Lang Stone

How to Build a Flagstone Patio

Creating a flagstone patio without using mortar is the easiest way to extend you home’s usable living space into the outdoors. The attractive patio adds to your home’s resale value, yet the project is simple enough for the average home owner to complete successfully.

Tools and Materials Checklist

  • Chipping hammer or stone hammer
  • Carpenter’s level and rule
  • Pick and shovel
  • Rubber mallet
  • Forming lumber or plastic Edging

How to Determine How Much Flagstone You Need

  1. Determine the size of the patio you wish to build.
  2. Multiply the width in feet by the length in feet to determine the patio’s size in square feet. Length in feet x width in feet = size in square feet Insert your dimensions here: _________ feet x _________ feet = _________ square feet
  3. Select your flagstone. Since flagstone varies in thickness and density, Lang Stone can use you square footage to determine the amount of stone you need. 3” Stone covers an average of 50-60 square feet per ton. 2” Stone covers an average of 80-90 square feet per ton. 1” Stone covers an average of 100-120 square feet per ton.

How to Construct Your Patio

  1. Use plastic edging (or an equivalent to maintain the edges) and string line to layout the size and shape of your patio.
  2. Excavate the area, removing the earth until the area is at least 6” deep. The depth will depend on the amount of crushed limestone, the amount of sand and the type of stone used. Ask your Lang Stone sales person how deep the excavation should be. Use fine line screening stone for leveling bed.
  3. Tamp the loose earth inside the excavated area.
  4. Install a ground stabilization mat to keep the base material from sinking.
  5. Place 3-5“ of crushed limestone in the area. Keep all material damp and compacted within about 1-3” of the form board, depending on the thickness of your flagstone. Remember: your stone is only as strong as the base below it.
  6. Using plastic edging, form the patio by placing the edging along the perimeter and the string line. Drive stakes every 1-2’ to secure them in place. If your patio has irregular or curved edges, use a heavy vinyl or steel edging available at Lang Stone. This step is not essential, but the edging makes it easier to set the stone and retain the sand if the patio is built above grass level.
  7. Put 1-1½” of sand or limestone screenings over the area for leveling. Note: for mortared joints, DO NOT level the area with sand. See below. 
  8. Beginning in a corner, lay flagstone in the chosen pattern by wiggling and tamping each piece in place.
  9. To level and adjust the height, tamp with the rubber mallet and add or remove sand. Keep the joints close and fairly uniform for an attractive appearance. Try to avoid long lines of continuous joints.
  10. Finish your patio by sweeping sand or pea gravel into the joints and wetting them down. The edging can be left in place to create a nice-looking border or mowing edge. It will be hidden under your grass.

Note: for mortared joints in sand, level the area with about 1-½” limestone screening or 2” mortar. Lay the stone as described in steps 8 and 9. To fill joins, mix a mortar grout that can be squeezed into joints using a common mortar bag. Tool the joints as desired.


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