How to Install a Flagstone Patio: Our Step-by-Step Guide

Elevate the style of your backyard patio beyond a slab of concrete with a flagstone patio. Follow our step-by-step guide and build yours.

flagstone patio sitting area with garden stream
Photo: Edward Gohlich
Project Overview
  • Working Time: 8 hours
  • Total Time: 3 days
  • Skill Level: Intermediate
  • Estimated Cost: $150+

Flagstones, bricks, or pavers are options to make a backyard concrete patio more than a cold, gray slab. To start creating a patio for your yard, pick a spot where you want to build it and sketch a basic plan. Then, before you break ground, contact your local utilities to make sure you don't disturb any underground lines, pipes, or cables. Also, decide which method you'd like to use to install your patio: sand or mortar. This piece covers both ways.

Budget Patio

Choosing Flagstone Patio Pieces

Flagstone patio paver pieces are fractured or cleft into flat slabs of various lengths, with 2 inches or more thickness and random edges. The flagstone most commonly used for patios include bluestone, limestone, redstone, sandstone, granite, and slate. Irregular shapes suit flagstone works for casual, free-form plans. Cut stone is flagstone finished with straight edges and square corners. It ranges from about 1 foot to 4 feet across and comes in different thicknesses. Cut flagstone is suited to more formal geometric designs.

Whatever type you choose for your flagstone patio pavers must be at least 2 inches thick to avoid cracking or breaking. A ton of stone covers about 120 square feet; order 5 percent more for breakage. Large stones cover a surface more quickly than smaller pieces but may prove more challenging to move, cut, and design.

Unlike ceramic tile, you can set flagstone in a sand base. A mortared installation, however, will give you years of maintenance-free use of your flagstone paver patio. A mortared patio requires a slab to provide a solid base. Cleft stone installations require an exterior mortar, generally Type M (which has high compressive strength) or Type S (high lateral strength).


What You'll Need

Equipment / Tools

Sand Method

  • Sledgehammer
  • Yardstick
  • Shovel
  • Tamper
  • Rake
  • Utility knife or saw

Mortar Method

  • Hammer
  • Small sledgehammer
  • Carpenter's pencil
  • Mason's trowel
  • Rubber mallet
  • Mortar box
  • Sponge
  • Shovel
  • Mortar bag
  • Height gauge


Sand Method

  • Crushed limestone or gravel
  • Builder's sand
  • Edging
  • 10 inch metal spikes
  • Flagstones, pavers, or bricks
  • Polymer sand (optional)

Mortar Method

  • Brickset
  • Flagstone
  • Mortar
  • 2x lumber


How to Install a Flagstone Patio Using the Sand Method

  1. Budget Patio

    Remove the Old Patio

    Determine the size and shape of your new flagstone patio.

    Wear safety goggles and use a sledgehammer when removing the old patio.

  2. Budget Patio

    Excavate Accordingly

    To facilitate drainage, excavate the area to a depth of at least 8 inches. The finished flagstone patio should be level with the surrounding yard. To determine how deep to excavate, add 6 inches (4 inches compacted base plus 2 inches sand) to the thickness of your flagstones. Our flagstones were 3 inches thick; we excavated to a depth of 9 inches.

  3. Budget Patio

    Add a Base

    Add base material. Gravel is good, but crushed limestone works even better to prevent settling. The deeper your base level, the less you'll see your patio shift during winter.

  4. Budget Patio

    Tamp after adding a couple of inches of base material to ensure a solid foundation. The compacted base should be 4 inches deep.

  5. Budget Patio

    Add Sand for Drainage

    Level a 2-inch layer of builder's sand with a rake. Sand helps with drainage and makes it easier to position the pavers and level the flagstone patio.

  6. Budget Patio

    Install Edging

    Install edging around the patio's perimeter, anchoring with 10-inch metal spikes. Cut and bend the edging as needed.

  7. Budget Patio

    Add Paving Materials

    Lay your paving materials over the bed of sand. Slide the individual pieces close together for a clean look; leave bigger gaps if you'd like to plant groundcover between them. Tamp them gently with the mallet to secure them in the sand.

  8. Budget Patio

    Fill Spaces with Sand

    Fill spaces between pavers with builder's sand or polymer sand. Because polymer sand acts like mortar when wet, it keeps pavers more firmly in place than traditional sand. It also discourages weeds and keeps sand from washing over pavers after rainstorms. Sweep off excess sand after you fill the spaces.

How to Install a Flagstone Patio Using the Mortar Method

  1. SCM_132_03.jpg

    Mix Mortar

    Lay out your pattern in a dry run next to the site. Mix enough mortar for about a 3x3-foot section, and trowel a 1-inch thickness on the slab. Then lift your stones from your trial run and set them in the mortar in the same pattern.

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    Lay Stones

    Set the larger stones first, keeping them in the pattern and using a height gauge to set them at a consistent height. Push the stones down; don't slide them. Fill voids with smaller stones, cutting them to fit and leveling them with a rubber mallet.

    To cut the stones:

    1. Mark a cut line on the stone. You can freehand the line or set an adjoining stone on top of the stone you want to cut.
    2. Score the line with a brick set.
    3. Tap and move the brick set a bit at a time along the line.
    4. Set the stone on a pipe or another stone, then break the stone with a single strong blow.
    5. Remove any excess stone along the contours of the cut line, shaping it with the sharp end of a mason's hammer.
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    Level and Let Cure

    1. Check the stones for level, remove low stones, add mortar, and reset them.
    2. Tap down the high stones. If tapping them down won't level them, lift them and scoop out just enough mortar to make them level.
    3. Clean off mortar spills with a wet broom before laying the next section. (Don't wait until you've finished the patio—the mortar will set on the first sections, and you won't be able to get it off.)
    4. Let the mortar cure for three to four days, then mortar the joints.
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    Fill Joints

    1. Mix mortar in a mortar box and fill the joints using a pointing trowel or mortar bag. The bag squeezes mortar through a spout into the joints—it's less messy and will reduce cleanup chores.
    2. Clean spilled mortar right away with a wet sponge.
    3. When the mortar holds a thumbprint, finish the joints with a striking tool.
    4. Cover the surface with plastic or burlap (keep burlap wet) and let it cure for three to four days.
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