Make the Chimney Vertical and Well Grounded

• 1). Build the chimney up from the basement floor. Consider cutting a 4 foot square hole out of the basement floor and putting in a six inch thick concrete slab. Chimneys are very heavy. When you have made an absolutely solid base for the chimney to sit on, begin building it.
  
  
• 2). Put lengths of clay flue liner inside the block chimney. This reduces heat transfer through the chimney and creosote buildup inside the chimney. Place the lengths of flue liner one on top of the other with a thin layer of mortar between them. Build the liner just ahead of the block chimney, surrounding one length with blocks before you install the next. Fill the space between the liner and the blocks with rubble in order to stabilize it.
  
  
• 3). Construct each layer of the chimney of six blocks. Alternate the joints between the blocks to keep the chimney interlocked. Check for level and plumb frequently. Install a metal cleanout door at the very bottom of the chimney.
  
  
• 4). After the blocks are done, cut a hole for the stove pipe with a hammer and cold chisel at about 6 feet off the floor. Install a clay sleeve there that is the size to fit your stove pipe, and infill between the sleeve and the chipped blocks with mortar.
  
  
• 5). Any exterior parts of the chimney should be faced with brick or covered with stucco. Although it is often seen outside, concrete block is not intended to be exposed to weather and will deteriorate over time.
  
  
• 6). If it is an interior chimney that goes out through the roof, you will have to flash around the chimney to prevent leakage. If the chimney is brick faced, install the flashing so that it goes into the mortar joints between the bricks, then under the shingles that are higher than it and over the shingles that are lower.