How to Build Simple Planter Boxes

May 11, 2019

When Kyle &  I bought our house, one of the first things I wanted to do was start a garden. I’d always wanted to grow a bunch of food and be able to live off what we grew for a while. It’s amazing to be able to walk outside and pick your own fruits and veggies – knowing exactly where they came from and how they were brought up. So last year, armed with my book about making the most of a garden in small spaces, I built myself a mighty 3’x3′ plot. I bought a stack of bricks from Lowe’s and made an embarrassingly shallow plot that I proceeded to plant way too many starter plants in, and my glorious little garden was born. It turned out pretty well, but after trying to plant 20sqft worth of plants in my 9sqft plot, I quickly developed the yearning for a much larger gardening space. This year I wanted an actual glorious garden & since I meant business, I started sketching out a plan to build two wooden planters that would fill some unused space in my yard. 

We have a really small side yard so I had to get creative with the dimensions of my boxes so they would cover the maximum amount of space without taking up the whole yard.  The dimensions that worked best for our situation were two boxes that measure 2.3′ x 10′ and 1.8′ x 7′ which would sit in an ‘L’ formation along the borders of the yard. This would allow them to fill an unused space and be out of the way of the rest of the yard.

The process of figuring those details out is definitely step one of building planter boxes.  

 

Step One

Measure your space and obtain your maximum dimensions

 

When looking at the space you have and determining what size your box (or boxes) should be, it’s important to not only measure, but map out the area. Line the space you want the box to be with bricks or sticks or anything you have laying around. This will help you visualize how big the box will actually be in real life. It’s one thing to draw out the perfect dimensions on paper, but as we all know from buying something in a huge store then bringing it home to find it takes up twice the space we thought, it’s best to see it in YOUR space before making a final decision.

Step Two

Prepare your space

It’s important that your box is placed on a plot that is flat and free of vegetation. My side yard is all zeroscape, so it was just a matter of moving rocks out of the way and leveling the ground. However, if you are building your box in the middle of your grassy backyard, you should shovel out the grass in that space, and loosen the dirt below with a spading fork. 

In my case, I had a bunch of bricks left over from my 3×3′ garden last year, so I decided to make a platform for the boxes to sit on. This also allowed me to create a level surface for the boxes without doing much digging. The outer sides of my yard are higher than the middle, so the platform is one brick tall on the ends and two bricks tall in the middle.  

Step Three

Plan your board size & type of wood

After doing lots of research, I’ve found that the best types of wood to use for a fruit/vegetable garden are cedar, redwood, hemlock, fir, pine, or ACQ pressure treated wood. Cedar and redwood are naturally water-resistant but are typically pretty expensive. Hemlock, fir, and pine will work well for this application, but typically aren’t very long-lasting.

After sorting through all the controversy with pressure treated lumber, I decided that option was the best for me. Alkaline Copper Quaternary (ACQ) treatment is one that’s been deemed low-risk by the EPA and designated safe for use around humans, pets, plants and vegetables. Avoid using creosote-treated wood for this project.

To decide which type of wood was best for my project, I spent quite a while on my hardware store’s website researching sizes and prices. I found that 16′ pressure-treated boards that were 5.5″ tall and 1″ thick would work well for my budget and my plan. Buying 16′ boards allows you to save more money than buying a bunch of shorter boards that might already be the length you need. The only problem is getting those longer boards home. Most home project stores that sell lumber will do a few wood cuts, but typically not more than five or so. (At least not without getting really grumpy.) 

Step Four

Plan your cuts & get materials

The easiest way for me to plan how much wood to buy and what cuts to make, is to first know exactly what boards I need. Using a 10′ x 3′ box as an example, I know I need four sides, two of them being 10′ long and two being 3′ long. I also know I need eight support beams that are just shorter than the height of the box. The larger your box is, the more support beams I would use. You don’t want your box bowing out or falling apart! I wanted my boxes to be pretty tall, so I made them three boards high – 5.5″ x 3 = 16.5″ tall. (You could easily make these two boards high and save on lumber and soil costs.) 

I decided to make the boards for the front of the box take up the full 10′ so when you’re looking at the front panel, it has a more professional look & you don’t see the end pieces of the side panels. This means that the width of the two 10′ panels is taking up part of my maximum 3′ (36″) width for the side panels. Since the two panels are 1″ thick, this leaves 34″ for the width of the side panels. 

