Simple, Durable DIY Window boxes

Today I’ve got a fantastic DIY project for you! In a new adventure that I’ve gotten ourselves into, we’ve decided that it’s time for a big change in our front yard. I’ve dubbed this project as “un-landscaping.” After a whirlwind year, and our front flowerbeds mysteriously being weeded (I’m assuming by our sweet neighbors) while we were away for the weekend, it’s time to step back and admit our limits. Flowerbeds aren’t beautiful when they are being taken over by weeds and untrimmed, disproportionate shrubs.

So, to make a long story short, we are going with the thought of less is more. We are removing all but two of the shrubs from our front flowerbed, putting down grass, and adding simple window boxes to the front elevation. In an effort to make sure that anything out front is easy to keep up with, I also built in a “self-watering” system to each flower box. In theory, I’ll only need to water these flowers about every two weeks. This will make vacations a breeze and it won’t be the end of the world if I forget to water the front due to crying babes, important blog posts, or an overdue sewing project!

So, now that you know the backstory, let’s get on with the tutorial! I’ve got an easy-peasy flower box DIY for you today:

How to make Window Boxes

Selecting Materials

When shopping for materials, I was willing to spend a bit more because I want these window boxes to last. I know that even the best materials would cost me less than two large custom sized window boxes from a retailer. I chose to go with Cypress lumber and plastic trim. This can get pretty pricey, but I would suggest going with a higher quality and durable wood like Cypress or Cedar wood. These are both noted for their durability and weather resistance. Both have a lovely wood grain as well, making them ideal for staining or painting.

In addition to a durable wood, I wanted to make sure that the moist dirt and constant watering didn’t rot or warp the wood over the next few years. So, rather than stapling in plastic lining, I chose to make the window boxes so that a cheap plastic pot would easily line the wood box; making it easily clean-able, removable, and replaceable!

What You’ll Need:

Each of my windows measured about 72″ long. Since the windows are lower on the exterior wall, I wanted to keep them relatively shallow. In all, my window boxes measured about 72″ Long, 8″ Tall, and 6.5″ Deep. You may need to adjust based on the measurements you’re hoping to get for your own boxes. This list accounts for one window box in the size I mentioned above, if you’re making two, you’ll need to double this list!

  • 2 Planks Cypress Lumber: 8’L x 8″ W (typically you’ll get a 1″ thickness that actually measures 3/4″)
  • 1-5/8″ exterior decking screws
  • Wood Filler
  • Trim
  • 2 plastic window box pots (I got mine at Lowes)

Building the Window Box

Note: All dimensions are based on an actual wood width of .75″

To get started, you’ll need to cut your front wood length. I wanted to hide as many edges as possible, so keep in mind that your front and back lengths will be different! You’ll cut the front to be the length of your window + 1.5″

Next, cut the back to length. This will be your front length – 1.5. I’d suggest measuring you wood thickness double check for accuracy. In my case, since my front was 72″ long, and my wood .75″ thick, I cut the back to 70.5″ long.

When cutting the sides, we’ve got a few things to keep in mind. We’re attaching the box to the exterior wall with another board (see below for the full details). You’ll need to leave enough depth for two widths of board (1.5″) and the flower pot.  I absolutely suggest “dry fitting” your back and liner before gluing and screwing these in!

The back side of your window box will look like this.

Since my window boxes were going to be so long, I chose to add a center support for the window box liners. You center support should be the same width as the liner (or the side length – 1.5″).

Putting the Window Box Together

I suggest “dry fitting” everything together before gluing and screwing the box!

Start by attaching the sides to the front of the box. Remember to keep the edges hidden when you look at the box from the front. I did this part by supporting the front and sliding the sides underneath, gluing, lining up, and screwing in. You could also attach with a nail gun for a speedy shortcut!

Attach your center support by centering an screwing in from the front of the box.

Next, wedge the back into place. It should sit on top of your center support and in between the sides. Screw from the sides into the back to secure. Add extra stability by screwing from the back into the center support.

Adding Trim

Lastly, we need to add some trim! I used plastic trim since I couldn’t find anything made out of durable cypress or cedar. This won’t be a problem for me, since I’m painting everything with spray paint!

Carefully cut your side and front trim pieces to size using a 45 degree angle. I did this for both top and bottom pieces. If your corners don’t match up perfectly, don’t sweat it! I’m working with a new saw and getting used to my blade width and laser—so, nothing was quite as perfect as I would have liked! If you have a gap, screw the molding into place and fill with wood putty.

Let the putty dry. Sand down for an even finish and wipe off before moving on to the next step!

Paint your Window Boxes

Now it’s finally time to paint! I chose to use spray paint to give myself nice durability and coverage.

How to Hang Window Boxes

Finally, the moment we’ve all been waiting for! It’s time to hang those window boxes! Since you don’t want to make more holes in an exterior wall than completely necessary, it’s important to carefully hang your window boxes. My house is brick, so I was careful to drill only into mortar joints, not the brick itself.

Cut a 1×6 to the same length as your back piece. Once attached to the exterior wall, this should allow you to drill the window box into the wood, rather than into the brick.

Have someone hold up the 1×6 under your window. Level and screw into place using a hammer drill and Tapcon Screws.

Once your board is in place, have someone hold the window box in place, level, and drill through the back of the box into the wood behind it.


Now it’s time to plant your window boxes and enjoy! Don’t forget to drill holes for drainage before filling with potting mix and plants. I can’t wait to update this post with pictures of my luscious window boxes once all my plants are established! For now, these little new plants will have to do!

Wondering what those little pipes are in each corner of the window box? Next week, I’m going to show you how to make these window boxes self-watering. So, be sure to check back in for that tutorial. For now, let’s get building!

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