How to Build a Firewood Oven

Choose a level site for your firewood oven. Make sure the site is not near a childrens' play area, home entrance or exit, or a pathway.

Build the base for your firewood oven. Dig a trench that's 18 inches deep and as large as your oven -- about 40 square inches. Fill the trench with gravel. Tamp down the gravel base using a hand tamp.

Place a plywood or aluminum cement form around your base, so the form fully encloses the area and rises at least 3 1/2 inches above the base. Pour concrete into the form, spreading it out with a trowel. By pouring and spreading concrete, you'll cover the base with a thin concrete slab that measures 40 inches by 40 inches, just like the base. Pour the slab so it's 3 1/2 inches thick. Wait for the concrete to fully cure, about four to five days, before moving on to the next step.

Build the firewood oven base using 4-inch-by-8-inch-by-16-inch cinder blocks. Lay the blocks around the perimeter of your concrete slab, using a thin, even layer of brick mortar between each brick. When you finish one layer, place a sheet of wire mesh over the top. Build another level of bricks on top of the mesh. Let the bricks dry for two days.

Pour gravel or sand inside the base for strength, tamping it down with your hand tamp. Fill the base nearly to the top, leaving 4 inches of head space.

Pour a 4-inch layer of concrete inside the base. Level the concrete with a wood plank so it lies flat. Allow the concrete to dry for about four to five days.

Sprinkle a fine, even layer of sand on top of the cured concrete. Lay firebricks over the sand so they touch. They need no mortar. This becomes the floor of your oven.

Stack firebricks to form the oven sides. Place three layers along the left and right sides and along the back to form a U-shaped oven.

Fit a steel shelf over the top firebricks to form the top of the oven. You'll need a steel shelf that fits the width of your oven chamber exactly. Trim the steel yourself with a cutting torch or find a metal shop that can trim steel.

Build two more courses of cinder block around the fire bricks, to form the top half of your oven. Place and mortar the bricks as you did before. You might need to trim some bricks to fit around the front face of your oven; if so, use a right angle grinder.

Pour a lightweight cement into the space between the cinder blocks and your firebricks, for insulation. Cement high in perlite works well, since perlite holds up to high heat. Allow the cement to cure for four to five days before you use the oven.