While homeowners typically build a patio over a cleared, flat surface, you can build a patio on grass. The ground needs to be fairly level, and you do put down a barrier that eventually kills the grass underneath the patio pavers. Building a patio on grass is a good way to build an inexpensive patio in an out-of-the-way nook of your backyard that may help you take advantage of shade or a special view. Be sure to build the patio large enough to accommodate any lawn furniture you plan to set on it.
Select your location. While you don't have to dig up the sod, you should remove any large stones or other objects that are within the perimeter of the patio.
Mark the location where you plan to build a patio. Use string tied to stakes to mark the edges.
Purchase a tarp the size of the patio you are building. While you can use landscape fabric, a lightweight tarp provides enough barrier to kill any grass under it within six months. Lay the tarp on the ground within your patio boundary. Hold it in place with a few shovels of mulch, pea gravel or sand, whichever you plan to use to hold the pavers in place.
Dig a trench for the landscape timbers to be set in. You can dig it deep enough so the top of the timbers are flush with the ground, or you can make the trench deep enough to allow the timbers to sit slightly above the ground.
Line the bottom of the trench with the edges of the tarp. Set the timbers in the trench. Back fill dirt around the edges of the timbers to hold them in position.
Put a layer of sand, pea gravel or mulch over the tarp. Use a hand tamper to press the material firmly into position.
Set the pavers on the sand, pea gravel or mulch. Wiggle them back and forth to set them firmly into the base material. Use a level to keep the pavers level with the outer perimeter. Arrange the patio pavers in whatever pattern suits you. You can pack the pavers close together or you can create a more informal area by spacing the pavers farther apart.
Add more base material until it comes to the top of the pavers. As the pavers settle, you may need to add more base material to keep the pavers level.
If your patio doesn't drain well, you may need to punch one or two small holes in the tarp to allow water to soak away into the ground beneath the patio. Plan the size of your patio to match the length of your landscape timbers. This saves you from the need to cut the timbers.