Wooden raised beds · Guide 28
Build a Low L-Shaped Cedar Raised Bed
Build a one-board-high L-shaped cedar bed, 60 × 48 inches outside, with 24-inch arms you can reach from both sides and a blocked inside corner.
01 / See the shape
View the project
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Every wall bottom and N bear on the prepared soil inside the strung outline.
02 / Plan your build
Before you start
An L-shaped bed wraps a path corner, so each 24-inch arm can be worked from two sides. The weak point in any L is the inside corner, where two walls meet with soil on the outside of the angle. This design puts a solid 4 × 4 block, N, in the path angle and screws both inner walls into it from the soil side. The joint is made first, on the bench, while it is fully accessible. Every wall has its own length and its own labeled datum end, so no two walls can be swapped. Each of the five outside corners has one wall running through and one fitting between, with a 2 × 2 block inside.
The main failure is an inside corner built as a plain butt joint with no block. Soil pressure pushes the two inner walls apart there, and the gap opens at the top. A second failure is a mirrored or swapped wall. That puts the screw marks over empty soil instead of a block. OSU Extension discusses bed width, reach and site choice. Those principles do not approve this corner connection.
Where it goes
Level, free-draining native garden soil with a clear 60 × 48-inch area and standing room in front, on the left and inside the notch. Do not place it on paving, a deck, a roof, a slope, against a building, or over unresolved buried services.
Footprint: 60 × 48 in L outline: the 2,880 sq in rectangle less the 36 × 24 in notch = 2,016 sq in. N occupies 3.5 × 3.5 in of the notch corner. Keep at least 24 in of standing room along the front, along the left side and in the notch
What to expect
Measure and mark accurately, make supported square cuts, and drill and drive clamped screws. Plan 6–8 hours including stock checks, scrap screw trials, dry-fitting and filling in layers.
A planning estimate for the hands-on work, once the materials are bought and the tools are set up. It has not been timed on a finished build.
Check the spot
- Clear, level native soil with a 60 × 48-inch outline and 24 inches of standing room along the front, along the left side and in the notch.
- Buried services, private irrigation, large roots, drainage paths and past soil use are known before any digging.
- A flat work surface large enough to clamp the 58.5-inch front wall without reaching across the saw.
Stop and check first if…
- Stop before ground disturbance when utilities, roots, drainage or past contamination are unresolved.
- Stop if measured stock differs from 1.5 × 7.25, 1.5 × 1.5 or 3.5 × 3.5 inches; reconcile the design first.
- Stop if a block or board end splits, a screw strips, or the screw maker's edge distances cannot be met at the 0.75-inch holes.
- Stop filling if the inside corner opens, any corner moves or F bows; remove the mix next to the joint before repair.
- Do not add a second course, raise the walls, lengthen an arm or mirror only some parts without a new review.
Work safely
- Keep the saw guard in place and clamp every piece. Cut the short C and N blocks from a longer supported length and never hold them beside the blade.
- Clamp each joint before drilling. A drill that catches can spin an unclamped block or board.
- Lift the empty frame with two people at the corners. Never move the frame after it is filled.
- Keep the path clear around N. Its 3.5-inch corner sits at foot level in the notch, so ease its top edges.
Budget
We have not put a price on this one yet. Lumber and hardware prices change by store and season, so price the list under What you need at your local supplier before you buy.
03 / Gather and cut
What you need
L — Left outer wall (runs through at both ends)
1 piece
Untreated western red cedar 2 × 8, surfaced; actual 1.5 × 7.25 in. From wall board 2 of three 2 × 8 × 8-ft boards. Board 2 layout: 0.5 trim + 48 L + 0.125 kerf + 36 H + 0.125 kerf = 84.75 of 96 in.
Measure the actual section first. Label end A at the front, the BOTTOM edge and the OUT face. Reject a twisted or split board.
F — Front wall (fits between at left, runs through at right)
1 piece
Untreated western red cedar 2 × 8, surfaced; actual 1.5 × 7.25 in. From wall board 1. Board 1 layout: 0.5 trim + 58.5 F + 0.125 kerf + 21 R + 0.125 kerf = 80.25 of 96 in.
End A is the left end, which butts against L. This is the longest span. Choose the straightest board for F.
B — Back wall of left arm (fits between at left, runs through at right)
1 piece
Untreated western red cedar 2 × 8, surfaced; actual 1.5 × 7.25 in. From wall board 3. Board 3 layout: 0.5 trim + 24 V + 0.125 kerf + 22.5 B + 0.125 kerf = 47.25 of 96 in.
