Relaxing by a backyard fire is the perfect way to spend an evening. Here’s how to build a classic in-ground fire pit.
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We built our fire pit with a patio surround, so you’ll need to apply the same steps for building a paver patio. To see detailed steps as well as tips on designing stone layout patterns, see How to Design and Build a Paver Patio. Other types of fire pits can be built from kits and traditional retaining wall blocks. See Fire Pit Ideas to learn how to build these styles.
For our pit, we used cast patio pavers that look like stone. The pavers are the same shape and size, and fit together several ways to create a natural look. The patio will sit even with the ground, and the depth of the pit will depend on the thickness of your patio stones and concrete block lining.
The installation for this in-ground fire pit has several layers:
Before beginning any excavation, call 811 to check for underground utilities. Also, before you buy materials or begin work, check local building codes, ordinances and homeowner association guidelines to make sure that fire pits are allowed.
Mark the fire pit layout. You can do so by creating a compass using a stake, string and marking paint, and marking the outline of the patio area.
Dig up the fire pit area. The actual fire pit itself will be deeper than the patio surround to accommodate the height of the concrete blocks. The ring doesn’t have to be a perfect circle — you can always fill in behind the blocks with dirt or paver base.
Keep sod slightly wet after digging up if you plan to reuse it.
Tamp the ground to form a solid surface for the paver base and concrete blocks. Consider adding a drain during this step to keep the pit from filling with rainwater. Run the drain pipe to a low part of your yard, a drainage ditch, or tie it into an existing drain (this option is best left to a professional). For more information see How Do I Create a French Drain?
Pour about 2 inches of paver base around the perimeter of the fire pit circle — the area on which the concrete blocks will sit. Wet it and tamp down, then sit the concrete blocks on top to form a ring. The blocks should be touching and level. If necessary, add or remove small amounts of paver base to level the blocks.
Pour a total of 4 to 6 inches of gravel paver base behind the concrete blocks, depending on their height. Start by adding the paver base 2 to 3 inches at a time and spreading as evenly as possible with a garden rake.
Wet the paver base and tamp it. Continue adding the paver base to about 1 inch below the tops of the concrete blocks. Also, fill the openings in the concrete blocks with paver base or gravel. Check the area for level.
Pour lava rocks in the fire pit to help hold the concrete blocks in place.
Only use stones that are specified as heat resistant in your fire pit.
Lay PVC pipes on top of the gravel paver base. The pipes should be about 1 inch in diameter to make the sand even with the tops of the concrete blocks.
PVC pipes are typically referred to according to their inside diameter, so a 1-inch-labelled pipe, for example, will actually have a total diameter greater than 1 inch. Keep this in mind when purchasing pipes.
Pour sand over the PVC pipes and paver base. Do not cover the concrete blocks.
Use a straight 2 x 4 to screed the sand to a flat finish. Remove the pipes, fill in the trenches with sand and smooth the surface area with a shovel. Check the area for level before proceeding.
Set the pavers in place around the fire pit ring over the concrete blocks. Use a piece of plywood to kneel on top of the sand. The joints between the pavers should be at least 1/2 inch wide to allow enough space for the polymeric sand that will be applied later.
As you work, let the pavers hang over the concrete blocks if needed. Mark any excess and cut using a circular saw with a concrete blade. See Cut Patio Block for detailed instructions. The pavers should be cut one to two inches short of the edge of the blocks.
Using a circular saw to cut pavers can be dusty. Consider having a helper use a shop vacuum to clear dust away while operating. Always wear appropriate safety gear and follow manufacturer’s instructions for all tools.
Wear work gloves when handling the pavers. Consider wearing a pair of knee pads to make the installation process more comfortable.
Continue installing the pavers. Vary the direction of the pavers for a natural appearance. There should be several ways that the pavers will fit together. Remember to leave at least a 1/2-inch gap in between.
When you reach the outer edge of the patio area, you’ll most likely need to cut the pavers again. To create a circular sitting area, pound a stake in the middle of the fire pit — avoid damaging your drain if you installed one. Tie a string and pencil to a nail on the top of the stake to create a compass. Mark the curve over the outer pavers.
To cut the pavers, create relief cuts up to the marked curve. Relief cuts are several initial cuts made up to the curve to prevent the saw blade from binding. Then cut the curve.
Replace the pavers after cutting and use a level to make sure the tops are even. Adjust if needed.
Mix mortar following the manufacturer’s directions and apply it with a trowel over the edges of the concrete blocks and pavers. This will hold the inside edge of the fire pit in place. You can keep the paver edges clean by covering them with painter's tape before applying the mortar.
Add edging along the perimeter of the patio with landscape spikes to keep the outside edge of the pavers in place.
After the mortar around the inside edge of the fire pit has completely cured, fill the joints between the pavers with polymeric sand — which has additives that provide a tighter bond — to lock the blocks in place.
Follow the manufacturer’s instructions on all products. Regular paver sand is another option for narrower joints. However, since it doesn’t have additives to form a tight bond, you’ll need to apply new sand every few years.
Sweep the sand into the joints, then use a hand tamper to settle the sand and blocks. Add more sand and sweep again.
Remove the excess sand with a leaf blower. Removing the excess is important when using polymeric sand. Any excess can cause hazing and change the color of the blocks.
Lightly spray the polymeric sand with a hose. The sand might settle between blocks, so you may have to reapply several times.
Allow the polymeric sand to completely cure according to the manufacturer’s instructions — typically 24 hours — then fill in around the perimeter of the patio with pebbles or soil and grass seed.
Surround the fire pit with comfortable furniture, and enjoy the crackling warmth of a backyard fire!
Keep a fire extinguisher or a bucket of sand or water near your fire pit area just in case, and always fully extinguish fires before leaving the fire pit area unattended.