Gathering around a crackling outdoor fire, telling stories and roasting marshmallows is a great outdoor activity for a cool evening. A fire pit, either elaborate or basic, makes backyard fires safe and comfortable. A contractor can build your fire pit, or you can pile stones in a suitable area for a temporary fire pit. Building a semi-permanent fire pit is a moderately difficult do-it-yourself project, requiring more muscle than construction experience, and a couple days investment in time.
Planning and Building
Select a location for the fire pit that is approximately 18 feet in diameter and fairly flat. The area should be at least 20 feet away from trees, bushes, buildings and other flammable items. Burning wood sends sparks into the air. Make certain that there are no overhead phone or electric lines. Do not build over a septic tank, drainage or sprinkler lines.
Compile your materials, the majority of which are your stones, gravel and sand. A fire pit can be built from cast concrete that has been moulded to look like real stone. It can also be made of natural boulders, quartz stone, firebrick or paving stones. Stone can be purchased at a home-building supply store, fireplace speciality store or directly from a local quarry. Select stones that have relatively flat sides for the face stones (the ones that form the wall) and smooth, rounded stones as the "cap stones" for the top row. The quantity of all materials depends upon the size of the fire pit. Staff at the building supply store will help estimate quantities using your measurements.
After your material is assembled, spray-paint to make a circle with a 9-foot radius, using a stake and a piece of string as a compass. From the inside of this circle, remove sod, plantings and obstructions. Dig the area so that the fire pit base stones will lay even with the surrounding lawn. If the base stones are 4 inches deep, dig 4 inches. If the ground is uneven from side to side of your circle, cut into the high side and line with stones to create a retaining wall. This creates a simple "patio" on which the fire pit will be centred.
Alternatively, pour a layer of fast-set concrete in a ring for the base of the pit stones, leaving dirt at the internal circle, which will be surrounded by the fire pit.The fire pit stones will be laid in a circle of about 48 inches diameter. Do not build smaller than 36 inches diameter because a fire needs air to start easily and burn evenly. If you are using a grilling grate over the fire pit, make certain that you don't build wider than the span of the grate.
Spread a level layer of sand over the pit area. Using large stones, create a ring around the perimeter of the sand. The weight of this first row should keep them stable. Place a second row of stones, staggering the joints and fitting the rocks next to compatible rocks. If you are working with concrete blocks, a layer of masonry adhesive between the blocks will add stability and permanence. Other types of stone can be filled with mortar that is mixed one bag at a time, following manufacturer's directions. Do not build higher than 12 inches. The objective is to build a wall with as little "free" space as possible.
Fit your stones together tightly, working to find coordinating sizes and shapes. If you must break the stone to create pieces that fit, use a chisel and mallet. Wear safety goggles. As the fire pit wall is built, the areas between the stones can be filled with small pieces of stone and filled with mortar. This adds stability. Building one side of the pit slightly higher than the others will help funnel smoke upward. Fill the completed fire pit with about 6 inches of gravel. Gravel provides a safe surface for fire and provides drainage.
Line the inside of the fire pit walls with a thick steel ring. The rings used for park campfires help protect the stones and keep sparks from spreading. Do not use galvanised metal for the internal ring as toxic fumes are created when exposing it to high heat. A mesh screen lid to place over the burning fire makes your fire pit safer by helping contain burning embers.
Before you build a fire pit, check with the city or municipal building department for local outdoor fire restrictions. Many areas require burning permits. Others prohibit fire pits and have size restrictions. An inspection of a completed fire pit may be required before use.
Stone can be purchased at a home-building supply store, fireplace store or quarry. Ask if the stone you are considering is safe at high temperatures. Some materials, like breeze block or certain river rock, may crack or explode when exposed to fire. A fireplace store is a good resource for materials.