How to Build a Window Box Planter in 5 Steps

Build your own DIY window box to add curb appeal and make your home exterior look amazing! This tutorial breaks it down into 5 easy steps to build a custom window planter box for flowers.

Increase your curb appeal even further with DIY wood window shutters, a fresh painted door, and these other idea for improving curb appeal. 

DIY Window Boxes to Add Curb Appeal

When the weather is warm and nice, there’s no place I’d rather be than on the patio.

Jamie was just making fun of me the other day because I was SO excited about the warm weather and eating dinner outside he goes, “What is it with you girls and patios?” I laughed so hard.

But seriously it made me think about why I LOVE them so much. I don’t understand what’s to not love about patios?!

Who doesn’t love a good patio?!

Related Reading: Concrete Patio Makeover Ideas and How to Add Ambiance to Your Patio

Beautiful weather, smiling faces, the sun, ambience…smell of fresh flowers…beautiful planters…

But seriously- once Minnesota hits 70 degrees, you can find me picking out my favorite flowers to start decorating our spaces outside- ya betchya- to enjoy that patio! And there is nothing more that I love to plant than window boxes.

Window boxes are a design you rarely see sketched up within a new design plan. Homeowners typically request them.

You have to have a specific taste to appreciate a good window box. But they can add so much to the overall look of your home.

Window box planters provide a unique perspective to your home, adding colors and textures and something you can change with the seasons. Don’t ever leave your window boxes empty.

Related Reading: DIY Cottage Style Cedar Window Box

And just because they’re called window boxes, doesn’t mean you have to only put them under you windows.

Window boxes look great along banisters, railings, and any other flat and boring surface you want to spruce up! They even look great just sitting along your sidewalk or edges of your deck.

So today- we are so excited to share with you a full tutorial on how you can build your very own window boxes for as little as $20!

How to Build a Window Box Planter

by Jamie and Morgan from construction2style

This post contains affiliate links. See our full disclosure policy here.

Materials

• Cedar boards in desired widths (i.e., 1×12, 1×10 and 1×3)
• 5 lag bolts (for installation)
• Caulk
• 1 quart exterior grade white paint
• 1 quart primer
• Paint roller and pan
• Wood glue
• Wood filler

Tools

• Miter saw
• Jig saw (for corbels)
• Table saw (optional)
• Hammer or nail gun
• Tape measure
• Electric drill
• Drill bits
• Sand paper
• Level

1. Design

The first step to any good build is a design plan. And I’m not talking about a full design layout here, just know exactly what style you want.

Window Box Style

Do you want just a simple four sided flat box, or angled ends, curves, bevelled edges and molding? There are so many well designed window boxes out there it’s hard to choose which one to go with!

You can make simple boxed window boxes for as little as $20 or you can go big with high quality material and high design for as much as $300. And if you hire it out you’re looking at $500+.

Window Box Size

If you are using a window box liner, it’s simple to build around the liner. Or if you’re like us and want to create your very own waterproofing liner within, your options are endless.

We always like to keep it classic, creating a simple rectangular box and trim work with decorative support corbels below.

Depending on where you’re going to place your flower boxes will also depend on your design plan.

If it’s under a window, measure the width of the window and cut to your specific window dimensions. We made our window boxes very large! A good general dimension for the depth and height is 11″ deep and 8 ” high.

2. Measure & Cut

Once you’ve decided on your design plan the next step is to get to work- measure and cut! Measure the width of the window and cut to your specific window dimensions.

We made our window boxes very large! A general rule we follow for window box dimensions is the width of the window by 11″ deep and 8 ” high.

Use the width of your cedar boards to save having to rip boards to width on a table saw.

Just remember that once full of plants and soil a window box can be extremely heavy, so you need to make sure you have support to drill into so it doesn’t tear your siding off.

Within these window boxes that we made, they held 160 pounds of dirt into each planter. So for that amount of weight we secured them with 5 large lag bolts. We also made wooden brackets to support the weight of the boxes.

If you’re adding trim pieces like shown, cut them to the fit the length and depth of the window box planter. Cut corbels from thicker 2×10 (or whatever depth) material, or use this method to combine thinner boards to create a vintage carved corbel style.

Related Reading: DIY Craftsman Corbels

3. Assemble

When securing and assembling your window boxes, make sure you place them on 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.

For more information and photos about assembling a window box planter, see this cottage window box tutorial. 

Add Window Box Trim

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. Either before your woodwork or after your woodwork is assembled make sure to sand you work of art down to give it a nice soft finished look.

Once assembled, make sure you drill holes within the bottom of the planters to create drainage. This is as simple as drilling small holes straight through the bottom of the window boxes, roughly around every 6 inches.

Add Corbel Support

You can attach the corbels directly to the window planter box, or attach them to the house to act as additional support when installing.

Related Reading: Vintage Corbel Tutorial and Template

4. Prime and Paint

Before you get to the fun, make sure to fill in any nails holes with some wood filler, let dry, and sand.

Once sanded down it’s time for the fun, apply the paint primer to the window boxes. I typically like to use a 2″ brush, but any paint brush will do.

As soon as the primer is dry add you fun window box color! And by fun- we mean white. Just kidding. Add any fun color you want.

We like to stay with white because we like to add the fun within the flowers we plant. That way when it’s spring, fall or winter I can add just about any color I want without it clashing.

Simple neutral colors are sometimes the way to go when you like to spruce it up with the decor!

5. Hang & Plant Your DIY Window Box

If you aren’t placing such large window boxes like we did, you can place with screws and nails and secure with a 2×4 block behind the window box and below the window for support.

But being these were so large we wanted to make sure they weren’t going anywhere so we secured with 5 large lag bolts. Jamie even hung from them to make sure they were going to sell with the home!

For another method of hanging window boxes, see this cedar window box planter tutorial. 

Planting a Window Box

If you’re using a liner, place it inside. If not, you can line your planter box with landscape fabric to protect the wood and prevent soil drainage.

Once your planter boxes are hung and you’re ready to plant, it helps to add an inch or so of gravel prior to adding in the dirt to allow for excess water to drain. You can then cover gravel with potting soil and add the beautiful flowers and water!

Related Reading: Tips for Planting Beautiful Flower Pots and Planters

And let me fill you in on a little secret…these flowers are fake! Aren’t they gorgeous?!

Sometimes when you can’t manage the upkeep you can just settle for some beautiful fake flowers. You’ll have everyone fooled.

Saves money year after year, creates a beautiful outdoor space, and you can have decorative flowers throughout the season…even the summertime! Because who wants to be gardening when they can be out on the lake?! Well, maybe me and especially my mom… haha!

Read about more ways to add curb appeal here and with these ideas:

• Add window shutters for under $40 a pair
• Paint your front door
• More quick and easy curb appeal ideas
• More exterior window treatments

Published 30 July 2016 // Last updated 24 Sept 2020