- Prep work and foundation:
1. Use a hammer to pound one of the pieces of rebar (or any firm straight stick) into the center of the spot you will build your backyard fire pit. Then tie a piece of string to the bar near the bottom. Measure out 1/2 the outer diameter of your backyard fire pit all (for example, if the outer diameter of your outdoor stone fire pit is to be 5 feet, then make the string 2-1/2 feet). At the end of the string, at the distance determined (1/2 the outer diameter) secure the can of spray paint. With the string taut, walk in a circle while spray painting a circle on the ground. This will help you to make a perfect circle to build a stone fire pit.
2. Next, use this circle as a guide to dig out an area 4 to 6 inches in this area. The dug out surface should be fairly level. Test with your large leveling tool to insure that you are level and make adjustments, moving dirt around as necessary to make the base for your outdoor stone fire pit level.
3. Then repeat the spray paint trick with the string shortened to the diameter of the inner edge of the wall of your stone fire pit. So, for example, if your outer diameter is 5 feet, then your inner diameter is 3 feet (5 feet minus the two 12 inch wall thicknesses). Therefore your string should be 1-1/2 feet. This will create a smaller circle within your bigger circle, but with the same center point (marked by the rod in the ground).
4. Mix premix concrete with water in wheelbarrow until it is a soft spreadable consistency (but not runny). Spread it in the area between the two circles (under where your backyard fire pit wall will eventually sit). Leave the inner circle free, to allow for drainage. Spread and push down the concrete using your mason tools (the iron rake works well for this) until it is about an inch and half below the ground level. Use your trowel to smooth down the concrete.
5. Now place rebar pieces in the wet concrete and tap them in so they are completely covered in concrete. This provides support for your fire pit and prevents cracking during weather changes.
6. Before continuing your backyard fire pit, leave the concrete to set fully. While this sets you can organize your stone and firebrick so it is easy to access. Leave room for you to work and for the wheelbarrow. Make sure to keep your side stones and capstones separate.
- Setting the stone in your outdoor stone fire pit:
1. Mix wheelbarrow of premix mortar. I recommend using just one bag at a time, using the directions on the bag, so that it does not dry out as you set stones.
2. Spread mortar on the outer half of the concrete base with trowel and begin setting stones. Start with the face stones all around the outer edge, leaving room on the inner edge for the fire bricks.
3. After the first row, place more mortar on the inner edge of concrete and start setting fire bricks. Set the first row of fire brick to make the flame retardant interior wall of your backyard fire pit. The inner edge of the bricks should be on the inner circle, at the edge of your concrete base or foundation. After setting the first brick, each subsequent brick should have a neat mound of mortar on the side of the brick to adhere it to the brick next to it. Push the bricks into the mortar and push them close to the brick next to them. There should be enough mortar to fill all the gaps. Tap the bricks with the trowel or handle of a tool to secure them snugly in the mortar and against the adjacent brick.
4. After each brick is placed, use your level to measure across their tops to insure that they are flat. Tap them with a tool to adjust them until they sit level.
5. When you get around the whole circle, if the last brick does not fit exactly, you will need to cut a piece of brick. Most of us don't have a diamond blade saw or brick grinder handy. So if you don't, you can usually make a pretty clean break in a brick with a stone hammer and chisel. Be sure to wear safety glasses when doing this so that you don't get brick shards in your eyes! Cut out a piece of brick to fit your last spot to finish the first layer of bricks.
6. Go to your next layer of face stones. Make sure to use enough mortar to fill all gaps but make sure it is set back enough from the outer edge of stones so that the outer wall of your fire pit will not get stained with mortar. You want that part to stay clean and pretty!
7. Avoid weak points in your wall by spanning joints between stones with larger stones above it.
- Some tips on stone setting:
1. Choose face stones that have a smoothly curving flat face to point out.
2. Incorporate stones of different size and shape into the wall of your backyard fire pit. You want as little free space filled with mortar in your wall so get creative and find good fits of stones like you would a puzzle. So pick stones that fit well together. If need be, you can shape stones a bit with a chipping hammer and safety glasses.
3. Make sure each stone is as close to level as possible. Crooked stones look bad and are less stable.
4. After each layer, use a jointer or other tool to dig out excess mortar which is sticking out between stones. You can then use a paintbrush or other firm bristled brush to brush the mortar joints to make the mortar smooth and even. This will make your backyard fire pit more beautiful.
5. After each layer of face stones, follow with layers of bricks to catch up to the same level. Just like the stones, span the joints with a brick. In other words, place one brick over the joint created by two bricks on the level below it.
6. As your wall is build, layer by layer, fill in the area between the back of your face stones and the inner layer of fire bricks with mortar and any junk stone you have (smaller pieces of stone that don't work for the outer wall or which you have chipped off the larger pieces). You can even throw in other types of stones you have laying around since this "filling" will not be seen and is just there to make the wall of your backyard fire pit solid and add support.