Outdoor flagstone tile can be a beautiful addition to your landscaping. Flagstone, a natural stone that must be quarried and sawed into tiles, has a natural pattern of veins and colors that are unrivaled. The tiles are cut into 12-by-12-inch or 16-by-16-inch squares that are 1 to 2 inches thick. They are extremely resilient to blunt force and extreme weather conditions, such as rain, sleet and heat.
The base of the tiles must be either concrete or crushed stone. If concrete is chosen, then the pad must be at least 4 inches thick. Make sure that the concrete is pitched for water runoff; a 5 percent pitch in the concrete will suffice. Make sure that the water drains away from foundations and footings of surrounding structures.
If you choose to use crushed gravel as a base, then pitch the gravel in the same way as the concrete. You will need to remove 8 to 10 inches of dirt from the proposed area in which the tiles will be installed---4 inches for the gravel, 2 inches for the sand and 2 inches for the flagstone. Installing the base on top of filter fabric will prevent weeds from growing through the installed tile. The entire gravel base should be installed in the following way: landscaping fabric, 4 inches of gravel tamped with a hand tamper, 2 inches of sand and then the flagstone.
When preparing to lay flagstone tile, it is best to provide layout lines on the surface of the base materials. Use chalk lines for your layout lines. Measuring off your layout area into four equal segments will allow you to work efficiently, while keeping your tile square. Use a carpenter's square to check the layout line.
There are several basic tools necessary for installing flagstone tile. You will need a notched trowel for spreading mortar onto a concrete base and a regular mason's trowel for spreading mortar onto a gravel base. Using a 4-foot hand level will help keep the tiles level once they have been laid onto the surface. Type S mortar should be used for laying flagstone tiles, but remember to seal the flagstone with a concrete sealer before you lay them. The mortar used to lay the flagstone will seep into the pours of the tile and will be very difficult to remove if sealer is not applied. Once the flagstone tiles are laid, using a grout bag to fill the joints will be the cleanest and easiest way to fill in between the tiles. After cleaning the flagstone, it is best to seal the grout joints to prevent stains from penetrating the joints, as well as to prevent water from entering the joints and freezing during the winter. Freezing water will expand and crack the flagstone.