A bit of greenery never hurt a railing. Building your own DIY railing planter box is a good way to reinvent an old railing or adorn a new one. You can grow flowers or herbs in it and enjoy it for years to come.
In this guide, we’ll show you how to build an over railing planter box that will last. We’ll also look at the different ways you can hang it to the railing and share some creative rail planter box ideas.
So, roll up your sleeves and get ready for this flowerful DIY project.
How to build an over railing planter box step by step
Measure and cut the wood, glue and nail the side pieces and the bottom, and drill drainage holes. Then stain the wood, add the French cleats to the back of the box, and you’re done. Check the more detailed step-by-step instructions below for guidance and tips.
Important: You can make your deck railing planter box as large as you need it to be. But bear in mind that the heavier it is, the more support it requires. As a rule, you should be able to hang or take down the planter box without great effort. If it’s difficult to handle, it’s probably too heavy for hanging.
Materials and tools you’ll need
- One 1 x 6 wood board (fence pickets, or similar)
- French cleats (or metal hangers)
- Exterior screws
- Wood stain & brush
- Nail gun
- Mitre saw
- Exterior wood glue
- Landscaping fabric
- Tape measure
- Corner brackets (optional)
Step 1 – Measure and cut the board
A 1 x 6 wood board is large enough for you to make a deck rail planter box. If you use fence pickets or leftover wood instead, make sure to get the measurements right.
Measure and cut the long side pieces first. Then measure and cut the bottom piece and the end pieces.
You should end up with 2 long rectangular side pieces, 2 square side pieces, and 1 rectangular bottom piece.
Step 2 – Glue the pieces together
Apply exterior wood glue to the inner edges of the long and short side pieces. Fix them in place, working one end at a time. Then glue the bottom piece on.
Important: Use exterior wood glue that is weather resistant. Apply the glue before you varnish the wood. If the wood is already varnished, you may have to sand the edges to ensure the glue sticks to them firmly.
Step 3 – Clamp and nail the pieces together
Good-quality exterior wood glue is strong. But it never hurts to nail the wood pieces together for extra support.
Before you start nailing the wood, clamp the glued pieces in place. The pressure that clamps put on the pieces will ensure a better hold for the glue. They’ll also make it easier to drive the nails in without another pair of hands to help you.
Note: Depending on the brand of glue you use, you may have to wait a few minutes before nailing the pieces together.
Once the glue has set, use the nail gun to drive the nails in at both ends, fixing the long and small side pieces together. Finally, nail the bottom piece.
Step 4 – Drill drainage holes
Turn the deck rail planter box upside down and drill at least 8-10 drainage holes at the bottom. Whether you plan on growing flowers or herbs in it, drainage holes are a must.
Step 5 – Apply wood stain
Give the wood one or more coats of a good quality wood stain. Even if you’re using rot-resistant wood like cedar, staining the wood is still important.
Tip: Plan on growing edible plants in your railing planter box? Use tung oil, raw linseed oil, hemp oil, or an eco-friendly wood stain.
Step 6 – Add corner brackets (optional)
Metal corner brackets can reinforce the wood boards and make your deck rail planter box look better. The glue and nails will hold the boards together but the wood may still warp at the edges after long-term exposure to the elements. Simple corner brackets can limit warping.
Step 7 – Install the French cleats
French cleats provide an easy and elegant way to hang an over rail planter box. They provide reliable support while being invisible.
They have a bevelled edge with a 45-degree angle, one at the top, the other at the bottom. They can be made from wood or metal, and you can find them in DIY stores or online.
Add the French cleat with the bevelled bottom edge to the railing planter box. You should attach it with screws, which are often provided in the package. Then fix the French cleat with the bevelled top edge to the deck railing.
Note: French cleats are just one way to hang a planter box to a deck railing. Later in this post, we’ll share more ideas on this.
Step 8 – Line the deck railing planter box with landscaping fabric
Use landscaping fabric or similar material to protect the interior of the wood and improve moisture retention. The fabric will also help prevent soil from dripping down the drainage holes along with excess water.
Fold the fabric in two or more and staple it to the planter box. The top of the fabric shouldn’t be visible over the edges of the wood.
Step 9 – Put in the potting soil and plants
Add your soil mix and plant the flowers or herbs into the box before you hang it over the railing.
Step 10 – Hang the planter on the railing
Hook the cleat at the back of the box to the one on the railing. Make sure the hold is good.
And with that, you’re done. Your over the rail planter box is ready.
Over the rail planter box ideas
If you’d like a more sophisticated over rail planter box, here’s a selection of other railing planter boxes you can build instead.
Pine over railing planter box with support cradle
Made from pine wood lined with plastic sheeting, this planter box has a simple timeless look. The support cradle adds a distinctive touch to it. It’s also spacious and herb friendly.
Small tiered square railing planter boxes
Got plenty of planting space already? Try a variation on the classic rectangular wooden planter box. Attach three or more small square planter boxes vertically to a wooden board. You don’t need much wood for this project, you can even use leftovers from another DIY project.
Lattice railing planter
Make your railing planter more interesting by incorporating a wooden lattice into it. Use lattice along the longer sides or on all sides. To make it look nicer, frame the lattice with wooden boards nailed to the planter box.
