Ways to Install a Flagstone Walkway

Concrete Base

• Installing flagstone on a concrete base is one of the most preferred methods of installation. The base, usually 4 inches thick, will support the flagstone for years, preventing it from settling and cracking. This type of installation will also support more weight and can be used for driveways and patios. Nonetheless, it will require more effort because of the extra work involved in forming and pouring the concrete for the base. However, if you need extra stability for your flagstone installation, then this is the best method.

Gravel Base

• Flagstone walkways that generally will not be required to support large amounts of weight are installed using a gravel base. The gravel is installed 4 inches thick and compacted with a hand or gas tamper. Crusher-run gravel is the best type of gravel to use for this base because it compacts tightly, creating a stiff, hard surface that resembles concrete. The gravel base will move slightly, but for walkways and smaller projects, it will more than suffice.

Mortar

• Using type S mortar is best when installing flagstone on a concrete base. This mortar will harden similarly to concrete; it is mixed in a wheelbarrow with sand and water. Applying a layer of mortar on top of dried concrete and pressing the flagstones into the mortar is the typical method of installation. However, many installers use a trowel to smear mortar on the back side of the flagstone first, pressing the flagstone onto the concrete with the mortar stuck to the back.

Thin-Set

• Thin-set mortar is best used to stick flagstone to a gravel base. Thin-set is waterproof and pliable, which will allow the flagstone to move slightly along with the gravel. This mortar will not break apart with the settling of the gravel base. Builders generally use this method for any flagstone application that may settle or move in the future. The thin-set mortar is applied in the same manner as type S mortar, either on the base or directly onto the flagstone.