A chimney breast is the area of a chimney that protrudes out from the main portion of the wall guarding the interior of a fireplace. Chimney breasts were most often used in older homes from before the invention of central heating. Removing one is a complicated process that requires many permits.
Work from the top floor down. Cut out the chimney breast outline with the masonry saw. Remove the breast bricks from the wall with a hammer and chisel.
Screw an MS steel plate as large as the base of the chimney to the top of the gallows brackets.
Support the remaining chimney stack with the steel gallows bracket and steel plate. Screw two brackets into the wall 1/4 inch below the bottom of the chimney stack using the 100mm bolts.
Fill in the gap between the plate and the chimney stack with semi-dry cement sand.
Fill in the flue gap behind the chimney breast with bricks and mortar or plaster. Brick up the bottom of the chimney stack to hide the gallows brackets holding the chimney stack in place. If you remove all floor layers of the chimney breast, you do not need to install the brackets.
Hire a professional to inspect the wall where the chimney breast is installed. Sometimes it is built right into the wall. If this is the case, removing it can cause the entire wall to collapse. In multistory houses, removal from a lower floor is likely to cause the chimney in the upper stories to collapse. Ask the inspector what support methods are necessary for the wall after removal. Obtain all permits and licenses to remove the chimney breast before proceeding.