Are you thinking about adding a planter box to your garden? A wooden planter box may be the first thing that comes to mind. That’s because wood is affordable, and chances are you already have some planks leftover from other DIY projects.
Stone is more resistant than wood, and you won’t have to worry about mould or rotting either. You don’t need any special skills to build a stone planter box. It’s a bit more complicated than making a wooden one, but you can manage without headaches.
Even staking the stones is easy once you get the hang of it. And you can use stone to create complex geometric patterns, something you can’t do with wooden planks.
How to build a stone planter box step by step
Decide on the size, gather your materials, and then start building the box. Let’s take a closer look at each of these steps.
Materials and tools you’ll need
- stone bricks
- larger stones for the top layer and masonry glue (optional)
- gravel base rock
- exterior-grade adhesive
- sheet of landscape fabric (optional)
- measuring tape
- rubber mallet
- hand tamper
- 24” spirit level
Step 1 – Decide the size of the planter box
Where is the planter box going to go? People often build stone planter boxes along the walls of the house or along the fence. Planter boxes are also great for decorating the driveway. You can even build a stone planter box in the middle of your garden, just make sure it won’t look out of place.
You have to choose between building a long planter box or several smaller ones. From a purely artistic point of view, one continuous long box might be a bit dull. Smaller ones allow for more variety in your garden.
Head outside and do some measuring. Deciding on the size of the planter box beforehand is essential as you’ll need to make sure you get enough stone. Calculate the perimeter of the rectangular box and multiply that by the number of layers you’re planning to use.
Once you have the total figure, head to a DIY store and they’ll help you figure out how much stone you need. It all depends on the size of the stone bricks you buy. Don’t forget to ask how much gravel you need for that type of planter box.
Tip: The height of your stone planter box depends on the type of plants you want to grow. For flowers, a 6” high planter box is enough. For vegetables, you can go as high as 12” so the roots have plenty of space to spread out.
Step 2 – Mark out the area
Grab some wooden stakes and start marking out the area of the stone planter boxes.
Start from one corner, preferably one that is close to a wall or fence, if that’s where you’re building your planter box. Place your first stake. Then use the measuring tape to mark the length of the box and place a second stake.
Next, you’ll have to measure the area for width. Make sure each size is equal. Place the remaining two stakes and check that the sides of the planter box are at a 90-degree angle.
Step 3 – Level the area
This step is especially important if your garden sits on sloping terrain. You want to level the ground as best you can, so your planter box won’t lean to one side.
Stake out the approximate location for your planter, get your shovel, and do some digging. If you want your stone planter box to be stable, you need to dig 6” into the soil.
Next, you need to spread at least 3 inches of gravel base rock. Use a rake to help.
Once it looks like the gravel base rock is spread evenly, you’ll have to compact it. For that, you’ll need a hand tamper. This part will be a bit hard on your back as you need to apply force to flatten the gravel base until it’s firm.
Step 4 – Start building the walls
If you don’t have much experience with bricklaying, this part may seem tricky. No need to be nervous, though. The hard part is laying the base layer. The rest is easy.
Start with one of the long sides of the rectangular box. Work your way around the perimeter of the box until you get back to your starting point. Keep the rubber mallet and spirit level to hand. Don’t hurry! Check that each stone is level before moving on to the next one.
Once the base layer is in place, have a good look at it to make sure you have a perfect rectangle. Then you can start stacking the next layer.
Use the adhesive to glue the stones together. Make sure to brush the stones in the base layer before applying a few blobs of glue on the upper side of each of them. Put glue on the whole length of one side and then start placing the second layer.
Don’t forget to alternate blocks to offset the seams. This will make your planter box more durable and look better, too.
Tip: When you’ve finished a layer, use the spirit level to check that the walls are perfectly vertical. Correct any irregularity with your rubber mallet.
You can build the top layer with the same type of stones as the lower ones. Another option is to buy larger bricks for the top layer, as these will give your planter box a more polished look.
If the top stones are large enough, you can even sit on the margins of the planter box to admire your plants or tend to them. This will be much easier on your back.
Important: If you decide to go with a wide top layer, make sure to use masonry glue or mortar when laying the stones.
Step 5 – Fill the stone planter box
Now that you’ve built your stone planter box, it’s time to fill it up.
You can use some gravel to create a thick drainage level. This will protect plant roots from mould, but also the planter box itself. If water accumulates at the bottom of the box, it might freeze in winter, leading to cracks in the stone walls.
Choose the gardening soil that’s most suitable for your plants and fill the planter box almost to the top.
Tip: To prevent dirt from seeping through the cracks, you can put a sheet of landscape fabric over the drainage gravel layer. To keep it in place, secure the margins underneath the top layer of stones.
How to make a stone planter box fast
The most difficult and back-breaking part of building a stone planter box is levelling the area. To bypass this step, you can use black Styrofoam pads, which you can find at any DIY store or online. Styrofoam pads are mainly used for building paver patios.
If you find that the pads are too thick, you can cut them in half lengthwise using a table saw. A retractable knife will also work, but it’s a time-consuming operation. Simply place the Styrofoam pads under the first layer of bricks. The material has enough give to make sure the layer will be level.
You can also skip the fabric layer. It’s not the laying it inside that takes time but securing it under the top layer of stones. If dirt does start seeping through the seams, you can easily clean that after all with a garden hose.
Planter box stones you can use
If you want to build a cheap stone planter box, look out for clearance sales. They may even deliver it to your front door free of charge. Just ask—you never know!
On the other hand, clearance stuff is sold cheaply for a reason. It’s not necessarily about the quality. Maybe it’s just stones that don’t look all that good.
If you’re willing to spend a bit on this project, buy weathered stones. They look way better than the cheaper flat ones.
Sometimes, these suppliers also throw alignment plugs and wall caps into the deal. The caps are not really necessary. But the alignment plugs will save you a lot of work as you won’t have to worry about the walls being perfectly vertical.
Another option is to go with river stones or whatever rocks you can gather yourself. This is an excellent option for building a rustic planter box. This method does require a lot of work and a skilled eye as you’ll have to figure out a way to fit uneven stones together. Also, instead of glueing the stones together, you’ll have to work with mortar, which can get messy.
The bottom line
A stone planter box is more durable than one made from wood and it doesn’t have to be expensive if you can find stone at a discounted price or collect your own.
In terms of skills required, the most complicated part is levelling the ground where the planter box will go. It’s best to use a gravel base rock to level the area, using Styrofoam pads is quicker and easier.
High stone planter boxes are better for growing vegetables. If you want to plant flowers, a 6 inches high planter box will be enough.
That’s about it. This DIY project calls for some work, but nothing you can’t manage, right?