Step 1
Measure and mark the appropriate size opening on the interior side of your brick wall, according to the air conditioner manufacturer's specifications. Use your tape measure to size the opening, and use masking tape to mark the outline. Use your level to check that the tape outline is plumb on all sides.
Step 2
Use your power drill and masonry bit to make a pilot hole completely through the wall at each corner of the opening marks. These holes will serve as the guideline for your exterior cutting. Cut along the tape outline on the interior side of the wall with your circular saw and masonry blade.
Step 3
Move to the outside of the wall and connect the four corner holes with masking tape. Cut along the tape the same way you did on the inside of the wall. Use your small sledgehammer to knock the bricks out of the wall starting at the top. Break off any remaining pieces of brick, and make a smooth opening edge with your hammer and masonry chisel.
Step 4
Cut outward along the top edge of the opening with your circular saw. Make a 1/2 inch notch about 4 inches long on either side of the opening, at the very top corner where the side of the hole meets the top. Slide a steel lintel into the notch, and use your hammer to position it firmly in place. Apply mortar to both ends of the lintel and wait for it to dry and set according to the manufacturer's instructions.
Step 5
Slide the metal wall air conditioner mounting sleeve into and through the wall from the inside. Use your level to create the proper amount of outward tilt so condensation drips out and away rather than into your home. The air conditioner manufacturer will indicate the amount of slope required. Use your hammer and masonry nails to fasten the sleeve to the wall opening. Drive nails through the sleeve pilot holes and into the mortar joints between the bricks in your wall opening. These fasteners plus the extended lip around the inside of the sleeve will hold the unit in place.
Step 6
Place the air conditioner into the sleeve, and fasten it in place according to the manufacturer's instructions. Move to the outside of the wall and apply a thick bead of waterproof silicone caulking to the gap between the wall and the mounting sleeve. Plug the unit in and test it.