I finally finished this project that has been on my to-do list for months and months! This DIY window box project is now complete.

Last summer, we added a flower box to our front windows, and we loved it so much we wanted to do the same in the backyard. The only difference this time is that I made the flower box instead of buying it from Etsy.

White Window Box with Flowers on a patio with adirondack chairs and a firepit. How to Build a DIY Window Box from start to finish

Window boxes are an easy way to add character and charm to your home – and you don’t need to use real flowers! The fake ones do just fine if you do it right.

This project cost us $63, not including the dirt and flowers. The pre-treated lumber was $15, the brackets were $17 from Amazon, the white exterior paint was $22 (I have a ton of it left), and the galvanized brad nails were $9 (I also have a ton of nails left). The dang paint was the most expensive thing on the list. Annoying! Everything else we already had (sanding discs, landscape liner).

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White Window Box with Flowers on a patio with adirondack chairs and a firepit. How to Build a DIY Window Box from start to finish

Things You’ll Need

Tips and Tidbits

It’s helpful to buy the steel brackets first. The width of the brackets you purchase will determine how wide of a box you need. We bought these steel brackets and knew our box had to be about 7 inches wide.

I think these planter boxes look best when they are the entire window width.

Read: Charming DIY Planter Box for Succulents

DIY Window Box Instructions

White Window Box with Flowers -How to Build a DIY Window Box from start to finish

How to build a DIY window/flower box from start to finish.

Total time: 1 day

  1. Measure and Cut Wood To Size

    Cut wood to size. How to Build a DIY Window Box from start to finish

    First things first. Measure the width of your window and determine how long your box will be. The brackets you buy will determine the width (see notes above). You want to cut two sides pieces the same length and one bottom piece.

    You’ll also need two side pieces, which I cut to fit inside the two side pieces, so my bottom piece was cut a bit short to accommodate this side piece (see photo).

    If your wood has rounded edges, cutting a straight edge on each side of the bottom piece might be helpful so it fits flush against the sides.

  2. Drill drainage Holes

    Drill Drainage holes. How to Build a DIY Window Box from start to finish

    We need drainage holes! Use a 1/2-inch spade or Forstner bit and drill holes across the bottom piece. I spaced mine about 8 inches or so apart.

  3. Glue Box together

    Assemble. How to Build a DIY Window Box from start to finish

    You might need a helper for this part! Use wood glue to assemble your wood box and clamp the pieces tight.

  4. Brad Nail Window Box

    brad nail box together. How to Build a DIY Window Box from start to finish

    While the wood glue was drying and the window box was clamped, I used our brad nailer to nail some galvanized nails in the edges and sides for added security. Any nails that poke out can be hammered in flush with the wood.

  5. Sand Window Box

    Sand your window box. How to Build a DIY Window Box from start to finish

    You can sand before assembly or after. I used our orbital sander and 120 grit sandpaper to make a smooth surface ready for painting.

  6. Paint Window Box

    Let’s paint! I used an exterior semi-gloss paint in Pure White to match our existing trim.

  7. Add landscape Liner

    Landscape liner helps keep the dirt from falling out of your drainage holes. I cut a piece to fit across the bottom and laid it there after the paint was completely dry.

  8. Install Brackets

    Install steel brackets. How to Build a DIY Window Box from start to finish

    Installing brackets along your window sill is the first step to hanging your window box. We evenly spaced four brackets across the window frame and attached them using heavy-duty 2.5-inch exterior screws.

  9. Hang flower Box

    Hang window box with steel brackets.

    Now that your brackets are hung set your box down and secure them to the brackets by screwing them together on the bottom.


Our outdoor firepit/patio area is much more inviting now.

Our patio area gets morning sun and afternoon shade, so I chose flowers that would thrive in those conditions. The only flower I added that I’m “testing” is superbells or Calibrachoa. These are supposed to thrive in full sun but also do ok in part sun; they produce fewer flowers. If they don’t do well here, I’ll take them out and replant them somewhere else and replace them.

Here’s a picture showing what I planted. These are all baby plants, so I’ll repost them in the future to let you know how it’s going. I plan to fertilize periodically with my favorite, Jack’s bloom booster.

Part Sun window box ideas

Lobelia: I’ve seen this in shades of blue, pink, purple, and white. It likes 4-6 hours of full sun.

White Window Box with Flowers -How to Build a DIY Window Box from start to finish

Polka Dot Plant: Beautiful, vibrant-colored foliage in pink/hot pink and green shades. It does well in the shade but can take some sun. We’ll see how it fairs this summer.

Close up look at flowers in a window box - How to build a window box from start to finish.

Variegated Vinca: One of my faves, and I use this plant everywhere! It can thrive in the sun or shade, creating a beautiful cascading look for your planters.

Coleus: Gorgeous plant in shades of pink, maroon, and green. It thrives in shade or part sun.

Close up look at flowers in a window box - How to build a window box from start to finish.

Calibrachoa: AKA superbells. This is in the petunia family and comes in many colors and varieties (try to find the double superbells – stunning). The flowers are smaller than petunias flowers but can be so pretty. While this one does like the sun, it can tolerate part sun. Time will tell if it wants its home here.

White Window Box with Flowers on a patio with adirondack chairs and a firepit. How to Build a DIY Window Box from start to finish

I hope this inspires you to create your own or get planting.

Xo Karen