Raised Garden Bed

1The finished project

A raised garden bed 96" long, 48" wide and 11" tall, with walls two cedar 2x6 boards high.

1. Read every step once before you cut anything.
2. The long sides A run the full 96". The end boards B are 45" long and fit between the long sides.
3. Six posts C stand inside the bed: one in each corner and one in the middle of each long side. Every screw goes through a board into a post, so no screw goes into the end grain of another board.
4. Inside, the bed is 93" x 45" with 11" of soil depth.

The bed has no bottom. It sits on the ground and the soil goes straight in.

2Tools & materials

Buy six cedar 2x6 boards, one cedar 4x4 post and 40 screws.

1. Buy six straight 2x6 cedar boards sold as 96" long. Four stay full length for the long sides: measure each one, and if one is shorter, trim all four long boards to the length of the shortest one.
2. Buy one 4x4 cedar post, 96" long. It makes all six posts. Avoid large knots or cracks near the ends.
3. Buy a box of at least 40 #10 x 3 in exterior screws, coated or stainless steel (40 are used, a box of 50 is fine). Indoor screws rust outdoors.
4. Before you cut anything, check both ends of the four long boards with the speed square. There is no spare length: if an end is not square, trim it and trim all four to the same length.

We recommend cedar for this bed. If you use pressure-treated lumber instead, follow the lumber maker's guidance for ground contact and garden use. This plan makes no claim that any lumber is food safe.

Wear eye and hearing protection when cutting and drilling.

3Cut the posts

Cut six posts 11" long from the 4x4.

1. Square one end of the 4x4: trim a thin slice off if the end is not square or is split.
2. Measure 11" from the square end and draw a line across all four faces with the speed square. Cut on the waste side of the line.
3. A 7-1/4" circular saw does not cut through a 4x4 in one pass. Cut along the line on one face, roll the post over and cut along the line on the opposite face. Keep the saw on the line so both cuts meet.
4. Measure the next post from the fresh cut and repeat until you have six posts C. Six posts and five saw cuts use 66-5/8" of the post.
5. Check every post: all six must be 11" long, so the top of each post is flush with the top of the boards.

Clamp the post to sawhorses or a bench before each cut. Never hold the post with your hand near the blade.

Most home centers will cut the post for you. Show them the cut list: six pieces 11" long.

4Cut and drill the end boards

Cut four end boards 45" long and drill four screw holes in each.

1. Cut two of the six boards in two: measure 45" from a square end, cut, then cut the second end board 45" long from the rest. Two boards make the four end boards B. Each board uses 90-1/8", kerf included.
2. Choose the better face of each end board as the outside face and pencil OUT on it. Lay the boards on the bench with OUT facing up.
3. At each end of each end board, mark two screw centers 1-3/4" from the end of the board, which is the middle of the post behind it. Mark the first 2" from the bottom edge and the second 2" from the top edge, so they end up 1-1/2" apart.
4. Drill a 13/64" clearance hole straight through the board at each mark and countersink it so the screw head sits flush. That is 4 holes per end board, 16 in all.
5. The screw slides freely through a clearance hole, so its threads bite only in the post and pull the board tight against it. The 1/8" pilot into the post is drilled later, when the board is clamped in place.

Cedar splits easily near the end of a board. Always drill the holes before you drive a screw.

Keep the drill square to the face, so the screw goes straight into the post.

5Build the two end frames

Screw two end boards to two corner posts. Build two identical end frames.

1. Lay two posts C flat on the bench, parallel, with an end board B on top of them, OUT facing up. Line up each post under the holes at one end of the board.
2. Each post must be flush with the end of the board, and the bottom end of each post flush with the bottom edge of the board. Clamp the board to the posts.
3. Through each of the 4 holes, drill a 1/8" pilot about 1-1/4" deep into the post with the long bit, then drive a #10 x 3 in screw.
4. Lay the second end board next to the first, tight against it, with its top edge flush with the top ends of the posts. Clamp it, drill the 4 pilots and drive its 4 screws. That is 8 screws per end frame.
5. Build the second end frame the same way. The drawing shows the frame standing up, as it will stand in the bed.

