How to Build a Raised Bed

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How to Build a Raised Bed

May 8 2011 9:42:20 am EST

Topics: Gardening,

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Benefits

• Better on the back

• More control over soil conditions: Since you’re building up, you add the soil you want. If you distrust the soil below, you can always put pavers under your raised bed to completely block root penetration or leeching.

• Improved drainage

• Faster spring thaw

• Readily accepts a hoop house for early spring and late fall plantings

Materials

Any type of brick or stone can be stacked to create a raised bed. Also, lumber can be used. In this article, I use pressure treated lumber.

People are often concerned over leaching of chemicals from pressure treated lumber. This concern stems from chromated copper arsenate (CCA) that was used in pressure treated lumber. Arsenic leaching was a concern. There is plenty of research on the topic indicating that arsenic leeching was minimal, but this has become a non-issue for most people, simply because preservatives have changed.

Now, there is a new preservative used. ACQ®, which stands for alkaline copper quat. ACQ is a mix of copper and a quaternary ammonium compound, nicknamed quat. Small amounts of copper and quat do leach, but nothing in ACQ is considered hazardous by the EPA, and no ingredient is a known or suspected carcinogen. The wood is expected to last as long as CCA-treated lumber.

So if you’re buying pressure treated lumber, just make sure it uses ACQ. If you use CCA lumber, don’t despair. Arsenic leeching has been shown to be minimal. You may reference this excellent article for more information on CCA, ACQ, and other pressure treated lumber concerns in raised bed gardening.

For this project, I created boxes measuring 2 feet by 2 feet 2 inches. I used 5/4” x 6” x 8’ pressure treated lumber. Each piece was $4.77. If you want something beefier than 5/4”, check out this article

I cut each 8’ piece of lumber into 4 pieces, 2’ long. When you put together all 4 pieces, you have a box measuring 5 3/4” high. If you want a higher raised bed, just stack boxes.

To join the pieces, I used 2” x 2” X 8’ pressure treated lumber as corner posts.

I stacked the boxes 3 high (17 ¼ inches) to accept fruit trees. So if one 8’ piece of lumber makes a box, you need 3 pieces to make a stack of 3 boxes. It’s simple enough to add or remove height for your own purposes.

Make sure when you buy your lumber that it is all uniform width, otherwise, you will have to rip it down to uniform width to create a level box.

Tools

• Circular Saw
• Speed Square
• Brad Nailer with 2” brads (optional)
• Drill
• Drill bits for pilot holes and countersink
• Exterior grade screws with appropriate drill bit (I used 2 inch screws)
• Tape measure
• level

• mattock or shovel

Instructions

1. Cut the lumber:

Cut lumber to the dimensions of your raised bed. I wanted approximately 2 foot square boxes for my fruit trees. From an 8 foot piece of lumber, I cut 4 pieces to a length of 2 feet. Since all the pieces are uniform length, one side of the box ends up being about 2 inches longer. This is due to the thickness of the lumber pushing out the dimensions of one side. If you want a perfectly square box, measure the thickness of the lumber; multiply this measurement by 2, then subtract this from two pieces. In the case of my lumber, I would have subtracted 2 inches from two pieces, to make the box a perfect 2’ x 2’.

Since I stacked my boxes 3 high, I needed to cut 12 pieces at a length of 2 feet. In order to have a straight cut, I used a speed square to guide my circular saw. Once I had all the pieces, I worked on the corner posts

The corner posts are easy. Just cut your 2” x 2” lumber to the height of your raised bed. In my case, I multiplied the width of the lumber I was using by the number of stacks (3) to get a height of 17 ¼”.

I cut 4 corner posts to the final height. If you are building an exceptionally long raised bed, consider adding additional supports along the sides.

2. Build two sides

If you cut two of your sides shorter to build a perfectly square box, use your shorter pieces for this step.

When I had all my pieces cut, I stacked 3 pieces of 5/4” x 6” x 2’ together on a level surface to form a side. I made sure the good faces of the wood were facing down. I then placed a corner 2” x 2” post on both ends. I used two straight pieces of scrap wood to help keep everything tight together. If you have clamps, feel free to come up with your own system. The important thing is that everything is straight and tight.

When everything is lined up, drill evenly spaced pilot holes with countersinks along your 2” x 2” posts. Pilot holes are critical for preventing the wood from splitting. Otherwise you have to use thicker, more expensive posts. I drilled two holes for every 5/4” x 6” x 2’ piece of lumber. The important thing to remember is that you are joining two sides with each corner post: make sure to leave enough room between holes so you can screw your other side to the corner post.

Now all you do is sink screws in your pilot holes. I used 2 inch exterior grade screws because they joined both pieces without passing through the other side. Once a side is drilled together, repeat the procedure for another side.

3. Build the final two sides

Now that you have two assembled sides, place them on a flat and level surface. This is where the brad nailer comes in handy. Stack one completed side up just as it would be positioned when finished. Now take a 5/4” x 6” x 2’ piece and carefully line it up with an end of your finished side. With your brad nailer, nail the free lumber to the edge of the finished side. Don’t nail it to the 2” x 2” corner post, you’ll screw it to the post later.

The brads will hold your pieces together while you take your other finished side and nail it to the other end of your 5/4” x 6” x 2’ piece. Once both sides are nailed together, your finished sides should be free standing. Now your hands will be free to nail in the remaining pieces to form a box.

The brads will provide some flexibility to make sure your box is square and level. However, you don’t want to move your box around just yet. The brads are not nearly strong enough to hold everything together.

To finish off, drill in pilot holes on the sides you nailed in. The pilot holes should lead to the 2” x 2” corner posts without hitting the screws that you already sank in from the finished sides.

Once the pilot holes are drilled, sink in the remaining screws and you should have a completed box.

4. Build your raised bed.

You can place your box on any surface you like. For this project, I placed it over a ground down tree stump. Since I wanted to plant apple trees and the old tree roots prevented me from digging down, I simply placed the box on top. There was enough soil between the root system and the box to level it out. I used a level to check all the sides. I added and removed soil with a mattock until everything was just right. I then filled the box with potting soil and leveled out the surrounding soil.

After I planted my apple trees, I put some red mulch on top. I must admit, it looks very nice. I hope to build a raised bed vegetable garden down the road.

I look forward to hearing your comments if you build one!

Dates:

2011

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