How to make a raised garden bed

Benefits of raised beds

Raised beds are among the most useful things you can have in the garden, especially if you’re planning to grow vegetables. 

• They make gardening easier because you can do all the work from the edges, without ever treading on the soil. 
• You don’t have to dig it every year like a conventional border – simply put a 10cm layer of organic matter, such as garden compost, on the surface each year and the worms will do the work for you. 
• The beds don’t have to be very tall. Just 15cm is enough for the soil to warm earlier in spring and improve drainage. That allows you to plant sooner in the year and benefit from earlier crops, which you can then quickly replace. 
• Finally, no matter what sort of soil you have in the rest of the garden, you can fill your raised beds with something better to improve your plants.

You will need

• Four 1.8m x 15cm pressure-treated gravel boards
• One 1.8m x 10 x 10cm pressure-treated fencepost
• 5-7cm long galvanised nails
• Tools: saw, hammer, spirit level, spade, rake, plus string and canes for marking out the site.

All the materials you will need are widely available from DIY stores and garden centres.

Step-by-step guide

1 Measure and cut boards and posts

To build the wooden frame for your raised bed, first measure and cut the gravel boards to length. For easy access, the frame should measure no more than 1.2m across but can be as long as you like. 

To support the sides, cut the fencepost into 45cm lengths – 15cm of which will be above ground and 30cm below ground. Any sides longer than 2.4m will each need an additional post for support.

2 Lay out your template

Make sure the site for your bed is level and free of weeds. Once you have cut all the wood to the right size, lay out the pieces on the ground. Use this as a template when deciding on the exact position for the bed. 

Mark the site using canes and string. You can ensure the bed is perfectly square by checking that the distance between the diagonally facing corners is the same.

3 Dig trenches and holes

To help support the sides of your bed, sink them slightly into the surrounding soil. This will also help prevent its contents leaking out of the bottom. 

The best way to do this is to dig shallow trenches along each edge. You should also now dig 30cm-deep holes, ready for the posts. Pile all excavated soil into the middle of the bed.

4 Construct the frame

To construct the wooden frame, lay out the pieces on flat, open ground. First, nail the posts to each end of the two shortest sides. Then, attach the two side pieces, joining the whole frame together. 

You’ll find this easier if you use your knee to hold the posts upright. Doing this will also help ensure all the joints are square.

5 Lower the frame into place

Move the assembled frame to the prepared site and lower it into place – you might need a friend to help you do this, particularly if your frame is longer than the one we feature here. Use a spirit level to make sure the bed is level – tap down or raise the frame as necessary. 

Once level, fill in around the post holes and side trenches with soil – firm down with your foot carefully to avoid displacement.

6 Add soil and compost

The bed is now ready to fill and this is the ideal opportunity to improve the soil it contains. If your soil is light and free-draining, incorporate lots of garden compost or composted bark to help it retain moisture. 

If your soil is heavy or badly drained, mix in both composted bark and sharp gravel. Once the bed is filled, water it well.

7 Cover adjacent paths with chipped bark

Now that your bed is ready to be planted up with your choice of plants, you need to complete the final step – make tending your raised bed as easy as possible. 

Cover any adjacent paths with chipped bark. This will make a convenient access point and will also mean that your paths are pleasant to walk on. Plus, the bark helps suppress weeds and will give you a more comfortable surface to kneel on.