An outdoor fireplace is a handsome feature in any backyard, but it’s also a way to extend the hours you spend enjoying your outdoor space. The right fireplace in the right part of your yard can take the chill out of nighttime stargazing, and can even make fall nights comfortable for outdoor entertaining. Pick a fireplace design that blends well with other hardscape surfaces in your yard, and build it with an eye on safety first.
Check local fire and building codes to determine how far from the house, other structures, and property lines your outdoor fireplace must be placed. Local regulations may also limit the size and dimensions of the fireplace.
Draw your fireplace design to scale on grid paper. Use this drawing to compile a list of materials and amounts you’ll need to complete the fireplace.
Clear the area around the fireplace site to ensure that no combustible plants, structures or materials are nearby.
Lay out a large plastic tarp as a staging area next to the fireplace site. Organize all your materials on the tarp before beginning construction.
Define the outline of the fireplace with landscape spray paint.
Dig a footing trench around the perimeter of the fireplace. The footing will need to extend below your local frost line, and should have 4 inches of gravel underneath to providing adequate drainage.
Form a crosshatched rebar grid across the area over which you’ll pour the fireplace slab, by wiring lengths of rebar perpendicular to one another. Support the grid on brick bolsters.
Pour the concrete footing and slab for the fireplace. The slab should be 4 inches thick. Allow it cure before proceeding.
Lay the cinder-block frame for the base of the hearth. Use the number of cinder blocks necessary to raise the hearth to the height of your design. Mortar the blocks in place, using guide strings and story boards to ensure the frame is level and plumb.
Mortar J-bolts into the cavities in the top of the corner cinder blocks, to hold down the hearth deck.
Mark and drill holes to bolt the 1-inch plywood hearth deck to the J-bolts. Secure the plywood deck in place.
Nail a frame of 2-by-4s to the outside edge of the plywood and pour a 3-inch layer of concrete for the hearth deck. Remove the frame when the concrete has cured.
Position the prefabricated firebox on the hearth deck, following the manufacturer’s placement directions.
Lay the floor of the firebox using fire bricks and refractory mortar. Attach the flue and chimney to the box.
Lay brick around the base, covering the hearth and around the firebox to finish the fireplace. Add a chimney cap as recommended by the firebox manufacturer.