Plan Your Fire Pit Design
Backyard fire pits are one of the most popular of all landscaping features. They are attractive, functional and provide an outdoor gathering place.
Ideally, a fire pit is constructed from fireproof material on a flat, level area at least 25 feet from a house or tree. Fire pits are strictly governed by local building codes. Some codes require the pit to be encircled by a border of sand or gravel. So before you decide to add one to your backyard, know the code in your area.
The style and shape of a fire pit can vary. Our circular fire pit is about 2′ tall x 5′ total diameter and a 3′ interior diameter.
Build the Foundation
Pound a rebar stake into the ground at the center of the fire pit then mark the circumference of the circle. For a fire pit with a diameter of 5′, attach a string to the stake, measure 2-1/2′ (or half the length of your circumference) and tie this end of the string to a can of spray paint. Pull the string lightly taut and walk around the stake as you spray paint your circumference (image 1).
Dig the space out to a depth of 6″. Then use the same method as above to mark an inner circle 12″ in from the outside circle. This inner circle will be the edge of the fire pit wall.
Make a foundation for the stones to sit upon. Mix concrete with water until it reaches the consistency of peanut butter. Lay the wet concrete in between the two circles so it is level to the ground (image 2). Leave the center area free of concrete to allow for drainage. Build up the concrete until it is about 1-1/2″ below ground level. Press rebar into the concrete for reinforcement. Smooth the surface with a trowel and let dry for 24 hours (image 3).
Build Outer Wall
With the foundation set, it’s time to lay the stones. Mix mortar and then shovel about 2″ of it on top of the concrete base. Working in small sections, lay the stones on the mortar (image 1).
If you are using natural stone, mix the sizes and colors of the stones, and choose stone faces that are attractive and match the slight curve of your outline. When necessary use a chipping hammer to shape individual stones (image 2).
As the first few levels of stones begin to take shape along the outside edge of the fire pit, begin to lay fire bricks to form the inner wall of the structure (image 3).
Build Inner Fire Brick Wall
Level each brick, then fill the gaps in between with wet mortar, scraping away any excess (images 1 and 2). Make sure to measure the inside and outside edges of the wall periodically to maintain the wall’s thickness and circular shape.
Continue to raise both the bricks (against the inside circle) and the stones (against the outside circle), filling in any gaps in between with stones and mortar as the wall grows (image 3). Staggering the seams of the stones and bricks makes the structure more stable and gives it a nicer look. Use a jointer to remove excess mortar from between the stones (image 4).
To finish the structure lay a cap of pre-selected flat fieldstones on top of the wall.
Add about an inch layer of mortar and then begin laying the stones, making sure the tops create a flat, even surface along the entire circumference. Add more mortar between these capstones (image 5) to complete the fire pit.
Finishing the Fire Pit
With the basic structure complete, you can now focus on a few finishing touches.
Using a standard paintbrush, brush the exterior of the stones to remove loose debris. Then, lightly spray with a garden hose to remove any leftover mortar.
To give the fire bricks on the inside of the structure a uniform finish, spray paint the bricks black using a high-heat stove paint (image 1). Fill the pit with a base layer of river rocks.
For our project, we dug out the area surrounding the fire pit. Filled it in with landscape fabric to prevent weeds (image 2). Then covered the space with crushed stone (image 3).
See the original article here: http://www.diynetwork.com/how-to/outdoors/structures/building-a-backyard-fire-pit