There has been a trend in the neighborhood towards planter boxes. I don't fully understand why vegetables can't just be grown in the ground like they did when we were kids, but I'm not about to buck this trend. Modern vegetables require way more care and attention than the rough and tough vegetables of yesteryear.
The vegibox as built has final outer dimensions of: Length=72", Width=21 3/4", Height=11 3/4
The frame brings the top of the box to 31" off the ground. After installation on concrete pavers, the top height will be about 32" high which is about normal kitchen counter height. Bringing the planter up to waste height is a definite back saver as you can tend your veggie garden standing upright.
The vegibox consists of a cedar box supported by an indestructable 2x4 pine frame that will most likely be capable of supporting 2 to 3 times the load it will ever see. Definitely overkill on the frame. The box can be separated from the frame. The weight of soil and water will clamp the box to the frame - a gravity clamp. Cedar has good outdoor rot resistance which makes it a good choice for planter boxes. It is also untreated which means that toxins won't leach out of the cedar box into the vegetables. I chose untreated pine for the base because it is strong ( people build houses from 2x4's ) and with a coating of deck stain, will hopefully last a number of years in the outdoors. I prefer to avoid treated lumber even though they stopped using arsenic ( or more accurately chromated copper arsenate) some time back.
Enough rambling - time to start building. With apologies to John Brown who I'm sure spent the day keeping the TV safe.
Step 1: Stuff You Need
- 2x4x96 Kiln Dried Pine studs x 6
- 1x8x12 Cedar Board x 2
- 1x8x8 Cedar Board x 3
- 1x4x12 Cedar Board x 1
- 1x4x10 Cedar Board x 1
- 1-1/4" Star Drive All Weather Self Tapping Screws Box of 100
- 2-1/2" Kreg All Weather Self Tapping Pocket Hole Screws
- Table Saw - for ripping and cutting ends to length. Boards are too wide for my mitre saw
- Mitre Saw - for cutting the 2x4's to length
- Power Drill for making pockets holes and screwing in screws
- Kreg Pocket Hole Jigs and Clamp
- Wood Glue (I prefer Elmers - sets fast and is crazy strong)
- Set Square for checking right angles
- Pencil or pen for marking cut lengths
- A 4ft clamp and a 6" clamp - not strictly neccessary but it serves as a third hand
- Measuring device (steel tape at least 10ft long will work the best)
- 5/8" Forstner Bit for making drain holes. Any other large size drill bit will work. I just happen to like Forstner bits.
- Sunscreen and a Springbok Rugby cap to keep the sun out of your face if you are working outside.
- Personal protective equipment like safety glasses, dust mask and whatever else you feel you need to keep you safe. Power tools can inflict massive amounts of life threatening injury in an instant, so please make sure you understand safe operation of your tools. If not, get training and always read the safety instructions that accompany your tools.
Step 2: Build the Box
The first thing to do is to remove the staples form the boards. I have no idea why, but just about every board had staples in. They come out easily as Cedar is pretty soft wood.
The base is built from 3 of the 8" wide by 6ft long boards. The boards are joined together using pocket hole joinery. This is a quick way to make really strong joints.
On one edge of 6ft x 8" board, set the Kreg Jig for 3/4" and make a pocket at 8 inch intervals. Then slide a second board next to the first and use a clamp to align the left edge and keep the boards together. Set the torque adjustment on the screw driver to prevent stripping the screw out. You can practice on a piece of scrap to get the torque setting right. Cedar is very soft so keep the torque low. Screw in the first 1-1/4" exterior self tapping screw.
Work your way down the board until you have all the 1-1/4" exterior self tapping screws in.
Now make pocket holes on the 3rd 6ftx8" board and screw to the first 2 boards so that you have a base 3 boards wide by 6ft long. All the boards are aligned on the left edge. If the wood is not all exactly 6ft long, the right end will be a bit raggedy. If this is too extreme, you can use a hand held circular saw to trim the far end flush. In my case the boards were all +/- 1/8 inch so I let them be.
Now it's time to do the long vertical sides. Make pocket holes every 8 inches along one edge of each of the two 6ft by 8" side boards. It is useful to clamp the side board to the base panel to keep it properly aligned while you screw the side to the base. Make sure you keep the left edges aligned with the base.
The 8" boards are not exactly 8" wide so use a tape measure to measure the inside distance between the 2 side boards. You should have 2 off-cuts from the original 8" boards that you can use as the end boards. They will need to be cut down on the table saw to match your inner measurement. In my case, the end boards needed to be cut to 20".
Do not cross cut the boards on a table saw with the fence in place. This is very dangerous. Measure the cut length using the fence and then move the fence out of the way before making the cut. Alternately, you can insert a 0.75" thick piece of wood between the edge of the end board and the fence, measure up and then slide the 0.75" piece of wood out of the way so that the edge of your board clears the fence. If you cross cut with the fence in place the board can get wedged leading to damage of the saw, the board and most importantly yourself.
