How to build a raised garden bed with sleepers

Start by selecting a suitable spot for your raised garden bed. Choose an area with plenty of sunlight and good drainage to ensure healthy plant growth. The size and shape of your garden bed—whether square or rectangular—will depend on the available space. Once you’ve decided on the location, measure out the area where the bed will go and use a line marker to outline the space. A common measurement is 2400mm from the edge and 600mm from the inside, but you can adjust it to suit your needs.

At each marked corner, dig a hole for your upright posts. The depth of the hole will depend on how high you want your garden bed to be. If you already have existing posts in place, additional ones may not be needed. For longer garden beds, it’s a good idea to add extra posts for additional stability and support.

Measure and mark where your sleepers will go, ensuring they fit your chosen layout. Use a circular saw and square to cut them to the correct size. When lapping or butting sleepers together, remember to allow for their thickness so that your measurements remain accurate. Once cut, lay the sleepers in position to form the shape of your garden bed.

Once the sleepers are positioned to form the shape of your garden bed, it’s important to secure them in place to maintain their alignment. Start by checking that each sleeper sits flush against the next, ensuring there are no gaps or uneven edges. If the ground beneath is uneven, adjust by adding or removing soil so the sleepers sit level.

To keep the sleepers steady while you work, use a nail gun to temporarily pin them together. This will help prevent movement and make it easier when screwing them into place. If you don’t have a nail gun, you can use clamps or temporarily screw the sleepers together with smaller batten screws before securing them fully. Taking the time to align and fix the sleepers now will ensure a strong and stable raised garden bed

To join the corners securely, align them at a 90-degree angle. Pre-drill two holes in each corner to prevent the timber from splitting, then drive galvanised screws (minimum 100mm long) through one sleeper into the adjoining sleeper. Once all the sleepers are screwed together, check that the structure is level.

Before securing the uprights, ensure your garden bed frame is properly aligned. Use a builder’s square in each corner to check that all angles are correct. To keep the structure steady while you work, attach a temporary timber offcut across each corner. This will help maintain the shape of the garden bed and prevent movement.

Next, determine how high you want your raised garden bed to be and cut your upright posts accordingly. The posts should be long enough to reach from the bottom of the post hole to the top of the bed. A common height for upright posts is 1400mm, but this can be adjusted based on your design. Before installing the posts, apply a coat of bitumen timber protector to help protect them from moisture and prolong their lifespan.

Position each upright post into its designated hole at each corner of the garden bed. Use a spirit level to check that each post is plumb and correctly aligned before securing it in place. Once positioned, attach the uprights to the sleepers using 100mm bugle batten screws, ensuring they are firmly connected.

Repeat this process for all uprights, double-checking the alignment as you go. Taking the time to secure the posts properly will provide extra strength and stability to your raised garden bed.

Once the upright posts are securely in place, mix up your concrete and fill each post hole, stopping just below ground level. Allow the concrete to dry completely before moving on to the next step.

Once the uprights are set, it’s time to build up the height of your garden bed by adding more sleepers. Stack another layer of sleepers on top of the first, ensuring the joints between layers are offset to increase strength and stability. Secure each layer by screwing the sleepers into the upright posts.

For longer garden beds, prevent bowing over time by installing galvanised metal straps on the inside of the structure. These should be evenly spaced along the length of the bed to help keep the sleepers aligned.

To protect the timber from rotting over time, line the inside walls of the raised garden bed with a protective barrier. This step will help extend the lifespan of your garden bed, especially if you’re growing plants that require frequent watering.

Now that your garden bed is built, it’s time to fill it with soil. Choose a high-quality garden soil mix that suits the plants you plan to grow. Fill the bed to just below the top edge of the sleepers, leaving enough room for mulch if needed.