Raised beds

How deep should a raised bed be?

The short answer

30cm is deep enough for salad leaves and strawberries; most other plants need 45cm or more (RHS). On open ground, where roots can carry on into the soil below, the sides can be much lower: RHS school guidance uses edging boards 10 to 20cm tall. Keep beds under 1.5m wide so you can reach the middle, with paths at least 45cm wide.

The right depth depends less on the crop than on what is underneath. A bed on soil only needs to lift and loosen the top; a bed on paving or tarmac is the whole root run.

How deep

30cm is deep enough for dwarf bulbs, salad leaves and strawberries.(RHS)
45cm or more for most plants.(RHS)
On open ground, sides of 10 to 20cm are enough, because roots grow on into the soil below.(RHS)
On tarmac, at least 50cm high.(RHS)
Deeper than 50cm: RHS removes the turf and topsoil underneath and puts rubble or subsoil in the base for drainage.(RHS)

How wide, and the paths

Under 1.5m wide lets you reach the centre without treading on the soil.(RHS)
Around 1.2m is the width RHS gives for no-dig beds, reachable from either side.(RHS)
Paths at least 45cm wide for a wheelbarrow; 1m for a wheelchair.(RHS)
Run long beds north to south for even sunlight.(RHS)

What to fill it with

Mostly soil. A bed filled mainly with compost slumps as it breaks down.(RHS)
RHS mix: 7 parts topsoil, 3 parts organic matter, 2 parts sharp sand (garden compost, leafmould or well-rotted manure for the organic matter).(RHS)
Fill to about 5cm below the rim and let it settle.(RHS)
On a hard surface, add plenty of drainage holes.(RHS)

How much it takes to fill

Length × width × depth. Allow a little extra for settling.

Volume to fill a raised bed, in litres
Bed	20cm deep	30cm deep	45cm deep
2.4 × 1.2m	576 litres	864 litres	1296 litres
1.8 × 0.9m	324 litres	486 litres	729 litres
1.2 × 1.2m	288 litres	432 litres	648 litres

Arithmetic, not a source figure: 1,000 litres is one cubic metre.

Raised beds dry out faster

Plants in raised beds suffer from drought more quickly and more severely than in the ground.(RHS, RHS)
Check a finger’s depth down before watering.(RHS)
The soil warms sooner in spring, one of the reasons to have them.(RHS)

Do you need a raised bed at all?

On an allotment the question is usually beds or rows: raised beds or rows on an allotment?

Where the sources differ
Question	RHS raised beds feature	RHS how-to page
When they are worth it	Only really needed where the garden soil is waterlogged; vegetables grow just as well in the ground.	Lists wider benefits: drainage on poor or heavy soil, warmer soil in spring, and easier access.

Pots and beds, on one plan

Add your pots and beds to Vercro with what is growing in each. It keeps the record, and Today shows the few jobs that matter each morning.

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Where this comes from

The growing advice on this page comes from the published sources below, each linked beside the point it supports. Where two good sources disagree, we show both rather than choosing the convenient one. Reviewed 19 September 2026.

How to Make a Raised Bed, Royal Horticultural Society. Read 19 September 2026.
Growing veg in raised beds, Royal Horticultural Society. Read 19 September 2026.
Creating raised beds (school gardening), Royal Horticultural Society. Read 19 September 2026.
No-Dig Gardening, Royal Horticultural Society. Read 19 September 2026.