Angled top railing planter
An angled planter takes a bit more effort to build—and calls for more precise measurements. But it’s a nice variation on the usual straight-lined planters. If you want to hang it over the railing, you can angle only its front side.
Wooden corner rail planter box
Reinvent your railing with a corner planter box. You can also adapt this idea to hang your planter over the railing. In both cases, you can use wide wooden boards. You can even cover your whole railing with planter boxes if you want.
Ways to hang an over railing planter box
Apart from French cleats, you can use brackets, heavy-duty cable ties, holders or baskets, rope, chains, and even bike hooks to hang an over the rail planter box. Each of these has its pros and cons. Let’s take a closer look at each so you can make an informed decision.
Providing a quick and effortless way to hang most planter boxes, over-the-rail brackets are often L-shaped. Don’t want to drill holes in the planter box? Look for brackets with a hooked or bent arm on which you can simply rest the flower box.
Need to hang an over rail planter box on a railing that has an irregular shape or is smaller or larger than average? Try brackets you can buy online. Brackets come in a variety of shapes and sizes including deck drapes, rectangular brackets, shelf brackets, and clamp brackets.
Some are made for specific types of railing, for example, 2×4 or 2×6 wooden deck rails. Some feature adjustable straps that make them attachable to just about any type of railing.
Good to know: Average-weight planter boxes of up to 48” in length generally require one pair of brackets. Larger planter boxes require two pairs or more. Check the instructions provided by the manufacturer of the brackets to be sure.
Over railing planter box holder or basket
You can also hang planter boxes over the railing using a holder or basket. Usually made from metal or vinyl, an over railing planter box holder or basket consists of a support frame for the planter with hooks at one end.
This type of planter doesn’t require any drilling or screws. You just hang the hooks over the railing. Look for one that’s long and wide enough for your planter box. Also, make sure it’s waterproof.
Note: This type of over railing planter box should be light to moderately heavy. If you buy it online, make sure to check the maximum depth it can hold. Some holders or baskets feature an adjustable width.
Heavy-duty cable ties
Heavy-duty cable ties can be a smart choice if you’re concerned about the safety of your railing planter boxes. They consist of a cable loop secured with a lock. You can tie them directly to the planter boxes or thread them through eyehooks that you fasten to the boxes.
Note: The downside to cable ties is that once you fix them in place, you may not be able to release them unless you cut the cable. If you decide to move the planter box, you may need new ties.
Strong, waterproof rope works well for wooden and resin flower boxes. Wrap the flower box with rope at each end and tie the rope in a tight knot behind the box. Make sure to use rope that’s thick enough to bear the weight of the box. Note that because of the weight of the planter, the rope may bite into the wooden railing in time.
You can also use chains instead of rope to fix a planter box over the railing. A strong chain can bear the weight of just about any flower box. But it often works best on metal railings since it may scrape and damage wooden ones. You can wrap the chains around both ends of the flower box and then connect the chain with a connector or clasp. You can also add eyehooks to the back of the flower box and hang the chains from them.
Got a spare pair of bike hooks in your garage? You could repurpose them into supports for railing planter boxes. These may work especially well for heavier planter boxes. Note that bike hooks usually require you to drill holes in the railings. For this reason, they are often best suited for use with sturdy wooden railings.
Railing planter boxes with built-in brackets
Finally, you could also buy flower boxes for railings with built-in brackets. Often made from plastic, these flower boxes don’t have the rustic feel of wood, but they can be a good investment if you want to line a long railing with flower boxes.
How to choose the right planter box to hang on a railing?
The right planter box for deck railing isn’t only nice to look at, but easy to hang. It shouldn’t be too heavy or bulky. Also, it should be made from a material that allows you to drill holes in it for support brackets if needed, as well as drainage holes.
Wood, resin, and plastic planter boxes are often the best for deck railings. Factor in their weight when they’re filled with soil to make sure the brackets, holders, or ropes you use can support them.
Are planter boxes for deck railing safe?
Yes, provided you attach them to the railing using appropriate brackets, holders, or ties. If you have a tall railing or are concerned that children or pets may upset the hanging planter boxes, opt for one of the safer hanging methods. Hang the planter boxes to the deck railing using brackets with screws, chains with connector locks or heavy-duty cable ties. These hanging methods provide better support than holders, baskets, or ropes.
Can you attach a planter railing box on top of a deck railing?
Yes! You can use rope or chain ties, brackets, or simply drill holes through the bottom of the box and into the wooden deck railing to fix the box in place with screws. You can also buy plastic, resin, or PVC planter railing boxes specially made for on railing rather than over railing installation.
However, putting a planter box on top of a deck railing may affect drainage and damage the wooden railing. In some cases, it may also increase the risk of it falling if accidentally hit. So, if you have a wooden deck railing, it’s better to use an over the railing planter box rather than install one on top of it.
The wrap up
Building and hanging a railing planter box only takes a few hours. You can choose from many different hanging methods, including brackets, French cleats, and heavy-duty rope ties. If you enjoy DIY projects, this one shouldn’t give you any trouble.