The smart compost.

Choose and prepare the site

Choose level, well-drained ground with convenient access and some shade. Avoid tree trunks, drainage channels and boundaries where local rules require clearance. For the standard build, remove turf, level a 1,050 × 1,050 mm area and compact 100 mm of coarse gravel.

For liquid capture, use a level paving base under the timber plinth. Leave at least 800 mm clear in front so the collection drawer can be removed without tilting it.

Check: The lid can open fully, the compost hatch can lift out and the capture drawer has a straight path forward.

Cut, label and protect the timber

Cut parts A–K square and label hidden faces. Ease exposed edges, then sand to the finish maker’s recommended grit. Treat cut ends where required. Finish exterior faces before assembly, leaving hidden joint faces clean if the coating instructions require it.

Check: All four posts match and opposite slats are equal. A twisted frame will make the hatch bind.

Build the two side panels

Lay two posts parallel, 810 mm apart between their inside faces. Starting 55 mm above the foot, fasten nine side slats across the posts with 11 mm spacers. Drill pilot holes and use two 50 mm exterior screws at each end. Repeat for the opposite side.

Dimension check: nine 95 mm slats plus eight 11 mm gaps occupy 943 mm, leaving 2 mm below the top of a 1,000 mm post when the first slat starts 55 mm up. Measure diagonals before tightening; the panels should be square and mirror one another.

Join the back and form the front opening

Stand the side panels and clamp them plumb. Fit nine rear slats at the same levels. At the front, fit three fixed slats across the upper 330 mm only. The lower 720 × 540 mm opening receives the removable hatch.

Add two vertical hatch guides inside the front posts, leaving 8 mm side clearance. Assemble the six hatch slats on two rear battens, then test that it lifts smoothly and seats securely. Fit two toggle latches so animals cannot pull it open.

Build the base you chose

Standard: screw the seven base slats across the two 940 mm skids, using 15 mm drainage gaps. Seven 100 mm slats plus six 15 mm gaps make a 790 mm-wide floor. Set this rigid timber base on the compacted gravel and fasten the four posts to it. The base supports the compost while allowing excess moisture to drain.

Liquid capture: build a square 140 mm-high timber plinth on the paving. Fix the same seven slats across its top so the compost load is carried by the plinth, not the drawer. Make a shallow plywood drawer that clears the opening by 6 mm on each side. Line it with one continuous removable liner, turn the liner up at least 50 mm on every side, and give the drawer bottom a gentle 2% fall toward the front. Fit a timber front and pull so the closed drawer sits flush. Do not add a permanent hose or tank.

Check: With the empty bin in place, the drawer slides out freely and the slatted floor does not flex under firm hand pressure.

Build the closable lid

Lay the six 940 mm lid boards face-down with 10 mm gaps between them. Centre the three 850 mm underside battens, check both diagonals match, then screw each board to every batten. Add the two short hinge blocks beneath the rear edge and mount the lid with two strap hinges.

Fit a lid stay or chain on both sides so wind cannot throw it backward. Add a positive front latch. The lid must shed rain but should not seal the chamber airtight.

Add the simple compost checks

Drill a close-fitting hole through an upper front slat for a long-stem compost thermometer, positioning its dial clear of the lid and latch. Mark a moisture reminder inside the lid: a squeezed handful should feel like a wrung sponge—damp, with only an occasional drop.

Check: The thermometer can be removed for cleaning, and its stem cannot touch the moving lid or hatch.

Commission the bin

Start with 100–150 mm of coarse brown material. Add roughly two to three buckets of dry carbon-rich material for each bucket of fresh nitrogen-rich scraps, then adjust from what the pile tells you. Mix new food scraps into the centre and cover them with browns.

Close and latch the lid. After several days, check temperature, moisture, smell and settling. If it smells sour, add dry browns and turn it. If it stays cold, check volume, moisture and the green-to-brown balance. On the capture version, inspect the drawer weekly at first and empty it before it becomes heavy.

Done: A closable 900 × 900 × approximately 1,100 mm composter with tool-free access to the finished layer. The capture plinth adds about 140 mm to the overall height.