Secure one of the 2-foot pieces of rebar in the center of the fire pit location with a stone hammer (Image 1). This rebar will serve as a guide throughout the project. Cut a piece of string to half the length of the fire pit’s diameter. The diameter of this fire pit is 5 feet, so the string is cut to a radius of 2-1/2 feet. Make a loop on one end of the string and slip it around the rebar. Loop the other end around a can of line spray paint. Pull the string tight, and spray the circumference of the circle. This method of marking a circle creates a fire pit that is perfectly round (Image 2).
Cut a second piece of string the length of the first piece minus the thickness of the fire pit wall. For example, if the wall is going to be 12 inches wide, cut the string to a length of 1-1/2 feet. Attach the string to the rebar and spray paint and mark a second circle inside the first.
Dig out the area inside the marked circle for the footing of the fire pit. Dig down 4 to 6 inches using your shovels (Image 1). Cut a second piece of string the radius of your fire pit minus the width of your fire pit wall. Dean and Derek’s fire pit is one foot wide, so they cut a piece of string 1-1/2 feet long (2-1/2 ft. – 1 ft. = 1-1/2 ft.). Attach the string to the rebar and spray a second, inner circle. This circle shows the shape of the wall and also marks where the footing will go (Image 2). The footing of the wall is the concrete pad that will provide the base or foundation of the stone fire pit.
Mix the premix concrete for the footing in the wheelbarrow using the mixing hoe. Slowly add water and mix until the concrete has a consistency of soft peanut butter. Spread the concrete in the outer circle with the mud shovel (Image 1). Leave the center area free of concrete to allow for drainage. Spread and compact the concrete using the iron rake until the concrete is one to 1-1/2 inches below grade (Image 2). Follow the iron rake by smoothing down the concrete with a trowel (Image 3).
Prepare premixed cement according to manufacturer's directions. Spread the cement in the area between the outside and inside circles. Leave the center area free of concrete to allow for drainage. Continue to add cement and level it until it reaches 1-1/2 inches below grade. Tap 2-foot pieces of rebar into the wet cement until completely submerged at various points around the footer. Allow to dry.
Place the 2-foot pieces of rebar in the wet concrete. Spread two pieces adjacent to each other like railroad tracks all the way around the circle. Tap the rebar into the concrete so it is completely covered. The rebar is going to prevent cracking and provide support during frost heaves in cold weather.
While the concrete sets up, organize your stone and firebrick. Place your stone in piles around your fire pit location. Divide the stone into a pile for each type of stone, a pile for capstones, and a pile for firebrick. Leave a 1-1/2 to 2-foot space for you to work between the edge of your wall and the piles of stone, as well as space in between each pile for your wheelbarrow. This is your working space and your stone should be close at hand.
Once you’ve organized your work area, mix up a wheelbarrow of the premix mortar for working with your stone. Mix one bag of mortar up at a time so that the mortar does not dry out while you’re building your wall. Follow the instructions on the bag for the consistency and don’t add any more water once you’ve mixed the mortar; this will weaken its bond.