Firebrick Installation in an Outdoor Fireplace

Lay the firebricks out, examining each carefully. Sort according to size, if the firebricks are part of a fireplace kit, to make installation quicker. Replace any flawed bricks, such as those with cracks and large chips, if purchased separately.

Pour a package of refractory mortar, a specially designed mortar meant to resist high temperatures, into a large bucket. Add water, according to the mortar directions, until reaching a pancake-like consistency. Alternatively, use premixed mortar, but skip soaking the bricks.

Place the bottom layer of firebricks -- the floor of the fireplace -- in a dry run to get a feel for the design and placement. Firebricks can be laid in simple rows, staggering the joints when possible to increase strength, in squares that decrease in size -- or any design conceivable. Cut bricks as necessary to adapt to the space involved.

Use a damp sponge to wet-mop the entire fireplace interior. Dust and dirt can inhibit proper mortar adhesion, and wetting the surfaces involved prevents leaching moisture out of the bricks.

Drop several firebricks in a bucket of water to soak them a minute or two before placement. Rotate the bricks as necessary until each is wet.

Use a small, square margin trowel to spread a thin layer of mortar across the floor base. Aim for a smooth application about 1/4-inch-thick. All mortar lines, when complete, should be about 1/8-inch-thick, but during installation some mortar will squeeze out or compress.

Butter the edges of each brick as you work, spreading a 1/4-inch-thick layer of mortar along each edge that will rest against another brick. An even, complete coating is essential for proper installation and fire safety.

Place the bricks according to the design specified by the fireplace manufacturer or your own pattern. Cut bricks as necessary, using a masonry saw.

Tap any bricks that appear out of alignment into place as you work, using a wide board. The board is both a straightedge, allowing you to see flush placement easier, and distributes the force evenly to avoid shattering your firebricks.

Air dry the firebricks about 30 minutes to allow them to harden in place. Follow with a fresh layer of mortar, spreading it across the entire brick surface. Pack it into joints as you work. Wait another 30 minutes before brushing or rinsing the mortar off the firebrick surface, leaving a freshly installed firebrick installation.