How to Repair a Flagstone Step

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Things You'll Need

  • Work goggles

  • Work gloves

  • Mortar or chipping chisel

  • Hammer

  • Hand brush or whisk broom

  • Wheelbarrow

  • Portland concrete type I-II

  • Masonry sand (3 parts to every one part of concrete)

  • Hose connected to water spigot

  • Shovel

  • Trowel

  • Flagstone replacement piece

  • Level

  • Tuck pointer

  • Utility sponge

  • Siloxane sealer (if other stones are sealed)

  • Paint roller

This job is small enough to use a wheelbarrow to mix the mortar in.

Flagstone steps can loosen over time, or excessive moisture can get in, weaken and crack them, requiring replacement. Replacing a flagstone step may seem like a daunting task; however, with the right tools, some sand and Portland cement mix you can quickly replace the step. Be sure to select a stone close in color to the one you are replacing and have the stone supply company cut your stone to size.

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Removing the Old Stone

Step 1

Put on protective goggles and work gloves.

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Step 2

Tap out the old stone using a chisel and hammer. Angle the chisel slightly as you tap to get under the step that needs replacing.

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Step 3

Chip away all old mortar--on joint edges and bed--once the stone has been removed.

Step 4

Brush all debris from the area you will be setting the new stone. Crumbled old mortar, dust or debris will prevent proper adherence of the new mortar mix.

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Attaching New Flagstone

Step 1

Mix concrete and sand (three parts sand to one part cement) in a wheelbarrow. Add water according to directions. You do not want the mix wet, but rather on the dry side.

Step 2

Wet with water and a sponge the concrete bed where the step will be placed. This will help the mortar mix adhere better.

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Step 3

Trowel the mortar mix onto the concrete slab to a depth of a half-inch and onto the back side of the flagstone.

Step 4

Set the flagstone into the mortar mix, pressing it into place. Use a level to make sure the stone is straight and flat.

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Step 5

Gently wipe off any mortar residue from the face of the stone with sponge and water.

Step 6

Using the tuck point, tuck each joint with additional mortar mix, filling each joint to the top of the stone, scraping gently with the trowel for a smooth, even finish.

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Step 7

Allow the flagstone to set and cure overnight.

Step 8

Apply the stone sealer with a roller brush according to the product's directions, if the rest of your steps have this protector.

Step 9

Allow to dry overnight.

Tip

Measure the thickness of your other stone steps before purchasing your replacement. Flagstone steps are typically 1¼ to 1½ inches thick.

Warning

Don’t do this job if rain is expected within 24 hours, as this can weaken the set mortar.

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