Tall planter plans, sized to your space

Parts

Cut list

Kerf 1/8″ included. Every cut runs edge to edge.

Steps

• Tape measure
• Speed square
• Pencil
• Drill/driver
• Clamps
• Safety glasses
• Hearing protection
• Dust mask
• Circular saw or miter saw
• Miter saw
• Staple gun
• Sander, 120 and 180 grit

Underlined words have a short explanation: hover or tap them. All of them are on the glossary page.

1. 1Before you start

   Read every step once, start to finish, before you buy or cut anything. Each step names the parts it uses by letter; the parts list gives their sizes.

   Set up somewhere flat with good light. A pair of sawhorses with a sheet of plywood on top makes a fine work table.

   Wear safety glasses whenever a tool is running, hearing protection for saws, and a dust mask for sanding and for cutting treated wood or sheet goods. Tie back long hair and loose sleeves. Keep children and pets out of the work area.

   • Tip At the store, pick straight boards: hold each one up to your eye and look down its length. Skip boards that bow, twist or have big knots near the ends.
   • Tip Measure twice, cut once. Most mistakes are a misread tape, not a bad cut.

2. 2Cut and label the parts

   Cut every part on the cut list. Cut the longest parts first: if one goes wrong, it can still become a shorter part.

   To mark a cut, hook your tape on the end of the board, make a small V with its point exactly at the measurement, and draw a square line through the point with a speed square. Put an X on the waste side.

   Cut on the waste side of the line, so the blade's kerf (about 1/8″) comes out of the scrap, not your part.

   Write each part's letter in pencil on a face that won't show, and stack the parts by letter.

   Sand the faces before assembly while they're flat and easy to reach: 120 grit, then 180.

   ✓ Lay the parts out and count them against the parts list. Measure a few: if one is off by more than 1/16″, recut it now.

   STOP. Let the saw reach full speed before it touches the wood, keep both hands clear of the blade's path, and never reach under a board you're cutting. Support long boards on both sides of the cut so the blade doesn't pinch.

3. 3Pick the boards and the screws

   Cedar for the planter: look for boards with mostly reddish-brown heartwood. Pale yellow-white streaks are sapwood, which rots years sooner; keep those streaks on the inside or skip the board.

   Sight down each board at the store like a rifle barrel. Skip boards that twist, bow more than about 1/4″ over 8′, or have big loose knots near where you will cut or screw.

   Use exterior screws only: coated deck screws (labelled for treated lumber, "ACQ compatible") or stainless steel. Plain steel reacts with the tannins in cedar and leaves black streaks running down from every screw. Indoor wood screws and drywall screws rust and snap outdoors.

   For food plants, both cedar and modern treated wood (labelled CA or ACQ, not the old green CCA, which hasn't been sold for homes since 2004) are widely used. If you want to be extra careful, staple landscape fabric inside so soil doesn't touch the wood.

   • Tip Buy one extra board of the most-used size. A split or a mis-cut then costs you nothing but a few dollars.
   • Tip Cedar splits easily: predrill every screw within 2″ of the end of a board with a bit about the size of the screw's inner shank.

   ✓ Every board is reasonably straight, and the screw box says exterior, coated for treated lumber, or stainless.

4. 4Build the front and back panels

   Lay two corner posts (C) flat and parallel, outside edges 14 1/2″ apart.

   Lay the front boards (A) across them, good face up. The lowest board's bottom edge sits 1 3/4″ above the post bottoms: that bit of post is the foot that keeps the box off a wet patio. Work up from there, boards edge to edge with no gaps. The top board ends flush with the post tops.

   Each board sticks out 3/4″ past the outside of each post. That space is where the side boards tuck in. A scrap of 1×6 held against the post is a perfect gauge.

   Predrill and drive two 1 5/8″ screws through each board end into the post, about 3/4″ from the board ends.

   Build the back panel the same way.

   • Tip Drill the pilot holes with a bit about as thick as the screw's inner shank. Cedar splits if you skip it this close to the end.

   ✓ Every board overhangs the posts by the same 3/4″ on both sides, and the diagonals of the panel match.

5. 5Add the side boards

   Stand the two panels up facing each other, posts inside, and hold them with a helper or a clamp across the top.

   Fit the side boards (B) between the overhanging ends of the front and back boards, so their faces sit against the posts. Each row lines up with the rows on the front.

