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Building a fixed raised bed is the recommended method for installing a FarmBot outdoors. In these instructions we show you how to build a simple but sturdy bed suited for FarmBot Express or Express XL. This design will fit into most yards, look great, and last a lifetime.

Maximum raised bed size

We recommend building your raised bed as large as possible to get the most value out of your FarmBot. See the economies of scale section for more information on maximizing FarmBot value.

Use the dimension guidelines in the table below to plan your raised bed design.

Model Outer Bed Width Outer Bed Length
Express 1.13m max 3m recommended
Express XL 2.3m max 6m recommended

Do not exceed the max width

While you can adjust a FarmBot to accommodate smaller width beds, you cannot adjust it for beds larger than the maximum width listed.

Longer length beds are OK

While FarmBot Express and Express XL kits only include enough hardware to allow for gantry travel up to 3m and 6m respectively, creating a longer length bed will not prevent the system from being installed.

Raised bed recommendations

  • Prevent bowing and warping of your bed and your tracks by reinforcing the bed walls every 1.5m with a sturdy post buried in the ground.
  • Use heavy duty 35 to 90mm thick (1.5 to 3.5 inch) walls so that your bed will last a lifetime and resist bowing under soil expansion pressures.
  • Fill your bed to the brim with rich, soft soil and compost. Leave out rocks and branches.

8 hours

This is the estimated time it will take to build a fixed raised bed.

Step 1: Acquire materials

  • Purchase some high quality wood from your local lumber yard. Preferably you will use thicker wood (1-2 inches thick) so that it does not warp easily. This is important because your tracks will need to be very straight for FarmBot to work reliably, and your tracks will be directly attached to the raised bed. When soil becomes wet and when plants grow, this can cause tremendous force on the wood walls of the bed, forcing them outwards. Thicker wood and extra posts are preferred. This example uses 2 x 12” nominal redwood (40 x 300mm), and 4 x 4” nominal wood posts (90 x 90mm) spaced roughly every 5 feet (1.5m).
  • You’ll also need to pick up some hardware for fastening your raised bed together. For example, 3/8” x 4” lag bolts (M10 x 100mm) and some large washers.
  • Depending on your climate, you’ll likely want to put some type of sealer, stain, or polyurethane on your wood to protect its color and water resistance like Thompson’s water sealer.

fixed raised bed materials

Step 2: Dig post holes

Position the lumber roughly where your bed will be so that you may find out where to dig your post holes.

Maintain access

Position the raised bed such that you will be able to access all sides of your FarmBot and garden.

positioned lumber

Dig the post holes. A post hole digger and pick axe can help greatly.

shovel in hole

Step 3: Prepare the materials

Sand all of the wood surfaces to remove any markings and splinters.

sandpaper on wood

Take extra time to sand the top surfaces of the long sides of the bed

FarmBot Express uses wheels to roll directly on top of the long sides of the bed. Knots, large splinters, and other surface defects in the top surfaces can cause the FarmBot to stall, or just have a more difficult time moving across the bed. Use a belt sander or circular sander to ensure there are no defects or uneven areas on these surfaces.

If desired, stain the wood or apply a protective coating of your choice.

sealed wood

Setup the lumber upside down on a flat surface. We’ll drill holes and screw together the bed in this orientation and then flip it over and position it in our holes.

lumber positioned upside down

Step 4: Assemble the raised bed

Measure out and mark where the posts will be. Remember this must correspond to where you dug your post holes!

measuring post placement

Clamp the posts into place, making sure they are square with the bed sides.

post clamped with square

Mark locations where you will drill holes and fasten the boards to the posts. This example uses 2 lag bolts and washers per board/post interface.

Don't let your bolts hit each other

On the corner posts, make sure to stagger the bolts slightly so that the bolts coming in from one side of the corner do not hit the bolts coming in from the other side of the corner.

mark post bolt hole locations

Pre-drill the holes for the lag bolts.

drill post bolt holes

Use a ratcheting socket wrench to quickly screw in the lag bolts.

Style counts

If you are using fancy washers like those shown, orient them all in the same direction before tightening down the lag bolt. Remember, you are assembling your bed upside down, so plan for the washers to be flipped when the bed is installed.

bolt and washer install with wrench

Notice how the corner bolts are staggered so that they do not hit each other, and the washers are oriented the same way.

drilling offset post corner holes

Step 5: Install the raised bed

Heavy lifting required

Grab a few friends to help with lifting and installing the raised bed in this step.

Once the bed is fully assembled, flip it over and position it in the holes. You may need to pull it out and dig out some of the holes a little more in order for the bed to sit properly. Use a level to make sure the bed is level.

Step 6: Install tensioning cables (optional)

With larger raised beds, especially those for FarmBot Express XL, it is possible that expansion and contraction of the soil will cause the longer sides of the raised bed to bend outwards, causing track misalignment. If you think that your bed will not be sturdy enough to resist bending, consider adding stainless steel tensioning cables every 3m to prevent the long sides of the bed from being pushed away from each other. The cables should be positioned in the lower half of the bed so as to not interfere with the FarmBot’s tools once buried in the soil.

Step 7: Fill the bed

Use a mix of soil and compost, and keep out large rocks and branches.

fixed raised bed filled with soil

Congrats!

Your raised bed is now ready for your FarmBot installation.