Step 3: Adding Depth
The process of attaching the 1x4x6ft extensions is the same as attaching the 8" side panels. Make pocket holes every 8 inches. Then clamp the 1x4x6ft piece to the top edge of the 8" side board and use the 1-1/4" self tapping screws to attach the 4" board to the 8" board. Theoretically 4"+8" = 12" but lumber dimensions are measured before drying so when lumber gets dried, it shrinks. The final size is always smaller than stated. For example, a 2x4 is actually 1.5" x 3.5"
The ends are attached in the same fashion. Drill pockets on the 3 sides as shown in the photo. A lot of pockets but we want the board to withstand the pressure of the soil.
With the remaining lumber, the long 6ft piece of 1x4 was ripped down to two 1-1/4" wide pieces and screwed to the side of the box both for decoration and to conceal the join between the 8" and 4" wide pieces. The Kreg pocket hole drill does a great job of drilling a counterbored hole. These holes were drilled every foot. The added benefit of these strips is that they will strengthen the boards and help to reduce flexing due to the weight of the soil and water. The base frame will help with this also but we will get to the frame later.
At this point the box should be complete. You can take a break if you wish. Or you can start building the base frame.
Step 4: Frame Legs
Now take a 19" piece and 24-1/2" piece and glue them together with wood glue. Clamp them together to prevent them from moving and counter bore holes on the 19" side. Then use the 2-1/2" Kreg all-weather screws to screw them together. I used 4 screws per leg for the first couple of legs and then dropped to 3. I think 3 is plenty since the faces are glued together.
The Box will be resting on the edge of the 19" piece which is very sturdy. The extended height of the 24-1/2 piece will provide support to the long vertical sides of the box keeping them from bowing out under the weight of soil and water. Practically the sides of the box are plenty strong but I don't take chances and the 2x4's are cheap insurance.
Keep gluing and screwing until you have 6 legs prepared.
Now turn the box over so that the bottom faces skyward. We will assemble the rest of the frame in-situ. I've always wanted to use in-situ in a sentence and now I have!
Step 5: Completing the Frame
5 x 19" long pieces for cross bracing.
4 x 28" pieces for rails across the front and back. Don't cut these until last. Measure your actual dimensions and cut accordingly because if you don't get the 30" pieces exactly right, you can compensate by adjusting the length of these pieces.
2 x 30" pieces for the top.
This will all become clear from the photos.
Attach the legs to each other using 3 pocket holes and glue on either end. When you are done, you will have 3 leg pairs.
Now make 3 pockets holes on each end of the 30" pieces and use these to join the legs together. Use glue in all joints and use the 2-1/2" Kreg screws. A box of 50 screws will not cut it.... buy 100 screws (you get 50 per box)
Now measure the spacing between legs and cut your final rails to match this measurement. It should be around 28" but you may need adjustment depending on the accuracy of your 30" cuts. These are screwed and glued in place 6 inches from the bottom ends (see drawing side view).
With everything screwed together, you now have a rock solid sturdy frame that will carry a ton of weight. Most of the weight is carried by the vertical 19" 2x4 which is the secret to the strength of this design. At least I like to think so! Try breaking a short 2x4... this stuff is very strong.
With the remaining Cedar off-cuts, I made a bunch of "feet" for the legs. This will isolate the pine from ground contact and improve the rot resistance. A 4x4 share of cedar will work fine. You do not have to be precise here.
Step 6: Final Touches
To capture the overflow from the drainage holes, the cross beams of the frame were notched to accept one half of a 2" PVC pipe. The PVC pipe was cut using a table saw. Please be very careful doing this and use a push-stick so that your fingers are far away from the blade at all times. A pipe cap was also slit in 2 and glued to the ends to ensure overflow always runs out of one end (within reason..... install with a slight tilt to the side you want to drain out of)
The notches were drawn onto the cross beams using the slit PVC pipe end as a template and then a jig saw was used to cut the notches. The cuts were smoothed using a rasp and then a file. The slit PVC tube sits slightly below the surface so that there is a small air gap between the bottom of the bed and the PVC tube. This should help things stay dry and prevent mold growth.
The shelf consists of 3 2x4 pieces that are screwed to the lower rails on either side. The shelf pieces are 20-1/2" long. Your measurement may vary if your rails are not exactly centered with respect to the legs. Measure your actual length and cut accordingly. Working this way allows you to make adjustments as you go. If you cut all the wood up front, you have to be very careful to get everything exactly right. Cutting a little later, allows you to correct for inevitable imperfections - this is hand made after all.
Flip the frame over and use pocket hole screws to secure the shelf pieces. The shelf pieces are spaced 4-1/4 apart, measured either side of the center piece.
The final staining was done using Olympic 6 year deck stain. Only the frame was stained. The bed was left natural so as not to contaminate the vegetables. A weight test was conducted - It handles 200 pounds no problem. The volume of the box is roughly 12 cubic feet. The density of potting soil wet is roughly 50 lbs / cubic foot (web sources - not sure how accurate this is ). This means the frame will be supporting 600lbs of soil. Each leg will therefore support 100lbs.
For soil, we followed the recipe for square foot gardening which calls for equal parts of cow manure, peat moss and vermiculite. In our case, roughly 4 cubic feet of each.
And that is that for the making of the planter box. We should be eating plenty of fresh home grown vegetables this season.