That's an excellent and very practical question! The short answer is: not always. Whether your outdoor bench needs a concrete foundation depends heavily on the bench's material, design, weight, and how permanent you want the installation to be.
For heavy, permanent benches made of materials like stone, cast iron, or solid hardwood, a concrete foundation is highly recommended. It prevents sinking, shifting, and wobbling on uneven ground, ensuring long-term stability and safety. Pouring a simple concrete pad or using footings is a wise investment for these types of benches.
However, many modern outdoor benches are designed for easy, foundation-free installation. Lightweight aluminum, resin, or cedar benches often come with integrated ground anchors or sturdy, wide-set legs that distribute weight evenly. For a simpler solution on level, firm ground like a patio or compacted gravel, you can frequently place the bench directly on the surface or use patio pavers as a stable base.
Before you decide, always check the manufacturer's installation instructions. For a DIY approach, consider your local climate—areas with frost heave require deeper foundations. Ultimately, while concrete offers maximum permanence for heavy benches, you have flexible and simpler options for most casual garden seating. The best choice balances durability, effort, and your specific outdoor aesthetic.