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A flower bed or a flower box is a beautiful way to brighten up your outdoor living space! It can add a lot of simple charm and color to your home. Here’s what you’ll need to know for how to build a window box for your home:


  • 1×10 and 1×3 cedar
  • 5 lag bolts
  • Caulk
  • 1 quart exterior grade white paint
  • 1 quart primer
  • Paint roller, pan
  • Wood glue
  • Hammer
  • Wood filler
  • Tape measure
  • Electric drill
  • Drill bits
  • Sand paper
  • Level

White Flower Boxes

How to Build a Window Box

Step One : Cut Boards

Measure the width of the window and cut to your specific window dimensions. We made our window boxes very large! A good dimension for the depth and height is 11″ deep and 8 ” high.

Just remember that once full of plants and soil a window box can be extremely heavy. My aunt had said she ended up putting 160 pounds of dirt into each planter.

Luckily, Jamie secured with 5 large lag bolts and hung from them with his body weight to ensure the planters were in for the long haul! We had also made wooden brackets to support the weight of the boxes.

Step Two: Assemble

Place bottom of window box onto a flat surface. Clamp the front and back boards onto the table and against the bottom window box board to hold securely into place while you drill the front and the back boards onto the bottom board. Repeat for the side boards.

DIY Flower Window Boxes

Adding trim provides a clean and finished look to your window boxes. To add trim, cut four pieces the length and height of your box for each side of your window box. Secure into place with a nail gun or nails.

DIY Flower Window Boxes

Step Three: Prime and Paint

For a smooth finish make sure to fill in any nail holes with the wood filler prior to painting. Make sure to sand down the wood filler once you have applied.

Using a brush, apply the paint primer to the window boxes. Once paint is dry, apply the paint color. We had used white to match the trim on their cabin.

Painting the planters

Make sure to sand down the entire window boxes prior to painting and in-between priming and painting.

Sanding the planters to get ready for paint

Step 4: Hang Window Box

At first we drilled holes into the siding to place our lag bolts. If you aren’t placing such large window boxes you could also secure with screws and nails and secure with a 2×4 block behind the window box and below the window for support.

DIY Pallet Flower Boxes

We clearly had forgotten a ladder… ????

DIY Pallet Flower Boxes

Step 5: Create Drainage

The next, and one of the most important steps, in how to build a window box is to create drainage. Drill holes straight through the bottom of the window boxes to allow for drainage. Drill a hole roughly around every 6 inches.

Jamie being the professional waterproofer that he is, waterproofed the boxes to ensure longer life and to protect the cabin so that the water didn’t leak onto the siding.

DIY Pallet Flower Boxes

DIY Pallet Flower Boxes

We also had gotten to the cabin on the beautiful spring day that the mayfly’s hatched. I had never seen anything so crazy in my life. But it made for good laughs and a good story!

DIY Pallet Flower Boxes
DIY Pallet Flower Boxes

DIY Pallet Flower Boxes

DIY Pallet Flower Boxes

Step Six: Fill Window Box

It helps to add an inch or so of gravel prior to adding in the dirt to allow for excess water to drain. Cover gravel with potting soil and add the beautiful flowers and water!

DIY Flower Boxes

Pallet Flower Holder

DIY Pallet Flower Boxes

Jamie also made me a beautiful pallet planter for our 1st Christmas. We had decided we wanted to make one another Christmas presents. And Jamie being the creative carpenter that he is made me a gorgeous pallet headboard. He had some leftover materials so he put together this pallet flower holder. He of course thought it was “junk” but knew the pallet treasure I would so appreciate!! And it makes for awesome yard art!!

DIY Pallet Flower Boxes

DIY Pallet Flower Boxes

DIY Flower Boxes

Did you like these tips on how to build a window box? If so, Country Living has a great article with 19 more DIY ideas just like it.