How to Make a Brick BBQ Oven

Build the Foundation

• 1

  Clear all vegetation from the area where you will build the oven. Dig a 40-inch square trench that is 24 inches deep. Fill the trench with screened stone or recycled concrete broken into 1 1/2-inch pieces. Fill all gaps with gravel, and tamp down the gravel firmly until it is solid.

• 2

  Frame the perimeter of the trench with 2-by-6-inch wood boards. Measure diagonally across the resulting box twice – once from each base corner. Both measurements should be exactly the same to ensure that the cement pad that will be in the box is not skewed. Support the boards with stakes.

• 3

  Mix roughly one-third of one 80-pound bag of cement mix according to the cement manufacturer's instructions. The general rule of thumb is to use a 1-to-3 ratio of cement to sand. Pour enough mixed cement in the wood-framed box to form a 40-by-40-by-3 ½-inch cement pad. Level the concrete pad with a screed, and allow it to cure for 48 hours.

Create the Base

• 4

  Apply pre-mixed cement mortar onto the bottom of a 4-by-8-by-16-inch concrete block with a trowel, and press the block onto the concrete pad's perimeter. Tap the concrete block to ensure it is level. Apply mortar to the end and bottom of another concrete block. Place that block against the first block on the pad's perimeter, and tap it until it is level. Scrape away excess mortar. Continue in the same manner to place the first course of concrete blocks along the concrete pad's perimeter. Lay a second course of concrete blocks on the first course of blocks, adding wire mesh reinforcement between the courses. Use as few cut or half concrete blocks as possible. Use a spirit level to make the blocks absolutely level and plumb. Allow the concrete blocks and mortar to dry for two days.

• 5

  Fill the space enclosed by the concrete blocks with a 6-inch layer of gravel. Tamp the gravel lightly, and then add another 6 inches of gravel. Tamp the gravel again.

• 6

  Mix 1 1/3 bag of cement mix, 13 pounds of perlite and water to form a lightweight cement mix. Pour this mixture over the gravel until the surface of the cement is level with the top of the cement blocks. Allow the mixture to cure for five days.

• 7

  Place a ½-inch layer of clean, fine sand on top of the cured cement. Use a straight edge to make the sand as level as possible. Measure the length of the front of the concrete block base, and find its center point. Place two medium-duty firebricks on both sides of the center point. Make the firebricks overhang the edge by 2 inches. Continue placing firebricks side by side without mortar or gaps. Make the first layer of firebricks 8½ inches from the back and 11 inches from the side of the base to allow room for the upper layer. Check the first course with a spirit level to ensure it is level. Tap down high spots with a hammer until all the firebricks are flush with each other. Stack other firebricks on edge along the edge of the first layer of firebricks, adding courses until the resulting firebox is the desired size.

• 8

  Place a steel lintel that is 1½ by 14¾ by 18 inches with 6-inch diameter center hole on top of the firebricks, flush with each side. Do not cover the lintel's center hole. Stack the remaining firebricks in place to form the base of the chimney.

Finish the Oven

• 9

  Lay additional mortared courses of concrete blocks on the outside of the firebricks with wire mesh reinforcement inserted between each course of concrete block. The top of the concrete blocks should be even with or slightly higher than the surface of the firebricks. Be very careful not to jostle the stacked firebricks, and leave a roughly 1/8 inch of space between the concrete blocks and firebricks to allow for their expansion. Allow the concrete blocks' mortar to dry for two to three days.

• 10

  Mix two bags of cement , 25 1/2 pounds of perlite and water to create a lightweight cement. Pour the mixture into the space between the firebricks and the concrete blocks. Allow it dry for 48 to 72 hours.

• 11

  Cut a piece of cement board large enough to cover the entire top of the oven. Place the cement board on the oven so it is aligned with the oven. The board should be balanced on the base of the chimney. Trace the outline of the chimney base on the underside of the cement board. Cut the shape of the chimney base out of the cement board. Check the fit of the cutout around the chimney base. Remove as much material as necessary for the cement board to fit.

• 12

  Nail four pieces of scrap wood around the edge of the cement board. The resulting structure should look like a 2- to 3-inch-deep tray. Place squares of rebar within the frame in a grid pattern. The rebar adds structural strength. Place 1/8-inch wide shims around the chimney base.

• 13

  Mix a 40-pound bag of premixed cement with water according to the manufacturer's specifications. Pour the cement into the form you created in the previous step. The cement will be a counter top. Level the cement's surface with the screed. Spread recycled glass chips on the surface of the still-wet cement, starting with the largest pieces and ending with the smallest chips. Press the glass into the surface of the cement with a bull float. Lightly trowel the surface until the glass chips are just barely covered by the fine particles of cement. Let the cement cure for at least seven days. Remove the shims and form, which should leave a 1/8-inch space for expansion between the concrete and chimney.

• 14

  Smooth the concrete counter top by wet-grinding its surface and edges with a heavy-duty concrete polisher. Start with the coarsest grit available on the polisher, and slowly work your way up to finer grit polishing pads until you achieve the level of smoothness you prefer and expose as much of the glass chips as you wish. Do not rush this step or you will damage the polisher and spoil the counter top's finish. Allow the counter top to dry completely and cure for a total of 28 days. Apply concrete sealant to the counter top by following the sealant manufacturer's directions.

• 15

  Place a 6-inch diameter, 10-foot long stovepipe into the chimney base. Seal the chimney's collar at the chimney's base to the top of the oven with silicone. Fill the gap between the stovepipe and chimney base with lightweight cement.