DIY Concrete Planters

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We haven't completed many DIY projects lately, but finally crossed one off the list: concrete planters! Jd and I have been wanting to make something with concrete for a while and finally spent a weekend completing this project while we had some free time. 

You will need:

  1. A styrofoam or polystyrene board
  2. Silicone caulk
  3. A homemade mold or old cabinet (we used a cabinet)
  4. Small plastic irrigation tubes (found in the plumbing irrifation section of your hardware store)
  5. Several screws (because taking the mold apart is easier to do with screws rather than nails)
  6. Quikrete 5000 or countertop mix (both work just fine)
  7. Something to mix the concrete in (we used an old cat litter container, but they sell mixing pans at the hardware store). If you are using a bucket, only mix small batches of concrete at a time, otherwise it will be difficult to stir.
  8. Hammer or electric sander
  9. Gloves (concrete will dry out your hands like crazy)
  10. Tarp or blanket
  11. Sandpaper

Since we do not own many tools, we walked through several alleys before stumbling across something we could use as a mold. We found this small shelf with two racks. If you have a saw, I suggest making a custom mold for your planter because you can pick the size. We were limited to 8x12, but it worked out for the better and we ended making two (2) molds. The cabinet we used was made of slick, melamine board, which worked great because the concrete may stick to regular plywood. 

First, you need to seal the inside of your mold using your silicone sealer. This prevents the conrete from seeping out of the bottom and sides.

To ensure that no concrete seeped onto our kitchen floor, we even glued an additional piece of wood to the bottom our mold. If you're doing this project inside like we did, then I would definitely suggest taking this extra step. We places books inside the mold to make sure the mold and piece of wood were sealed together.

Next, take your Styrofoam and cut out several pieces that will be the placeholders for the inside of your conrete mold. We cut out three (3) pieces (with a kitchen knife oops) and glued them together. Then glue the group to the bottom middle section of the mold.

Next, push the irrigation tubes into the styrofoam to act as drain holes. Let the styrofoam and silocone dry for an hour or so before pouring in concrete.

***If you're making a tall mold, tie rope around the outside walls to keep it from expanding***

Mix up your concrete and get ready to pour it into the mold. Concrete is really easy to mix . If you don’t know how to mix the concrete you can watch this video or this video on YouTube. Pour the concrete onto the styrofoam about an inch thick.

At this point you need free the air bubbles in the wet concrete by knocking on the sides of the mold. If you have an electric sander to vibrate the bubbles out this is when it would come in handy. Really all you need is a hammer and to knock on each side for a few minutes. After you have hammered down all sides you will want to let the concrete dry for 24 – 48 hours.

After 24-48 hours,  you can release the side of the mold and remove the concrete piece. If you tapped all of the air bubbles out your mold should be nice and smooth (ours came out slightly rocky because we were unable to tap the inside of the mold). Begin cutting out the Styrofoam. This stuff is going to get everywhere so if you have a tarp I would suggest doing it on that. You can use a spoon to scoop out the foam, which ever works for you. Once its basically all out you can sand the random pieces out with some sandpaper.

When all the styrofoam is out you can use a knife to cut down the plastic drainage holes. Then use the rest of your silicone caulk to seal the inside so no water can damage the concrete. Try not to get any silicone into the drain holes which will result in clogging.

If you want to go a step further you can get concrete sealer. Lowes was out when we tried to get some so we opted for spray sealer or lacquer, which in my opinion looked just as good. Let it dry completely in between coats.

Now you can choose what will go inside of your planter! We decided to grow moss in ours because it's easy to maintain and looks great! We put rocks in first to help filter the water so that it didn't get moldy, I suggest taking this extra step. The steps are similar to another project we did, which you can find here.