How to Build Raised Beds

Raised bed photo.
David Beaulieu
Overview
  • Total Time: 3 hrs
  • Skill Level: Beginner
  • Estimated Cost: $250 to $300

Raised garden beds offer a number of benefits. They give you a fresh start with a load of new soil that contains no weed seeds. Their tall sides also help prevent weed growth by stopping seeds from blowing into the soil. Beds add a structural element to your garden or yard, creating a nicely contained space that makes tending more fun. And perhaps best of all, raised beds bring the plants up to a comfortable height, making weeding, watering, and maintaining or harvesting plants easier, especially for anyone with limited mobility.

This easy-to-build raised bed delivers particularly well on all of these benefits because it is extra tall and has a solid, structural look with two sturdy posts at each corner. The top of the bed is capped with flat boards to provide a finished look as well as a functional seating area. The bed as shown measures about 3 feet square (plus a few inches all around for the cap) and stands about 2 feet tall. If desired, you can modify the project as shown to build a similar bed with a different size or shape.

Call 8-1-1, the national "Call Before You Dig" hotline, to arrange to have all underground utility lines marked on your property before you dig the post holes for your new bed.

What You'll Need

Equipment / Tools

  • Tape measure
  • Circular saw
  • Drill and screwdriver bit
  • Shovel
  • Post hole digger
  • Level

Materials

  • 4 4x4 posts, 8 feet long
  • 4 2x12 lumber boards, 8 feet long
  • 2 2x10 lumber boards, 8 feet long
  • 3-1/2-inch deck screws
  • 8 galvanized L-brackets
  • 1-1/2-inch deck screws
  • Soil blend

Instructions

  1. Cut the Frame Pieces

    Cut two 8-foot 4x4s in half to create the four 48-inch corner posts, using a circular saw. Cut four pieces of 2x12 lumber to length at 36 inches for the long side pieces. Cut four more 2x12s at 33 inches for the short side pieces.

    Use rot-resistant lumber for the raised bed. Pressure-treated lumber is the longest-lasting and least expensive, but for a vegetable bed, you may prefer to use cedar or redwood (or another naturally rot-resistant wood), to prevent the possibility of pressure-treatment chemicals leaching into the soil.

    Lumber cut to the needed lengths
    David Beaulieu
  2. Assemble the Sides

    Assemble each long side by placing two of the 36-inch 2x12s across two corner posts so the posts are flush with the ends of the boards. The top board should be flush with the top ends of the posts. Fasten the boards to each post with three 3 1/2-inch deck screws. Repeat the same process to assemble the two shorter sides, using the 33-inch 2x12 boards

    A wall of the raised bed, pre-assembled.
    David Beaulieu
  3. Join the Sides

    Assemble the frame with large, outdoor-rated L-brackets and 1 1/2-inch screws, using two brackets at each corner. The two short sides fit against the inside faces of the long sides to form a 36 x 36-inch square.

    Photo showing how to secure raised garden beds with braces at the corners.
    David Beaulieu
  4. Dig the Holes and Set the Frame

    Position the assembled bed frame in the precise location where you want to install the bed, standing it upright on the posts. Mark a 12-inch-diameter circle around the posts at each corner, then lift up the frame and set it aside. Dig a 24-inch-deep hole at each marked location.

    Set the frame into place so the posts are centered in each hole. Check the top of the frame with a level, and adjust for level as needed (adding or removing soil under the posts) so the top edges are level. Backfill around the posts with the removed soil, stopping several times and tamping the soil thoroughly with a scrap board or a shovel handle.

    A post hole digger is handy for digging the deepest portions of the holes. If you don't have a post hole digger, loosen the soil with a shovel, then scoop it out by hand.

    Post holes for raised garden beds.
    David Beaulieu
  5. Add the Cap Boards

    Cut four pieces of 2x10 lumber to create the cap boards. You can decide how long these should be, based on how much they will overlap the inside and outside of the bed frame. It's easiest to cut two equal long pieces and two equal short pieces, so the short pieces fit inside the long ones. Alternatively, you can miter the pieces with 45-degree angle cuts at the corners, like a picture frame.

    Fasten the cap boards by driving 3 1/2-inch screws through the caps and into the frame's side boards and post ends.

    Cap off raised beds to create outdoor benches.
    David Beaulieu
  6. Fill the Bed

    Fill the bed with the desired soil mixture. You can optimize the blend to suit the plants you plan to grow. Most raised bed soil is a mixture of top soil and compost, and many gardeners like to add a smaller amount of peat moss, black loam, or potting soil.

    If you have problems with gophers or other tunneling garden pests, this is a good time to take ​control measures. Line the bottom of the raised bed with galvanized wire mesh or chicken wire before filling the bed with soil.

    Photo showing the raised garden bed filled with filler, dirt and compost.
    David Beaulieu