How to Build a Raised Garden Bed
From railway sleepers to bricks - build productive raised beds that last.
Difficulty
Easy
Time
2-4 hours
Cost
£50 - £300
Before You Start
If using old railway sleepers, check they are not creosote-treated (banned for garden use due to harmful chemicals). New landscaping sleepers are safe. Wear gloves when handling treated timber. If building on a patio or hard surface, ensure there is drainage so water does not pool. Do not place raised beds directly against house walls where they could cause damp.
Raised beds are one of the best investments for any garden. They warm up faster in spring, drain better than ground-level beds, and save your back from bending. You can build one in a few hours from timber sleepers or scaffold boards. The height is up to you - 300mm is fine for most vegetables, but 600mm or higher is better for root crops and makes gardening more accessible. Fill them with a good soil and compost mix and you will grow better crops than in most garden soil.
What You Will Need
Tools
- - Drill/driver
- - Saw (hand saw or circular saw for timber)
- - Spirit level
- - Tape measure
- - Spade
- - Wheelbarrow
- - Set square
Materials
- - Timber sleepers, scaffold boards, or treated timber
- - Coach screws or timber connectors
- - Weed membrane (for the base)
- - Topsoil and compost mix
- - Drainage material (broken pots, gravel)
- - Staple gun and staples (to fix membrane)
Step-by-Step Instructions
Choose Your Size and Position
Standard beds are 1.2 metres wide maximum - you need to reach the centre from both sides without stepping on the soil. Length can be whatever suits your space. Choose a spot that gets at least 6 hours of sun per day. Avoid overhanging trees.
Prepare the Ground
Clear the area of weeds and turf. You do not need to dig the ground out. Simply level it roughly. Lay weed membrane over the footprint to suppress weeds growing up through the bed.
Cut and Assemble the Frame
For timber sleepers: cut to your desired lengths. Stack sleepers on their sides to the height you want (typically 2-3 sleepers high, giving 200-300mm). Drill pilot holes and secure each corner with long coach screws or timber screws. Check the frame is level and square.
Line the Inside (Optional)
For timber beds, lining the inside with heavy-duty plastic (pond liner works well) protects the wood from constant soil moisture and extends its life significantly. Staple it to the inside face, leaving the bottom open for drainage.
Add Drainage Layer
Place a 50mm layer of broken pots, coarse gravel or rubble in the bottom. This ensures excess water drains freely. This is especially important on clay soil.
Fill with Growing Medium
Fill the bed with a mix of topsoil and compost (roughly 60/40 ratio). Leave 30mm from the top to prevent soil washing over the sides when watering. The soil will settle by about 10% over the first few weeks - top up after a month.
Plant and Mulch
Plant your chosen vegetables, herbs or flowers. Water well. Apply a 50mm layer of bark mulch or compost around plants to retain moisture and suppress weeds.
Pro Tip: The Lasagne Method
Fill deep raised beds in layers like a lasagne: cardboard on the bottom, then woody prunings, then leaves and grass clippings, then compost, then topsoil on top. This saves buying huge amounts of topsoil and creates incredible growing conditions as the layers decompose.
Pro Tip: Free Timber
Scaffold boards make excellent raised beds and are often available cheaply from building sites or recycling centres. They are thick, robust and last many years.
Common Mistakes to Avoid
- - Making the bed too wide - you cannot reach the middle and end up stepping on the soil, compacting it
- - Using untreated timber - it rots within 2-3 seasons and the bed collapses
- - Filling entirely with compost - pure compost shrinks dramatically as it decomposes and becomes waterlogged
- - No drainage layer on clay soil - the bed becomes a waterlogged bath that drowns plant roots
- - Placing in deep shade - most vegetables and flowers need minimum 6 hours of direct sun
When to Call a Professional
Raised beds are a genuinely straightforward DIY project. However, if you want brick or stone beds built on permanent foundations, or beds integrated into a larger landscaping scheme with retaining walls and steps, a landscaper will ensure structural integrity and proper drainage.