Custom Cedar Raised Garden Beds

If you have ever stood in the lumber aisle holding a crooked board and thinking, “How hard can a garden bed be?”, welcome. Cedar raised beds are one of the most satisfying weekend builds because they are straightforward, they look great, and they last. Cedar contains natural extractives (oils and resins) that improve decay resistance, which means you spend more time harvesting tomatoes and less time rebuilding soggy corners.

Below is the exact approach I use at my own 1970s fixer-upper in Michigan: clean, square boxes, beefy corners, and a soil strategy that does not require taking out a small loan at the garden center.

Plan your bed size

Before we talk boards and screws, let’s pick a size that works with how humans are shaped.

• Best width: 3 to 4 ft. You can reach the middle from either side without stepping into the bed and compacting soil.
• Common length: 6 to 12 ft. Longer beds are great, but they need more bracing to stay straight.
• Good height: 11 to 12 in for most vegetables (one 2x12). Go 22 to 24 in if you want less bending or you have poor native soil (stack two 2x12s).

My rule: If you are unsure, build one 4 ft x 8 ft bed at 11 to 12 in tall first. You can always add more beds next season. Your enthusiasm will outpace your compost supply anyway.

Materials that last

Best lumber choice

Western red cedar is the classic. It is lightweight, rot-resistant, and safe for vegetable gardens. You will also see “cedar” that is actually a mix of species. That is fine, just inspect boards for straightness and knots near edges.

Quick board-picking tip: All else equal, more heartwood and fewer loose knots usually means longer life. Tight knots are fine. Knots that look cracked or ready to fall out are future weak spots.

Fasteners and hardware

• Exterior screws: 2-1/2 in coated deck screws for single-layer beds. For double-stacked walls, add 3 in screws.
• Corner reinforcement: Cedar 4x4 posts, or 2x4 cleats, or heavy-duty galvanized corner brackets.
• Optional liner: 1/2 in galvanized hardware cloth for the bottom if you have burrowing critters.

Metal note: Cedar tannins and constant moisture can be hard on cheap fasteners. Use quality coated deck screws, or go stainless if your yard is consistently wet (or you live near salt air).

What to avoid (or at least think through)

• Pressure-treated lumber: Modern ACQ/CA pressure-treated wood is widely used and generally considered acceptable for raised beds when used as labeled. That said, if you want zero second-guessing in your salad bowl, cedar is the stress-free choice.
• Plastic sheet liner on the inside walls: It can trap moisture against the wood and speed up rot. In some setups it can also reduce soil-to-wood contact, so results vary. If you use plastic, keep drainage paths and do not seal it like a bathtub.

Tools you will need

• Measuring tape and pencil
• Speed square or framing square
• Miter saw or circular saw (a straightedge guide helps)
• Drill and driver bit
• 1/8 in drill bit for pre-drilling
• Clamps (helpful, not mandatory)
• Staple gun (for hardware cloth)
• Work gloves and eye protection

Safety note: Cedar splinters are tiny and determined. Gloves are your friend, especially when handling rough-sawn boards.

The build: 4 ft x 8 ft

This plan uses 2x12 cedar for the walls and cedar 4x4 posts at the corners. The posts act like built-in clamps, keeping everything square and strong.

Shopping list (for one bed)

• 2x12 cedar boards, 8 ft long: 2 (the long sides)
• 2x12 cedar boards, 4 ft long: 2 (the short sides) or 2x12 cedar board, 8 ft long: 1 (cut into two 4 ft pieces)
• 4x4 cedar posts: 4 (corners)
• 2-1/2 in exterior deck screws: about 40
• Optional: 1/2 in hardware cloth: about 4 ft x 8 ft plus a little extra for overlap

Cut list

• Long sides: (2) 2x12 at 96 in
• Short sides: (2) 2x12 at 45 in (see note below)
• Corner posts: (4) 4x4 cut to your wall height (see note below)

Important measuring note: If your short sides fit between the long sides, you subtract the thickness of two 2x boards. A “2x” is typically 1-1/2 in thick. So for a 48 in overall width: 48 - 1-1/2 - 1-1/2 = 45 in.

