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

flagstone patio sitting area with garden stream
Photo: Edward Gohlich

A backyard patio can be so much more than a slab of concrete.
Follow these step-by-step instructions to create an affordable outdoor oasis in your backyard using flagstone pavers.

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Before You Begin

Budget Patio

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.

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Choosing Flagstone


Flagstone paver patio pieces are fractured or cleft into flat slabs of various lengths, with a thickness of 2 inches or more 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 in size 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 paver patio 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 harder 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).

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What You Need for the Sand Method





Crushed limestone or gravel


Builder's sand



Utility knife or saw

10-inch metal spikes

Flagstones, pavers, or bricks

Polymer sand (optional)

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Step 1: Remove the Old Patio

Budget Patio

Determine the size and shape of your new patio.

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

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Step 2: Excavate Accordingly

Budget Patio

To facilitate drainage, excavate the area to a depth of at least 8 inches. The finished 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.

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Step 3: Add a Base

Budget Patio

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.

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Step 4: Create a Solid Foundation

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.

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Step 5: Add Sand for Drainage

Budget Patio

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 patio.

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Step 6: Install Edging

Budget Patio

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

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Step 7: Add Paving Materials

Budget Patio

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, such as creeping thyme, between them. Tamp them gently with the mallet to secure them in the sand.

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Step 8: Fill Spaces with Sand

Budget Patio

Fill spaces between pavers with builder's sand or polymer sand. Because polymer sand acts like mortar when it's wet, it will keep 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.

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What You Need for the Mortar Method



Small sledgehammer

Brick set

Carpenter's pencil

Mason's trowel

Rubber mallet

Mortar box



Mortar bag

Height gauge



2x lumber

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Step 1: 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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Step 2: 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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Step 3: Level and Let Cure

  1. Check the stones for level, then pull out 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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Step 4: 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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