Once you decide to build a fire pit, where are you going to put it? If you have a patio already, you might want to place it on the patio. Or you could create an addition to the patio just for the fire pit. Or maybe just off the patio, in a near-by but separate area. Or you may have a spot in your yard where it is hard to grow grass that beckons for a touch-up.
If you are considering placing a fire pit within an existing patio, you need to evaluate both your fire pit and your patio materials. Although some fire pit designs will support being placed on top of an existing patio, it is generally not the best approach. If your patio is made from manufactured or natural stone pavers dry set on sand or stone dust, you can remove the patio materials where you want your fire pit and place the fire pit directly on the patio base. If your patio is concrete or a wet set installation, you will not have the option to remove it. In that case, you will be limited in what type of fire pit you super-impose on top of your patio.
If the design of the fire pit places the fire on the ground, the fire pit cannot be built on top of existing patio materials without damaging the patio. If the material in the fire pit is not completely flat on the bottom and / or the surface of the patio is not completely flat, the fire pit cannot be built on top of the patio without being unstable, i.e., wobbling or potentially falling over.
If you want to create a new area, adding an extension to the patio or creating a nearby free-standing fire pit area can be the easiest options. If placing the fire pit on what is currently dirt or grass, the area needs to be dug out, lined with separation fabric, and filled with 4-6 inches of stone. (This will create a base for your fire pit very similar to the base that is placed under a paver or natural stone patio.) This base will create a solid underpinning for the fire pit so it will not move (wobble) or sink while also avoiding the risk of burning dead branches or roots in the ground.
One final thought on location: Avoid areas under trees or too close to your house or other flammable objects on your property. You don’t want your beautiful warm and inviting addition to produce a catastrophe.