1. Gather Materials and Supplies
Our raised garden beds measure approximately 4x6 feet each (51.5x72 inches to be exact). You can think of the structure as a box with no top or bottom. We designed this raised garden bed to be small enough for you to easily reach the middle of the box. If you have short arms, you may want to consider shortening the side by 51.5 inches.
To build a box, you will need the following supplies:
4) 2x8x8PT wood
8) 2x4x8PT wood
5 lb box of 3" long stainless steel screws
2) 10ft corrugated galvanized steel sheet
Foundation paver blocks (optional, but highly recommended)
2. Cut all your wood to size
The easiest way to do this project is to cut all the wood at the same time. We'll have all the parts ready, rather than just building it and then continuing to assemble it when everything is ready.
There are only three different sizes of wood for the main frame. Here is your cut:
8) 17 inches long 2×4 pieces
4) 72 inches long 2×4 pieces
4) 48 inches long 2×4 pieces
For shorter sections, you can use a miter saw if you have it handy. We set up a site for our site so that we could make the same length cuts over and over. This makes the job of all the repetitive clips fast.
That's it! The 2x4s make up the entire frame of the raised garden bed. Inside, we will place and secure the corrugated steel. But for now - let's cut the pieces needed to make the main box. Once you have cut the above pieces, you can move on to the next step.
Remember - if you want to make two raised garden beds, double everything we said. The point of these instructions is to make a garden bed to keep it simple.
3. Assemble the Raised Garden Bed Top and Bottom Frames
If you haven't reached the final location for this step, you may want to move outside. Start by securing the bottom rectangle of the bed together. Use those 3" stainless steel screws. These will stand the test of time and resist rusting. Of course, if you live near the beach - all bets are off!
Use a large rafter square to make sure you keep the box square when holding the planks together. Go ahead and make the top and bottom frames before attaching the vertical struts. Remember - we try to be more efficient by making as many repetitive tasks as possible!
4. Build vertical pillars
Since we will have two 17" vertical pieces connected to each other before they are attached to the top and bottom frames, we want to go ahead and prepare these first. Start by placing three screws on the edge of one of the short boards.
We use impact drivers to connect the boards together.
5. Attach the vertical struts to the top frame
Once assembled, attach the vertical struts to the bottom frame. Do this by pre-drilling with a 1/8" twist drill bit. Follow up screwing the vertical pieces onto the bottom frame.
6. Attach to bottom frame, level and square
Now, did I mention you attached the struts to the top frame? I did not lie. Once all four double posts are connected, it's time to get a friend to help you turn the whole thing over and place it on top of the bottom frame.
Then do your best to level and straighten everything. Start your drilling and tightening process again. However, do one more round of squaring everything before tightening the final fasteners.
7. Prepare the base for your raised garden bed
Once you're ready to place your raised garden bed, you'll need to mark its final location and prepare the area. You can use a tape measure and spray paint or some other marking material to create an exact outline of where the box will be.
If you want to put the box on the ground, it needs to be level. This might mean digging a "ditch" for the 2x4 to sit in so they don't wobble or tilt.
We actually decided to put our raised garden bed on a circle of pavers. This will keep the pressure-treated wood off the ground - extending the life of the bed. This may be a standalone project. You'll need a flat surface to place this glorious masterpiece, so to speak. This requires some preparation of the area so that the raised garden beds lie flat on the ground.
8. Cut the corrugated steel to size
Once the frame is placed, you can start cutting the corrugated steel to size. It goes inside the frame. The idea is to completely separate the dirt from the pressure-treated wood. That's what makes these 25-year-old or more raised garden beds.
If you can, cut out these panels with a pair of metal scissors. Metal saws are really messy.
9. Use a stapler to fasten the corrugated steel to the wood
We recommend using a narrow crown stapler to secure corrugated steel to the inside of a pressure-treated raised garden bed frame. Some great wireless tools we love include the RyobiP360 Narrow Crown Stapler and the Milwaukee M18 Narrow Crown Stapler.
The height of the corrugated steel should allow it to fall slightly below the frame into the ground. That's a good thing, but you might need to dig a bit. It ensures that the runoff water is drained completely through the pressure-treated wood into the ground.
We actually recommend running a large silicone bead across each of the four corners before filling the box with dirt. This further prevents water from flowing through the steel and hitting the pressure-treated wood.
10. Place your top
Instead of pre-cutting the top 2×8 boards, we put them on top and marked them in place. Once we knew the amount of overhangs we liked, we cut them to 45 degree miters. Pre-drilled both ends, then secured them together with more stainless 3" screws.
You will also want to screw these 2×8 boards into the frame from the top along the perimeter. Overall, we like that they sit more or less in the center of the frame. This allows you to have as much inner overhang as outer overhang.
When we're done using our raised garden bed, you can easily sit on top without feeling like it's going anywhere.
11. Fill in the topsoil and enjoy!
The final step involves filling the raised garden bed with topsoil. Hopefully you can find some cheap fill and sprinkle nice garden soil on top to grow your veggies or plants. You may also want to consider incorporating some gravel for proper drainage. Broken rock might just as well be enough.
As a tip, use a hose to flush out dirt while filling and release any areas that might be problematic or create large voids later. If you need advice, check out our best garden hose article for inspiration.
