The real thing ended up remarkably like the digital plan. I'm impressed, and for that I have to thank Patrick, who made this plan into a reality.
Step 1: The Plan
Creating a detailed plan also helps you conserve your resources and use only as much material as you really need. We decided to make the long planter 12 feet long, 1 foot wide, and 18 inches deep. Short one in 5 x 1 x 18. The seats are 4 feet and 11 feet, and 15 inches deep.
Once you have the plan, it's time to get the materials...
- Wooden boards for the outside - cedar, cypress, or black locust are most advised for outdoor use as they are all very rot-resistant. I asked a cabinetmaking friend of mine what he thought of black locust, since it's all the rage in "green" circles, and he said it's good, but very hard to mill. In the end, our local place only had cypress or cedar anyway, and the cypress was very cheap (as it turned out, mainly because they were crappy boards), but seemed like a good bet.
- Plywood for the inside- We went with pressure treated plywood, since it will stand up best to the elements.
- Pressure-treated 2x2 - for the corners
- 1 1/2 inch, 14 gauge steel square tubing- for the structure. Oh by the way, you're going to have to know how to weld...
- Inch by 1/2 in steel channel - For holding up the seat boards.
- Decking screws - specially coated stainless steel screws to hold up to the elements.
- Plastic lining
- Rocks, dirt - to fill. I got my topsoil amended with leaf compost (50/50 mix) in bulk from a local place in Alexandria. $15 for half a cubic yard, which didn't quite fill up the whole planter.
- 115V flux core wire feed welder
- Abrasive cut off saw
- Chop Saw
- Cordless drill
- Vacuum - this wasn't technically used in the creation of the planters, but you're sure going to need it afterwards...
Step 3: Build the skeleton
Make sure you have enough support. Don't forget, when you add wood, rock, and dirt, this things going to way a ton (possibly literally). So err on the side of too many legs. Plus, it makes it less dangerous 20 years down the line when this thing is rusting out. Patrick couldn't stop thinking about the potential lawsuit down the road. But I guess there's plenty of time to save for that contingency...
Step 4: It's ply time
Drill holes in the bottom of the plywood, approximately a dime-sized hole every 6 inches (we did kind of a zigzag pattern, so 6 inches along the hypotenuse).
You might want to spraypaint the metal where it touches the plywood, as the chemicals in the pressure-treated plywood can make the metal corrode faster. In the end, we actually just lined the plywood with plastic which folded over between the plywood and the metal, so it should not be a problem.
When you line the box with plastic, make sure to cut the bottom open so that the water can drain out of the holes you've made.
Step 5: Attach the boards
Next, sand them and seal them, or don't. I haven't decided, but I'm leaning toward either plain old butcher block conditioner (oil and beeswax) or teak oil. I'd like to keep it natural, and I like that gray, weathered look that the wood gets eventually.
Step 6: Finish it and watch it grow...up!
Next up: plant seedlings and watch them grow!
Next up after that is probably building a rainbarrel irrigation system, but at least give me some time to bask in the glow of a mostly complete project...