How to Lay a Flagstone Patio

Supplies List and Easy Instructions for Beginners

Image of bluestone paver patio
David Beaulieu

Laying flagstone patios in the sand, as opposed to mortar or concrete, is known as "dry construction." Dry construction is easier for do-it-yourselfers than wet construction. Not having to worry about finishing your stone placement before a layer of mortar hardens makes for a much more happy-go-lucky project. You can make adjustments as you go, on your own timetable. However, wet construction is more permanent.

Stone laid in the sand will have to be re-adjusted over the years. As settling occurs, you will have to add sand, to keep the desired level. If you do not mind tinkering with a project after it is "done," this should not present a problem. While the dry-construction technique for flagstone patios has both pros and cons. On the plus side, the building is easy, as is the repair. On the minus side, it is almost certain that it will need to be repaired.

Supplies That You Will Need

  • String
  • Four stakes
  • A garden hose
  • Four two by fours lumber planks,
  • One 10-inch plank
  • Landscape fabric
  • Tamping tool and rubber mallet
  • Protective eyewear and gloves
  • Back brace
  • Flagstone
  • Sand
  • Broom
  • Carpenter's level
  • Tape measure

How to Lay a Flagstone Patio

  1. Pick as level a spot as possible for your structure. If you start on level ground, it will be easier to ensure that the finished product's surface will turn out level. 
  2. Measure before you do anything. If your flagstone patio is to be, say, 10 feet by eight feet, then stretch out a tape measure to the length of 10 feet on one side of the proposed flagstone patio, and mark this length with a string tied between two stakes. Measure out the eight-foot width, in the same way, marking both sides with string and stake. After closing the rectangle with the fourth piece of string, check that you have a perfect rectangle. Just measure the two diagonals, they should be of equal length.
  1. Use a spade to dig down four inches deep all around the perimeter of the rectangle that you just plotted out for your flagstone patio. Then, switching to a digging shovel, excavate all that sod and soil, down to a depth of four inches. This measurement represents a bare minimum. Digging deeper and using larger flagstones will provide a better foundation.
  1. Set a scrap 10-foot plank down on the ground, so that it runs the length of the rectangle on the left-hand side. Place a carpenter’s level on the plank, and check for a level reading. It will not be exactly level yet, but it will not be difficult to correct that. Just scrape away more dirt on one end or the other, as needed, to achieve exact levelness. Repeat this process on the right-hand side of the rectangle and in the middle.
  2. Then set the plank down so that it runs the width of the rectangle and repeat the process, checking for levelness on the left and right, as well as in the middle.
  3. Moisten the soil in the excavated area with a garden hose and tamp it down with a tamping tool. Set landscape fabric down over the base you have just established for your flagstone patio, to suppress potential weeds later. With a level base now, you are ready to frame in the rectangle with a form, using four two by fours nailed together to enclose a 10-foot x eight-foot area. The idea behind the form is for it to act as a mold and contain the two-inch layer of sand that you are later going to apply.
  4. Excavate down another one and a half inches outside of the rectangle’s perimeter and place the two by fours. The width of this trough will also be one and a half inches, building a form that will be level and slip snugly into this trough.
  1. Shovel two inches of sand over the landscape fabric. Cut a scrap two by four to a length of eight feet two inches, to act as a screed.
  2. Starting at one end of the rectangle, you will slide this screed across the full 10-foot length of the sand layer. Slide the screed along the top of your form, thereby leveling the sand. If you can't slide the screed easily, you will have to remove some sand. Tamp the sand down with the tamping tool.
  3. Begin in one corner, placing your stone pieces down on the sand base. Keep the gaps between stones as small as possible.
  4. Tamp each stone down with a rubber mallet. Using the carpenter's level, keep checking for levelness between stones. If a stone is resting too far down into the sand, remove it and place more sand under it. If a stone is sitting up too high, do the opposite: scrape away some sand from under it.
  1. After all the stones are in place, dump a bit more sand on the flagstone patio. Take a broom and sweep it into the cracks between the stones.
  2. Remove the two by four form. Fill in the form's now vacant trough with sand and tamp it down firmly.

Tips to Help Beginners

  1. The instructions above assume a location away from the house. If you choose to lay a flagstone patio up against a house, ensure that the surface slopes slightly away from the house, for drainage purposes. The last thing you want is to end up with water in your basement. 
  2. If your yard is wet, or you would simply prefer a better foundation, you may want some additional drainage under your flagstone patio. To achieve this, simply excavate deeper at the beginning of the project. Then apply a layer of crushed stone before shoveling in any sand. Another improvement you can contemplate is purchasing stones with a thickness greater than two inches. You will pay more, and they are heavier, but they are also more durable. Adjust your excavating measurements accordingly.

Patio Design

Flagstone patios have an irregular pattern, visually, because not all of the individual pieces are the same shape. Sometimes, and especially if you are pursuing a formal landscape design style, you will want a patio that is composed of pieces that do all bear the same shape. In that case, you may be interested in learning how to build a brick patio.