More in Outdoors
Determine the size of your new fire pit and excavate the entire inner area. The stone border of the fire pit will sit on top of concrete but in order to set this concrete, you need to build a circular form. Cut two lengths of bender board, one for an outer circle and one for an inner circle. The bender board piece for the outer circle should be the length of the perimeter. The piece for the inner circle should be small enough so the gap between the two pieces is about 5 inches. Nail the ends of the bender board pieces together to form the two circles.
Mix dry concrete with water and pour this in between the two circles. Smooth out the concrete with a trowel, adding pressure to force out any air bubbles. Let this dry overnight.
We used a black mariposite slate for this border but you can use any stone you prefer, as long as the pieces are one to two inches thick. Place one layer of stones on top of the concrete base before adding mortar. Choose pieces that fit together like a puzzle without jutting out much beyond the concrete base. To lay the stone, mix mortar with water until it becomes a medium consistency, like a thick brownie mix. Lift one of the stones, and use a trowel to apply the mortar to the concrete. Set the stone back on top and settle it into place. Don't worry about the mortar that squeezes out from underneath the stone; you'll use a sponge later to clean it up. Repeat this for all of the stones in the first layer. For each additional layer, offset the stones to cover the seams of the layer below it.
Take your trowel around the outside of the fire pit, scraping off the excess mortar that has accumulated. You can do the same to the inside but you won't end up seeing the inside. Once you've scraped most of it off, go back around with a wet sponge and a bucket of water to remove any excess mortar from the stones.
First, add lava rock to cover the very bottom of the fire pit in one layer only (Image 1). Second, attach the fire ring to the gas line. Third, pour in 3/8" crushed lava rock up to the point where it covers the fire ring (Image 2). Last, add fireplace glass to completely cover the lava rock. Fireplace glass is a tempered, decorative glass that won't pop in the heat of the fire. It comes in a few shapes and many colors.