DIY Redwood Raised Garden Beds Built Over Poor Soil
Two 4 × 8 ft raised beds framed in Douglas fir and clad in garden-grade redwood, with a smoother redwood cap that doubles as a bench. They were built on the site of a demolished house, where the ground was not considered safe for growing food.
Raised bed number one, planted. Photo: Kathy Nativi, Public domain, via Appropedia
The story behind this build
When a campus sustainability center moved houses, the old building was demolished and left an empty plot. The center wanted to use the land for growing, but the soil around the old foundation was considered unsuitable for food.
The answer was raised beds that keep the growing soil separate from the ground below. The builder flagged out two 4 × 8 ft plots where the center wanted them and built both beds with screws rather than nails, so they could be taken apart without wrecking the wood if the center ever needed to move them.
How it is designed
Two beds, each 4 × 8 ft.
A frame of Douglas fir 2×4s, reinforced so the bed could be moved if needed.
Sides of garden-grade redwood 2×8s, screwed on so the beds can be dismantled.
A cap of smoother, better-grade redwood along the top so people can sit on the edge without splinters.
A layer of cardboard under each bed to stop weeds from the ground growing up, and gravel for drainage.
A coat of boiled linseed oil to protect the wood from rain.
Materials they used
Garden-grade redwood 2×4 and 2×8, about 133 ft
Redwood 2×8, about 60 ft (including the smoother cap boards)
Douglas fir 2×4: 8 ft and 10 ft lengths for the frames
About 2 lb of screws and 2 lb of nails
Cardboard
Gravel
Potting soil
Boiled linseed oil
Tools
Electric drill
Hammer
Wood saw
Clamps
Ruler and pencil
How they built it
1Mark the plots
Two 4 × 8 ft plots were flagged out where the center wanted the beds.
2Level the ground
The ground inside each plot was dug over with a garden hoe and levelled so the frames would sit flat.
3Lay cardboard
A layer of cardboard went down over the ground to stop weed seeds in the old soil from growing up into the beds. Cardboard breaks down over time.
4Build and reinforce the frames
The Douglas fir frames were measured, pre-drilled and screwed together, with extra reinforcement added.
5Add the redwood sides
The garden-grade redwood was screwed to the outside of the frames, so the beds can be taken apart later.
6Fit the top cap
Smoother redwood was fitted along the top edge to make a comfortable place to sit, and all the edges were sanded.
7Add gravel, oil and soil
Gravel was added for drainage, the wood was coated with boiled linseed oil, and the beds were filled with donated potting soil. Then it was time to plant.
More photos
Raised bed number one from another angle. Photo: Kathy Nativi, Public domain, via AppropediaOne of the two redwood beds. Photo: Kathy Nativi, Public domain, via AppropediaRaised bed number two. Photo: Kathy Nativi, Public domain, via Appropedia
Use and upkeep, from the builders
Re-oil the wood every year or two to keep it protected.
Top up the soil each season as it settles and is used up.
Our notes if you build one
Cardboard stops weeds but rots away within a season or so. If you suspect contamination in your ground, get the soil tested and look up local advice on barriers before growing food.
Rags soaked in linseed oil can catch fire by themselves as they dry. Spread them out flat to dry or keep them in water in a closed metal container.
A wide cap on a raised bed is a cheap upgrade: it makes a seat and stops rain soaking into the end grain.
Credits and license: Built and documented by Chelsea, a student at Humboldt State University (now Cal Poly Humboldt). Originally published on Appropedia: “CCAT Raised Garden Beds” under CC BY-SA 4.0. This page is our summary of their documentation and is shared under the same license (CC BY-SA 4.0); photos are credited individually. Measurements and costs are the builders' own and refer to their site and year. DIY Outdoor Builds did not build this project.
Building work can be dangerous and may need a permit. Check local rules and use a qualified professional for electrical, gas and structural work.
Built something like this?
Share your own version with your photos, measurements and what you changed.
Guide
