DIY Cedar Raised Garden Bed: Board and Post Sizing
By Greenes Fence Company: Cedar Raised Garden Beds ... | Published: 2026-10-22
Category: How-to Guides
Learn how to choose the right cedar board sizes and post lengths for your DIY raised garden bed, with step-by-step guidance and common mistakes to avoid.
Quick Answer
For a sturdy DIY cedar raised garden bed, match your board lengths to your desired bed footprint and choose post heights that support the number of board layers you plan to stack. Start with 36-inch boards and short posts for a low bed, then add layers as needed.
Why Board Length and Post Height Matter
The size of your cedar boards determines the footprint of your raised bed, while the post height controls how many layers you can stack. Getting these two measurements right from the start saves you from buying extra materials or ending up with a wobbly structure.
A common mistake is choosing boards that are too long for your space or posts that are too short for the number of layers you want. Measure your garden area first, then decide on the bed height based on the plants you'll grow.
Understanding Board Layers and Post Stacking
Each board layer adds 3.5 inches of height to your bed. Short posts hold two boards high, adding 7 inches per layer, and they can stack on top of each other or on tall posts for quick expansion. This modular approach lets you start small and add height later without rebuilding.
If you're unsure about future changes, plan for extra post height now. It's easier to adjust board length than to replace posts after assembly.
Step-by-Step Sizing Process
- Measure Your Garden Space: Use a tape measure to determine the length and width of the area where the bed will go. Leave at least 18 inches of walking space around the bed for access. Sketch the area with measurements to avoid ordering mistakes.
- Choose Your Board Lengths: Select board lengths that match your bed dimensions. For a 3x3-foot bed, use 36-inch boards. For longer beds, combine multiple boards or choose longer options if available. Check that the number of boards covers the perimeter: two per side for a square bed.
- Decide on Bed Height: Determine how many board layers you want. One layer (3.5 inches) suits shallow-rooted greens; two layers (7 inches) work for most vegetables; three or more layers are better for deep-rooted plants or easier access. If you plan to sit on the edge, aim for at least 14 inches total height.
- Pick the Right Post Length: Match post height to your chosen layers. Short posts (8 inches) hold two boards high. For taller beds, stack short posts on top of tall posts or use longer posts if available. Ensure posts are rated to hold the weight of soil and boards—check the product specs.
- Account for Future Expansion: If you might enlarge the bed later, choose posts that can stack and boards that can be added to. This lets you extend without rebuilding the entire structure. Consider buying a few extra boards and posts upfront to match future needs.
Cedar Boards and Posts at a Glance
- Premium Cedar Board 36 in x 3.5 in (3/4 in Thick) RCB36: The Premium Cedar Board 36 in x 3.5 in (3/4 in Thick) is a mid-sized board that fits into short and tall posts, made from smooth, sanded untreated cedar. This board size is versatile for small to medium beds and can be stained or left natural, giving you design flexibility.
Premium Cedar Board 36 in x 3.5 in (3/4 in Thick) RCB36 - Discontinued Premium Cedar Short Post 8 in x 3 in x 3 in RCS3X3: The Premium Cedar Short Post 8 in x 3 in x 3 in holds two 3.5-inch boards high, adding 7 inches of height per layer, and stacks on top of other posts for expansion. Using short posts lets you build a low bed initially and then add height later without buying new boards, saving money and effort.
Discontinued Premium Cedar Short Post 8 in x 3 in x 3 in RCS3X3
