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Inspiration & Advice

How to erect a raised garden bed
with Retain-iT

How to erect a raised garden bed with Retain-iT

Ready to lift your outdoor DIY game? Raised garden beds are great for growing small plots of veggies and flowers. They also offer other benefits, including improved drainage and soil preferences. Look difficult? You don't know Jack!

Whether you want to add a raised bed to a small front yard or create rows of boxes and become a green-thumbed pro, Jack Retain-iT System makes the job easy. Plus, as they’re made from galvanised steel, they stay rust-free for years.

Retain-iT is also super flexible and comes in three types – corner, joiner and end posts. You can also choose from four post heights to suit heights of one, two, three or four sleepers, as well as two post widths – 50mm or 75mm.

Ready to give raised garden beds a go? Just follow the steps below!

Jack Retain It project - equipment

What you'll need

Before you get outdoors and start building your raised garden bed, make sure you grab everything on the list. Plus, check your local council’s retaining wall regs.


Suggested Jack products:

Retain-iT 50mm classic posts
Retain-iT® Classic 50mm System View Product
Retain-iT 75mm classic posts
Retain-iT® Classic 75mm System View Product

Additional tools & materials

All Retain-iT are available in a galvanised steel or black powder-coated finishes.

  • Wooden sleepers (ask your timber merchant to cut to size)
  • Quick set or regular concrete
  • Post hole shovel
  • Heavy grade plastic (builder's film 100/200um), a weed mat, or drainage fabric (geo-fabric)
  • Timber slats
  • Topsoil and irrigation (optional)
  • Circular saw & drill
  • Essentials - Pencil, tape measure, spirit level, hammer & timber block (buffer)
  • PPE (safety glasses and protective footwear)

Your step-by-step guide

  1. Plan & design

    Plan your layout and measure out the area of your soon-to-be garden bed. A good sunny spot shielded from the wind is ideal. Then work out how many posts are needed as well as what type of posts – joiner, end or corner.

    If your raised garden bed is longer than 2.4m, a joiner post will do the trick instead of extra-long sleepers. If it butts up against another structure, an end post will make your wall tidy and secure.

    Retain-iT 50mm wide posts work great for most raised garden beds. 75mm posts, on the other hand, are stronger, chunkier and ideal for retaining walls.

    Handy Jack tips! • Retain-iT can go four sleepers high (800mm above ground), but three sleepers (600mm) give better access – saving your back! • A raised garden bed should be level, so use different heights of Retain-iT on sloping blocks. For gentler gradients, simply push the lowest sleeper part into the ground.

    Now it’s time to determine the length and number of sleepers you need. Ask your local timber supplier for timber species and size recommendations. 75mm sleepers are typically less likely to twist than 50mm.

    Use ACQ-treated pine sleepers when growing edibles. You can easily add a suitable liner to your garden bed if needed.
  2. Level, mark & prep post holes

    Level the area using your post hole shovel, then mark where each post will go. Now it’s time to start digging!

    A petrol-driven post-hole digger can make light work of those holes.

    Dig holes for each post, ensuring a snug fit. A 200mm diameter is enough.

    For stability, posts should be roughly halfway below the ground. The measurements above provide a guide but make sure the tops of your posts are level, and the sleepers fit neatly.

  3. Build & concrete

    Grab your first two posts and slip them into two adjacent holes. Then pop one of your sleepers between them to ensure it all aligns. We recommend two pairs of hands for this part – and don’t forget your spirit level!

    Use a line level and string line to ensure your post heights are correct. Once your heights are set, you can position your posts and start concreting them in.

    When positioning your posts, concrete one at a time, adding sleepers as you go. The sleepers will help you align the posts for a squarer finish.
  4. Secure, level up & line

    Once you’re happy everything’s in line, pour in your concrete and add water. Before it sets, there’s still time to adjust the levels if needed. Repeat this process on each side of the garden bed.

    A simple way to make sure your garden bed is square is to measure the diagonals. If they’re the same length, then you’re good to go!

    Start adding your sleepers to form your bed until you reach the top – and don’t forget to keep checking those levels. Next, grab your heavy-grade plastic and line the inside. Once done, add a couple of drainage holes to the base.

    Finally, add some timber capping. For this, cut and lay timber around the top edge of your garden bed structure and screw-fix in place. We recommend a timber sleeper mitre cut to fit.

    This step is optional but looks good and provides a handy place to sit!

  5. Time to plant!

    Now your raised garden bed is assembled, fetch those bags of soil and start filling it up! The final step is putting in those baby seedlings.

    With your keen green fingers, they’ll be shooting up in no time!