Flagstone Patio DIY Instructions

Introduction:

During the summer of 2016, my wife and I decided to create a flagstone patio for our back porch. After several hours of research, design, and work, we created the patio as seen below in figure 1. The final product was a 200 square foot limestone patio with a base of granite gravel, a layer of sand, and the joints filled in with crushed granite. The total cost of materials was right at $1,000, and the time spent on the project was 3 weeks. I wrote the following set of instructions to provide readers with a step-by-step guide to follow in case you want to build something similar. I should note that I have no background in building patios; my degrees are in technical writing, not engineering or landscape architecture. As always when doing home projects on your own, you should do your own research and consult with local experts to ensure that your patio is guided by professionals.

Figure 1: Finished Patio

1) Research patios.

There are several types of patios. Here are some basic differences, based on materials:

• The foundation is either on sand (dry-laid) or on a concrete foundation (wet-laid). We decided on a dry-laid foundation, since we don't have a current concrete foundation. 
• The patio can consist of concrete pavers or flagstone. We chose flagstone because it is prettier, but much more complicated to level and design. It added a significant amount of time to our project.
• The joints can be filled with sand, crushed granite, jointing sand, or concrete. We chose crushed granite since we wanted it to be heavier and stronger than sand, but not as permanent as jointing sand or concrete.

Remember that each of these types has its strengths and weaknesses. For example, concrete pavers are easier to level, but not as attractive. Or sand is easier to work with into joints, but can be easily moved by ants. For more help with researching patios, there are dozens of types of DIY (do-it-yourself) instructions for building patios and explaining these strengths and weaknesses. We relied heavily on The Home Depot's excellent guide (their materials list is extremely helpful) and several hits that came up in Google. 

The most important part of researching was finding someone that we trusted to help us. My wife and I visited three local landscape companies and stone masonry supply stores. The first two were unhelpful, but we found a company owned by a woman named Cindy who has been selling stone and building patios for a number of years. She was most helpful in providing us with materials, delivery, and information. Having a professional's phone number became important at several moments in our project.

2) Purchase materials.

We decided on a 200 sq. ft. patio. I wanted less; my wife wanted more. So we compromised. We ended up purchasing:

• 2 tons of limestone flagstone (one full pallet and part of another). See figure 2. The thickness of each stone varied from half and inch to nearly 2 inches, and total, we had 250 pieces to work with. We tried to use the thickest pieces possible, and we ended up using 200 of the best pieces.
• 1 cubic yard (27 square feet) of base material and 1.5 cubic yards of sand. All together, this provided a three inch foundation for our 200 square foot patio. 
• 200 square feet of landscape fabric to help with weed prevention.
• 1 can of flagstone sealer.
• 40 feet of metal edging and stakes.

All of these supplies were delivered for $150. We didn't have a truck, so the company placed all the materials on our front driveway.

We also had to buy several tools, such as a hand edger (described below), shovels, a tamper, and a four foot level.

Figure 2: Purchasing Materials from a Local Masonry Supply Store

3) Outline your patio.

This is a fun step. Using something that is flexible (string, a garden hose, or a metal border), draw a rough draft of your patio. Remember that it needs to have about a 1 degree drop to ensure proper drainage during heavy storms. My ground was already at a 2-3 degree slope, so I didn't have much to worry about. A four foot level helps immensely.

Figure 3: Outline of Patio

4) Look underground.

Ensure that you haven't blocked access to underground utilities, such as electrical, gas, or sprinkler lines. We had to cap one of our sprinkler heads with a PVC cap, and we re-positioned another so that it didn't water our patio.

5) Excavate the soil.

Most people recommend digging down multiple inches, as few as 3 to as high as 12. A good median is around 8 inches, 3 for a base and 3 inches for sand, and a couple of inches for the stones. Two factors decide how deep you should go: drainage and freezing. We live close to a desert in Texas, where the average rainfall is about 20 inches, and the average low in January is still above freezing. Because we don't receive huge amounts of rainfall or significant deep freezes, we decided on excavating approximately 4 inches. We ordered 1 yard of a base layer of granite gravel, and 1.5 yards of a sand layer. When spread over the 200 sq. ft., the base and sand layers equaled 3 inches of depth. This depth is much less than the average, but we also talked with a local company that creates flagstone patios, and this is what they recommended, as well. With the average flagstone being about 1 to 1.5 inches deep, we excavated just enough so that the patio was level with our 4 inch metal edging.