End A is the left end, which butts against L. Do not confuse B with V; they differ by 1.5 in.
V — Inner wall along the notch, Y direction (runs through at the inside corner)
1 piece
Untreated western red cedar 2 × 8, surfaced; actual 1.5 × 7.25 in. From wall board 3. See the B layout.
End A is the front end, at the inside corner. OUT is the notch face. Screws enter from both faces; mark each face separately.
H — Inner wall along the notch, X direction (fits between at the inside corner, runs through at right)
1 piece
Untreated western red cedar 2 × 8, surfaced; actual 1.5 × 7.25 in. From wall board 2. See the L layout.
End A butts against the notch face of V. OUT is the notch face. Screws enter from both faces.
R — Right end wall (fits between at both ends)
1 piece
Untreated western red cedar 2 × 8, surfaced; actual 1.5 × 7.25 in. From wall board 1. See the F layout.
End A is the front end. R fits between F and H, so it must be exactly the arm width less two wall thicknesses.
C — Outside-corner block
5 pieces
Untreated western red cedar 2 × 2; actual 1.5 × 1.5 in. One 2 × 2 × 8-ft board: 0.5 trim + 5 × (7.25 + 0.125 kerf) = 37.375 of 96 in.
Block length must equal the measured wall width so the block sits flush top and bottom. Reject blocks with checks or knots.
N — Inside-corner block in the path angle
1 piece
Untreated western red cedar 4 × 4; actual 3.5 × 3.5 in. One 4 × 4 in the shortest stocked length: 0.5 trim + 7.25 + 0.125 kerf = 7.875 in used.
Use heartwood free of the pith and of open checks. This block carries both inner walls.
Wall-to-block screws
26 items
#9 × 2-1/2 in type 316 or type 305 stainless steel exterior wood screws, flat or trim head suited to cedar Buy one box of at least 26, plus enough extra for scrap trials. Keep spares separate from the installed count.
20 at five outside corners (4 each) + 6 at the inside corner = 26. Follow the screw maker's clearance, pilot and edge-distance instructions. No connection capacity is inferred.
Cut list
| Piece | How many | Cut length | Note |
|---|---|---|---|
| L — Left outer wall (runs through at both ends) | 1 | 48 × 7.25 × 1.5 in | Square both ends. End A sits at the front-left origin. |
| F — Front wall (fits between at left, runs through at right) | 1 | 58.5 × 7.25 × 1.5 in | Cut F first from board 1. |
| B — Back wall of left arm (fits between at left, runs through at right) | 1 | 22.5 × 7.25 × 1.5 in | Finished length × width × thickness; square ends unless the detail says otherwise. |
| V — Inner wall along the notch, Y direction (runs through at the inside corner) | 1 | 24 × 7.25 × 1.5 in | Finished length × width × thickness; square ends unless the detail says otherwise. |
| H — Inner wall along the notch, X direction (fits between at the inside corner, runs through at right) | 1 | 36 × 7.25 × 1.5 in | Finished length × width × thickness; square ends unless the detail says otherwise. |
| R — Right end wall (fits between at both ends) | 1 | 21 × 7.25 × 1.5 in | Finished length × width × thickness; square ends unless the detail says otherwise. |
| C — Outside-corner block | 5 | 7.25 × 1.5 × 1.5 in | Finished length × width × thickness; square ends unless the detail says otherwise. |
| N — Inside-corner block in the path angle | 1 | 7.25 × 3.5 × 3.5 in | Finished length × width × thickness; square ends unless the detail says otherwise. |
Tools
- Tape, combination square, framing square, pencil and marker
- String line and four stakes for the layout
- Guarded saw suited to 2 × 8 and 4 × 4 cedar, with supported work
- Drill/driver with the clearance, pilot and countersink bits specified by the selected screw maker
- At least four clamps, a flat work surface and scrap backing
- Level, fine abrasive and a soil scoop or bucket
Protective gear
- Eye protection when cutting and drilling
- Hearing protection and dust control matched to the actual saw; cedar dust irritates some people
- Closed footwear, and gloves for carrying boards only; no gloves near a rotating cutter
04 / Put it together
Build steps
- 01
Check the site and mark the L outline
Choose level native garden soil with room for the 60 × 48-inch outline. Allow a 24-inch standing path along the front, along the left side and in the 36 × 24-inch notch. Resolve buried services, irrigation lines, large roots, drainage and past soil use before disturbing the ground. Set the origin at the front-left outside corner. String a 60-inch front line and a 48-inch left line. Mark the notch corner 24 inches in from both lines. Compare the front-arm diagonals to 64.62 inches. Compare the left-arm diagonals to 53.67 inches.
