Raised bed lifespan claims from manufacturers are often measured under ideal conditions, not the wet soil, freeze-thaw cycles, and constant moisture contact a real garden bed experiences. Here is what to actually expect from each common material.
Untreated pine or fir
The cheapest option, and the shortest-lived — expect 4 to 6 years before the bottom boards need replacing due to constant soil moisture contact, even with a liner.
Cedar or redwood
Naturally rot-resistant oils extend life significantly over pine — a reasonable expectation is 10 to 15 years, with the corners (where end-grain is exposed) typically failing first.
Galvanized steel
Properly galvanized steel beds regularly last 15 to 20 years or more, with the main failure point being scratches or cuts in the coating that expose bare metal to rust, rather than uniform wear.
Composite or recycled plastic lumber
Effectively immune to rot, and a realistic 20-plus-year lifespan, though composite boards can warp or sag over long unsupported spans more than wood or metal, and are the most expensive option upfront.
The variable that matters more than material choice
Drainage matters more than the material itself — a cedar bed sitting in permanently waterlogged soil will fail faster than a pine bed with excellent drainage. Elevate beds slightly and ensure they are not sitting directly on non-draining surfaces like concrete.
