Pavers are a versatile, strong paving material used to build walkways, driveways and other outdoor surfaces. You have several ways to install pavers, including directly over dirt, in mortar or over a bed of gravel and sand. While you don't need to lay a gravel foundation for pavers, you should assess the condition of the base and make it as solid as possible before laying the pavers.
Pavers Over Concrete
If you want to pave over concrete, you can set pavers in sand or mortar over the existing surface. Repurposing a plain concrete slab as a foundation saves you the trouble of removing the concrete and results in a strong, long-lasting base. Check the condition of the concrete prior, and patch any pits or cracks. Set the pavers over a 1-inch layer of grit sand or 1/2 inch of mortar, and use edge restraints to secure them.
Pavers Over Dirt
A simple way to landscape a paver walkway or patio is to set the pavers directly over dirt, which is a fitting option if your yard has good drainage and the ground doesn't freeze in winter. To set pavers over dirt, remove growth and root systems from the path, and stabilize the dirt with a hand tamper. Lay down weed barrier fabric to prevent weeds from growing between the pavement, and use edging to block wayward grass.
While building a gravel base is a labor-intensive process, it offers a number of benefits for your surface. Tamped gravel creates a strong support that prevents pavers from sinking while allowing moisture to seep through and escape. Gravel is a flexible base that absorbs ground tension to prevent frost heaves while reinforcing pavers under the stress of frequent traffic or heavyweight loads.
Types of Gravel
Landscaping gravel comes in a wide range of sizes and compositions. The best type of gravel for a paver base is medium 3/4-inch crushed rock. This gravel comes in irregular shapes with sharp edges that wedge together when compacted. Small gravel typically contains sand-like particles that compact into a dense base that won't allow moisture to escape. Larger gravel is not as stable but can be used as a first layer beneath medium gravel if your soil has a heavy clay consistency.