Check with the speed square that each post is square to the boards before you drive the second screw into it.

6Drill the long boards

Drill six screw holes in each of the four long boards: two at each end and two in the middle.

1. Choose the better face of each long board A as the outside face and pencil OUT on it. Lay the boards on the bench with OUT facing up.
2. At each end, mark two screw centers 3-1/4" from the end of the board. That is the 1-1/2" end board plus the middle of the 3-1/2" post behind it. Mark the first 1" from the bottom edge and the second 1" from the top edge, so they end up 3-1/2" apart.
3. In the middle, mark the same two screws 48" from the end of the board, for the middle post.
4. Drill a 13/64" clearance hole through the board at each mark and countersink it. That is 6 holes per long board, 24 in all. The 1/8" pilots into the posts come later, with the board clamped in place.

The long-board screws sit 1" from the edges and the end-board screws 2" from the edges, so the screws that meet inside a corner post pass each other. Keep to these numbers.

7Add the long sides

Screw the four long boards to the corner posts, and square the bed before the last screws go in.

1. Stand the two end frames on a flat surface, posts inside, about 93" apart.
2. Clamp the bottom front board A1 to the frames, OUT facing out, bottom edge on the ground, ends flush with the outside faces of the end boards.
3. At each end of A1, drill a 1/8" pilot about 1-1/4" deep into the post through the bottom hole only, and drive one #10 x 3 in screw. Do the same with the bottom back board A3. On 4 screws, the bed can still be pushed square.
4. Measure both outside diagonals, corner to corner. They must be equal: 107-5/16" each. If they differ, push the two corners of the longer diagonal together until they match.
5. Without moving the bed, drill the pilots and drive the second screw at each end of A1 and A3.
6. Add A2 above A1 and A4 above A3, top edges flush with the posts. Clamp, drill the pilots and drive 4 end screws in each: 16 screws into the corner posts. Leave the middle holes empty.

Work with a helper, or clamp a scrap board across the frames so they stand on their own.

8Add the middle posts

Screw a post to the middle of each long side.

1. Stand a post C inside the front side, behind the middle holes. Its center is 48" from each end of the bed, so its sides are 46-1/4" from the outside of each end.
2. Set its bottom end on the ground, flush with the bottom edge of the boards, and its top flush with the top edge. Clamp it to the boards.
3. Through each of the 4 middle holes, drill a 1/8" pilot about 1-1/4" deep into the post, then drive a #10 x 3 in screw.
4. Do the same on the back side. That is 8 screws into the middle posts.

If the ground is soft, work on a flat patio or a sheet of plywood so the posts and boards stay flush at the bottom.

9Check it is still square and flush

Measure both diagonals again. They must still be equal: 107-5/16" each.

1. Measure the diagonal from the outside of one corner to the outside of the opposite corner, along the top edges. Then measure the other diagonal.
2. For a bed 96" x 48", both diagonals are 107-5/16". What matters most is that the two numbers are the same.
3. If they differ by more than 1/8", back out the long-board screws at one end, push the two corners of the longer diagonal toward each other until both numbers match, and drive the screws again.
4. Check that the top edges of the boards and posts are flush all around.

If you trimmed the long boards shorter than 96", the diagonal is shorter too. The two diagonals must still be equal.

10Place it and fill it

Set the bed level on the ground, then fill it with about 26 cubic feet of soil.

1. Choose the spot and clear it. Level the ground where the bed will stand, about 96" x 48".
2. Set the bed in place. Lay the level on each long side and each end. Scrape away soil under the high corners until the bed is level and every bottom edge touches the ground.
3. Fill the bed with soil to the top edge: about 26 cubic feet (0.97 cubic yards, about 740 liters). That is the 93" x 45" x 11" inside, minus the six posts.

Bags of soil are heavy. Lift with your legs, not your back.