The best way to secure an outdoor bench on grass or dirt is usually a two-part approach: create a stable, compacted base under the legs, then anchor the bench with hardware that bites into undisturbed soil. You don’t need a concrete slab, but you do need to stop the bench from sinking, rocking, or sliding.
Start by looking at the bench legs. If the bench has flat feet or wooden legs, galvanized screw-in ground anchors are my favorite option. These look like large screws with a bracket or loop on top. You screw them into the soil at each leg location, then bolt the legs or brackets to the anchor heads. They work well in grass and dirt because they cut through the sod and grip the firmer soil below. If your soil is sandy or loose, use longer anchors so they reach more stable ground.
The second part is the base. Grass and dirt are soft, so even an anchored bench can slowly sink if the legs sit directly on the surface. Dig out a shallow area about 4 to 6 inches deep under each leg, or clear the full bench footprint. Put down landscape fabric, then add 3 to 4 inches of crushed stone or paver base. Compact it with a hand tamper until it feels solid. Add a thin layer of sand or stone dust, level it, and place a concrete paver or pressure-treated timber pad under each leg. This spreads the weight and keeps the legs out of wet soil. Then install the ground anchor through or next to the paver into the soil.
For a quick and cheap fix, heavy-duty steel stakes or rebar can work. Drill a hole through the bottom of each wooden leg at an angle, then drive a 12 to 18 inch galvanized stake through the hole into the ground. This stops sliding and reduces rocking, but it can loosen over time in soft soil. If the bench is light or exposed to wind, don’t rely on stakes alone.
If the bench has post legs, metal post spikes are a solid choice. These are U-shaped or box-shaped brackets with a long spike attached. Drive the spike into the ground, set the post in the bracket, and bolt it in place. For a more permanent hold, dig a hole at each post, set the bracket in the hole, fill around it with crushed stone or a dry concrete mix, and tamp it down. This is still not a full concrete slab, but it creates small, sturdy footings.
For heavy benches or high-traffic areas, buried concrete deck blocks work well. Dig them in so the top is just above grade, level them on compacted stone, and attach the bench legs with anchor bolts or brackets. This gives you concrete-like strength without pouring a large slab. You can hide the blocks with mulch or let grass grow around them.
A few practical tips: remove sod and organic topsoil before anchoring, because loose thatch doesn’t hold. Slope the area slightly away from the bench so water drains. Check the anchors after the first heavy rain since disturbed soil settles. If you live where the ground freezes, use anchors rated for frost or set footings below the local frost line for a permanent bench.
If I had to pick one best method for most backyard benches on grass or dirt, I would level a compacted paver base under the legs, then secure the bench with galvanized screw-in ground anchors. It’s strong, low-profile, removable, and you never have to pour concrete.