A dramatic patio fireplace can set you back a hearty chunk of change. Traditional masonry units can cost upwards of $10,000. Happily, this basic fire pit can give you all the warmth of a more elaborate fireplace without the drain on your wallet.
Don't lift a shovel or buy a brick before you contact your local building department. Explain what you plan to do (you can even print out and bring in this article) and bring along a diagram showing where you plan to situate the fire pit. Failure to notify the authorities risks breaking the law and endangering yourself and your home.
1. Insert a wooden rod where you want the center of the fire pit. Connect the rod to a can of spray paint with a 10-1/2-inch-long string, hold string taut, and paint a circle. Attach a 22-1/2-inch-long string to the spray paint can; repeat the procedure. Following the outline, dig a trench 10 inches deep and 12 inches wide.
2. Line the trench with 2 inches of gravel, then tamp it firm. Cover the gravel with concrete up to ground level. Use a shovel to remove air pockets, level with a scrap of 2x4, then smooth the surface with a trowel. After the concrete is hard to the touch, cover it with plastic for several days, then let it cure in the open air for a week.
3. After the concrete has cured, mist it with water and spread it with refractory mortar. Press a 6-inch manhole block into the mortar, then place another flush against the first, using a scrap of 2x4 to keep the tops of the blocks even. Leave three equidistant 3/4-inch gaps in this first course to serve as air vents.
4. Dry-lay a second course of 6-inch manhole blocks over the first (do not use mortar). Position the blocks so they are flush with each other. The internal edges of the blocks in the second course should line up with those in the first course. This will result in a slight lip along the outer edge.
5. Mist the blocks of both the first and second course with water, then apply surface-bonding cement to the exterior. Smooth the surface with a wet trowel. Keep the top edge clear of cement to ensure that the cap will bond with the wall, and do not cover the air vents.
6. Cut fireproof brick capstones into wedges using a circular saw with an abrasive masonry blade and chisel (wear goggles). After surface-bonding cement has cured, mist the fire pit with water. Fill in the block hollows then add a coating of mortar to the top edge. Top mortar with brick wedges. Let the fire pit cure for 30 days.