Following this logic creates the following list:

  • Six 10′ boards (front and back panels)
  • Six 34″ boards (two side panels)
  • Eight 15″ 2x4s (eight support beams)

The best way to proceed after knowing exactly what boards you need, is to fit as many boards as you can into the longer boards that home improvement stores stock. For this example, I would buy three 16′ boards and cut one 10′ and two 34″ boards out of each. (You’ll have ~4″ excess.) That would give you three 10′ boards and all six 26″ boards. Then I would buy three 10′ boards to finish off the sides. The eight 15″ 2x4s can be perfectly cut from a 10′ board with no excess. So that

 

leaves you with a shopping list of three 16′ x 1″ x 5.5″ boards, three 10′ x 1″ x 5.5″, and one 10′ x 2″ x 4″.  You will also need a drill, wood screws, a drill bit that is slightly smaller than your screws, and a Phillips bit. The wood screws you select need to be long enough to go through the 2×4″ and approximately halfway through the side panel. For my boxes & this example, the screws should be 2.5″ long.

Step Five

Assemble the four panels

One of my favorite parts about this design is how seamless the front and back panels are. You can’t see any screw heads – just wood boards that come together to create a box. In order to achieve this look, the support beams that hold the boards together should be screwed to the inside of the box. This is an important detail to remember when laying out the boards to create your side panels. The opposite side to the one you’re screwing into is going to be the one that’s visible so make sure it’s the best looking side!

The easiest way to go about fastening the support beams is to lay them across a table or bench and hold them tightly together with C-clamps. The side panels of the box are the easiest to assemble so start with those!

1. Align the bottom of the 2×4″ support beam with the bottom / center of the panel. Since the support beam is shorter than the panel, you want the beam to set lower than the top edge of the box. This way you can potentially cover the tops of the support beams with soil.

 

2. Clamp the support beam down so it doesn’t shift.

3. Drill pilot holes in each place you wish to drill a screw. The image to the right shows how I oriented my screws, but just make sure that each panel board has a screw that is holding it in place.

4. Drill the wood screws into the pilot holes.

Next are the front and back panels – the only assembly difference is step one:

1. When aligning the support beams on the two ends of the front and back panels, it’s important that you account for the width of the side panels. Hold up the side panel to the end of the front panel, then place the support beam up against it.  It’s important that you take special care when aligning these pieces because this support beam will be used to assemble the box. If the beam is crooked, too far out, or too far in, your  

side panel won’t align properly with the front and back panels. Once you have the distance from the ends figured out, again align the bottom of the support beam with the bottom of the box. The other two support beams for the front and back panels should be equally spaced between the ends to provide the most support.

2. Follow steps 2 – 4,  above.

Step Six

Assemble the box!

Now that all of your panels are complete, it’s time to put it all together! Depending on the dimensions of your box, assess whether or not it will be feasible to carry the box to it’s final location, or if you should assemble it in place. When you’re ready to assemble, stand up all four panels in the orientation they’re going to end. The support beams should be flush with the ground so the panels should stand on the own; but if not, prop them up with spare pieces of wood (or anything really.)

All that’s left is to screw the side panels to the support beams of the front & rear panels. As you can see in the photo, I used two screws per board and lined them up so they look more aesthetically pleasing. Be sure you drill the pilot hole like you did for the support beams so you don’t crack any of the boards. 

 

Step Seven (optional)

Line the box with plastic liner

If you purchased a weather/water resistant wood or are not worried about the longevity of your planter box, it’s not imperative that you do this step. However, I wanted to take every precaution to make sure the wood on my box was protected from enzymes in the soil and trapped water. Though it’s a given that this box will not last forever, wood decays over time and having soil/water constantly in contact with it will expedite this process. 

That being said, I purchased a roll of heavy duty painter’s plastic and a staple gun and lined my boxes before adding soil. Though you can see the plastic peeking above the soil line, it’s worth it to me for the peace of mind that my boxes will last longer.

When lining the box, make sure you don’t line the ground in addition to the sides. As you water your garden, you don’t want to trap the water at the bottom, but allow it to drain into the ground below. 

 

Step Eight

Fill the box with soil!

Perhaps the most expensive part of this project is purchasing soil. This is something to take into consideration when determining the height of your box in the beginning. Regardless, once you get to this step, measure the inner dimensions of the box, with the height being the distance from the ground to where you want the soil line to be. Use these dimensions to get the volume of soil you need, and purchase it! If you’re buying bags of soil, they’re typically sold in sq ft so it’s useful to measure your box in this dimension. 

 

Step Nine

Plant your plants!

Now the fun part – fill your box with fruits, vegetables, herbs, flowers, whatever you want! This year I started some plants indoors and transplanted them in addition to planting some seeds straight into the soil.

I hope your garden provides lots of foods or flowers, as well as something fun to do during the spring and summer! Though gardening can be a decent amount of work, it’s a fun way to escape the indoors and enjoy the (literal) fruits of your labor. 

If you build a planter box using this post, don’t forget to tag me in your photos (@thegoblinden) – I’d love to see what you created!