Flagstone – How to Buy for Patios, Walkways and Driveways

Buying flagstone may seem like a daunting task to the everyday homeowner, but it doesn’t have to be. You just need to understand some basics and you can have a good grasp of what your potential dream flagstone patio, walkways or driveway may cost you.

Here are some things you should know:

How is it sold?

Flagstone is typically sold by the weight, specifically either in lbs or tonnes. The reason it is sold by weight is because of how it is sold by the quarries and because of the irregular shape of each piece of flagstone.

How do I measure or figure out how much I need?

There is an industry standard that everyone goes by to determine the amount of flagstone one needs to purchase. For every 100 square feet of coverage, you will need approximately 1 tonne or 2000 pounds of flagstone that is between 1″ to 1.5″ thickness with spacing between each flagstone around 1/2″ to 1″ wide gap.

What varieties are available of flagstone?

Slate, limestone, and sandstone are just a few varieties of flagstone that are available in the market today. In Ontario, the most common type of flagstone available is called Wiarton since the quarries are located in Southern Ontario. Wiarton is a form of limestone that comes in various colors. However, the most common color range is from light grey to charcoal grey.

What thickness should I use?

Flagstone thickness ranges from 3/4″ up to 3″ and possibly even more. The most common thickness from 1″ to 1.5″ thickness. This flagstone thickness is good for paved concrete surfaces. The reason for a thinner flagstone is because of there little chance the flagstone would be affected by winter on a concrete pad. For surfaces where the base is gravel, you would want to purchase flagstone that is at least 2″ to 3″ thick. The reason for this thickness is that the weight and the thickness of the flagstone will to help counteract heaving during the freeze thaw cycle that happens each year and minimize any potential for cracking that may occur.

What are the jointing materials that I need to finish the flagstone project?

As it was mentioned earlier, there are different types of jointing materials that can be used. If your flagstone base is a concrete platform/pad, then you should use cement or other types of mortar. If you have a gravel base, then you should use sand (fine or coarse), pea gravel, or even polymeric sand (wide joint variety) as a mortar. The sand or pea gravel is a more forgiving and will not show cracks should the flagstone have movement after the freeze-thaw cycle of winter.