HOW TO BUILD AN OUTDOOR FIRE PIT:
A homemade outdoor fire pit is a permanent backyard campfire place, with sturdy walls of stone that help contain the flames and heat for safety and design. It is important to make sure your fire pit location is far from your home, overhanging trees, workshop, dog house, and any other flammable structure. We suggest at least 50 feet.
To make building stone walls easier, you can use bricks made from cast concrete and molded to look like real stone (available at any Home Depot or Lowe's). Most designs of these type bricks are flat on the top and bottom so they stack neatly, and some interlock for added strength. Glue them together with masonry adhesive. Choose a brick with angled sides, meant to form curves when butted against each other. The optimal size for a fire pit is between 36 and 44 inches inside diameter. That will create enough room for a healthy fire in your homemade fire pit.
Shop Outdoor Fire Pits
As an added precaution, you can line your fire pit with a thick steel ring. These protect the concrete in the bricks from the heat, which can cause them to dry out and break down prematurely over time.
It is important to have your fire pit sit low to the ground, with walls rising no more than a foot off the ground. The base of the wall must be buried below ground in a hole lined with gravel to assist in its overall stability. The gravel plays a very important role since it creates a level foundation for the stone bricks to rest on. Most concrete bricks are about 4 inches high, so if the first course and a half sit underground, and there are two and a half courses above ground with a cap on top, you'll end up with an approximately a one foot high wall. Anywhere from 12 to 18 inches high off the ground will give you the right height for safety and stability. The more heat you want your fire pit to produce, the lower your homemade fire pit should be!
FirePitSource.net provides the following 8 step instruction in building your homemade fire pit. Watch the animated step-by-step rotating pictures at the top right of this page for a clearer illustration. Brought to you by: This Old House
(see pictures - top right)
Lay Out your Bricks:
Dry-lay a ring of your selected bricks on your chosen fire pit location, placing them end to end until you have the shape positioned where you want the finished pit to be. To adjust the size of the circle, you may need to cut or break a brick. Hold the brick over the gap it will fill, then mark it on the underside at the proper width.
Using a 3-inch cold chisel and a regular size brick hammer, score the brick on the mark, and continue the score all the way around the brick. Place the brick on a hard surface (flat rocks or gravel). Hold the chisel in the score line, then hit it with the brick hammer until the brick splits at the scored point.
Clean up jagged edges with the end of your brick hammer. Place the cut brick into the fire pit ring.
Mark the Pit Location
Make sure all the joints between the bricks are tight and the front and back edges line up. Using a spade, mark a circle in the ground about an inch outside the perimeter of the ring.
Take note of how many stones make up the ring, then remove them and set them aside.
If the bricks you are using are interlocking, remove any tongues on the bottom of the first-course bricks so they will lie flat in the trench. Chip them off with the tail of a brick hammer.
Create a Level Trench for the Bricks
Using a spade, dig a straight-sided trench, 12 inches deep and as wide as one brick, within the circle marked out on the ground. Then dig down 6 inches in the area encircled by the trench.
Lay the ring of bricks in the trench to see if all the pieces fit in a circle. If not, dig more to widen the trench. Remove bricks.
Fill the Trench
Fill the trench with 6 inches of 3/4-inch drainage gravel. Using a hand tamper, compact the gravel. If necessary, add more gravel to keep the trench level and even.
Always make sure the fire pit bricks line up perfectly in the front and back when you lay them out; a difference of 1 inch in the circle's diameter could create a 3-inch gap between bricks.
Lay and Level the First Course
Place the first brick in the ring. Using a 2-foot level, check that it sits level both side to side and front to back. Where the block is too high, tap it down with a rubber mallet. Where it's too low, shim it slightly with a handful of patio base. Make sure this first block is perfectly level and positioned correctly in the trench before moving on.
Lay another brick next to the first one. Butt the sides together tightly and line up the front and back edges. Using the first brick as a reference, level the second brick side to side and front to back.
Lay the rest of your fire pit bricks in the trench in this manner until the ring is complete and all the bricks you counted earlier are used. Make sure each brick is perfectly leveled and lined up tight with its neighbor before moving on to the next one. (You may have to coax the last brick into place with a mallet.) Using a 4-foot level, occasionally check level across the ring.
A small hit with a mallet can make a big adjustment; work slowly and carefully, block by block.
Assemble the Walls
Using a caulking gun, squeeze a zigzag bead of masonry adhesive across two adjacent blocks (see Step 6 Picture). Lay a block on top of the glue-covered pieces, centering it over the seam between the two. Make sure any interlocking parts on the blocks fit together well. Continue until the second course is finished.
Fill the Pit
Fill the pit with 6 inches of gravel, which will help support the first two courses as they set up. Glue and lay the third and fourth layers, continuing to stagger the joints.
Insert the iron campfire ring into the circle. Adjust it to sit even with the top of the block wall. Fill any space between the ring and the block wall to the top with gravel.
Work quickly and only in a small area at one time; masonry adhesive sets up quickly.
Cap the Blocks
Loosely arrange the cap pieces on top of the homemade fire pit walls - (If you are using natural stone, try to arrange the pieces together like a puzzle the best you can). Lay one stone edge over the next and mark the upper stone where they meet. If you want an overhang like the pictured example, roughly mark the stone for a 2-inch overhang on the outside of the circle and an inch on the inside. Using a brick hammer and a chisel, score the stone on those marks. On thick natural stone, use a grinder fitted with a diamond blade to score it more deeply.
Lay the stone on a hard surface. Split it by hitting a chisel in the score mark (like descrbed in Step 1), or by tapping against the stone's edge with the brick hammer until it breaks. Score and split each stone this way, moving around the circle in one direction until you've made a cap that fits together tightly.
If you're using regular bricks, glue the pieces on top of the wall. If you're using natural stone, combine the dry mortar with enough bonding additive to make a mix with a peanut-butter like consistency. Do not use water!
Wet the wall with some bonding agent. Lay a large mound of mortar on two blocks. With the point of the trowel, make a groove across the mortar. Lay the capstone on top, push it down, then tap it with the rubber mallet to set and level it. Continue to lay the capstones in this manner until the wall is finished. It is important to wait at least 48 hours before lighting your first fire in your homemade fire pit.
Enjoy your new homemade fire pit for years to come!