Actual size note (the one that saves headaches): A 2x12 is about 11-1/4 in tall in real life. If you want the posts flush with the top of the boards, cut your corner posts to about 11-1/4 in. If you plan to add a top cap, you can cut posts flush, or leave them slightly proud for a chunkier look. Pick one and stay consistent.

Step 0: Site prep

Do not skip this. A bed that starts level stays square and drains better.

• Mark it out: Lay the boards on the ground to visualize spacing.
• Remove sod: Slice and lift grass where the bed will sit. If you are feeling lazy, scalp it low and use cardboard inside the bed as a weed blocker.
• Level: Rake and shovel the high spots down. A long straight board with a level on top works fine. On a slope, you can terrace the spot, or dig the high side down so the frame sits solid.

Step 1: Cut and prep the lumber

Cut your boards to length, then do a quick check for crown (a slight curve). Put the crown facing outward on long boards. That way, soil pressure helps push the board straighter over time.

Lightly sand any nasty splinter zones at the top edge where your forearms will rest while weeding. Your future self will thank you.

Step 2: Build two L corners

Set a 4x4 post on end. Position one long board against it, flush at the top. Pre-drill holes, then drive screws. Repeat with a short board to form an L-shape.

Screw pattern that works: Use 3 screws per board end into each post, staggered vertically (top, middle, bottom). Keep screws at least 3/4 in from board edges. Pre-drill near ends to prevent splitting.

Do the same for the opposite corner, creating two L-shaped assemblies.

Step 3: Connect into a rectangle

Stand the two L-shapes up and connect them using the remaining boards. Pre-drill to prevent splitting, especially near board ends. Use clamps if you have them.

Measure corner-to-corner diagonals. When both diagonals match, the bed is square.

Step 4: Add mid-span bracing

For an 8 ft bed at 11 to 12 in tall, you can often skip mid bracing if your boards are straight. If you are stacking to 22 to 24 in tall or going 10 to 12 ft long, add bracing.

• Simple brace: Screw a 2x4 cedar cleat vertically at the midpoint on the inside of each long wall.
• Best brace for tall beds: Add a cross-tie (a 2x4 spanning the bed) near the top, fastened to the cleats. It also gives you a handy place to rest a watering wand.

Step 5 (optional): Install hardware cloth

If moles, voles, or other underground snack enthusiasts are common in your yard, staple hardware cloth across the bottom.

• Lay the bed in place.
• Roll out hardware cloth with a few inches of overlap at seams.
• Staple it to the inside bottom edge of the boards and or to the posts.

Tip: Wear gloves. Hardware cloth bites back.

Easy upgrades

Add a top cap

A 1x4 or 2x4 cedar cap around the top edge gives you a clean finished look and a comfortable place to lean while planting. Miter the corners if you are feeling fancy, or do simple butt joints and call it rustic charm.

Add a trellis end

For cucumbers, peas, and indeterminate tomatoes, add two taller 4x4 posts on one end and run galvanized wire or cattle panel between them. Fasten the panel with exterior screws and fender washers.

Go taller without bowing

For a 22 to 24 in bed, stack two 2x12s per wall. Use taller corner posts (24 to 30 in) and add mid-span cleats. Soil is heavy. It will push.

Finish options

Cedar can be left unfinished. It will weather to a soft gray and still last a long time.

If you want to keep the warm cedar color, use a penetrating exterior oil or stain on the outside faces only. Avoid coating the inside faces where soil stays damp. And skip film-forming finishes that can peel.

• Do: finish the outside and top cap
• Do not: seal the inside like it is a boat hull

Soil that saves money

The fastest way to ruin the raised-bed vibe is to fill the whole thing with bagged soil at full retail price. You can, but your wallet will feel personally attacked.

