How to Build a Wooden Window Box Planter

Window box planters can add a splash of color and charm to your home’s curb appeal. I fell in love with the look that window boxes gave a home when I visited my family living in Germany several years ago. All across Europe, so many cute little houses had the most beautiful flowers just exploding beneath their sills. I had to have it!!

I knew I wanted the look, but I was always so lost as to how to actually mount them, since we have a brick exterior. Never fear! It was not as difficult as it seemed, especially with the right tools. It only took me 7 years to actually get around to figuring this out. Oh well.

How can you get the look? With a few great tools and a day or two. Plus, I found some great inspiration across Instagram to create bottomless window planters, so the water can drain out instead of rotting the wood beneath it!

This is to build two 36″ window box planters.

Tools

1. Hammer Drill
2. Regular Drill
3. Masonry Bits
4. Drill bit for wood screws (it depends on what their head looks like if it will be Phillip’s or star)
5. Drill bit for drilling small holes in the planters
6. Hammer
7. C-Clamps
8. Sandpaper (80-120 for removing small imperfections)
9. Tape Measure
10. Miter Saw
11. Level
12. Paint brush

Materials

1. 1″ x 5″ L-Brackets (to hold up the planters
2. Wood glue
3. Wood filler
4. 1 x 10 Board 6 ft (2)
5. 1 x 2 Board 6 ft (3)
6. 1 x 3 Board 6 ft (3)
7. 1 1/2″ Finish Nails
8. 10 x 2 or 2 1/2″ Interior Wood Screws (self tapping)
9. 1/4″ x 1 3/4″ Concrete Anchors
10. Exterior paint
11. 36″ Long Rectangular Planter Boxes (2)

Cut List

One area I ran into some trouble with was the front of the box – it should be longer than your original measurement because it will need to cover the side pieces to give you that solid piece look.

1. 1 x 10 Board @ 39″ (2)
2. 1 x 10 Board @ 8″ (4)
3. 1 x 2 Board @ 39″ (2)
4. 1 x 2 Board @ 8″ (4)
5. 1 x 3 Board @ 39 ” (2)
6. 1 x 3 Board @ 8″ (4)
7. 1 x 3 Board @ 36″ (2) – these are the support boards. I would wait until you have the shells built before measuring and cutting for these.

Here We Go!

1. Measure and cut your boards – wait until your shell is built for the support boards to ensure a snug fit. If you have a bigger or smaller window, you would want to adjust your dimensions so that the edges of the box line up with where the window edges are.

2. When you have all of your boards cut, I first attached the trim to the 1 x 10 boards. Using wood glue and clamps first, I lined everything up and clamped it in place to dry. The 1 x 2 goes on the top and the 1 x 3 goes on the bottom.

3. Once the wood glue has dried, hammer them into place with the finish nails and hammer.

4. Align the front piece (39″) in front of the side pieces. Using your self tapping wood screws, secure into place. The first time I put it together, I did NOT account for the extra length on the front that was needed to give it the appearance of a solid piece, so it turned out like this:

That’s why I broke them both down and re-made them… ugh.

5. Now is the time to measure for your support boards! Measure the inside of your box. Your support boards should fit snugly against each wall. Another important thing to remember – align the support board with where the actual planter will sit.

6. Now that you have them assembled, time to get the minor imperfections fixed up. Wood filler filled in whatever holes I didn’t like, and the sand paper took care of the bumps.

7. Next up, paint them in whatever color you would like. I was dead set on white for years. Then suddenly I chose black after seeing how great it looked against red brick! Surprise!

8. Now is the hardest part, in my opinion – actually mounting those L-brackets. You will definitely need some power behind your masonry bits, so I finally get to introduce you a little bit more to my husband! He has a bunch of tools I borrow and he does not like that. 🙂

He helped me do the drilling into the brick, since it was on track to be 102 that day and so, so humid. We couldn’t keep hydrated.

First, we lined up the window boxes with where we wanted them to sit. I used a pencil to mark the insides and bottom of the box on the brick so I could place the brackets properly.

Using the 1/8″ masonry bit, we started each of the 3 holes in the brick for the exterior brackets. Remove the brackets and finish drilling all 3 holes with the small bit. Then, for the size of concrete anchors we were using, we followed the instructions on the box and used the 3/16″ bit to enlarge the holes. Next up, we placed the bracket where it needed to go and switched out the drill bit to a Phillip’s head in order to screw in the anchors.

When we repeated for the opposing side, we used a level and a board to place it across from one bracket (secured already) to the other (to be placed), using a pencil to mark where the next set of holes should be drilled.

9. Next, we mounted the center bracket. With the exterior brackets already secure, we placed the board across again and then used that to guide us for the placement of that third, center bracket.

10. Place the window box on the brackets and, using either your pencil or a hand punch to mark where the holes fall on your box shell.

11. Pre-drill your holes, which makes it easier for you when you go to mount the brackets to the actual planter box.

12. Grab your screws (we used the concrete anchors because their heads were larger than the wood screws we had on hand) and mount up the boxes!

13. Place your planter boxes in on top of the support board. I cut the back of the planters down a bit so that they were easier to place into the window box shell. I used a box cutter, but you could always modify your window boxes to not give you this problem to begin with.

14. Finally the big moment has arrived! You have beautiful new planters ready to be filled. <3 Now, I should probably take my Christmas lights down already… almost July.