Raised beds on an allotment
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Raised beds are worth it on poor, heavy or waterlogged soil. Keep them under 1.5m wide and at least 30cm deep, with paths of 45cm or more. On good soil they're optional, and they need more watering.
Raised beds look tidy and they're easy to plan around. They also cost money, and they need filling. Whether they're worth it depends on your soil, your budget and your site rules.
When raised beds help
The RHS lists a few clear benefits:
- Poor or heavy soil. You fill the bed with a fertile, free-draining mix, which helps if your soil is poor or gets waterlogged.
- Earlier starts. The soil warms up sooner in spring.
- Drainage. On heavy, wet ground, better drainage is one of the ways the RHS suggests reducing clubroot in brassicas.
There's a practical plus too: with fixed beds and paths, you never walk on the soil you grow in.
When they don't
- They dry out faster. Plants in raised beds suffer from drought sooner and worse than plants in the ground, so you'll water more. Check the soil a finger's depth down.
- They cost money. Timber, fixings and fill add up, and you may need to buy a lot of soil.
- Your site may have rules. Ask before building anything permanent. Some councils, Bolton for example, need written permission for structures such as sheds. Check whether yours counts raised beds too.
On good, free-draining soil, plain beds marked out with paths can do the same job for much less.
Sizes that work
| RHS guide | |
|---|---|
| Width | Under 1.5m, so you can reach the middle from both sides |
| Depth | 30cm suits salad leaves and strawberries; most plants need 45cm or more |
| Paths | At least 45cm for a wheelbarrow; at least 1m for a wheelchair |
Length is up to you. Shorter beds mean less walking round the end.
How much soil and compost?
Work out the volume: length × width × depth, all in metres. That gives cubic metres, and 1 cubic metre is 1,000 litres.
Worked example. A bed 2.4m long, 1.2m wide and 0.3m deep holds 2.4 × 1.2 × 0.3 = 0.864 cubic metres, or about 864 litres.
The RHS suggests a fill of mostly topsoil with organic matter and horticultural sharp sand (not builders' sharp sand). Our raised bed fill guide goes through the mix and the order sheet.
Allotment plot planner
Enter your plot size and the crops you want. Get a to-scale bed layout, a 4-year rotation, how many plants fit, and how long clearing will take at the hours you have.
Materials
Pressure-treated timber is a popular, long-lasting choice for the frame. Untreated wood is fine but doesn't last as long. For timber quantities and cutting lists, Plankley covers raised-bed timber.
FAQs
How deep should a raised bed be for vegetables?
30cm is enough for salad leaves and strawberries. The RHS says most other plants need 45cm or more. On an allotment the bed sits on soil, so roots can grow down into the ground below.
How wide should the paths be?
At least 45cm if you need to get a wheelbarrow through, or 1m for a wheelchair.
Are raised beds worth it on an allotment?
They help most on poor, heavy or waterlogged soil. On good soil they're optional, and they mean more watering.
Your next step
Measure your plot and try a layout in the plot planner. It works out the soil volume for each bed. Then read the raised bed fill guide before ordering.
Allotment plot planner
Worked example
For a half plot (5 poles, about 126 m²), a quarter already clear, 4 hours a week, a shed and compost bays:
- 10 beds of 1.2 m with 45 cm paths, beds running across a plot about 19.5 m by 6.5 m
- Rotation: 8 beds in four groups, moving one step each year
- Broad beans: room for about 68 plants; Onions (sets): room for about 256 plants; Cabbage: room for about 68 plants; Carrots: room for about 1080 plants; Potatoes: room for about 86 plants; Courgettes: room for about 14 plants
- Clearing: about 95 m² to clear, roughly 12 weeks at 4 hours a week (our rule of thumb of 2 m² an hour)
- A 5 cm compost mulch over all the beds: about 3.9 m³, or 78 bags of 50 litres
Based on: National Allotment Society (NSALG), RHS. Crop spacing from RHS grow-your-own guides.
Sources
- National Allotment Society (NSALG): A traditional full allotment plot is 10 poles (rods or perches), about 250 square metres checked 24 Oct 2026
- RHS: RHS crop rotation: group crops (brassicas, legumes, onions, potato family and roots) and move each section a step forward every year to limit soil pests and diseases checked 24 Oct 2026
- RHS: RHS raised beds: fertile, free-draining fill helps on poor or waterlogged soil and warms up sooner in spring; beds dry out faster and suffer drought more; keep beds under 1.5m wide to reach the centre from both sides; 30cm deep suits salads and strawberries, most plants need 45cm or more; paths at least 45cm for a wheelbarrow, 1m for a wheelchair; pressure-treated timber is popular and durable, untreated wood has a shorter life awaiting check
- RHS: RHS clubroot: Plasmodiophora brassicae; swollen, distorted roots and stunted, wilting plants; resting spores contaminate soil for up to 20 years; liming and better drainage reduce it but don't eliminate it; raise transplants in pots at least 9cm; some resistant cultivars; avoid moving soil on tools and boots; no chemical control for gardeners awaiting check
- Bolton Council: Bolton Council example: tenants must get written permission before erecting a shed, greenhouse or polytunnel, or planting fruit trees (a local rule, not UK-wide) checked 24 Oct 2026
- RHS: RHS raised beds: a mix of mostly topsoil with organic matter and horticultural sharp sand (not builders sharp sand); beds on hard surfaces and drainage-loving plants need adjusted mixes; depth depends on the plants checked 24 Oct 2026