Adding window boxes to your home can be a daunting task, especially if you've never had them. It may feel like you need to hire a professional, but with the right knowledge I will walk you through the process.
The first step is determining which windows on your house are good candidates. 9 times out of 10 a window box will go on the front elevation of the home and be used for curb appeal. Occasionally it can go on the side of the home, especially if the house is on a street corner and is side facing to a street. Occasionally it goes on a back window but this is more often used for gardening or privacy rather than curb appeal.
An ideal window for a window box is one that is accessible and on a part of the front of the house that would look great with flowers added. Sometimes a window is right above a bush or shrub and this makes it less than ideal since the shrubs or landscaping will block most of the view. Other times the windows are directly over a slanted roof and there may not be enough space to actually put a window box under the window since it touches the roof line. And finally, sometimes the windows are not very accessible like an attic window above the garage or a closet window next to one of the kids bedrooms. All these might be bad candidates for a window box unless you're wanting to add artificial flowers to the box so that you're not having to worry about watering. Some companies make self-watering window boxes that can come in handy if you do have a hard to reach window.
Once you've determined the windows that will make a good candidate for a window box the next step is measuring your windows. If you are on siding I recommend to get a box the size of the window plus the surrounding trim around the window. It's a good idea to include the trim in your measurement because often there is a stud behind the trim that you may want to grab during installation. If you're on brick then you can simply measure the size of the brick opening. You'll want to get a window box that's as close to these measurements as possible. If you're going to be off by a few inches then better to be a few inches longer than a few inches shorter as it tends to make the window look more balanced and aesthetically pleasing this way.
The next step is to do an online search for a window box company and see what sizes they carry. Some custom window box companies can make window boxes any size you want to the nearest 1/4" while others may only carry 2-3 sizes. You can use a roll of paper towels as a mock up to get a feel for how a certain window box will look. Take the paper towels and roll out to your measured length then cut with scissors. Next, tape the rectangle to your window and step back and view it from the street. This will allow you to see what a window box will look like on your window as well as see what various lengths will look like so you can order with confidence.
Installing Window Boxes
Once you've measured your window and ordered your window box it's time to install them. Some boxes uses support brackets underneath while others are bolted directly to the home. To determine if you should use a support bracket you will need to read up on the manufacturer of your window boxes as there is a lot of differences from one company to the next depending heavily on what material the window box is made up of. Wooden boxes usually use a wooden support bracket underneath. You'll need to make sure your load bearing studs are symmetrically placed first as otherwise this can be a problem with using this method.
Fiberglass boxes sometimes use a cleat system for installation. This entails screwing a metal cleat to the house wherever the studs are located and then hooking the window box into the cleat. Hollow plastic boxes may use a metal support bracket underneath. These metal support brackets are sometimes less visible which allows you to hit studs that aren't symmetrically placed and not have visible supports underneath that look out of place. Lastly, some solid plastic boxes can be directly mounted to the house with lag bolts. For these boxes you can pass lag screws through the back board and into the studs behind your siding. This can solve asymmetric problems since the screws are usually hidden inside the box where the dirt will be.
Many manufacturers have videos on their website of how to install window boxes. Make sure you distinguish between siding and brick since the install methods are different. If you aren't comfortable drilling into your house to install your window boxes then it's very common to hire a handyman or contractor to help you with this.
Planting your Window Boxes
Once you've acquired and installed your window boxes it's now time to plant. For wooden window boxes make sure you to get a liner to protect the boxes so they don't rot out easily. For PVC, composite, or plastics you can usually plant directly in the boxes. Make sure to use potting mix for the best result since the loose soil structure makes it easy for plants to take root and thrive. You can search online for window box planting tips and ideas for the various seasons.
About the Author
Matthew Buquoi is the owner of Flower Window Boxes, an online PVC window box company specializing in custom, no rot, self-watering window boxes.