24″ × 72″ garden trellis plans

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, or circular saw in two passes, for 4×4 posts
• Post-hole digger
• Wheelbarrow and hoe for mixing concrete
• 4′ level
• Line level and string
• 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 trellis: 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.

   Pressure-treated pine: read the end tag. Parts that touch soil, sit in wet mulch or go in the ground must say "ground contact"; "above ground" lumber is fine for everything else. New treated boards are often wet and heavy: stack them flat with scrap sticks between them for a week or two in the shade so they dry and stop twisting.

   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. The copper in treated wood eats plain and zinc-plated steel within a few years. Indoor wood screws and drywall screws rust and snap outdoors.

   The posts are always ground-contact pressure-treated: they sit in wet soil and concrete for decades. The rails, lattice and cap are cedar.

   • 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. 4Call 811 and check the spot

   At least 3 working days before you dig, call 811 (or use call811.com). It's free. They send people to paint or flag buried gas, electric, water and cable lines near where the trellis will go.

   Check your property line on your survey or plot plan, and ask your town about setbacks, easements and whether this needs a permit.

   Pick ground that drains: not a low spot where puddles sit after rain, and not over a septic field.

   STOP. Don't dig until the marks are down. Hitting a gas or power line can kill you and is expensive to repair.

5. 5Mark the post holes

   Stretch a string where the face of the trellis will be, a little longer than 24″. Plants grow toward the sun, so the face usually points south or west.

   Mark 2 post centres along the string, 20 1/2″ apart; the end marks are 1 3/4″ in from where the outside edges of the end posts will be. Spray a small circle of marking paint at each.

   Keep the trellis at least 12″ in front of a wall or fence so air moves behind the plants; still air breeds mildew.

   ✓ The marks are on the string, 20 1/2″ apart centre to centre.

6. 6Dig the post holes

   Dig 2 holes 10″ wide and 30″ deep with a post-hole digger.

   That depth is 24″ for the post plus 6″ of gravel underneath so water drains away from the post end.

   Make the holes slightly wider at the bottom than the top, like a bell. Frost then can't grip the concrete and lift it.

   Pour 6″ of gravel in each hole and tamp it with the end of a 2×4 or the post itself.

   • Tip Your town knows the frost depth: it's how deep footings must go so winter frost can't push them up. Enter it in the options and the holes will be dug deep enough.

   ✓ Every hole is 30″ deep before the gravel and 24″ deep after it.

7. 7Set the posts plumb

   Stand a post in each hole. Run a string between the end posts at the height you want, to line up the ones in between.

   Hold a level against one face of a post until the bubble is centred: that face is plumb. Then check the face around the corner. Both faces must read plumb.

   Brace each post with two 1×4 or 2×4 boards: screw one end to the post and the other to a stake hammered into the ground, one brace on each of two sides at right angles.

   ✓ Every post is plumb on two faces, in line with the string, and the braces hold it there when you let go.

8. 8Mix the concrete

   You'll use 4 bags of 80 lb concrete mix for the 2 post holes. Mix one or two bags at a time in a wheelbarrow: concrete starts to stiffen in about 30–45 minutes (faster on a hot day), so only mix what you can place right away.

   Pour about 2 quarts of clean water into the wheelbarrow first, then empty one bag on top. (Each 80 lb bag needs about 3 quarts in total.)

   Mix with a hoe or square shovel: pull the dry powder from the corners and bottom into the wet middle and chop through it. Keep going until there are no dry pockets.

   Add the last of the water a cup at a time, mixing between each.

   Get the thickness right. It should look and feel like thick oatmeal or stiff peanut butter. A hoe dragged through leaves ridges that stand up, and a handful squeezed in a gloved hand holds its shape. Too dry: it crumbles and won't stick together, so add a little water. Too wet: it flows flat, water pools on top, and the concrete will be weak and crack. Then add some dry mix from a spare bag.

   • Tip More water makes concrete easier to push around and much weaker. Resist the urge.
   • Tip Rinse the wheelbarrow, hoe and shovel before the concrete sets on them. Don't wash concrete into drains or onto the lawn: let leftovers harden in a scrap box and throw them out.
   • Tip Buy one more bag than you need. Running out halfway through a pour is the most common mistake.

   ✓ Even grey colour throughout, no dry powder, no puddles of water on top; a ridge made with the hoe stands up.

   STOP. Wet concrete is caustic and burns skin. Wear waterproof gloves, safety glasses, long sleeves and long pants. Open bags slowly and wear a dust mask: the dust has silica. Rinse any concrete off your skin right away.

