How to build a Flagstone Patio


©  2008  by Raymond Alexander Kukkee



Why Build a Flagstone Patio?

The random pattern and colour of a flagstone patio can be a wonderful addition to your yard that will be unique, natural, functional, and beautiful. It can add curb appeal, provide an area for simple relaxation or sophisticated entertaining, and can also add substantial value to your home at the same time.

Flagstone comes in blue, green, moss-coloured, gray, white, or red, and in several textures, so do take advantage of the possibilities offered in combination of colours and shapes. There are many choices.

Building a flagstone patio necessitates the evaluation of the conditions of the location chosen. If drainage is poor, preparation for drainage must be included in the project. Build a French drain if necessary to improve drainage. (See How to Build a French Drain’)

Consider the location carefully to maximize the use of your yard and landscaping possibilities offered by the installation and careful location of a flagstone patio. Consider sun, shade trees, line of vision from the street, and privacy when determining the location.  Consider drainage characteristics of your yard and correct any drainage problems if necessary. Install a French drain for problematic areas. Reroute water from roof leaders as necessary.

Do obtain building permits if required, and check with your local utilities to determine if utility lines are in the area chosen before you begin excavating.


Special Conditions:
This procedure is for a “sand-based” flagstone patio. Alternatively, a 4″ layer of packed, crushed stone with a 2-3″ layer of bedding sand compacted on top of it may also suffice in relatively good conditions.

Take precautions. Stone is heavy, so ensure you have adequate help to place larger flagstones! Do use safety protocol and wear eye protection, leather gloves, and steel-toed boots to protect your feet.


You will need the following equipment and supplies.

  • Wooden stakes or pickets
  • Carpenter’s line
  • Level (Line level, laser level, or transit level if available)
  • Stiff-bristled broom
  • A tamper (or vibrating plate packer if available)
  • Shovel and Pick (A tracked mini-excavator or backhoe will save you a lot of work if the project is large)
  • Coarse gravel (Uniform sized , medium gravel that will pack, including no large stones, roots, or trash. Grade “A” or “B” or “road base” gravels are suitable)
  • Builder’s Sand (Clean, coarse grade sand that will pack. Ensure it contains no rocks, roots, or other debris
  • Flagstones        Your choice, size, and colour. It takes approximately one ton of flagstone to cover 120-130 square feet of area, depending upon the thickness of the stone chosen
  • Edging (metal or dimensioned lumber framing may be necessary if you choose small stones)
  • Mallet or heavy hammer
  • Stone chisel (Preferably with a hand guard)
  • Stone cutting blade for skill saw ( a diamond stone-cutting blade is best!)
  • Safety equipment as required; safety glasses, leather gloves, and foot protection.


Let’s excavate and build the patio!

1. Outline the site chosen using wooden pickets and a line to visualize it. Change the design as necessary.  It  is much easier to alter your project in the planning stage than after it has been started.

2. Remove the grass layer or sod carefully from the whole area chosen. Use the sod and soil removed to do other landscaping, fill in holes, or even donate it to someone that volunteers to help!

3. Excavate the area to a dept of 8″ and make it as level as possible.

4. Install a 4″ layer of coarse gravel to ensure drainage. (Some consider this optional)

5. Pack the gravel as firmly as possible with water and tamper, or use a vibrating plate packer if possible)

6. Install a 2″ layer of bedding sand. Screed it with a long 2×4, making it as level as possible.

7. Install edging if required, keeping it as level as possible.

8. Pack the sand layer and perfect it. Remember, the better the bedding layer is packed, the less the flagstones will settle. ( *Hint: if installing adjacent to the foundation of a newly built home, raise the elevation of the sand bed a couple of inches . Settling of the soil around the foundation of a new home is inevitable. Allow perhaps four feet of ‘ width for the increased height and taper it to the proposed final patio height. The elevation at the foundation must be higher for correct drainage.

9. Lay out the flagstones, choosing the colours, shapes and sizes as desired, keeping in mind the pattern chosen, or the randomness and natural look inherent in flagstone design. Break the stones with a hammer and chisel (use a chisel with a hand guard!) to obtain a natural-looking edges instead of sawing if possible. The spacing between stones is not critical, but should be as uniform as possible for maximum aesthetic appeal.

10. Tap the flagstones carefully ensuring they are bedded securely. Fit the flagstones as closely as is reasonable, trimming if necessary with stone saw or chisel to achieve a reasonable fit. Add or remove sand as necessary to control the top elevation.

Flagstones are not always the same thickness either, so remember the objective is to keep the top surface as uniform and flat as possible. Choose installation of the top surface even with adjacent grass surfaces to make the patio lawnmower friendly for maintenance of adjacent grass.

11. Cut any stones required to complete the patio or fit carefully to match the edging.

12. Fill the cracks with sand, wetting it down to help compact the sand.

13. Sweep off the excess sand and wash the surface down as required.

14.  After the stone is dry, to ensure your flagstone patio remains beautiful and avoid stains with grease or other spilled materials,  seal the surface of the flagstone with clear sealant recommended by your supplier. Allow the sealant to dry as recommended, usually 24 hours.

Now it’s time to hold a party set up the barbeque, tables and accessories.  Enjoy that beautiful flagstone patio–you deserve it.



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