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How to Build a Flagstone Patio

Flagstone patio being built.

Take the time to learn how to build a flagstone patio and give yourself the tools and information you need to transform the exterior of home into a fully-functional space for hosting parties, enjoying dinner outside or simply relaxing outdoors with your favorite book. Of course, before you can start enjoying your splendid new patio, you have to put in the work building it.

Materials and Tools Needed

  • Flagstone
  • Sand
  • Broom
  • Landscape fabric
  • Small sledgehammer
  • Chisel
  • 2 x 4 plank
  • Tamping tool
  • Rubber mallet
  • Saw
  • Hammer and nails
  • Tape measure
  • Carpenter's level
  • Protective eyewear and gloves
  • Spade
  • Shovel
  • Wooden stakes
  • String

Building a Flagstone Patio

Before You Begin

Choose a spot for your flagstone patio. Ideally, the ground will already be as level as possible to greatly reduce your prep work. Take measurements before you start any work. Mark the dimensions of the patio using wooden stakes with string. If you want a patio that's perfectly defined, take a measurement diagonally from corner to corner on one side and another measurement of the other two corners. Both measurement readings should be the same if your design is true.

Removing the Sod

Inside your string border, start removing the sod using the spade. A spade is just a flat version of a shovel that's designed to lift sod. Plunge the spade into the ground, about four inches deep, all the way around the border of the patio. If you're planning on keeping the grass for use elsewhere in your yard, scrape it off using the spade. If you're not interested in keeping the grass in shape, just start digging the entire patio space out to a depth of four inches using a regular digging shovel. A four-inch depth is the minimum recommendation for a flagstone patio.

Level the Ground

Set a length of 2 x 4 plank along the floor of your patio and set the carpenter level on top of it to take level readings across the space. Add or remove soil wherever it's needed to maintain the level reading. Perform this with the plank running the width and the length of the patio space.

Apply Landscape Fabric and Sand

Moisten the ground with a water hose and use the tamping tool to tamp the ground down. Apply a layer of landscape fabric over the dirt to help prevent weeds from growing up through the flagstones.

Dig a trench all the way around the inside of the perimeter approximately an inch and a half in depth so you can set 2 x 4s into the trench along the outer edge of the space. Approximately two inches of the 2 x 4 will be above the surface level of the space which is exactly how much room you need for sand. Digg the trench and insert the boards, so you can fill the mold up to the top with the sand, making the installation that much easier. Fill the mold with sand and slide a length of 2 x 4 across the surface of the sand to make it level. Since most flagstone pieces are two inches thick, your surface is now at the perfect level for the flagstone.

Installing the Flagstone

Start in one corner, place the first flagstone and tamp it down with a rubber mallet. Set the next flagstone, keeping the gap between the two as small as possible. Continue laying flagstone pieces down while tamping each one and checking for level as you go.

If you come across a piece of flagstone that's too thin or thick, simply add or remove sand until it fits. If a piece of flagstone is too big for a space, draw a cut line on the stone with a pencil, score the line with a bolster chisel and use the small sledgehammer to remove the excess.

Finishing the Flagstone Patio

Once all the flagstones are in place, spread a layer of sand over the surface of the patio. Use the broom to sweep and spread the sand into the cracks and crevices between the stones.

Remove the 2 x 4 mold from around the edge of the patio and fill in the area with sand. Tamp the sand down using the butt-end of a 2 x 4, do not use the tamping tool or you may accidentally hit a piece of flagstone, which may crack it.

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Additional Tips

These instructions are for a flagstone patio that sits away from the house. If your patio is being built up against the house, install it on a slight grade away from the house so water will flow away from the building.

If your yard has poor drainage or you're installing the patio in a spot where the yard is always wet, add some additional drainage under the patio. To do this, simply excavate down two more inches and apply a two-inch layer of crushed stone before you apply the sand.

Inexpensive flagstone is usually two-inches thick, which is good for most patios, but if you prefer a little more durability, purchase thicker stones for an increased cost. These stones are more expensive and more difficult to work with because they can be quite heavy, but your patio will be stronger and more durable.

How to Build a Flagstone Patio