Great question—and the short answer is: yes, many urban benches are suitable for a rooftop garden in terms of weight, but the deciding factor is usually your roof's load capacity, not just the outdoor bench weight.
Most standard urban benches made from aluminum, powder-coated steel, or wood/composite slats weigh about 40–80 lbs for a 5–6 ft unit. Because that weight is spread across the bench footprint, the added dead load often works out to roughly 8–15 lbs per square foot. For comparison, an occupied rooftop in many residential buildings is designed for a live load of about 60–100 lbs per square foot. In that context, a single lightweight urban bench is normally not a structural problem.
That said, a few weight-related checks matter for rooftop garden benches. Avoid cast iron, solid concrete, or oversized stone pieces unless a structural engineer has approved them—they can be extremely heavy and create concentrated point loads. Check the bench legs too: small metal feet can press into waterproofing or deck tiles, so look for wide feet, rubber pads, or a sled-style base. Also remember furniture is only part of the total roof load; people, planters, wet soil, pavers, and snow all add up.
If the rooftop is classified as an occupied roof terrace or roof deck, a lightweight urban bench is generally fine. If it is a balcony, an older building, or a green roof with limited structural capacity—or you plan to add several benches and heavy planters—confirm the allowable load with a structural engineer or building manager first.
So practically: yes, lightweight urban benches are suitable for a rooftop garden weight-wise when chosen carefully, placed to spread the load, and kept within the total rooftop furniture weight your roof can handle. When in doubt, get an engineer's approval.