Honestly, the overall process feels similar at first because you still have to position the bench, mark your holes, and make sure everything is level. But once you get past that point, installing a park bench on grass and installing one on pavement become very different jobs.
On grass, the main challenge is keeping the bench stable over time. Soil moves, softens when wet, and can settle. If you just place a bench on the lawn, the legs will likely sink unevenly within a few months. So for a permanent installation, I usually dig post holes for each leg or at least for the two main support points. You want to go deep enough to get below the loose topsoil, often around eighteen to twenty-four inches, depending on your frost line and soil type. Then I pour a few inches of gravel into the bottom of each hole for drainage. After that, the bench legs can be set in concrete footings. The concrete should be mixed fairly stiff and sloped away from the metal or wood so water does not pool around the base. Some people prefer ground screws instead of concrete because they are faster and create less mess. A ground screw anchors into the soil like a large metal corkscrew, and the bench bolts to a bracket on top. That can work well if your soil is not too rocky. But in loose sandy soil or heavy clay, concrete footings are still the safer bet.
The other thing on grass is drainage. If the area stays wet, the bench legs will sit in moisture and rot or rust faster. I usually recommend placing a compacted gravel base under the bench footprint or at least raising the footings slightly above grade. This keeps the hardware out of standing water. You also need to think about mowing. If the bench legs are surrounded by grass, trimming around them becomes annoying. A small mulch bed or paver pad under the bench solves that and looks intentional.
On pavement, the job is less about digging and more about drilling. You are anchoring into concrete or asphalt, so the bench needs to be attached with bolts or anchors rated for that material. For concrete, I typically use wedge anchors or sleeve anchors. You mark the bench base holes directly on the slab, drill with a hammer drill and masonry bit, clean out the dust, then drive the anchors through the bench base. Tighten them down gradually and check for level. If the concrete is old or cracked, you may need to move the bench slightly to avoid anchoring into a weak spot. For asphalt, the process is a little less rigid because asphalt can soften in summer heat. Some installers use longer lag anchors or concrete footings poured beneath the asphalt. In many cases, it is better to anchor benches on concrete pads rather than directly into asphalt, because asphalt moves more with temperature changes.
One big advantage of pavement is that the base is already hard and level, so you do not need to worry about sinking. The downside is that pavement can hold heat, so a metal bench in full sun gets hot. You also have to be careful not to crack the slab by over-tightening anchors or drilling too close to an edge. A common rule is to stay at least three to four inches away from any slab edge.
In both cases, use stainless steel or galvanized hardware. Outdoor benches take a lot of weather exposure, and cheap bolts will rust quickly, leaving stains on the concrete or weakening the connection. I also recommend using a level before you finish tightening everything. On grass, you can adjust the footing height with extra gravel or concrete. On pavement, you can use stainless steel washers or small shims to fix minor unevenness.
If you want the simplest comparison: grass installation is mostly digging, drainage, and pouring footings or driving ground screws. Pavement installation is mostly drilling, cleaning holes, and bolting with the right anchors. Both are doable for a confident DIYer, but pavement work usually requires a hammer drill and good masonry bits, while grass work requires a post hole digger or auger and some patience with concrete.
Whichever surface you are working with, take the time to get the base right. A park bench that wobbles or tilts after one season feels worse than no bench at all. And if you are installing in a public area or park, check local guidelines for footing depth and anchor requirements before you start.