Get the base and the height right before choosing what to plant.
Raised beds are popular for good reason — better soil control, easier weeding, and for some households, easier access without bending or kneeling. But the design decisions that actually determine whether a bed performs well happen before planting: what material holds the soil, how tall the bed needs to be for its purpose, whether the base allows drainage, and how much soil volume is genuinely needed to fill it properly.
Underestimating soil volume or skipping base drainage are the two most common raised bed mistakes — both are cheap to get right at the build stage and comparatively annoying to fix once the bed is planted.
01 · Compare bed materials
Timber, corten steel and block, compared.
Timber (sleepers or boards)
CharacterWarm, adaptable, easy to build in irregular shapes
DurabilityNeeds ground-contact-rated treatment class where soil sits against it
CostGenerally the most accessible option
Corten / weathering steel
CharacterClean, modern lines with a distinctive rust-toned finish that stabilises over time
DurabilityCorrodes to form a protective surface layer; performs well long-term above ground
CostHigher than timber, priced by panel or custom fabrication
Block / besser block
CharacterSolid, architectural, can be rendered or left as a textural finish
DurabilityVery durable with minimal ongoing maintenance
CostMid-to-higher depending on finish and whether it's rendered
02 · Design decisions beyond material
Four factors that decide how well the bed actually works.
Height for purpose
A bed intended to reduce bending or improve accessibility needs to be built noticeably taller than one purely for soil control — decide the purpose before setting the height.
Base drainage
Even a raised bed needs excess water to escape at the base — a solid, undrained base can waterlog roots just as effectively as poor ground drainage would.
Sun orientation
For vegetable or productive beds, orientation relative to the sun's path matters as much as the bed itself — this should be checked before finalising placement, not after building.
Corner and joint detailing
How corners are joined affects both structural stability and how well the bed holds its shape as soil settles and expands with moisture over seasons.
03 · Working out soil volume
The calculation most people underestimate.
04 · Before building
Confirm these before construction starts.
- Decide the bed's primary purpose (accessibility, soil control, aesthetics) before setting its height.
- Confirm the base allows drainage rather than sitting on a fully sealed surface.
- Check sun orientation against the bed's intended planting before finalising placement.
- Calculate soil volume from actual measured dimensions, and order slightly extra to account for settling.
Raised garden bed design: common questions
How tall should a raised bed be for easier access?
This depends on the specific accessibility need, but beds built for standing or seated gardening are typically built substantially taller than the shallow soil-control beds common in most gardens.
Does the base need to be lined?
Not always, but if the bed sits directly on a hard surface like paving, a drainage layer or gap is worth including so water can actually escape rather than pooling at the base.
Can I use treated timber for a vegetable bed?
Modern timber treatments are generally considered suitable for garden use, but if you have specific concerns, a liner between the timber and the soil, or an alternative material like corten steel, are both reasonable alternatives.
Sources & methodology
Designed to show its working.
Timber treatment suitability for edible garden use is a common question without a single universal answer; if in doubt, use a liner or an alternative material. This guide is general design guidance, not horticultural advice for specific crops.