Drag an orange dot to resize; a dashed line shows when it snaps to a common size. Click a dot, then use the arrow keys to nudge 1/8″ (hold Shift for 1″). Every size can also be typed in the panel.
Checks
- The lid slopes 22°: steep enough to shed rain.
- On sunny days above about 50°F, prop the lid open or the plants overheat.
- Site rules shown are typical, not your town’s. Confirm with the building department before you build.
Shopping list
| Qty | Item | Est. |
|---|---|---|
| 4 | 2×6 cedar, 8′ (board) | $76.80 |
| 1 | 4×4 cedar post, 8′ (board) | $25.60 |
| 2 | 2×2 cedar, 8′ (board) | $14.40 |
| 1 | Polycarbonate twinwall panel, 6 mm, 4′ × 8′ (sheet) | $65.00 |
| 1 | Roofing screws with sealing washers (bag of 100) | $14.00 |
| 1 | 3″ exterior screws (box of 75) | $12.00 |
| 1 | 2 1/2″ wood screws (box of 100) | $10.00 |
| 2 | 8″ strap hinge, exterior (each) | $18.00 |
About $236 · rough estimates, check the store
Parts
| Part | Qty | Length | Width | Material | |
|---|---|---|---|---|---|
| A | Back board Rip to 4 3/4″. | 4 | 36″ | 4 3/4″ | 2×6 cedar |
| B | Front board Rip to 5″. | 2 | 36″ | 5″ | 2×6 cedar |
| C | Side board Rip to 4 3/4″. | 4 | 21″ | 4 3/4″ | 2×6 cedar |
| D | Side board, tapered Rip to 4 3/4″. Cut the top edge from 4 3/4″ at the back end to 1 1/8″ at the front end. Make a mirrored pair. | 2 | 21″ | 4 3/4″ | 2×6 cedar |
| E | Side board, tapered Rip to 4 3/4″. Cut the top edge from 4 3/4″ at the back end to a point at the front end. Make a mirrored pair. | 2 | 11 7/8″ | 4 3/4″ | 2×6 cedar |
| F | Back corner post | 2 | 17 1/2″ | 3 1/2″ | 4×4 cedar post |
| G | Front corner post | 2 | 10 1/2″ | 3 1/2″ | 4×4 cedar post |
| H | Lid rail | 2 | 36″ | 1 1/2″ | 2×2 cedar |
| I | Lid stile | 2 | 23 7/8″ | 1 1/2″ | 2×2 cedar |
| J | Prop stick Notch at 6″ and 12″. | 1 | 18″ | 1 1/2″ | 2×2 cedar |
Cut list
2 × 2×6 cedar, 96″ → A 36″ · A 36″ · C 21″ each
2×6 cedar, 96″ → B 36″ · B 36″ · C 21″
2×6 cedar, 96″ → C 21″ · D 21″ · D 21″ · E 11 7/8″ · E 11 7/8″
4×4 cedar post, 96″ → F 17 1/2″ · F 17 1/2″ · G 10 1/2″ · G 10 1/2″
2×2 cedar, 96″ → H 36″ · H 36″ · J 18″
2×2 cedar, 96″ → I 23 7/8″ · I 23 7/8″
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
- Table saw or track saw for ripping
- Sander, 120 and 180 grit
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.
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.3Build the back and front walls
Lay the two back posts (F) flat, 1 1/2″ in from each end of the back boards. Screw 4 back boards (A) across them, edges tight, bottoms flush. Two 3″ screws per board per post.
Build the front wall the same way: 2 front boards (B) on the front posts (G).
✓ Both walls are square.
4Add the sides
Stand the walls up, 24″ apart outside to outside, posts inside.
Fit the side boards between them, the full ones (C) first, then the tapered ones (D, E) on top. Screw through the walls into the side board ends and into the posts.
✓ Diagonals match. The sides slope from 19″ at the back to 10″ at the front.
5Build the lid
Lay the two rails (H) 26 7/8″ apart outside to outside with the stiles (I) between them at the ends. Two 2 1/2″ screws through the rail into each stile end.
Cut the twinwall to 36″ × 26 7/8″, flutes running down the slope. Screw it to the frame every 8″ with the washer screws. Do not overtighten.
✓ The lid frame is square and flat.
6Hinge the lid
Set the lid on the box, flush at the back and 1″ past the front. Hinge the back rail to the back wall with 2 strap hinges.
Cut the prop stick (J) and notch it at 6″ and 12″ to hold the lid open.
✓ The lid closes flat all round with no rocking.
7Place it
Set it on level ground with the low side facing south. Bank soil against the outside walls for extra warmth.
8Finish
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.
Conceptual layout, material estimate and assembly guide from the sizes you entered. Not engineering, not a building plan, not stamped or approved. Confirm measurements on site; follow local codes and product instructions; anchor tall pieces before use. Using this plan means you accept the Terms of Use.