A Cedar Raised Garden Bed
- Hands on
- 160 min
- Start to finish
- 2.7 hours
- Level
- easy
- Makes
- one 1200 x 900mm raised bed, about 280mm deep
This is a stacked-board bed screwed to a post let into each inside corner, rather than mitred or notched corners — fewer cuts, and nothing that needs to fit precisely. Two courses of board give a 280mm-deep bed, enough for most vegetables, and the posts double as stakes that hold the whole thing square once it is set on the ground.
What you need
Step by step
-
Cut the four corner posts to 450mm on a mitre saw, clamping each short length rather than holding it by hand while it's cut.
15 min -
Cut the eight wall boards to length: four long boards at 1200mm and four short boards at 900mm.
20 min -
Predrill and countersink two holes near each end of every board, about 20mm in from the ends, so the screws don't split the board.
15 min -
Stand a post inside each corner and screw the first course of long and short boards to it, keeping the bottom edge flush with the underside of the post.
30 min -
Add the second course above the first and check the frame is square by measuring both diagonals — adjust until they match.
25 min -
Set the assembled frame in position and drive the posts into the soil evenly at each corner with a mallet, about 170mm deep, until the bottom board sits flat on the ground and the top is level.
25 min -
Line the base with permeable landscape fabric, stapling it to the inside faces of the bottom boards.
15 min -
Backfill around the outside of the frame to bury the posts, then fill the bed with soil.
15 min
Afterwards
Sweep or vacuum sawdust rather than blowing it, and put preservative-treated offcuts out with normal household waste rather than burning them. Check the frame sits level and every post is driven firm before backfilling — a bed that rocks will work its screws loose over a season of wetting and drying.
Questions
Does the wood need to be rot-resistant?
Yes — anything in contact with wet soil rots eventually. Cedar or pressure-treated softwood both last for years; untreated pine will need replacing within a couple of seasons.
Do I need to line the bottom?
Not underneath — roots and drainage both want open contact with the ground below. The permeable membrane only needs to cover the base to stop grass and perennial weeds growing up through, and it still lets water drain away.
How deep should the bed be for vegetables?
280mm, two courses of 140mm board, suits most vegetables. Root crops like carrots and parsnips do better with a third course added, taking it to about 420mm.
Can I build it bigger than 1200 x 900mm?
Yes, extend the long boards as far as you like. Keep the width to about 1200mm or less so you can reach the centre from either side without standing on the soil.