Step 1: Planning the dimensions

Before I go over the construction of this planter box, I would like to mention that making a quality planter box does not require working with expensive equipment. In fact, I am using a range of inexpensive & easily accessed tools.

Here are the tools I'm using to build the planter:

1) Task Force compound miter saw (Lowes ~$100.00)
2) Black and Decker drill (Fred Meyer's ~$30.00)
3) Craftsman Flat and Phillips screwdrivers (Sears ~$15.00 as a set)

That's it!

Most of you DIY types likely already have these tools in your arsenal, and if you don't - here's that opportunity you've been looking for to purchase that miter saw!

Now for the planning stage:

The first thing I had to do before starting this project was to figure out the maximum size the planter could be. I started with the maximum dimension figures instead of a set of desired dimensions because when you design and build something from scratch you often find yourself at the mercy of the raw material dimensions. In my case I decided to use a cedar tongue and groove material for the sides, which are 3.25 inches across when glued together.

OK, let's do some quick math:

My preferred planter length is 72" long, when I did the math I got the following lengths:

21 boards * 3.25" = 68.25"
22 boards * 3.25" = 71.50" 
23 boards * 3.25" = 74.75"

It's clear to see I can't make a perfect 72" side. To pick the final dimension I also have to take into account the legs. They are going to add an additional 3" the to each side. That brings the final lengths to 71.25",  74.50", and 77.75" respectively. You can see in the picture below that the maximum length I can achieve is 76.5", and my preferred length going into this project was 72". Since I would like this planter to fit snug in the space I decided to go with 22 boards and the final length of 74.75". Using this same logic, I figured out the width of the planter at 19.25" when my preferred was only 18". I am now using 5 boards, because if I would have went with 4 boards the planter would only be 16" in total, and that would be too narrow for the rest of the dimensions to look proportionally correct. Sometimes you also have to think about the visual aesthetics of the piece as well.

 

As far as the height of the box, I asked for my wife's opinion. I'm  6'3" so I prefer everything to be built taller than average. She came out and put her hand out at the height she thought it should be. It appeared to be roughly 2' 5" from the ground so I went with 30". 

By working through all of that up front I went from wanting to build a planter box that would be 72" x 18" x ?" to a planter that is going to be 74.75" x 19.25" x 30". Knowing the I am going to need space under the planter for a drain and possibly future expansion of its capabilities, I decided the box itself would only be 2' deep with 6" of clearance.

Below is a 1/12 scale Power Point drawing of the planter that has been further scaled to fit the page.

 

In Step 2: How to construct the planter, I will be going over the specific design considerations that are required to build this planter as well as the actual construction of the outer frame (all sides connected).