Gilles' Outlet

May 24, 2010

Building a Raised Vegetable Bed

Filed under: Carpentry — Gilles @ 5:31 am

Two cedar vegetable raised bed are built by section and installed. Metal brackets are installed to provide additional strength.

 
Skill Level: 2~3 (Basic~Moderate) Time Taken: About 8 hours

There are countless designs for vegetable raised beds. In this article, we built two raised bed using techniques borrowed from fine furniture construction: beds are divided in four sections which are built in the shop and then assembled on site.

Since we were concerned about the possibility of chemicals used for pressure treated lumber seeping out, we decided to build the beds with 5/4’’ non treated cedar decking.

Left: The starting point of the project. Several days before, I located a suitable spot for the raised bed: a nice nook exposed to the sun for the longest possible time.

I used scrap lumber to precisely mark the position of the two raised beds.

 

Right: The lumber for this project: 5/4’’ cedar decking (left) and 2×4 cedar (right). It is exactly the right amount of lumber and there will be only minimal waste.

Cedar is sold green and it is typically not a good idea to store it in direct sunlight for long periods of time: this cause it to dry prematurely and create bad checks.

Left: I cut three pieces of 5/4’’ cedar decking to length and held them side by side with two clamps. I chose the best looking side and made sure it will face outwards. Clamps allowed the boards to be tightly  pressed against each other, leaving no gap in between boards.

This will become a side of the raised bed.

Right: I cut one 2ft long piece of 2×4 cedar and clamped it on the right side of the previous assembly. This piece of lumber will eventually be buried underground.

Left: I marked an “x” at the center of the 2×4 and the side board. Since these will be visible, I made sure these marks where perfectly aligned.

 

Right: I drilled a 3/8’’ hole at each mark.

Left: A 3/8’’ galvanized carriage bolt, with flat washer and hex nut. This is the fastener I will use to attach the sides to the 2×4. There will be two fasteners per board which accounts for a total of six fastener per side.

 

Right: The carriage bolt gets inserted into the previously drilled hole, then the washer and the nut.

Left: I used an impact driver equipped with a socket to tighten all carriage bolts.

 

Right: After repeating the previous steps on the other side, I easily completed one section of the two raised beds.

Left: The design called for a raised bed to be rectangular with one side almost 1ft bigger than the other. The picture shows the “larger" side at the top and the “smaller” side below.

 

Right: Top view of one of the raised bed’s corner when assembled: the two 2×4 were located so that they would fit snuggly …

Left: … giving a clean outside edge. This design was preferred over a mitered corner because it gives a more rustic appearance. Also, mitered corners on wood exposed to weather eventually always open, leaving unsightly gaps.

 

Right: View of the same corner from the inside: because the 2×4 are snug, corners can be reinforced with metal brackets for added strength.

Left: I dug four holes which will act as the foundations for the project. These are almost 18’’ deep. In this area, the frost line is at 1ft so any foundation must be at least 12’’ in the ground to avoid frost jacking.

 

Right: Detail of one of the holes: the bottom is flat, lays on undisturbed soil and any organic matter was removed.

Left: I installed the fist section in the foundations and leveled it.

 

Right: Be Level. I made sure the side stood level.

Left: Be Plumb. Each side was tweaked to be perfectly plumb. This is harder than it looks. I had to use several pieces of scrap lumber to hold the side in place as I was leveling.

 

Right: When I reached the desired position, I dropped crushed rock at the bottom of the foundation. This will help stabilize the side as a well as provide extra drainage.

Left: I used a scrap 2×4 to compact the crushed rock. It is important to compact often when backfilling to avoid settling.

 

Right: Other sides can be installed by repeating the previous steps. As I installed more sides, I also made sure they were square.

When everything was plumb, level and square, I completely backfilled foundation holes with soil, making sure I compacted often.

Left: I installed three galvanized metal brackets per corner to make sure they would stay plumb and true. These bracket are manufactured Simpson Strong Tie.

 

Right: I secured them with four 2 1/2’’ exterior screws.

Tools Used:

  • Power Miter Saw.
  • Clamps.
  • Power Drill + 3/8’’ Wood Drill Bit.
  • Impact Driver + Socket
  • Various Spirit Levels
  • Speed Square / Framing Square.
  • Spade Shovel.

Materials Used:

  • 2×4 Cedar.
  • 5/4 Cedar Decking.
  • 3/8’’ Carriage Bolt + Washer + Hex Nut.
  • Simpson Strong Tie Galvanized Brackets.
  • 2 1/2’’ Exterior Screws.
  • 3/4’’ Crushed Rock.

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