DIY Outdoor Flower Boxes

One of the final details of my shed construction project from last year was to add flower boxes under the windows. You can’t have the cutest shed in the neighborhood without flower boxes. I had a lot of lumber scraps left over from building the shed, and was able to reuse pieces I had laying around, making the total cost of this project free.

Here’s how I did it:

Final measurements of box: 2′ long x 5.5″ high x 6″ deep

Materials (for one box):

2- 2′ x 5.5″ boards (I used all 3/4″ thick boards)
2- 6″ x 5.5″ boards
1- 2′ x 4.5″ board (it’s best if these are pressure treated because they become the bottom of the planter)
2- L-brackets that are at least 3″ on each side of the L
Wood glue, nails, screws, hammer, drill, and a saw (if the boards aren’t the right size to begin with), primer, paint, and a paintbrush


1. Cut all of the boards to the dimensions above. Don’t cut your fingers off.

2. Place the 2′ x 4.5″ pressure treated board 1″ from the bottom of one of the 2′ x 5.5″ boards. This will become the bottom and front of the box. I wanted to raise this bottom piece up 1″ from the bottom of the box so you wouldn’t see the edge sticking out anywhere. This also helps take weight out of the planter since there’s less space to fill with dirt. Once the bottom piece is placed where you want it to be, nail it into place. Attach the second 2′ x 5.5″ board in the same way to become the back of the planter.

3. Attach the 6″ x 5.5″ end pieces by nailing them into place as shown. This will create the box structure. Use both wood glue and nails where possible to make it as sturdy as possible.

4. Drill a few holes into the board at the bottom of the box. I suppose you could’ve done this first, but I was making this up as I went along. This allows extra water to drain out so the box doesn’t get all soggy and your plants don’t drown.

5. Use a good primer to seal all of the boards. I used white since I’m matching the trim of my shed. I did 2 coats of primer and then 1 coat of paint. Let it dry completely before attempting to hang the box.

6. Decide where you want the box to hang and attach the L brackets to the structure. I used a drill and screws to make sure the boxes were securely attached. Then place your planter on the bracket and use screws to secure it to the bracket underneath the box.

7. Add a good potting soil and your favorite plants. Don’t forget to water enough!

I may have already forgot to water before I even wrote this post. I do plan to take the boxes of and store them inside for the Minnesota winter. But for now, I love how they look!


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