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Short answer: Metal lasts two to five times longer and costs more up front; wood is cheaper, warmer to the touch, and you will rebuild it. Over twenty years metal is almost always the cheaper choice. Over three years it isn't. Pick based on how long you intend to garden in that spot, not on which material sounds more natural.
Most comparisons of this kind are written by someone selling one of the two. Here's the version with the trade-offs left in.
The comparison at a glance
| Galvanized metal | Untreated softwood | Cedar / redwood | Treated lumber | |
|---|---|---|---|---|
| Lifespan | 15–30 yrs | 3–7 yrs | 10–20 yrs | 10–20 yrs |
| Up-front cost | Moderate to high | Lowest | Highest | Low to moderate |
| Cost over 20 yrs | Lowest | Highest (4–6 rebuilds) | Moderate | Moderate |
| Assembly | Bolt together, under an hour | Cutting, drilling, squaring | Same as softwood | Same as softwood |
| Shape options | Rectangular, oval, round | Rectangular only, realistically | Rectangular only | Rectangular only |
| Summer heat | Walls get hot; soil largely unaffected | Cooler walls | Cooler walls | Cooler walls |
| Spring warming | Faster — earlier planting | Slower | Slower | Slower |
| Chemical questions | Zinc; coating quality varies | None | None | Copper-based preservatives |
| Repairability | Replace a panel | Replace a board | Replace a board | Replace a board |
| Appearance over time | Dulls to soft grey | Greys, then rots visibly | Weathers to silver | Greys, can warp |
Cost, properly calculated
Comparing purchase prices makes wood look obviously cheaper. That comparison is misleading, because the two materials aren't buying the same span of time.
Run it over twenty years for a single 8 × 4 ft bed:
- Untreated pine at roughly 5 years per build: four to six rebuilds. Add the lumber each time, the hardware, and a weekend of work.
- Cedar at roughly 15 years: one build, possibly a second. Expensive at the start.
- Galvanized metal at 15 to 30 years: one build.
There's a cost people leave out of these calculations: rebuilding means emptying the bed. That's several cubic yards of soil moved twice, and it's the part of the job nobody enjoys. It's also when soil gets lost, mixed with subsoil, or simply not put back properly.
The honest summary: if you're gardening in a place you'll be for ten-plus years, metal wins on cost. If you're renting, or trialling whether you'll stick with gardening at all, cheap softwood is the rational choice and there's no shame in it.
Where wood genuinely wins
Three things, and they're real:
Extreme heat. Wood insulates; metal conducts. The difference at the root zone is small — soil thermal mass dominates — but in Zone 10 and 11 it isn't zero, and a gardener in Phoenix who replaces beds without complaint has a defensible position.
Lowest possible entry cost. A few boards and some screws will get you growing this weekend for very little.
Custom dimensions. If you need a bed to fit an odd space exactly, wood is cut to whatever length you want. Metal comes in the sizes it comes in.
A fourth, softer point: some people simply prefer how wood looks in a garden. That's a legitimate reason and doesn't need justifying with performance claims.
Where metal wins
Longevity, by a wide margin. The primary failure mode of a wooden bed is that the wood is in permanent contact with wet soil, which is exactly the condition wood is worst at surviving. Metal doesn't have that problem.
No rot, no splinters, no annual sealing. Wooden beds want re-sealing or oiling to reach the upper end of their lifespan. Most people do it once and then stop.
Assembly. Bolt-together panels versus cutting, squaring and joining lumber. If you're building four beds, this difference stops being trivial.
Shapes wood can't do. Oval and round beds are impractical to build from lumber at any reasonable effort. Curves change how a garden reads — and an oval bed has no interior corners, which is where soil warms last in spring and gets planted least.
Earlier spring planting. Metal warms the soil faster, and soil temperature governs germination. A week or two at the front of the season is a real gain.
Thinner walls, more growing area. A 2-inch board on each side of a 4 ft bed takes about a third of a square foot out of the footprint. Sheet metal takes almost nothing.
The safety question, briefly
Both materials attract concern, and both concerns are manageable.
