A DIY concrete planter–it’s easier than it looks

A few weeks back we shared a few ideas for making an entry more welcoming, in which we included some photos of a concrete planter we made and a promise to follow-up with a how-to.

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We’re here today with the how-to.

I first made one of these probably 7 or 8 years ago. It was my first step into the realm of cast concrete. I was super-excited at the time to have pulled it off. I loved that the materials were cheap and readily available.

That first planter was just the beginning. I later went on to make counter tops and a tile back-splash from concrete. Recently I made the top for our bathroom vanity with cast concrete. (I’ll write up a post on that one soonish.)

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The concrete countertop in progress.

The cool thing about concrete is that it’ll take whatever shape you pour it into. I don’t remember exactly where I got the idea for this particular shape and form? It may be a copy of one I saw somewhere else. It may be a unique design. I can’t quite remember. This one is essentially a copy of the one I made back then. I improved the build a bit and did a better job creating the form for the cast.

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Here’s the complete form–keep reading for directions.

I love sharing this kind of project because it’s one of those kind of things that looks impossible when you first see it, but it doesn’t require advanced skills or special tools. There’s something empowering about tackling a new project like this, and I really hope that someone out there reading this will try their hand at making one (and let us know how it goes for you).

This won’t be an exact step-by-step, but it should be detailed enough that if you decide you want to make one, you can figure it out from my directions. Feel free to ask follow up questions in the comment section if you have any, and we’ll do our best to help out if you plan on trying this. It really is a cool project to do, and unlike many things we tackle it could be done in a weekend.

Suggested Materials:

  • 1-2 bags of Quickrete 5000
  • Melamine board or plywood
  • Wood screws
  • 1×1 inch lumber (for toekick reveal)
  • 8 L shaped brackets (To hold the inner box together)
  • Cardboard
  • Foam pipe insulation
  • Scrap lumber (for handle on inner box)

Tools:

  • Table saw
  • Drill
  • Hot glue gun

The first thing was to build a form, which requires an outer box (which is the size of the finished planter) and an inner box. The concrete gets poured in the space between the two boxes.

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Step 1- Create outer box.

The outer box was fairly straight forward. The key to the concrete form is that you have to be able to remove it after the concrete cures. This wasn’t a problem with the outer box. The inner box that creates the void for planting was a different issue.

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This is the outer box. I built it from melamine coated particle board. This is a great choice for cement casting. In this case it was an old desk that got broken when we moved into this house. I took it apart and cut up.

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Here you can see how I screwed everything together. I pre drilled all the holes with my cordless drill.

Because all the screws in the outer box could be easily accessed after the cement cured, I just built a simple box with the dimensions I wanted. I added a couple of more details.

I used some foam pipe insulation to make drain holes in the bottom of the box. I also put some small strips along the edges to create a toekick detail to make the planter appear lighter. The toekick wood is placed in without any glue or screws. I cut them so that they would sort of wedge in tight without having to screw them in place. Since the wood is not screwed or glued in it should be easy to remove.toekick A DIY concrete planter  its easier than it looks

The black pipe insulation is hot glued to the bottom of the outer box. It’s just tall enough that the inner box will sit right on top of it. This will create a cylinder shape void in the bottom of the finished planter. Perfect for drainage.

Step 2- Create the inner box.

The more difficult box was the inner box. This one needs to be able to be taken apart from the inside, since the outside of it will be up against the cured cement. The trick is to have all the screws holding the parts together inside the box instead of on the outside since the outside of the box won’t be accessible to take the thing apart when the cement is cured. I solved this by using some strips of wood in the corners. I suppose you could use some L shaped brackets like these:

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This would be an easy way to put the inner box together from the inside so that it could be taken apart later.

I didn’t use them because I had some lumber handy and just made some wooden braces for the corners instead.

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Here’s all the parts for the inner box. The wood strips are going to be used to hold it together.

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Once the inner box was all done I had to figure out how to suspend it inside of the outer box. A  strip of wood running across the top of the inner box was just what I needed. You can see that it’s not attached to the outer box. This is by design. I planned to fill the bottom of the outer box with cement, and then put the inner box in place before filling the sides. (But I’m getting a bit ahead of myself.)

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Step 3- Add decorative details.

I decided to add a bit of design detail to the side. Some cardboard, scissors, and a hot glue gun were all that was needed.

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The cardboard will create some nice detail on the sides of the planter. You are looking at the inside of the outer box with the inner box removed.

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Here’s a birds eye view of the inner box all done, with wood strips for the toekick and pipe insulation for drain holes.

That’s the form. Pretty simple really. For extra measure you can caulk all the joints to make sure that everything stays put, but for this project I didn’t bother. Off to Home Depot I went in search of concrete.

Step 4- Mix the concrete.

I went with the Quickrete 5000. This is what many people use for counter tops. I bought 2 bags. They are cheap–around 8 bucks, I believe.

This was a good choice. It has gravel in the cement mixture which gives it strength. I mixed it up in a wheel barrow using a shovel and hose. The trick is to put the water in a little at a time until you get the right consistency. You don’t want it runny or it’ll be weak. You don’t want it too dry or you will get voids.  Think of thick oatmeal and you have the right consistency.

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Quickrete 5000. This is a good choice. It’s supposed to set faster than other brands.

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This is about the right consistency. Not too runny and not so dry.

 Step 5- Fill the form.

Once the cement was mixed, Rita and I shoveled it in. I took the inner box out and put a layer of cement in the bottom of the outer box.

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Once the bottom of the box was full right up to the top edge of the pipe insulation I put the inner box in place. I then filled up the sides. I used a small garden trowel to make sure I had the form full and packed tight.

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The form almost filled and smoothed out.

To get everything packed in tight and remove all voids and air bubbles, we needed to vibrate it for a bit. An electric palm sander placed up against the side did the job nicely. We moved the sander around to all 4 sides and vibrated for 5 or so minutes. What I was looking for were air bubbles coming to the surface. When I didn’t see any more air bubbles I was done.  If you don’t have a sander to use you can use a hammer and gently tap the side to accomplish the same thing.

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No, it’s not warm enough for Rita to dress like this yet. We did this project last summer.

Step 6- Remove the form.

I let the planter sit overnight so that everything firmed up before taking it apart.

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Part way through the un-molding process.

It was a bit of a chore to get everything taken apart. The inner box was a bit difficult. It took some prying and banging with a hammer but it finally came apart. I think my mix was a bit dry because you can see some voids and open spaces.

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We’re not too worried about it though. We like the rustic look.

Just so you know, the thing weighs a million pounds. It took a bag and a half of cement. If you’ve ever picked up one of those bags you know how much they weigh. We moved it into place with a hand truck. The good news is that it isn’t going to be moved by wind or rain or anything else.

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It’s held up fine so far (which is now through a fall and winter). I’m looking forward to the bamboo plant we put in it growing new shoots this spring.

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Our original idea was to make two of these and place one on each side of the front landing. We decided not to make the second one as we think it would be too crowded. We may think about making a square one or two for the steps. It might be nice to have plants leading up the steps to create a visual line of green all the way up to the front door.

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Anyway, I like working with concrete. As soon as I can find all the pictures I’ll share how we made a cast concrete counter top for our bathroom. This was a bit more complicated form to make but the process was very similar.  Stay tuned.

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 So, what do you think?

Ready to jump in and make one of these? Have any opinions on whether we should make more for the other steps? Anything you’ve tackled that looks much more difficult than it really is? Hope you’ll share your experience and opinions in the comments.