How to build raised garden beds in four easy steps

Close up of a women watering vegetables in a raised bed
(Image credit: Getty Images)

If you need more growing space in your garden, learning how to build raised garden beds is a quick and effective way to create room for flowers, plants, shrubs and vegetables. They provide a versatile and quick access platform that offers easy maintenance.

That’s why raised garden beds are often an integral part of garden design. When designing a new outdoor space you can choose where you want them to go and decide what type of foliage and greenery will enhance the space.

Here we give you the knowledge and know how to start building your own today.  

How to build raised garden beds: step-by-step

When building a raised bed there’s plenty of choice on materials and sizes. Here we show you how to build a raised bed with wood. But the same principles can be applied to other materials. 

Before starting, you'll need a couple of key materials and tools, including:

  • Wooden planks/boards 
  • 1” x 1” timber (optional)
  • Drill 
  • Screws
  • Topsoil
  • Compost

1. Plan ahead

Before you start, work out where you want to place your raised bed. Ideally you want to make sure that the bed will be exposed to sunlight and not hidden in the shade from shrubs, bushes, hedges and fences.  

2. Prepare the ground 

Once you have decided on where you are going to build your raised bed you need to prepare the ground. Typically, raised garden beds are placed on top of turf. 

Measure and mark out where the bed is going with wooden pegs and string. Get a spade or a lawn edger like the Draper Carbon Steel Lawn Edger from Amazon and cut the turf around the marked out area. 

Now get a spade and skim off the top layer of turf across the whole marked out area and place out of the way. Once the turf has been removed, get a garden fork and turn over the soil and remove any weeds.

3. Build your raised bed

With your chosen wooden planks, start to assemble your bed. If using scaffold boards, or pine decking planks you will need to use some 1” x 1” timber to hold the boards or planks together. 

Cut four lengths the same height as the boards/planks and cut a shallow point on the end of each length. Now screw each length – an inch or two down from the top edge – into the boards/planks on each corner to create the rectangular base of your raised garden bed.

Now measure both diagonals to make sure the frame is straight. If both diagonals are the same length you have done a good job. 

If you are using timber sleepers you can simply use long screws to join the sleepers together. 

If you want a higher raised bed simply make longer pegs for decking planks or place another layer of sleepers on top of the original and screw into place. But remember the higher the bed the more soil and compost you will need.

4. Add topsoil and compost 

Raised beds are for growing plants or vegetables, so you don't want to be using any old soil from your garden. You need to fill your new beds with a mixture of topsoil and compost to make sure that the soil has enough nutrients to grow the plants or vegetables you choose.

You will also need to regularly add more compost or organic material to make sure that the soil stays healthy for growing. On this note, now is a great time to try organic gardening methods to make your raised garden beds more environmentally friendly.

Make sure to leave the soil for a week to let it settle. If needed, add more soil/compost mixture in areas that have sunk further than others and leave to settle again.   

What size should I make my raised beds? 

Raised garden beds are typically around six to eight feet long (1.8-2.4m), around four feet (1.2m) wide and anywhere from six inches (around 15cm) to three feet (90cm) or more high. 

The length of a raised bed is subject to choice. An ideal size is around eight feet, but can be shorter or longer depending on space and what you want to grow. 

The width of a raised bed is more important. You don’t want to be treading on the bed and compacting the soil. So four feet is probably the maximum, but make it narrower if you are not comfortable leaning across this distance, or can't gain access on both sides. 

The height is typically the width of the wood chosen, but you might want to double or even triple up on the height depending on what you are growing. 

What wood should I use when building raised beds? 

The popular choice is pine as this is relatively inexpensive and easy to get hold of. Oak and cedar are also popular but more expensive than pine. You could look for recycled scaffold planks or decking to keep the price down.

The issue with wood is that it will rot over time and needs replacing. It’s a good idea to treat it with a suitable preservative like Ronseal Matt Decking Protector from B&Q before you build the raised bed.  

What is the cheapest way to build raised garden beds?  

Pine decking is one of the cheapest easy ways to build a raised garden bed. If you do some scouting around on the web you can find some really good deals. Reclaimed scaffold boards are another inexpensive wood that does a good job. 

If you want something ready to go you can take a look at the Verve Large Raised bed kit from B&Q. It's not as cheap as building your own raised bed, but it does mean you can start planting sooner.

Wood is not the only cheap option for building a raised bed. Concrete blocks and some bricks can be relatively cheap, easy to lay and will last longer than wood.  

How high should you fill a raised bed with soil? 

The simple answer is that you fill to the top of the raised bed and leave to settle. The height of a raised bed needs to be high enough to contain whatever you are planting or growing. Most plants and vegetables need around one foot (30cm) of soil to grow, but if you are placing your raised bed on soil, six inches (around 15cm) is enough.

If you want easier access to the soil – maybe you don’t want to be bending over too far – building a higher raised bed is the answer.  

Do you need a membrane under raised beds? 

Typically you wouldn’t need to place a membrane under raised beds if they have been placed on open soil and weeded. 

However, if you have a shallow raised bed that has a lot of weeds in the soil, it is a good idea to lay down a membrane. 

Cardboard is a good cheap choice as it will suppress weeds and grass and will naturally decompose making it an ideal choice of your looking for low maintenance garden ideas. Alternatively, a designated weed membrane can be used.

Steve Jenkins

Steve is Homebuilding & Renovating's DIY content editor, and has been a writer and editor for two decades. He is an avid DIYer with over 20 years of experience in transforming and renovating homes. He specialises in painting and decorating, but has strong all-round building skills, having previously worked in the industry for 10 years.