Williamsport Herb Guild - Building a Raised Bed

Building a Raised Bed

Why raised beds?

There are many advantages to using raised beds in the home garden. Few of us are blessed with perfect soil. When using a raised bed, the gardener can create whatever type of soil that is preferred by the crop to be grown. Whether sandy, loamy or average, the gardener controls the soil, not the other way around. Root crops no longer have to grow around rocks and stones in the soil. Drainage is never a problem in a raised bed because excess water can freely pass through the soil and exit. Because the soil and roots are above the ground level, the soil will warm faster in the spring, allowing the plants to begin growth sooner. Because a raised bed has a defined barrier, people will not be walking on the soil and compacting it. There is no need to roto-till the soil every planting season; the soil will turn over easily with just a garden spade. Also, working in a raised bed can be much easier on your back. The beds can be built to whatever height puts the soil at a comfortable working level. The beds could even be built as a table-like structure so that a wheelchair bound person can enjoy "hands in the dirt gardening". Finally, raised beds add another element of design to the garden. They add structural definition, as well as order to the plantings, and give a certain amount of vertical depth. Imagine bush nasturtiums cascading down the front edge of a raised bed.

The following describes the construction of a basic raised bed ruggedly made of wood. The design is simple, to compliment most garden styles. It is capped off with a trim piece to give it a finished look as well as a place to rest garden tools and harvest baskets. The dimensions of the bed used in this example are 48x48x12-1/2 as it is very easy to reach into the bed from all sides to the center of the bed. You can, however, adapt the plans to build a bed best suited to your situation. The choice of wood product to use for the project is a personal one. Natural pine will decay with time and is not a good choice. Cedar is naturally resistant to decay, but without regular treating with chemical sealers it too will go through the processes of nature. It is also an expensive material to use. Pressure treated lumber, while less expensive is a gardening "hot potato". The debate over trace chemicals contaminating the soil continues. There are arsenic-free treated lumbers available, if you chose this material, make sure it is suitable for direct contact with the soil. Another alternative is artificial lumber. These are new on the market and vary greatly in their composition from totally synthetic to wood/plastic composites. Some cannot be used in direct contact with the soil. The brand Trex is a wood/plastic composite which is widely distributed and can be used in contact with the soil. The material used in this example is common pressure treated lumber. I chose this material for my own herb beds over much debate, finally deciding that I would worry about arsenic poisoning when I started serving parsley as a meal. (My vegetable beds, however, are constructed of Trex lumber.)

Materials list:

(4) 2x6x10 pressure treated boards

(2) 2x4x10 pressure treated boards

(1) 10' piece of pre-punched angle iron

(1) 10' piece of channel strut

Stainless steel washers

1" and 3" deck screws

(4) "L" or angle brackets

* Note that the actual thickness of lumber will vary even when purchased from the same retailer. Please take measurements before every cut to ensure that all pieces will fit as planned.

Step 1

Begin by cutting the 2x6's into 49-1/2" boards (48" + the thickness of the 2" side*). Using the 3" deck screws, screw through the left hand side of one 2X6 boards into the right hand end of the next. Use three evenly spaced screws to prevent "cupping" of the board. Counter-sink each screw. Attach the third board to the second in the same manner. Attach the forth board as above, finishing by screwing into the end of the first board. This will be the bottom layer. Repeat the process to make the second layer.

Step 2

Stack the second layer on top of the first and measure the overall height (approx 11" *). Cut 8 pieces of angle iron and 8 pieces of channel strut to the length just measured. Using the stainless steel washers attach the angle iron to the four inside corners of the bed using the 1" deck screws. Measure to the center of each side and attach the channel strut (flat side back), again, using the stainless steel washers and 1" deck screws. (This step may seem like overkill, but it is recommended to keep the sides flush with each other).

Step 3

Measure the inside of the bed to verify an inside dimension of 48x48. Cut the 2x4 boards into lengths 48" + 2 widths of the 4" side (approximately 54" *). Cut each end of each board off at a 45 degree angle. Lay the first board on top edge of the first side of the bed, lining up the inner edges of each. Center the the board so that the left and right sides of the bed line up with the insides of the 45 degree cuts. Using the 3" deck screws attach the 2x4 board to the top edge of the side of the bed. Repeat for each of the remaining sides, working in a counter-clockwise manner. When all four sides are attached turn the bed up-side-down. Using the 1" deck screws attach the "L" brackets near the edge of the underside of each of the corners of the 2x4 trim pieces. (This step will help keep the top even in the case of warping). Turn the bed right-side-up again and sand any unevenness smooth at the angle cuts on the 2x4's.