Good question—most standard urban benches weigh between 60 and 250 pounds (27–113 kg) once assembled, but the real number depends heavily on material and length. A typical 6-foot park bench with cast iron or steel legs and wooden slats usually weighs around 120–180 lbs (54–82 kg). All-steel benches tend to run 150–250 lbs (68–113 kg), while aluminum frames can be as light as 40–80 lbs (18–36 kg). Recycled plastic benches usually land between 60 and 120 lbs (27–54 kg). Concrete or stone benches are the outliers: a small concrete bench can start around 300 lbs (136 kg), and larger precast units can exceed 600 lbs (272 kg).
For a rooftop installation, do not just look at the bench’s total weight. You need to check your roof’s structural capacity, including dead load and live load, and think about point loads from the legs or mounting feet. A 150 lb bench sounds light, but if all of that sits on four small feet, the pressure per square foot can be high. Use a structural engineer or check the building’s load ratings before placing heavy furniture. On typical residential roofs or balconies, aim for lighter options under 120 lbs, and distribute the load with pads, pavers, or a leveling base. On a commercial roof, you may have more capacity, but you still need to protect the membrane and account for wind uplift.
If you are installing rather than just placing the bench, anchoring is another weight-related issue. Bolting through a roof requires proper flashing and waterproofing, and it may not be allowed in a rental or condo. Freestanding or ballasted benches avoid penetrations, but they need enough weight or a wide base to resist wind. For most rooftop projects, I would look for aluminum or recycled plastic benches with a wide footprint, keep the total weight under about 150 lbs unless a professional says otherwise, and add rubber pads or a protective mat underneath.
So for planning, use 80–180 lbs (36–82 kg) as a realistic range for a normal metal-and-wood urban bench, and stay closer to 60–120 lbs (27–54 kg) for a rooftop unless you have verified the structure.