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Drag to turn. Pinch or use + / − to zoom. The written step covers workholding and tool use.
Scroll or swipe the enlarged drawing to read its dimensions. Choose Fit to see the whole drawing again.
Planning reference only: the wall outline shows where the string lines and the notch corner fall on the ground.
Check: Each diagonal pair matches within the proposed 1/8-inch target, and no site question remains open.
- 02
Measure and record the stock
Measure each 2 × 8 cedar wall board at both ends and the middle. This plan requires 1.5 × 7.25 inches. Measure the 2 × 2 at 1.5 × 1.5 inches and the 4 × 4 at 3.5 × 3.5 inches. Sight every board for twist, cup and bow. Mark splits, loose knots and damaged ends as waste. Different actual sections need a reconciled design before any cut.
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Loading the 3D view…
Drag to turn. Pinch or use + / − to zoom. The written step covers workholding and tool use.
Scroll or swipe the enlarged drawing to read its dimensions. Choose Fit to see the whole drawing again.
Three stock sections to measure before any cut: wall board, small block and large block.
Check: Three wall boards each have at least 85 usable inches, and all sections match the listed sizes.
- 03
Cut and label the six walls
Trim 0.5 inch to square one end of each wall board. Board 1: cut F at 58.5 inches, then R at 21 inches. Board 2: cut L at 48 inches, then H at 36 inches. Board 3: cut V at 24 inches, then B at 22.5 inches. Keep the 1/8-inch kerf on the waste side of every line. Write the letter and A on the squared datum end of each piece. Write BOTTOM on one long edge. Write OUT on the face that will face away from the soil; for H and V this is the notch face.
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Six walls are cut from three boards in pairs, and every length is different.
Check: Six walls measure 48, 58.5, 22.5, 24, 36 and 21 inches, and every piece carries its letter, A, BOTTOM and OUT.
- 04
Cut the corner blocks C and N
Trim 0.5 inch to square one end of the 2 × 2. Cut five C blocks at 7.25 inches, matching the measured wall width. Trim the 4 × 4 the same way and cut one N block at 7.25 inches. Clamp the stock for every cut. Cut short blocks from a longer supported length and never hold a block beside the blade.
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Five small blocks and one large block, all cut to the wall width.
Check: Each block stands flush with the top and bottom edges of a wall laid on edge.
- 05
Mark and drill the wall clearance holes
Lay each wall OUT face up. Measure along from end A and up from BOTTOM. Mark L at 2.25 and 45.75, heights 1.5 and 5.75. Mark F at 0.75 (heights 2.5, 4.75) and 56.25 (heights 1.5, 5.75). Mark R at 0.75 and 20.25, heights 2.5 and 4.75. Mark B at 0.75 (heights 2.5, 4.75) and 20.25 (heights 1.5, 5.75). Mark H at 33.75 (heights 1.5, 5.75). Mark V at 23.25 (heights 2.5, 4.75). Turn H and V soil face up. Mark H at 1.75 and V at 3.25, each at heights 1.5, 3.625 and 5.75. Clamp each wall over scrap. Drill the screw maker's clearance size square to the marked face, through the wall only.
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Each wall carries its own pattern, measured from end A and the bottom edge.
Check: There are 26 holes: 4 each in L, F, R and B, and 5 each in H and V, each drilled from the marked face.
- 06
Build the inside corner first
Stand V and H on their BOTTOM edges on a flat surface. Butt end A of H against the OUT face of V. Set the soil face of H flush with end A of V. Set N in the notch angle so it touches both OUT faces, flush top and bottom. Clamp N to each wall. Trial the screw in cedar scrap first. Through the soil-face holes, drill receiving pilots into N, as the screw maker specifies. Drive 3 screws through H and 3 through V.
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The inside corner is closed on the bench, where both soil faces are still open to the driver.
Check: H and V meet at 90 degrees with flush tops, N does not move, and six screw heads are seated without splitting.
- 07
Dry-fit the outer walls and blocks
Lay L with end A at the origin, BOTTOM down and OUT facing away. Butt end A of F against the inside face of L. Fit R between the inside face of F and the soil face of H. Butt end A of B against L so its far end covers the back end of V. Set C blocks in the five outside-corner angles, flush top and bottom. Clamp every corner. Measure the outside: 60 front, 48 left, 24 at the back of the left arm, 24 at the right end. Measure the notch at 36 × 24. Check the front-arm diagonals at 64.62 inches. Check the left-arm diagonals at 53.67 inches.
