I want to build a raised garden bed from scratch - what materials to use and what to avoid?

[IronQuarry98]

Raised beds have become one of the most popular garden projects and for good reason: better drainage, better soil control, fewer weeds, easier on the back. The range of materials available is wide and the advice online is contradictory. Untreated wood rots. Treated wood may leach chemicals. Galvanised steel is expensive. Recycled plastic is durable but polarising aesthetically. Brick and block last forever but require proper construction. What has worked for people here and what would you do differently.

[Daemon82]

Douglas fir or larch untreated is the answer for most people. Both are naturally rot-resistant, both last 10-15 years in contact with soil, and neither has the chemical leaching concerns of pressure-treated timber. The treated wood debate is mostly settled for timber that is not in direct food contact but I still prefer untreated for edibles

[BigDog26]

Galvanised steel corrugated beds are worth the extra cost if you are doing this long-term. They look good, they last effectively forever, they warm up faster than wood in spring and they require zero maintenance. The upfront cost is the only real barrier

[Oscar73]

Line the inside of wooden raised beds with heavy-duty pond liner stapled to the frame. It does not affect drainage if you leave the bottom open but it extends the life of the wood significantly by reducing direct moisture contact. Adds about three to five years to the lifespan

[Delulu66]

Fill with a mix of topsoil and compost rather than buying expensive raised bed compost alone. A 60/40 or 70/30 topsoil to compost ratio is both better structured and significantly cheaper than all-compost fills which can compact and lose structure quickly

[RayOfLight99]

Avoid railway sleepers unless you can verify they are new ones not actual reclaimed railway sleepers. Old sleepers were treated with creosote which absolutely does leach into food-growing soil and is genuinely toxic. New decorative sleepers are fine

[ShawnMichaels99]

The depth question matters more than the material. For most vegetables 30cm is the minimum useful depth. For root vegetables you want 40-45cm. Most pre-made raised beds sold in garden centres are 20cm which is too shallow for anything except salad leaves and herbs