Raised Garden Bed Construction

Ok, so I’ll admit this is probably going to be a little dry, but when I was trying to figure out how to build my raised beds I appreciated all the info I could find.  Unfortunately, when I was building these I hadn’t yet thought of doing a blog, so there aren’t a lot of photos.

The first step was figuring out what we wanted.  I knew that I wanted to max out the growing space in the part of our yard that we allotted for veg.  I had an area about 22 feet by 13 feet.  I figured three middle beds measuring 3 feet by 12 feet with two beds on either end measuring 2 feet by 12 feet was the most efficient use of space.  This left about 22 inches, or just less than two feet between each of the beds; just wide enough to fit our wheel barrow through (an important consideration when you realize that your beds will in fact need to be filled with soil at some point).

The next step was figuring out what we wanted to use as a construction material for the sides of the beds.  When reading up on raised beds I quickly realized one of the really great things about them is you can build them out of nearly anything.  New lumber, old lumber, rocks, bricks,  old tires, basically anything that will hold the amount of dirt you want and that won’t poison the food you plant there.  That’s an important consideration as well.  Many people might be tempted to use treated lumber because it will last a long time and is relatively cheap.  Don’t.  Although apparently the chemicals used to treat lumber today aren’t as bad as they used to be, there is still much controversy over the safety of growing fruits and vegetables in soil contained in treated lumber beds.  Think about it, you’re growing your family’s veg next to something soaked in a chemical cocktail. I figure you might as well play it safe and choose another option, especially considering how many other options that are available.

After thinking about it I chose to use new lumber for our raised beds.  That left us with two choices.  My first choice was to use cedar planks.  Cedar contains natural substances that help slow rot.  This means the beds can last longer than non-cedar lumber beds.  I’ve read estimates that using cedar your raised beds will last 15 years plus.  Not bad.  The issue I had with cedar however was the price.  My wife is on maternity leave at the moment, meaning our household income is somewhat reduced (young parents – you’ll know what I mean). With this in mind, I decided on using spruce lumber.

So, with my wife’s blessing (the most important consideration) I purchased the lumber needed to build our five new raised beds.  I decided on using 2×8 planks, one on top of the other two get a height of about 15 inches. This was important to me as our existing top soil was not very deep (in our area we have about 3 to 5 inches of top soil resting on clay that is compacted to what seems like the density of granite).  I wanted to the veg that we grew to be able to have a deep root system and that was only possible with having a deeper layer of soil.  Also, the higher the beds the less you will exert yourself bending over to work your garden. To reduce the amount of wasted wood I purchased 16 foot planks.  This way each bed would only need four planks with a minimum of wasted material at the end.

The posts I chose to use were 4×4 cedar.  I tend to go a little overboard with things like this.  You probably don’t need to use 4×4 posts.  2×4 posts would probably work for most beds.  I however want the option of building my beds even higher at some point in the future.  I bought 8 foot 4×4’s so that each post would be 24 inches and I wouldn’t waste any wood.

You’re also (probably obviously) going to need either some scews or nails.  I used screws.

Once the lumber was delivered I cut each 16 foot plank to 147 inches to accommodate the 1.5 inches of each end plank.  I then cut each of the 8 foot 4×4’s into 2 foot sections.  I then pre-assembled one 147 inch plank to four posts.  This allowed me to use each as a template of where I would need to dig my holes for the posts.

Six of the pre-assembled sides stacked together.

Then, using each pre-assembled side as a template I would figure out where I needed to dig the post holes.  Once digging the holes was complete (this was the most labour intensive part of building these beds, largely due to the presence of the aforementioned clay and the fact that a cement truck had obviously picked our yard to clean itself our before our house was built) I ensured each side would rest level on the ground.  This involved a little bit of trenching with a shovel.  Ensuring your beds are level is important, just remember they don’t have to be perfect, you’re not building a house here.

My 2 1/2 year old son Liam helping me build the beds while wearing both a toque and a hat. New style I guess.

Once each adjacent lengthwise side was in the ground and leveled, I back filled the post holes with clay. I then added the ends (either 2 feet or 3 feet planks).  After that I then added the second layer of planks, screwing each into the posts as I went.

The first two beds completed.

I repeated each of the above steps for the other four beds.

Once they’re built you’ll need to fill them with something.  There are options here as well. In Mel Bartholomew, the ‘creator’ of square-foot gardening, insists that you use what he call’s Mel’s Mix.  This is a mixture of one part vermiculite, one part peat moss and one part compost.  There are advantages to using this, less weeds (at first) and it is extremely lite.  It is however expensive, especially for the amount that I needed.  There’s also the matter of buying that many bags of vermiculite (usually comes in smaller bags).

Some use top soil.  This may be the cheapest and every landscaping supply outfit carries screened tops soil and will deliver it right to you.

I chose a premium garden mix from North Edmonton Landscaping Supplies. This is a mixture of screened topsoil, peat moss, garden sand and mushroom compost. I had nine yard delivered, though about a third of that went into some of our other garden beds. You’ll have to figure out how much you need before you order it as you probably only want to pay for delivery once.  If you figure out how many cubic feet you need, there are 27 cubic feet in a yard.  If you’re not math inclined, the landscaping supply company will be able to help you figure it out.

Now you all you need to do is get the soil (or whatever you decided on using) into your beds.

Five raised garden beds completed and filled with dirt. Now for planting…

The other great part of raised garden beds – you don’t have to be done here.  There are many options you can add to them.  As you can see in the above photo, we chose to add a grid with string to aid in our own version of square-foot gardening (I hope to cover this in another post).  You can make a grid out of wood stakes as well.

Raised beds are tailor made to add such things as floating row covers, cold frames and trellis for growing vertical. I hope to cover these in other posts as well.

Anyway, there you have it…raised garden beds.  If you have any questions about the construction or anything else relating to the raised beds that I built, please do not hesitate to ask.