   Two 1 5/8″ screws through each side board end into the post. Then drive one more screw through the front board into the end of each side board to close the corner.

   ✓ All four corners are closed with no gap you can see light through, the rows line up all the way round, and the planter stands on its four feet without rocking.

6. 6Fit the false-bottom cleats

   The floor rests on two cleats. Mark a level line on the inside of two opposite sides 12 3/4″ up from the bottom of the feet: that is the top of each cleat.

   Set a cleat (D) under each line between the posts. Predrill and drive three 1 5/8″ screws from the outside through the side boards into each cleat, plus one screw through the cleat end into each post.

   Why so high? A false bottom 14 1/4″ up holds 14″ of soil, which is all most plants need, and the box below stays empty. You buy less soil and can still move the planter.

   ✓ Lay a level across the two cleats: it reads level both ways.

   STOP. Every soaked cubic foot of soil weighs about 100 lb, and the cleats carry all of it. Don't skip any screws.

7. 7Lay the floor slats

   Drop the 3 floor slats (E) onto the cleats, running from cleat to cleat, with 1/2″ gaps between them.

   One 2 1/2″ deck screw through each slat end into the cleat.

   The gaps and the open corners next to the posts are the drainage holes. Water must be able to leave, or the roots rot.

   • Tip Cut a 1/2″ scrap as a spacer between slats.

   ✓ The slats sit flat on the cleats, don't rock, and water poured on them falls straight through.

8. 8Put on the cap

   Miter both ends of each cap piece (F) at 45° so the outside (long) edge is 17 1/2″.

   Lay the four pieces on top, overhanging the outside of the boards by 3/4″ all round. Spread waterproof glue in each miter joint.

   Predrill and drive two 1 5/8″ screws down through each piece into the post below it. The cap covers the end grain of the boards and posts, which is where rot starts.

   • Tip Cut the first pair, check them on the box, then cut the second pair. If the miters gap, adjust the saw by half a degree and recut.

   ✓ The miters close tight at all four corners and the overhang is even on every side.

9. 9Line the box

   Staple landscape fabric over the floor and up the four inside walls to about 1″ below the top of the boards, every 6″ along the top edge.

   Fabric keeps the soil in and lets water out. Don't use plastic on the floor: it holds water like a tub.

   ✓ No bare floor shows, and a cup of water poured on the fabric drains out under the planter.

10. 10Protect it from the weather

    Decide how you want the planter to look in five years. Bare cedar and bare pressure-treated wood both weather to silver-grey and still last many years; doing nothing is a real option.

    To keep the colour, use an exterior oil or semi-transparent stain: brush it on, let it soak in 15 minutes, then wipe off whatever is still shiny. Renew it every one or two years. Avoid clear varnish or polyurethane outdoors: sun cracks the film, water gets under it, and it peels.

    Leave the inside of anything that holds soil for food plants bare. Finish only the outside faces and the top edges.

    • Tip Finish on a dry day above 50°F with no rain forecast for 24 hours.
    • Tip Oil-soaked rags can catch fire on their own as they dry. Lay them flat outside to dry or keep them in a sealed metal can of water.

    ✓ The finish is dry to the touch everywhere, with no wet or shiny puddles in corners.

11. 11Place it and fill it

    Set it in its final spot before you fill it, on a level surface. On a deck, the feet keep the boards off the wet deck and let air under it.

    Fill with potting mix: about 1.7 cu ft, which is 2 bags of 1.5 cu ft. Firm it lightly with your hand, water it, and top up where it sinks.

    • Tip Potting mix shrinks as it settles in the first month. Add a few inches more after a few waterings.

    ✓ Water drips out under the planter within a minute or two of watering.

12. 12Finish

    Ease every sharp edge and corner with 120-grit sandpaper so nobody gets a splinter.

    Sand all over with 180 grit, always along the grain (the direction the wood fibres run). Scratches across the grain show through stain.

    Wipe off the dust with a barely damp rag and let it dry.

    Outdoors, use an exterior finish: a penetrating deck oil or exterior stain, or primer and exterior paint. Leave cedar bare to weather silver if you like. If it holds soil for food plants, leave the inside unfinished.

    Let it dry for the time on the can before using it.

    • Tip Try your finish on a scrap of the same wood first: stain looks different on every board.