How to Make Your Own DIY Indoor Window Planter Box

How to Make Your Own DIY Indoor Window Planter Box

You don’t actually require a lot of space to grow your own plants and flowers. Urban gardening becomes even more intriguing when you realize that you can make something as simple as your own indoor window planter box.

This adds beauty to your home while helping you to nurture your gardening bug, even if you don’t own an outdoor garden.

A window planter box makes it easy to care for beautiful plants and flowers—they’ll be right there, in your home. If you choose the correct drainage methods, having a window planter box can also make gardening easier.

Read on for the steps to make a DIY indoor window planter box. In this article, I’ll explore the materials and tools you will require for this DIY project and provide step-by-step instructions on how to make it. 

What You Need to Make a DIY Indoor Window Planter Box 

What You Need to Make a DIY Indoor Window Planter Box 

Since you’ll be making your own indoor planter box, you should consider how you want it to look—you may want it to match your home’s design and decor.

For example, you might want to stencil or paint it in colors that you already have in your home. Depending on how much window space you have, you can also customize its size.

And, if you’re keen on a hydroponics system of gardening that doesn’t require soil, you can make a hydroponic-friendly window planter box—but this will require extra supplies. The options are endless!

Here’s what you’ll need to build a simple, straightforward DIY planter box:


  • Circular saw 
  • Plane
  • Cordless drill 


  • 1 ” x 8 ” lumber 
  • 1 ” x 6 ” lumber 
  • Measuring tape
  • Rubber sanding block 
  • Sandpaper (80-grit and 220-grit)
  • Finishing nails 
  • Sealant 
  • Wood glue
  • Masking tape 
  • Hanger bolts (or L-shaped brackets)
  • Washers and nuts
  • Clamp
  • Small paintbrush
  • Paint (optional) 

Tips for Building a DIY Indoor Window Planter Box

Tips for Building a DIY Indoor Window Planter Box

When gathering all your supplies to build your window planter box, there are some important things to consider. These include the following.

Figure Out the Correct Size 

Make sure you measure the length of your window, the planter box should match it. 

When it comes to the height of the window box, a general guideline is to make the window box approximately 25 percent of the height of the window, or 20 percent if you’ve got very tall windows. 

Both of these points will affect how much lumbar you purchase. Note that you can also upcycle wood that you already have, which is environmentally friendly and saves money.

Consider the Plants You’ll be Growing

You need to consider what plants you’ll be growing in your planter box, as this will affect its size.

For example, if you’re growing herbs, your planter box can be about six inches in depth, giving the herbs enough space to grow. Also, ensure that your planter box is six inches from front to back. 

By comparison, if you’re growing vegetables, you should aim for between eight and twelve inches of depth. The box’s measurement from the front to the back should match this measurement, giving your plants enough room. 

Ensure the Right Drainage

Your window planter box will require adequate drainage. For this, you’ll need an inch of crushed stones that you’ll place at the bottom of the planter box. Cover them with some landscape fabric before adding the soil and plants. 

I recommend K-Brands Weed Barrier Landscape Fabric from Amazon. It’s easy to cut to size and prevents weeds. You can easily keep it fastened to the box with some landscape staples. 

Alternatively, you could place small potted plants directly into the planter box. This is the easier option and makes adding or removing plants at a later stage is convenient. 

Use Potting Mix for Container Plants

To have a thriving window planter box, you need to feed your plants a healthy potting mix that’s ideal for container gardening. A good choice is Miracle-Gro Moisture Control Potting Mix.

This mix feeds your plants, flowers, and vegetables for up to six months while protecting them from the adverse effects of under or overwatering. 

Step-by-step Guide on Building a DIY Window Planter Box 

Step-by-step Guide on Building a DIY Window Planter Box 

Now that you’ve considered the size you want your window planter box to be—based on your window height and what you’re growing in it—here are the steps to follow to build your DIY window planter box. 

Step One: Cut the Wood Pieces 

Based on the sizes we provided earlier, which you can adjust according to your specific window size, use your circular saw to cut two of the 1 x 8-inch lumber pieces so they provide the correct height for the planter box.

Cut two side pieces so that they have a five-inch long base and a six-inch long side. This will make them trapezoidal.  

Step Two: Form the Base

For the bottom of the planter, you should adjust your saw’s bevel to 5 degrees and cut the 1 x 6-inch lumbar piece, so it’s five inches wide.

For the back and front pieces, use a hand plane to make a 5-degree bevel along the bottom of each piece.

You should ensure that the bottom piece is about ¾-inch shorter than the length of both the front and back pieces. This will ensure that it fits correctly when you assemble your planter box.

Remember, you will need to make a drainage hole in the base of the window planter box. Use a drill and drill bit to make them. 

Step Three: Sand the Wood 

With your rubber sanding block and pieces of sandpaper, you can now go ahead and sand the wood. 80-grit sandpaper is rough, so it will work well to remove any scraggly or rough spots on your wood.

If you’re going to be painting the wood, make sure you smooth it with 220-grit sandpaper. 

Step Four: Drill the Holes 

Clamp both ends onto the bottom of the planter box so you can drill holes for your fasteners. Use galvanized finishing nails to fasten the ends to the bottom.

Note: Use glue to fasten the front and back edges of your end pieces together before clamping and attaching the front pieces to the ends and bottom.

Step Five: Apply Sealant 

Place masking tape along the top edges of the planter box before applying a sealant to the inside of your planter. Sealant is vital as it provides a waterproof lining, so you can add soil and water to the planter without damaging it.

I recommend the Garden-Seal Clear Wood and Plant Sealant, available from Amazon. It’s non-toxic and eco-friendly. It’s safe to use as a coating inside wooden planters and pots to help them retain water. 

Step Six: Paint the Planter Box (Optional) 

Once you’ve allowed the sealant to dry, you can go ahead and paint the interior and exterior of your planter box if you like.  

Note that if you’re painting your planter box, you can ensure it has a smooth finish by filling holes with wood filler prior to painting. 

How To Hang Your DIY Window Planter Box 

How To Hang Your DIY Window Planter Box 

You’re ready to hang your planter box! You can do this easily with some hanger bolts.

Here are the steps to follow. 

  1. Drill two holes (½-inch in size) about a quarter-inch of the way from the ends and about 1½ inches below the top.
  2. Get a friend to hold the planter box underneath your window while you install a ⅜-inch hanger bolt through the holes.
  3. Hammer the hanger bolts, making sure you leave some of the bolts sticking out 
  4. Hang the planter box on the bolts.
  5. Install a washer and nut on the end of each bolt. 

You can also hang your planter box with brackets. Just make sure that you use two heavy-duty L-shaped brackets that are strong enough to carry the weight of your planter box, even when it’s filled with plants and wet soil. 

For heavy window boxes, you can make cleats to secure them. To make these, you’ll need to cut three eight-inch pieces of 2 x 4-inch wood. Hold the cleats against the wall and drill holes where you want to add the screws to secure them. 


Growing your own plants indoors doesn’t have to take up a lot of space. Make use of vertical space by installing a window planter box.

In this guide, we’ve provided you with all the information that you need to know to make your own DIY interior window planter box. We’ve also explained how you should hang it, so you can now start growing your favorite flowers and plants. 


About The Author

Gina Harper grew up dreaming about farms and growing her own food. She began an urban garden to feed herself and turned it into an incredible hobby. Gina is here to teach you everything from raised beds to container gardening, how to keep plants alive and well in a smoggy city, and the works. It’s time that we carve our own piece of green earth and reap what we sow—she’s here to help you with that.