Breeze blocks are a quick and inexpensive material for wall construction. With proper interior support and adequate mortar they can support standard doors and windows safely. Adding new doors will require the creation of an opening. Careful measurements to ensure proper placement is essential. One of the biggest challenges you will face is aligning the interior and exterior openings in the wall.
Mark the door on the inside of the wall where you intend to position your door. Mark the opening up both sides and across at the top. Make the opening 3 1/2 inches wider and 2 inches taller than the outside dimensions of your prehung door frame.
Install a 12-inch-long, 1/4-inch rotary mason's bit into your drill. Bore through the wall precisely on each corner mark at the top of the door opening. Use a small torpedo level fastened on top of the drill barrel to ensure the bit is travelling level through the wall. Apply steady pressure making sure not to push harder as the bit comes out the exterior, to prevent breaking the breeze block face.
Mark the opening on the exterior face of the wall, connecting the two holes horizontally at the top. Draw perpendicular lines at a 90 degree angle down from each corner to the bottom of the door using a large drywall square to ensure square corners.
Cut the opening in both faces of the wall with a concrete saw and an abrasive disk blade. Hardware stores rent them by the hour or day. Wear safety glasses during saw operation. Cut all three sides of the opening on both faces.
Knock the cut block from the opening with a sledge hammer. Pound a brick chisel into the mortar seams to separate stubborn blocks from each other. Clear the rubble from the bottom of the opening.
Cut two pieces of 2-by-10 lumber 1 1/2-inches shorter than the sides of the opening. These will serve as jambs. Cut one piece the width of the opening. This is your header. Position the header in the top of the opening and stand the two jambs underneath it, driving them with a hammer firmly under each corner until they are flush against the cut block on either side.
Cut four pieces of 1-by-6 lumber to the height of the jamb pieces, two for each side of the door. Nail them to the 2-by-10 edges with 16 d nails every 12 inches. Do this for both jambs on both faces of the door.
Measure between the top corners of the 1-by-6 trim and cut two pieces of 1-by-6 to that length. Position them atop the 1-by-6 trim pieces on the side and nail to the edge of the 2-by-10 header with 16 d nails.
Stand the door unit centred in the opening. Wedge shims between the wall jamb and the outside of the door unit at the top right corner, as you face the inside. Place a level on the edge of the right hand jamb and adjust the bottom in or out until it is level. Repeat, wedging shims behind the left jamb and levelling.
Add shims between the 2-by-10s and the outside of the door frame at the bottoms and in the middle of each side. Nail through the jamb and shims into the 2-by-10s at the top, bottom and middle of both jambs to secure the door.