9. 9Fill the holes

   Shovel concrete into each hole around the post. Every 6″ or so, poke it hard with a stick or a piece of rebar to work out air pockets.

   Fill to about 1″ above the ground and shape the top into a little mound with a trowel, sloping away from the post so rain runs off.

   Check plumb again on both faces while it's still wet, and adjust the braces if needed.

   ✓ Posts are still plumb and in line after the concrete is in.

10. 10Let the concrete cure

    Concrete hardens by reacting with water, not by drying out, so keep the concrete around the trellis posts damp for the first 7 days: mist it with a hose morning and evening, or cover it with plastic sheeting held down at the edges.

    Keep it from freezing for the first week. Don't pour when it's below 40°F (5°C) or frost is forecast in the next two days. On hot days, pour in the early morning and shade it.

    You can walk on it or remove braces after 1–2 days. Wait 3 days before putting real weight on it. It reaches full strength in about 4 weeks.

    ✓ The surface is hard and grey-white when dry, with no powder when you rub it.

11. 11Trim the post tops level

    The posts were cut 2″ long on purpose, because holes are never dug to exactly the same depth. Now mark the real tops.

    On the post standing on the highest ground, measure 72″ up from the ground and make a mark. Carry that height to the other 1 post with a long level on a straight board, or a string with a line level pulled tight.

    Wrap a speed square around each post at the mark and draw the line on all four faces.

    Cut on the line with a circular saw from two opposite sides (the blade won't reach through a 4×4 in one pass), or with a handsaw from a step on a sturdy stepladder.

    • Tip Brush a coat of end-grain preservative (copper naphthenate, sold as "end cut" treatment) on each fresh cut of treated wood: the treatment doesn't reach the middle of the post.

    ✓ A level laid across the tops (on a straight board for the far post) reads level, and every cut is square to the post.

    STOP. Never cut above shoulder height. Stand on a stable platform so the saw is in front of your chest, and wait for the blade to stop before lowering it.

12. 12Fit the rails

    In each space between posts, fit a top rail (B) flush with the post tops and a bottom rail with its bottom edge 10″ above the ground.

    Set the rails 3/4″ back from the front faces of the posts (a scrap of 1×2 held against the post face is the perfect gauge), so the lattice strips will finish flush with the posts.

    Toe-screw each rail end into the post: two 3″ screws angled in through the rail face about 1″ from the end, one from the top edge side and one from the bottom.

    • Tip Predrill the toe-screw holes at a 30° angle; started straight, the screw just splits the rail end.

    ✓ A level on each rail reads level, and the rail fronts are the same distance back from the posts all along.

13. 13Screw on the vertical strips

    Set 1 vertical strips (C) in each bay, 8 1/2″ apart on centre, running from the bottom of the bottom rail to the top of the top rail.

    Hold each one plumb with a level and drive one 1 5/8″ screw into each rail, predrilled.

    • Tip Cut a spacer board as long as the gap between strips: set it on the rail, push the next strip against it, screw, move on.

    ✓ Every strip is plumb and the spaces between them are even; measure at the top and at the bottom.

14. 14Screw on the horizontal strips

    Lay 9 horizontal strips (D) across the front, the full 24″ width, 7 9/16″ apart on centre. The lowest lines up with the bottom of the bottom rail and the highest with the top of the top rail.

    Drive one 1 5/8″ screw into each post, then one 1 1/4″ screw at every crossing with a vertical strip. Predrill every hole: 1×2 splits if you look at it wrong.

    ✓ The squares are square: measure the diagonals of a few openings; they match within 1/8″.

15. 15Fit the cap

    Centre the cap (E) on the post tops, overhanging 1 1/2″ past each end and about 1″ in front of the lattice, so rain drips clear of the top strips.

    Predrill and drive two 3″ screws down into each post.

    ✓ The cap is flat on every post with no gap you can slide paper into.

16. 16Protect it from the weather

    Decide how you want the trellis 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.

    Pressure-treated wood must dry before any stain or paint. Sprinkle a few drops of water on it: if they bead up, wait; if they soak in within ten minutes, it is ready. This can take a few weeks to a few months.

    • 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.

17. 17Plant and train the climbers

    Plant climbers about 12″ in front of the trellis, not against the post: the concrete and dry soil at the post starve roots.

    Tie young shoots loosely to the lowest strips with soft garden twine or cloth strips. Twining plants (beans, clematis) find their own way after that; roses need tying every few weeks.

    Weave new growth through the lattice rather than letting it bunch on top, where it catches wind.

    ✓ Ties are loose enough to slip a finger under, so they don't choke the stems as they thicken.

18. 18Finish

    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.