I recommend renting a sod cutter from The Home Depot. For under $100 for a day, you can have a machine that excavates the top layer at a maximum depth of 2.5 inches. If you use a sod cutter, be aware that you'll need a truck to haul it, and you'll need some friends who are strong; the machine weighs 300 pounds.When we decided to rent a cutter, the machine was broken, so we decided to excavate the sod by hand using a hand edger. It took several days, and I hurt my foot pushing this tool into the soil over and over again. But all in all, it was worth it. The edger went 4 inches deep, rather than 2.5.

After excavating, be sure to level the soil with a rake. Then, tamp down the soil with a tamper.

Figure 4: Excavating the Soil 

6) Lay the foundation.

Begin by installing the edging. We used metal edging, purchased from The Home Depot. We wanted something that was flexible, since we wanted several curves to our patio. We used metal stakes and a hammer to lock each edging piece into place.

Then, we laid the fabric on top of the soil, and we dumped three layers of rock and sand: 1) We dumped over an inch of crushed granite for the base layer on top of the fabric. See figure 5. Then, we cut the fabric to shape and tamped down the granite. After the granite, 2) we placed about an inch of sand on top of the granite and tamped it down and watered it heavily. Then, 3) we placed another inch of sand on top of the first layer (no tamping!). All the rocks have uneven sections on the base, so the final loose layer helps ensure that all the crevices are filled with sand. All of this step took about 1 full day.

Figure 5: Installing the Foundation

7) Lay the flagstones.

For us, this was by far the most difficult part and the most time-consuming step. We did this project during the summer, when daytime temps were hitting over 100 degrees, so we could only work in the late evening from around 6 to 9. It took us over a week to lay and level all the stones.

I took this part in two stages: 1) I would piece together a small section of about 10 stones, and then 2) I would install each one individually. The most tedious aspect was trying to level each stone. Each stone has to be leveled with all the stones around it; it has to not rock or move when weight is applied; and it has to have a drop of at least 1 degree (our patio has about a 2-3 degree drop) for rain run-off. All of this meant that some parts of the patio are not perfectly level. I was somewhat OCD about each stone at times, which is partly why it took so long. Even then, my wife still found places that were not quite level. Use a rubber mallet to hit each corner of the stone to make sure it is level. I found that placing a bit of dry sand on the stone helped me determine if the stone was level: the more the sand shook and bounced with a hit of the rubber mallet, the less stable it was. It also helps to wet the sand a bit so that it holds its shape better. Use the handle of the mallet to pack wet sand around all the exposed edges to make sure it is stable. Then, move on to the next piece.

Figure 6: Nearly Halfway Done

My best advice is to start in one corner and work outward, using the larger pieces toward the edges for better stability. At times, I would mistakenly start to enclose sections (seen in the upper left of figure 6), and it would be nearly impossible to find pieces that correctly fit in a pre-defined area. The more sides you leave yourself open (always leave 2 sides open), the easier it is to work with the stones.

Leave as much or as little space between the pavers as you want. I wanted a more compact look, so I had anywhere from no space to up to an inch in places.

I didn't have much luck chipping the rocks with a hammer. I could chip small pieces off to shape the rocks that didn't quite fit, but I had no luck with breaking large sections off of big stones. The limestone lays horizontally, so each chip would break a top or bottom layer off, but never both. For chipping, use the corner of the hammer, and lightly tap to break.

Figure 7: Almost Finished!

Step 8: Place crushed gravel between the joints.

My wife and I debated and researched the different types of jointing materials for quite some time. We initially planned on sand, because we had an abundance of it already, and we liked how easy it was to work with. Later, we nearly used polymer jointing sand (which is a sand with glue) to hold it together; the reviews are usually polarizing - some say it works well to as a type of near-concrete, and others say it was the worst decision they made. The other option is concrete. We never selected concrete since it will crack as the stones shift during freezes and rains. We eventually chose crushed granite because we wanted something in-between the light weight of the sand and the permanency of the jointing sand/concrete. I'm happy with the choice. It bonds well when watered, and it made the patio quite stable.

We placed most of the larger pieces of granite at the base of the joints, and then filled in the top with the smaller particles by moving it around with a broom. Make sure to water it to settle the granite.

Conclusion:

We are very pleased with the final result. See figure 1 at the top of the article. We've already used our ping pong table on the patio several times, and we grilled out chicken and hamburgers with some friends within a week of finishing. It is still settling, but I'm quite happy with the final result. Also, we still need to seal the stone, but we are waiting for a big rain to help settle the base layers and clean off the stone. And during July in Texas, it never rains, so we may be waiting for a while.

Oh, and it pays to have good help. Her official title was Apprentice Holder, Unpaid Internship. See figure 8.

Figure 8: Helpers