Metal. Galvanizing is a zinc coating. Zinc is an essential nutrient for plants and people, and migration into edible tissue under normal garden conditions is minimal — it rises mainly in acidic soil below about pH 5.5, and most vegetables want 6.0 to 7.0 anyway. The variable worth checking isn't metal versus wood, it's coating quality: ask any manufacturer whether the steel meets ASTM A653 and what the coating designation is.
Treated lumber. Modern residential pressure-treated wood uses copper-based preservatives. Arsenic-based CCA was withdrawn from residential use in the US in 2003. The genuine risk is reclaimed lumber of unknown age — old decking, railway sleepers, and salvaged timber whose treatment history nobody knows.
Untreated wood. No chemical questions at all. It just rots, which is the trade you're making.
What about other materials?
Concrete block. Effectively permanent, cheap, and heavy. It can raise soil pH over time as lime leaches out, which matters for acid-loving crops. Old blocks may contain fly ash. The look is divisive.
Plastic and composite. No rot, moderate lifespan, and additives that vary a great deal by manufacturer. Degrades under UV, and can become brittle. Rarely the cheapest or the longest-lasting, which makes it hard to recommend on either axis.
Stone and brick. Beautiful and permanent. Expensive, immovable, and a real construction job rather than an afternoon.
Fabric grow bags. Cheap, excellent drainage, and genuinely good for a season or three. They're containers rather than beds — smaller soil volume, so more watering — and they wear out.
How to choose, in one page
Choose metal if: you'll be in this garden long-term, you want to build once, you want a shape other than a rectangle, you're in a cool or temperate climate, or you're building several beds and assembly time matters.
Choose untreated softwood if: you're renting, you're not sure gardening will stick, you want to start this weekend for very little, or you need an exact custom size.
Choose cedar if: appearance matters to you, budget isn't the constraint, and you want wood that lasts.
Choose treated lumber if: you want wood longevity at a lower price than cedar and are comfortable with modern copper-based treatment. Buy new, not reclaimed.
Choose concrete or stone if: this is a permanent landscape feature and you're prepared for a construction project.
The question that actually resolves it: how long do you expect to be gardening in this spot? Under five years, cheap wood is rational. Over ten, metal is. Between the two, it's genuinely a toss-up and you should pick on looks.
Frequently asked questions
Are metal or wood raised garden beds better?
Metal lasts 15 to 30 years against 3 to 7 for untreated softwood, so it's cheaper over the long run despite costing more up front. Wood is cheaper to start, cooler in extreme heat, and can be cut to custom sizes. The deciding factor is usually how long you plan to garden in that spot.
Do metal raised beds last longer than wood?
Considerably. Galvanized metal typically lasts 15 to 30 years depending on coating weight. Untreated softwood lasts 3 to 7 years because it sits in permanent contact with wet soil. Cedar and treated lumber fall in between at 10 to 20 years.
Are metal raised beds more expensive than wood?
Up front, usually yes. Over twenty years, usually no — untreated wood needs four to six rebuilds in that time, and each rebuild means emptying and refilling the bed.
Is treated wood safe for a vegetable garden?
Modern residential pressure-treated lumber uses copper-based preservatives and is generally considered acceptable. Arsenic-based CCA was withdrawn from residential use in the US in 2003. Avoid reclaimed lumber whose treatment history is unknown.
Do metal raised beds get hotter than wooden ones?
The walls do. The soil largely doesn't, because a filled bed holds enough soil and water to buffer daily temperature swings. In very hot climates the difference is worth managing with mulch, drip irrigation and afternoon shade.
Can you make round or oval raised beds from wood?
Not practically. Curved beds from lumber require steam bending or segmented construction, which is a woodworking project rather than a garden one. Metal panels curve easily, which is why oval and round beds are almost always metal.
Which raised bed material is best for a rental property?
Untreated softwood or fabric grow bags. Both are cheap, and neither is a loss if you move. Save the long-lifespan materials for a garden you own.
Decided on metal? Next: choosing between 12", 24" and 36" heights, planning your layout, and working out how much soil you'll need.