Check the site and timber sizes
Mark the frame and walk around it before buying timber. This open-bottom bed has sides about 2.44 m long and end boards roughly half that length. Three layers make walls about 55 cm high. Check that you can reach the centre from both sides.
The parts below follow a published UF/IFAS frame design, with measurements converted to metric and rounded. Use finished dimensions when buying timber: its trade label can differ from its actual thickness and width.
Ask the supplier to confirm the actual sections and lengths before ordering. Different timber sizes need a plan that suits their dimensions and connections. If the specified stock is unavailable, choose a suitably documented kit rather than substituting thinner boards into this frame.
Use level, suitable garden ground with clear access to water. Locate buried services before digging. Choose durable heartwood or timber with documented ground-contact suitability, such as EN 335 Use Class 4, and confirmation that its treatment is permitted for vegetable planters. Avoid creosote sleepers and reclaimed wood with unknown coatings. The timber selection guide compares materials and the questions to put to a supplier. This frame has no floor and is not a balcony or roof planter.
Prepare the parts
Have a tape measure, pencil, square, level, clamps, a suitable saw, and a drill/driver. Use eye protection when cutting and drilling. A timber merchant can make the cuts if you do not have suitable tools. Follow the timber supplier's handling and cut-end treatment instructions.
| Buy | Prepare | Check |
|---|---|---|
| Nine boards with a finished section about 38 × 184 mm, each about 2.44 m long | Keep six full length for the long walls. Cut the other three into six matching end boards. | Measure the actual thickness and width. All nine boards need matching sections. |
| Two square posts, each about 2.44 m long | Cut six supports to the height of three measured board widths stacked together, about 55 cm. | Finished section when dry: about 89 × 89 mm. Confirm the actual section with the supplier and match every support to the stacked wall height. |
| Ninety stainless-steel screws about 76 mm long, compatible with the timber treatment | Use three screws per board-to-post connection. | Ask for a screw and pilot-drilling specification suited to the selected timber. |
A saw removes a strip of wood called its kerf. Allow for that cut before choosing the common end-board length: dividing a 2.44 m board does not leave two exact 1.22 m pieces. Measure all three blanks, then cut and trim the six ends to one matching finished length, slightly under 1.22 m. Record that length as E.
Keep the six long boards at one matching full length, L. Measure their actual thickness, t. Before drilling, dry-fit the pieces on level ground to check the layout and your reach.
Place the six supports
The end boards fit between the long walls. Four posts sit inside the corners; the other two sit inside the midpoint of each long wall. The drawing shows their positions. Use the cut list for sizes; the post symbols are not to scale.
The outside length is L; the outside width is E + 2t. The inside growing area is E wide and L − 2t long, before allowing for the space occupied by the posts. Measure the finished frame before ordering soil.
Assemble and level the frame
- Make each short end with three boards stacked against two corner posts. Keep the top and bottom flush. Clamp the boards against the posts and use a carpenter's square to check right angles, then fasten each board to both posts with three screws per connection.
- Position the two end assemblies on the site. Attach the three full-length boards along each side to the corner posts. Offset screws entering a corner from perpendicular faces so they do not meet inside the post.
- Fit one remaining post inside the midpoint of each long wall. Fasten every long board to that post with three screws. The ninety-screw total covers 36 screws in the end connections and 54 in the long walls.
- Measure from one outside corner to the opposite corner, then measure between the other pair. Adjust the frame until these diagonals match so the rectangle is square. Check all six post tops align and use a level along the walls and across the frame. Adjust the ground beneath it as needed. Check for loose joints or projecting screw tips before filling.
Follow the fastener maker's pilot-hole instructions; hard timber can need pre-drilling. Extending or raising this frame changes the support requirements. Use a suitable plan for that size rather than simply adding more boards.
Measure, fill and inspect
If using a planter-safe wall liner, secure it to the inside faces while leaving the bottom open. Keep water from collecting behind it. Remove persistent weeds and loosen compacted ground beneath the frame without working waterlogged soil. Start with suitable loamy topsoil and mature compost, about three parts soil to one part compost by volume, adjusted to your materials and soil-test results. Avoid filling entirely with compost or adding a gravel layer as a routine drainage fix. The soil and drainage guide covers material checks and drainage problems.
For an initial 40 cm soil depth, inside length × inside width × 0.40 m gives the gross filling volume. This frame is roughly 1.15 m³ at that depth before deducting the posts. Check actual dimensions and the supplier's delivery allowance for settling. Leave room for mulch and clearance below the rim.
Inspect the walls and joints as you fill and after watering. If a wall moves or bows, stop and correct the structure before adding more soil. Keep access clear so future repairs remain possible.
Before planting, run the irrigation and check the first and last outlets. After water soaks in, feel the soil near planting positions and between lines; use a small trowel to check its depth. Adjust lines that leave dry strips. The irrigation setup explains the fittings and wetting checks. For crops and sowing steps, continue with planting the first bed.
Sources and further reading
- University of Florida IFAS: Gardening in Raised Beds, the frame design, stock list, support arrangement and assembly sequence. Measurements here are metric conversions; they do not validate substitutions of different timber sizes.
- NIST: American Softwood Lumber Standard (2025; PDF), Table 3, for the finished dry post section corresponding to the source design's trade size. Confirm actual dimensions with the supplier.
- Wood Protection Association: Preservative-treated wood resources, for exposure specifications and buying suitable treated timber.
- Oregon State University Extension: How to Use Compost in Gardens and Landscapes. Trial soil blends and limits on compost content.
- University of California: Drip Irrigation in the Food Garden (PDF). Setup and wetting checks.
- University of Maryland Extension: Drainage in patio planters. Why gravel beneath fine soil can retain water above the layer.
- University of Maryland Extension: Safety of materials used for building raised beds. Timber treatments and reclaimed materials.