How much soil you need

Volume (in cubic feet) = length (ft) x width (ft) x height (ft).

• 4 ft x 8 ft x 1 ft (roughly a 12 in bed) = 32 cubic feet
• 32 cubic feet = about 1.2 cubic yards (since 1 yard = 27 cubic feet)

A solid vegetable mix

I like a simple 3-part blend:

• 50% topsoil (bulk delivered if possible)
• 30% compost (a good quality municipal or farm compost is great)
• 20% aeration and structure (pine fines, perlite, pumice, or a small amount of coarse coir or peat to balance moisture)

If you buy a “raised bed mix” in bulk from a landscape supplier, ask what is in it. You want it to be soil-based, not 100% compost. Straight compost settles fast and can be a little intense if it is not fully finished. Immature compost is the stuff that can run hot.

The layered fill trick for deeper beds

For beds taller than 12 inches, you can fill the bottom 6 to 10 inches with cheaper, organic “bulk” material and top it with your good growing mix.

• Bottom layer options: small sticks, chopped leaves, old straw, untreated wood chips, half-finished compost
• Top 10 to 12 inches: your vegetable soil blend

This is not a magic science experiment. It is just using the bottom of the bed as a settling zone that will break down over time. Expect the bed to sink a bit the first season and plan to top-dress with compost each spring.

Drainage and weed control

• Skip landscape fabric under the bed if you want deep roots to reach native soil. Cardboard works well as a temporary weed blocker and breaks down.
• If your area stays soggy, consider raising the bed slightly on compacted gravel at the perimeter, or choose a higher spot in the yard.

Placement tips

• Sun: Most vegetables want 6 to 8 hours of sun.
• Access: Leave 24 to 36 inches between beds so you can wheel a cart through and kneel without doing yoga.
• Water: Put beds close enough to a spigot that watering is not a daily workout.
• Level: Do a quick level check. A slightly out-of-level bed means water pools on one side and plants grow unevenly.

Maintenance

• Top-dress annually: Add 1 to 2 inches of compost each spring.
• Mulch: Straw or shredded leaves reduce watering and keep soil from splashing onto plants.
• Check fasteners: Once a year, snug up any screws that loosen as wood moves.
• Watch the corners: If you see bowing, add an interior cleat or a cross-tie before it gets dramatic.

Also, accept this truth: you will end up building another bed next year. It happens to good people.

Common questions

How thick should cedar be?

A 2x board (actual 1-1/2 in thick) is ideal for longevity and stiffness. Thinner boards can work but they tend to bow sooner, especially in longer runs.

Should I line the inside with plastic?

Usually, no. Plastic often traps moisture and can reduce cedar’s lifespan. In some designs it can help by reducing direct soil contact, but only if drainage and airflow are still decent. If you absolutely want a barrier, keep it loose at the bottom so water can drain and do not wrap the bed like a gift basket.

Do I need a bottom?

For vegetables, I prefer open-bottom beds so roots can reach native soil and drainage is natural. Use hardware cloth if you have burrowing pests.

Best height for tomatoes and peppers?

They do great in 11 to 12 inch beds if your soil mix is solid and you water consistently. If your native soil is poor or you want easier access, 22 to 24 inches is a nice upgrade.

How long will cedar beds last?

In a wet climate like Michigan, a well-built cedar bed commonly lands in the 8 to 15 year range, but it is highly variable. Cedar grade, thickness, ground contact, and drainage matter a lot. Using 2x lumber, adding bracing, and keeping the bed out of standing water can push the lifespan longer.

Quick build checklist

• Choose a reachable size: 3 to 4 ft wide
• Use cedar 2x12s and exterior screws
• Pre-drill near ends to prevent splitting
• Square the frame by matching diagonals
• Add bracing for tall or long beds
• Fill smart: bulk soil + compost, not all bags
• Top-dress yearly and mulch to reduce watering

If you build one, you are officially the person on the block who “knows how to do stuff.” Enjoy the power responsibly.