apart. Time, and my willingness to reapply polyurethane, will tell.

The door is recessed under an awning, and runs past the front of the floor.

Enough about dealing with water in the wood, how does this mailbox keep water off the mail? Mostly, the door and the back are each under a small awning. For the back, this is just providing protection for a sealed seam. For the door, the awning is hopefully enough to keep water away from the small gap necessary to ensure that the door doesn't rub on the shell when opening and closing. As a backup, the floor of the shell is fully inside the door. If water makes it onto the inside of the door (for example, if the mail is delivered while it's raining), it should run straight down the door and out of the gap around the hinge, missing the floor entirely. Wind will be the big question, especially with fine snow. But, the door faces east and almost all of our wind comes from the west, so I'm hopeful.

Door front design, with angled strips and inset tile, suggestive of an envelope flap sealed with a wax stamp.

I wanted the door to stand out a little bit, visually. While visiting our favorite local potters this summer, we got to talking about how both prefer the winter to the summer up here. A tile of theirs was for sale on the wall next to me, depicting two snowshoes, and I saw an opportunity. I think the door's strip pattern with the inlaid tile looks like an envelope with a wax seal.

Flag shape marked out on brass sheet.
Flag cut and bent to shape.
Flag painted. Yes, it does match my snowblower.

I left the flag to nearly the last minute. I really wasn't sure if I wanted to try more wood, or if I could scavenge sheet metal from an old license plate. In the end, I sprang for a small sheet of brass at the hardware store. The shape and size were mostly eye-balled, until everything looked in proportion. I bent a quarter inch of the shaft out to a right angle. That gives a nice place to push when raising or lowering it, but also adds some rigidity. I painted the flag red for two reasons. The first is that, as shiny as the brass was, there was no way it would contrast enough with the honey-colored oak. (Requirement 3.10) The second is that I am absolutely not the kind of person that likes to polish brass to keep it shiny.

Finally, a mailbox needs a post. After getting over the size, the second thing everyone asked me is, "What if a plow hits it?" Indeed, our old aluminum box had a lean to it that suggested force had been applied at some point. There are at least two commercial solutions to this problem. I decided to test my own.

Demonstration of snow plow compatibility.

The hinge on the side allows the cross beam to swing away easily. I know it's going to bug a lot of you that it's mounted crooked, but that's for a reason. After the box swings away, I want it to swing back! Tilting the hinge this way means that the box also swings up slightly, and the weight imbalance across the hinge causes it to pull the cross bar back down afterward.

Late morning sun shining on the south side of the installed mailbox.
The brick pattern of the top gleaming in the late morning sun.

The mailbox has been installed for almost a week, and I'm quite happy with it. Neighbors agree it looks great. We've had at least one rain storm, and the mail has stayed dry. No complaints from our mail carrier yet, though it has been a sub for the holiday, so I'll be anxious to check in with our normal delivery person.

On to holiday gift building season!

Footnotes

[1] Assuming a 10% moisture content change over the year, an article in Fine Woodworking suggests I made this tradeoff:

Orientation Change in length (in.) (nominally 1/2) Change in thickness (in.) (nominally 18)
Plain-sawn (coef. 0.0037) face along length 0.00666 0.00009
Quarter-sawn (coef. 0.0018) face along length 0.00324 0.000185
Difference -0.00342 +0.000095

Categories: Woodworking