Here's another one I did a few years back, but documenting the project now for Instructables.

I had some leftover railroad ties from another project, so came up with this idea as a way to make some very strong shelves for a new raised garden. It is strong enough to support many heavy ceramic pots and the weight from their soil, water, and the plants as they grow.

They turned out really well and have been in use for 3 seasons now with no needed fixes or improvements since the initial build.

Another great advantage to this project is I can move these around the yard if needed (not easily, but at least possible). The raised bed these replaced was constructed from stacked (and construction adhesive bonded) cinder block filled with dirt to get it to this height. So that was pretty permanent.

This also has the added bonus of creating an additional partly shaded area underneath for plants that cant tolerate full sun.

CAUTION: Railroad ties are soaked in creosote as a preservative, which is toxic. All railroad ties you will find for sale in Landscape Centers or Nursery's were removed from old railroads, so the toxicity levels are much lower than when they were first produced and installed by a railroad company. That said, you want to wear gloves when handling them as a precaution. Also, the shaded area I mentioned above should not be used for anything edible, since water from above may carry some of those chemicals down with it.

Supplies

Recycled Railroad Ties
1" Electrical Conduit (EMT)
Cheap Plastic Containers to Mold the Concrete
Heavy Strap Ties
Outdoor Wood Screws
Cheap Plastic Bucket/Pail
Standard Concrete

Tools:

Wood Spade Bit (1-1/8")
Drill
Metal Cut-Off Saw
Vibrating Sander (Optional)

Step 1: Railroad Ties

The railroad ties I used were:

9 Inch Wide
7 Inch Thick
8-1/2 Feet Long

At the place I purchased them from, these were the smaller of two available sizes.

NOTE: If the place won't allow you to pick from the pile, find a different place. At around $25 a piece, they are too pricey to risk getting badly warped or damaged ones.

Step 2: Electrical Conduit

Also called EMT for Electrical Metal Tubing. Unthreaded is easiest to work with.

Cut these to the length you require per this equation:

Conduit Length = Desired Final Raised Bed Height - 4"

(This will allow for the conduit to penetrate the RR Tie fully minus 2", and be embedded into the concrete footing fully minus 2".)

Step 3: Drill Holes & Install Conduit

Using a 1-1/8" sharp spade bit, drill each hole for the conduit to a blind depth 2 inches less than the thickness of your RR Tie. (See image above.) Hole center spacing from the edge was 2".

1" EMT has an outer diameter slightly larger than 1.125", so the conduit will need to be hammered into the hole, but this makes for a very tight and permanent fit. (No glue is needed.)

TIP: Use a block of wood on top of the end of the conduit to hammer against to limit damaging the conduit end.

Step 4: Pour the Concrete Footings (Bases)

Get some cheap plastics buckets approximately this size:

8" Diameter at Base
10" Diameter at Top Opening
12" Tall

These will be destroyed when removing them after the concrete has set, so use something cheap. I know I got some cheap pails at Ace Hardware that were less than $5 each, but could not find a link.

Cut/drill holes that are the proper spacing for the two pieces of conduit into the bottom of the pail
Install the pail over the two conduit ends
Adjust the height so the tips of the conduit will be 2 inches below the surface of the concrete
Place duct tape over ends of conduit to keep concrete from going into the hole
Brace and support the pail from beneath (Even this gallon or so of concrete will be very heavy. See red arrow in image above.)
Level the pail in relation to the RR Tie (It helps to do this step on a good level surface. I used my concrete patio floor)
Fill each pail with concrete and allow to setup overnight at a minimum. A soupy mix will help to get a smoother finish

TIP: If you have a vibrating wood sander, use that to help settle the concrete in the mold and get bubbles to rise to the surface. Just lightly press it against the side of the pail and move from the bottom to the top going all the way around.

Step 5: Break Away the Pail Molds

After waiting at least a full 24 hours (longer is better), its time to break away the molds.

Step 6: Stabilize Each Pair by Connecting Them Together

So, individually, these are not stable (at this height) on their own. Position two next to each other and use a Heavy Duty Strap Tie to connect them together. Use wood screws (not nails) appropriate for outdoor use and fill every possible hole in the strap.

I used two closely spaced to each other at both ends and one additional one in the center.

Step 7: Finished

Thanks for taking the time to read through my Instructable. Please send me any questions or comments you might have. I try to answer them all. Stay safe and healthy! Happy Gardening!