How to Build a Custom Window Flower Box + Greenhouse!

Ever since I raised the windows in the Green Kitchen Glamazon and patched the stucco exterior myself, I always knew a window flower box would one day call this spot home and be custom made to fit this exact space. 

The design was inspired in two ways: to visually mimic the former height of the raised windows (while covering up a decent stucco patch) and bring a little bitta Charleston, South Carolina to my front door. ‘Cause that’s where I’ll call home one day.

Check out the video tutorial:

In tandem, its confused counterpart, affectionately dubbed “The Greenhouse”— a hinged, below-grade cedar window cover with a deep, toasty basin great for germinating vegetables as the weather warms—was restored to match the look of the exterior and flower box above with a few additional aesthetic upgrades.

A quick before + after:


  • Planks of wood, based on custom size
  • Miter saw
  • Measuring tape
  • Nail gun
  • Wood glue
  • Wood putty
  • Orbital sander
  • Wood stain
  • Polyurethane
  • Paintbrush
  • Impact driver drill
  • Spade drill bit, ⅞
  • Shelf brackets, 5
  • Masonry drill bits, 1/16 → 5/16
  • Masonry screws, 5/16
  • Wall anchors, 5/16 
  • Level
  • Painter’s tarp, preferably used
  • Staple gun
  • Potting Soil
  • Flowers!!!


First, decide on the width, height and depth of your window box. Then, pay a visit to your local lumbah yahd to purchase a few planks of wood. My window box measures six-feet wide, 10-inches high, 9-inches deep. 

Next, mark your cuts for the two fronts and two sides. Make your adjoining cuts on a miter saw. Grab a pneumatic nail gun, wood glue and assemble! Use wood putty to fill in corners and holes.

Use an orbital sander to smoothen out the rough cuts and excess wood putty. Flip the window box upside down and add several drainage holes with a spade. I call mine David.


Next up, stain! Since this window box will permanently live outside, I upped the ante with ZAR’s Deck & Siding Stain in Oxford Brown to not only make this some long-lasting good wood, but armor it to the elements for a loooong time.

This stain is exceptionally viscose similar to paint. I recommend using a paintbrush following the wood grain in quick, swift strokes. Apply one to two coats and let each layer cure for about an hour, weather-depending. 

While the stain dried, I installed five 10-inch tall shelf brackets in my stucco exterior with wall anchors and masonry screws. Use a level to mark placement on the wall. Start with a small drill bit and work your way up to the exact wall anchor size.


Once the stain is dry, seal the deal with an application of an oil-based exterior polyurethane. Big fan of a satin sheen. 

Finally, for added protection, I used an old painters’ tarp stapled to the sides to shield this good wood from making direct contact with the dirt. 

Now screw ‘er in, add primo potting soil and get to planting!


The funky little greenhouse received the same treatment except with the addition of exterior wall paint to match the rest of the home in Benjamin Moore’s luxuriously historic color, Lafayette Green. 

Not to mention, the most precious hand-punched brass signage, appropriately and always affectionately dubbed, The Greenhouse. 

Are you ready to build a window flower box?!

Let me know in the comments below.

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