Installing urban benches on soil rather than concrete requires careful preparation to ensure stability and longevity. The key lies in creating a proper foundation that prevents sinking, tilting, and weathering. First, assess your soil type. For stable, well-draining soils like sandy loam, a compacted gravel base is often sufficient. Excavate an area slightly larger than the bench footprint, about 6-8 inches deep. Fill this with crushed gravel or road base, compacting it in 2-inch layers using a hand tamper or plate compactor until you have a solid, level base.
For less stable or clay-heavy soils that retain water, a more robust solution is needed. Consider using ground screws or helical piers. These are metal posts screwed deep into the ground, bypassing unstable topsoil to anchor in firm subsoil. The bench legs are then securely bolted to the posts' above-ground brackets. This method provides excellent stability with minimal site disturbance.
Another effective method is using concrete footings discreetly placed below grade. Dig holes for each bench leg, approximately 12-18 inches deep and 10 inches in diameter. Place a form tube and pour concrete to just below the soil surface. Embed a galvanized steel post anchor or J-bolt into the wet concrete. Once cured, attach the bench legs. This "buried concrete" approach offers a permanent hold while maintaining a natural soil appearance on the surface.
Always ensure proper drainage by sloping the foundation base slightly away from the bench center. Use pressure-treated or naturally rot-resistant timber for any wooden components in contact with the soil. With the right foundation, your soil-installed bench will remain a sturdy and welcoming public fixture for years to come.