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The outer walls close the L around the finished inside corner, with one wall running through at each corner.
Check: All outside sizes and both diagonal pairs agree within the proposed 1/8-inch target, and no wall is forced into place.
- 08
Fasten the five outside corners
Keep all clamps on and fasten one corner at a time. Drill a receiving pilot into the block through each clearance hole. Drive two screws per wall face. C0, front left: L and F. C1, front right: F and R. C2, right inner: R from outside and H from the notch face. C3, back left: L and B. C4, back right: B and V from the notch face. Recheck both diagonal pairs after C1 and after C4.
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Twenty outside-corner screws, two per wall face, staggered in height inside each small block.
Check: Twenty screws are seated at the outside corners, and the diagonals still match after the last corner.
- 09
Inspect every joint before placement
Release the clamps. Check that all six corners stay closed and the frame lies flat. Look for split blocks, split board ends near the 0.75-inch holes, stripped holes and screw points showing through a block face. Each C screw stops 0.5 inch short of the far block face. Ease hand-contact rim edges and wipe the rim with a cloth to find splinters. Record the outside sizes while every joint is still visible.
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The inside corner and the board ends near the 0.75-inch holes are where splits show first.
Check: No split, stripped hole or exposed point is found, and the inside corner gap reads zero at top and bottom.
- 10
Place the frame on the marked outline
Carry the empty frame with two people, lifting at corners and never by one wall. Set it on the strung outline with the origin corner at the marked origin. Check ground contact under all six walls and under N. Check level along F and L. Correct a high spot by removing soil. Do not wedge loose scraps under a wall.
Close-up · Whole model shows the complete partLoading the 3D view…
Drag to turn. Pinch or use + / − to zoom. The written step covers workholding and tool use.
Scroll or swipe the enlarged drawing to read its dimensions. Choose Fit to see the whole drawing again.
Every wall bottom and N bear on the prepared soil inside the strung outline.
Check: The frame does not rock, every wall bottom touches soil, and the outline still measures 60 × 48.
- 11
Mark the fill line and fill in layers
Mark a fill line 6.25 inches above the soil on the inside of every wall. Add the selected bed mix, about 6.1 cubic feet in total, in layers about 2 inches deep across both arms at once. Fill the inside-corner area at the same rate as the rest. Never fill one arm completely before the other. Do not stand on the rim or compact the mix by foot. Stop and check the H to V joint after each layer.
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The fill line sits one inch below the rim, and both arms rise together.
Check: Mix reaches the 6.25-inch line with 1 inch of freeboard, and the inside corner stays closed.
- 12
Water and make the first inspection
Water as the selected mix requires. Watch drainage through the open bottom without flooding the site. Recheck the H to V joint, the contact between N and both walls, all five outside corners and wall straightness along F. Top up settled mix only to the 6.25-inch line. Repeat this inspection after the next heavy watering and again after one week.
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After the first watering, the inside corner and the long front wall show movement first.
Check: No corner has opened, F has no visible bow, and water drains without ponding against a wall.
05 / Keep it sound
Care
After the build
- Fill only after the joint inspection, in layers across both arms, to the 6.25-inch line. Choose crop spacing for 21-inch clear arms, and consider the native soil beneath the open bottom.
- Work from the front, from the left side and from the notch; do not kneel or stand on the rim.
Check it each season
- Each season, check the H to V joint at top and bottom, the contact between N and both walls, all five outside corners and the straightness of F.
- Keep mulch and soil off the outside of the walls and away from N, so the wood dries between waterings.
- Replace a softened or split part completely. Do not add a screw beside a crack or cover damage with trim.
If something looks wrong
- The inside corner opens at the top during filling
- Stop filling. Remove the mix next to the joint, then inspect N and the six screws for splits or stripping before repair and review.
- Screw marks do not land over a block
- A wall is reversed or swapped. Check the wall letter and confirm end A faces the origin before drilling a pilot.
- The diagonals will not match during dry-fit
- Check the R and B lengths and look for twisted stock. Recut or replace the part; do not pull the frame square with screws.
- The frame rocks after placement
- Lift it off empty and remove high soil under the wall. Do not wedge it with scraps.
- The front wall bows outward after watering
- Stop, lower the mix near F and refer the span to review. Do not add fill to hide the bow.
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