A chimney liner is a liner made of metal, clay or ceramic material that is installed inside a masonry chimney. The chimney liner protects the inside of the chimney from excessive heat, keeps ash and other combustible products from escaping through any gaps in the chimney walls and directs ash and exhaust out through the top of the chimney. When purchasing a chimney liner kit, you must first measure the chimney.
Climb up to the top of your chimney with a ladder.
Measure the height of the chimney and fireplace opening by running a tape measure down to the bottom of the fireplace. You can also tie a small weight to a piece of string and lower it to the bottom of the fireplace and measure the length.
Go into your home and measure the height from the bottom of the fireplace to the bottom of the chimney. Subtract that number from the measurement you took from the outside to calculate the height of the chimney.
Measure the length and width of the chimney opening at the top of the fireplace.