DIY Railing planter

These DIY cedar railing planters are really easy to make and all you need are fence pickets, a couple of balusters and a 2×4!

Hey guys!

I have been working on revamping almost all of the closets in the new house, but instead of boring you with back-to-back-to-back closet built-ins, I thought I’d split it up a bit with another project that was a “must-make” to ‘homey’ up the place.

At our last house we had cedar planters as window boxes which you can see here. Ex-Hubby built them and they lasted, quite literally, for over 15 years! There were a couple of things about them that I wanted to improve, so this was the perfect opportunity.

One thing I didn’t like about the previous planters was how often they needed watering. Granted, it was less than you need in plastic planters, but still more effort than I liked. I wanted these new deck railing planters to be deep enough that roots have a chance to grab on, the box won’t heat as quickly, and water will be slower to eke out.

I worked with 1×6 cedar fence boards and tried to minimize the waste, so these planter boxes are large… like 4 FEET long!

Okay, some tips/ideas:

This post contains Amazon affiliate links to items I used in this project. These links are for your convenience, but do provide the blog with a small commission. For full Amazon affiliate disclosure, please see the bottom of the page.
For Cedar, while a LOT more expensive than pressure treated wood, will also last longer. It is lighter to carry (and hang), and will patina beautifully without any maintenance whatsoever. There is the added bonus that mosquitos don’t like cedar, so there is a bit of pest control as well.
Not all wood glues are the same; as in you have to use outdoor-specific wood glue for this build.
These railing planters are way over-built. I know it, I said it – but my reasoning is that these are hanging over a walkout basement and the last thing I would ever want to happen would be for it to come apart, fall and hurt someone.

You will need:

(10) 6 foot cedar/or pressure treated fence pickets (approximately 5/8″ thick)
outdoor wood glue
1″ course pocket hole screws
(2) cedar or pressure treated deck balusters (approximately 2×2)
1 ¼” deck screws
landscape fabric
(1) 2″ x 4″ x 6″ pressure treated lumber
3 to 3 ½” construction screws

DIY Railing planters

For the best glue-up, the edges of each fence picket need to be straightened. I ripped about 1/8″ off of one side of 6 boards, and off of both sides of 2 boards (which becomes the middle section).

Cut your fence boards to 48″ long.

Pre-drill pocket holes in alternating spaces; one on each side of the boards with only one straight edge, and on both sides of the picket with both edges straightened.

Apply outdoor wood glue liberally, then attach the boards together with 1″ pocket screws.

You’re going to glue up two side sections of 3 boards each (remember the double-ripped board will go in the middle), and then a third section that is 2 boards wide.

The bottom section of two boards will need pocket holes on the outer edges (including the ends) so that it can be attached between the side pieces.

While the glue is drying, measure the height of the side boards. The building plan above indicates that the overall height of these cedar railing planters is 18″, but after ripping the boards down to get straight edges, you’ll find that the finished height is closer to 16″. Verify that measurement, then cut the remaining wood bits to that length.

Drill pocket holes and glue-up as we did with the sides.

Using wood glue and 1″ pocket screws, attach the sides to the bottom of the railing planter, allowing space for the end pieces to be attached to the base next.

Glue and attach the end pieces with pocket hole screws.

Note: it’s really the wood glue that holds these planters together; you’d be surprised at how incredibly strong it is. The pocket screws are more to bring the boards tight together while they dry, and give me a bit of extra peace-of-mind that these are solid.

Okay, here is where some of my over-building comes into play… these planters are already strong with both screws and wood glue, but because they are also large, heavy, and will fluctuate in weight with rain etc, I really wanted some extra reinforcement for hanging.

This is where your balusters come into play.

I cut mine to about 1″ below the top of the planter and attached to the corners and middle of the deck box with deck screws drilled in from the outside.

Don’t worry, we’re going to cover the screw holes with some trim in a minute.

Trimming out your railing planters

Now it’s time to rip down your remaining boards to create your trim. I chose to use a 2″ trim on three sides.

Use your outdoor wood glue and some finishing nails to attach the trim pieces to the sides and front of your planter boxes.

Drill some drainage holes in the bottom of your planter boxes, then line with landscape fabric to stop the soil from washing through.

Making a French cleat for your DIY deck rail planters

I looked up several different options for hanging these window boxes; from sitting them on top of the railing itself (the moisture would rot the rail), to attaching l-brackets (which would rust and likely stain the deck). The easiest, least expensive, and sturdiest option, in my opinion, is to use a French cleat.

A French cleat is basically a single piece of wood that has been ripped down at a 45° angle through its centre. One piece will drop into the other easily, making hanging these large boxes a cinch!

Finding the centre can be a bit tricky – there is a hypotenuse calculation that you can do, or you can just test out the spacing on some scrap bits of wood until you have it correct. (guess which I did lol)

Remove the table plate from your table saw, set the blade angle to 45º, and very carefully rip down your 2×4.

Once rip cut, you’ll cut to length; this will depend on the spacing of your deck posts. On one area of my deck I could use a full 4′ section, but on the other two, I had to cut my French cleat to fit on either side of a post.

Use 3- 3 ½” deck or construction screws to attach the narrow edge to your deck with the point facing upwards, and the other to the DIY railing planters with the pointed edge fitting downwards.

You may have noticed that I removed the upper handrail from my deck railing. You absolutely don’t have to, but I wanted my railing planters to tuck just under the lip for a nice, finished edge.

Slowly lower the French cleat on the cedar planter down into the French cleat attached to your deck rail.

It’s tough to see in the photo below, but it sits perfectly and nicely hidden under the deck handrail.

Overbuild: I added additional 3- 3 ½” construction screws from the railing side into the balusters. Safety first.

Adding soil to your DIY railing planters

Calculating the cubic feet of soil needed for your planters is a simple formula of length x width x depth. If you followed these building plans and ended up with an approximate 4′ x 16″ x 12″ deck planter, then you’ll need 6 cubic feet (or .14 cubic metres) of soil to fill it. If you went with a different size, then this calculator will help you determine so you don’t over or under-buy.

That’s it folks! Just over-built boxes that should last you roughly 2 decades (depending on the weather in your area).

I won’t lie, this ended up being a fairly expensive project, partly because I went with cedar over pressure-treated, partly because they are huge, and partly because I built three of them. I believe my total came in just shy of $500 CDN – so about $167 Canadian per planter which includes the landscape fabric and soil.

But, I like to break things down into what I call “rental fees”; if these planters last say 15 years, then my rental fee on each planter is $11.11 per year.

WAAAAY less than the plastic deck planters you buy at greenhouses that always end up cracked and leaking after a season or two.

#girlmath

Even at 4′ long (1.2m) each, these still look somewhat small for the width of my deck!

Mums and leftover summer filler for Fall, I’m thinking wooden Christmas trees lit up with twinkle lights for Winter, and then overflowing annuals for Spring and Summer!

I love them so much!