Raised Planter Box with Corrugated Metal Panels
by Makeit_official
Build a waist-height rectangular planter with square softwood corner posts, bright galvanised corrugated sheet infill panels and a wide flat 2x12 rim you can sit a mug or a seed tray on. It suits a confident beginner with a mitre saw and a drill who wants a good-looking herb and salad planter for a patio, balcony or garage-door frontage.
Wood frame
2x12 softwood boards
Actual size 38 mm thick × 286 mm wide. Total length required = 2 × (L + 40 mm) + 2 × (D + 40 mm), plus 300 mm spare for mitre setup (these are the wide flat rim caps)
30
4x4 softwood posts
4 pieces, actual size 89 × 89 mm, each cut to [MEASURE: overall height H] − 38 mm (the four corner posts)
17
2x4 softwood rails
8 pieces at [MEASURE: overall length L], 5 pieces at [MEASURE: overall depth D] − 178 mm; actual size 38 × 89 mm (upper and lower side rails, end rails and one mid-span tie)
24
Metal panels
Corrugated galvanised roofing sheet
0.5 mm bright galvanised sheet; total area = 2 × (L − 183 mm) + 2 × (D − 183 mm) in width, by the rail-to-rail gap + 80 mm in height. Add 10% for cutting waste. See Step 4 for exact panel sizes.
20
Hex-head screws with sealing washers
40 pieces, 20 mm long with EPDM rubber washer (fix metal panels to inner rail faces)
10
Base, liner & hardware
Exterior structural screws 80 mm
60 pieces, 5 mm diameter, corrosion-resistant (rails to posts and mid-span tie; 36 used, rest spare)
14
Exterior structural screws 65 mm
40 pieces, 5 mm diameter, corrosion-resistant (rim caps down onto the frame)
12
Wood plugs 10 mm
70 pieces, softwood, 10 mm diameter (cap every counterbored hole: approx. 36 frame screws plus approx. 30 rim-cap screws)
8
Exterior plywood 18 mm
1 sheet, cut to the measured inner opening of the finished carcass (the base the soil sits on)
45
Batten for base cleats
About 6 m of 38 × 38 mm softwood (perimeter cleats plus one or two mid-span bearers under the plywood base). Also required: 1 × 250 ml waterproof exterior wood glue (D4/PVA) for the plugs.
10
Pond liner or planter liner
0.5 mm butyl or PVC, roughly 1 m² larger than the inner box all round (protects the wood from wet soil)
30
Landscape fabric
1 piece to cover the base area (stops soil washing through the drainage holes)
5
Stainless staples
1 box of 10 mm staples (hold the liner to the inner rails)
5
Finishing & planting
Clear exterior wood oil
1 L, matte clear penetrating oil (protects the timber and keeps its pale honey tone)
10
Sandpaper
Sheets in 120 grit and 180 grit (smoothing plugs and edges)
8
Peat-free multipurpose compost
Volume = inner length × inner width × soil depth; 1 m³ = 1000 L (filling)
29
Coarse drainage gravel
Volume = inner length (m) × inner width (m) × 0.03 m; typically 25–40 L (approx. 40–65 kg) for a 1.2 m × 0.6 m planter
17
Plants
1 tall upright plant in a 2 L pot for the centre, plus 6–8 low bushy herbs in 9 cm pots (approx. 3–4 per end), spaced about 200 mm apart
20
Step 1 of 9
Measure up and write the cut list
TOOLS
Tape measure
MEASURE AND WRITE CUT LIST
- ✓Record L, D and H dimensions first
- ✓Calculate post and rail lengths from formula
- ✓Write mitred rim cap sizes on cut list
Instructions
• Write down three numbers: [MEASURE: overall length L], [MEASURE: overall depth D], [MEASURE: overall height H] to the top of the rim. • Posts: 4 pieces of 89 × 89 mm, each H − 38 mm long (the 38 mm rim cap makes up the rest). • Rails: 4 long rails at L, and 5 pieces at D − 178 mm (4 end rails plus one mid-span tie). End rails fit BETWEEN the posts, so their length is D minus the two 89 mm posts. • Rim caps: 2 boards of 2x12 at L + 40 mm and 2 at D + 40 mm, all mitred 45° at both ends. • Check D leaves at least 250 mm of open soil: inner soil width = D − 178 mm − 76 mm of cleats = D − 254 mm. If less than 250 mm, increase D; the 286 mm caps then overhang 20 mm outside and the rest inside. • Note: L is the length over the outer post faces; the long rails run the full L and are screwed to the post outer faces.
Time & Waiting
Active work
30 minutes
People
1 person
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