Installing a built-in fire pit for the patio can be a fairly easy endeavor if approached correctly. Making a built-in patio fire pit out of retaining wall stone requires no mortar, no cap stone for finishing and no set time for an interior concrete base. By using pre-cut granite retaining wall stones, the hardest part of building a patio fire pit is digging the pit itself, especially if the chosen location of the pit requires breaking up existing concrete. The alternative is to build in the fire pit next to the patio and incorporate flag stone around it to extend the patio area to include the fire pit area. Either way, a built-in fire pit makes a warm and beautiful permanent patio fixture.
Things You'll Need
- Metal detector
- Landscape spray paint
- Power jack-hammer
- Skill saw
- Steel-cutting saw blade
- Sledge hammer
- Builder's sand
- 12 to 24 granite retaining wall stones
- Lava rock
- Fire logs
- Fire/grill grate
Investigate all state laws and local ordinances that are relevant to backyard fires and fire pits, and incorporate any requirements into the building design.
Decide where to place the fire pit. This is perhaps the most important step since this decision determines how much preparation is involved in excavating the pit. If the patio is covered, does that overhang present any safety or legal problems with building the fire pit into the existing patio? If you decide to build the fire pit into existing concrete, rent a construction metal detector to determine the spacing of the concrete slab's re-bar grid, and select a location that requires the least re-bar removal.
Tie the end of a 4-1/2 foot length of twine to a pole and the other end to a can of landscape spray paint. Ask a friend to hold the pole, or push it into the ground, and mark out an 9-foot diameter circle for placement of the pit with the landscape spray paint. If the 9-foot diameter circle of the fire pit takes up too much of the existing patio, you can shorten the twine to 2-1/2 or 3 feet for a smaller fire pit, or you can move the fire pit into the yard adjacent to the patio.
Break up any existing concrete within the painted circle with a rented or borrowed power jack-hammer, then cut out any criss-crossing lengths of re-bar that interfere with the pit area with a skill saw outfitted with a steel-cutting blade. Finish breaking the edges of the pit out of the concrete with a sledge hammer.
Excavate the pit to a depth of about 12 inches and remove the dirt with a shovel. Lay a 6-inch layer of builder's sand in the bottom of the pit.
Place 12 granite retaining wall stones around the perimeter of the inside of the excavated pit, corners touching. Use only one layer if building the fire pit into an existing patio area. Use a level on each stone to make sure each is level. If building the fire pit in an open area next to an existing patio, stack a second tier of 12 retaining wall stones on the first tier, setting the middle of each second-tier stone over the joined corners of the first-tier stones.
Fill the area inside the granite stones with lava rock, leaving space between the rock and the top of the pit for kindling and fire logs. Place the kindling and fire logs on the lava rock, then cover the pit with a fire grate to keep sparks and drifting embers from spreading and accidentally causing fire damage to surrounding structures and trees.
Connect an existing patio to a fire pit built into the ground away from the existing patio by setting flagstones every few feet all the way around the fire pit and up to the concrete of an existing patio. Use the level to level the stones. Laying sod between the flagstones gives the area a finished, established look.
- Photo Credit Life of fire image by Skilled from Fotolia.com
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