Flagstone Patios & Walkways

About Flagstone

• Quarry operations use several varieties of stone to produce flagstone materials, particularly limestone, sandstone, granite and slate. Of the common types of stone used to produce flagstone, granite is the most durable but also the heaviest and most difficult to cut. Flagstone from sandstone is generally the lightest flagstone and easiest to cut. However, sandstone and other lightweight, soft stones break and crack more easily than dense, heavy stones. Manufacturers split the stones into slab-like forms that range from about 1- to-3 inches thick. Flagstones are available in rectangular form or randomly shaped, natural edges.

Installing Flagstone Over Concrete

• Installing flagstone over concrete is much like installing ceramic or stone tiles over a prepared substrate. However, the most important aspect of flagstone-over-concrete installations is the condition of the concrete slab or pathway. A concrete surface with deep, long cracks and uneven areas is an unsuitable base for flagstone. Damaged concrete surfaces require refinishing before flagstone installation. Many builders form and pour brand new slabs for flagstone patios and walkways. Like tiles, a layer of mortar adheres the natural flagstone materials to the slab's surface.

Preparing a Base for Dry Installation

• The term "dry installation" refers to pavers or flagstones set directly atop a level base of gravel and sand. The gravel acts as a buffer between the flagstones and the heaving and settling of the ground's surface. Atop the gravel, a layer of sand provides a smooth, even base for the final placement of flagstones. Builders place thick gravel layers, often 12 inches or more, for heavy traffic areas and thin layers, less than 6 inches, for low traffic areas.

Laying Flagstone-Dry Installation

• Builders lay flagstone atop the paver base's sand layer and tap the material into place with a mallet. To cut flagstone to size, builders use either a hammer and chisel or power tools, such as a motorized circular saw or a tile wet saw. With all flagstone pavers in place, the builder fills the joints between pavers with either fine sand or mortar. Whether sand or mortar, the builder wets the joints with a hose and sweeps away excess filler.