This is by far the most difficult project I have done in our backyard. The labor was not difficult part. Finding all the information on how to build such a simple circular pit took a lot of research. Most sites dedicated to backyard pits are about building elaborate pits that require lots of time, money and skill comparable to a mason. I wanted a simple pit for burning weeds, shrubs and roasting the occasional marshmallow. My criteria was simple: be level, build it in under 4 hours, cost less than $100, and be removable. This meets all those criteria and it isn’t too bad looking.
Spray Paint, flour, or marking chalk
Stackable interlocking retaining wall bricks (we used 57)
1. Choose a location for your fire pit that isn’t close to trees, buildings or anything that could catch fire from a spark. A level location is best, but the design can accommodate a slight slope as well. Be sure there aren’t any underground wires, cable or pipes in your chosen location. Call 811 before you dig!!! Also, check with your city hall about fire pit ordinances in your community you may be prohibited by law from having an in-ground pit.
2. Determine the amount of materials you need. Get your calculator because here comes the math:
To determine the square feet in the area of your circle use this formula:
Diameter* in feet x Diameter in feet ÷ 4 x 3.14 = Square feet in your circle
Example: My pit is 6 feet across so I used the formula: 6ft x 6ft ÷ 4 x 3.14 = 28.26 sq. feet
To determine the amount pea gravel you need use this formula:
Square Feet in circle x base thickness in feet* =___ ÷27 =___cubic yards x 9 =___cubic feet
Example: It is a good idea to add a 1-2 more feet so you don’t come up short in materials so I rounded to 30 sq. ft. for my circle area and used the following formula: 30 x .32 (4 inches of pea gravel) = 9.6 ÷ 27 = .3555 cubic yards x 9 = 3.2 cubic feet. My bags of pea gravel came in .5 cu. ft. so I bought 7 bags
To determine the amount of sand you need use the pea gravel formula but change .32 to .16 (2 inches of sand)
To determine the number of bricks use the following formula:
3.14 x diameter in feet = circumference^ ÷ length of brick in feet = number of bricks needed for one row around
(multiply by 2 for 2 rows subtract one brick from each row you build up)
Next divide the circumference by the length of the brick you choose.
Example: 3.14 x 6 ft = 18.84 ft around my pit ÷ .64** (8 inch bricks) = 29
*Diameter – length across a circle
**Base thickness for inches is determined by multiplying the number of inches by .08
^Circumference – distance around a circle (3.14 x diameter = circumference)
3. Drive a stake into the ground where you want to put the fire pit. Tie a piece of string to the stake and cut it at half the distance of the diameter (radius) of your intended pit size away from the stake.
4. Scribe a circle all around the stake and mark the line with spray paint, flour, or marking chalk.
5. Remove the grass inside the circle and dig out the hole to a depth of about 1 foot (keep the sides as straight as possible).
6. Pour in about 4 inches of pea gravel. If your fire pit is on a slope you can level the bottom out by adding more pea gravel to one side. The pea gravel will help the fire pit drain. Use the level to help you.
7. Add about 3 inches of sand on top of the pea gravel – the sand will help prevent any fire from spreading to roots under your pit.
8. Place your first row of bricks inside the pit on top of the sand. They will be anywhere from 0-2 inches higher than grass level. Stack the next row of bricks on top.
Note: Dry stack the pavers to make it easy to replace any that might break. Don’t use adhesive to hold the pavers together; it can melt and give off fumes that could be toxic.