Bed Construction – Build Your Own Box!
Our raised garden boxes are 4′ wide x 12′ long x 20″ tall. There is a 2″ x 4″ centre support at the centre of the box that is used to help prevent the walls from bowing with the weight of the soil. There are 18″ 4″ x 4″ inside corner posts for additional support. They are made with treated lumber to ensure box longevity. Cedar can also be used but it can be quite pricey.
Boxes are lined with landscape fabric approximately 15″ up the wall of the bed. This is a porous fabric that helps prevents grass from coming up through the bottom, prevents soil from sloughing out of the lumber seams (as lumber is inevitably uneven!), and helps to minimize water evaporation. This fabric will degrade with time.
Lumber order (per 2 boxes):
-8, 2″ x 10″ x 12′
-4, 2″ x 10″ x 8′
-1, 2″ x 4″ x 8′
-1, 4″ x 4″ x 12′ (or 2 6′ lengths)
-There is no wastage with these measurements.
-Suggest using 2 1/2″ deck screws for all work. Require 80 screws per box.
- Double cut treated lumber (trim the ends to make them square). Ensure not to trim too much! Watch for poor lumber, now is the time to exchange it.
- Cut treated lumber to desired lengths:
- Trim 12′ 2×10 length for 12′ sides.
- Cut 8′ 2×10 length for 4′ ends.
- Cut 6′ (or 12′) 4×4 into 18″ sections.
- Cut 8′ 2×4 into 45″ sections.
- Prepare wood for assembly (lay out on ground).
- (Easier with a second person) Stand 12′ 2×10 and 4′ 2×10 so that bed is maximum 4′ wide (4′ length is on outside of 12′ length). Hold so top is relatively level and affix with a single screw through 4′ length into 12′ end.
- Stand 18″ 4×4 inside of new corner (ensure bottom is level with bottom of 2×10 by sliding hand underneath, as the ground may be uneven!). Affix with a single screw through 4′ length into top of 2×10, into centre of 4×4.
- Repeat steps 4 and 5 for remaining 3 corners.
- Stand one side of second level on top of first. Repeat Steps 4 and 5. The treated lumber won’t be a perfect length and may be warped so split the difference where needed to help keep the TOP of the garden bed even. (the landscape fabric will help close gaps between levels.)
- Shimmy and shake and bump structure as needed until your corners square up!
- Add 2 more screws into 4′ 2×10 into end of 12′ 2×10 on each corner for each level.
- Add 2 more screws into 4′ 2×10 into 18″ 4×4 on each corner for each level.
- Add 3 screws into 12′ 2×10 into 18″ 4×4 on each corner for each level.
- Mark midpoint of 12′ 2×10 (6′), 6′ – 0.75′, and 6′ + 0.75′. This is where the 45″ 2×4 will align. Use a straight edge to mark these points on the inside of the box at the 1st and 2nd level seam.
- Have a helper hold the 45″ 2×4 on the inside of the bed at these points that you’ve just marked. Ensure it straddles the 1st and 2nd level evenly.
- Affix 2×4 with 4 screws (outside in; through 12′ 2×10). 2 in each top and bottom 12′ 2×10. These screws will be close together.
- LANDSCAPE FABRIC: I used 6′ width by 14′ length to line the boxes. Centre the fabric on top of box and then push down inside box. Stand up sides and shimmy around to make even-ish. Make a single cut in fabric around the 2×4 so that fabric can go around support. Staple securely to sides. Fold up corners (it will seem bulky) and staple down. Don’t be too fussy – it will all be covered with soil!
- Each bed takes 1.5 to 2 cubic yards of soil. If you need to mix peat moss in and would like to top dress the bed with ProMix then go with 1.5 cubic yards. Use 2 cubic yards if you’re good to go without additions!