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Flagstone: Choosing the Right Type for Your Project

Q. I'm baffled by all the choices in flagstone. Are all types of flagstone equally long-lasting?

A. Flagstone is a generic term for any sedimentary rock that can be cut or split into layers. It varies considerably not just in color and appearance but also in the amount of sandstone, silica and other materials. Sandstone, limestone and bluestone are all considered types of flagstone.

After you narrow your choices to color and type, suiting the look you want to create, also consider its durability. You can tell a lot by its look and feel, says landscape architect Dean Hill.

"Does it look flaky? Does it have a grit? Does it look porous? Are there big voids where water can get into it?" Dean suggests asking. "If it looks uniform across the top and there are no other layers, pockmarks or different heights, it's probably going to be a bit more durable than something that has those things.

"My suggestion would be to look at all the options, talk with the contractors who have used various types, look for examples and ask to see projects that are 5 to 10 years old," he adds.

He also suggests buying locally produced stone, "You'll be reducing the carbon footprint and saving on transportation cost."

The most important factor in flagstone's longevity is how it's installed, says Dean. He offers these tips:

  • The thicker the flagstone, the better. "Going for pieces that are half-inch thick doesn't work in the long run," Dean says. "I usually go with 1 to 1-1/2 inch thickness."

  • If you're using a leveling sand, make sure it's uniform all the way across. If there's a void beneath, the stone will crack.

  • Make sure the stone is firmed in and won't settle very much.

    "If flagstone is installed correctly," Dean says, "it should last as long as you do, if not longer."

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