Flaunching is the mortar base holding the chimney pot in position on top of the chimney stack. If there are minor cracks in the mortar, these are easily repaired with mastic applied with a gun or pressed into the cracks.
 

 
If there are more serious cracks evident, then the flaunching should be completely replaced. It is important to support the chimney pot before removing the flaunching. Tie a length of rope around the top of the pot (A) and a second rope around the chimney stack (B). Then secure by attaching a rope from A to B on both sides of the stack. This should hold the pot in position before removing the flaunching.

Use a cold chisel and club hammer to remove the damaged mortar. Brush away the unwanted material and dampen the surface of the stack. This is necessary, especially in warmer weather, to stop the mortar from losing moisture too quickly, which would result in cracking. Use mortar consisting of approximately a 1:4 cement:sand mix to replace the flaunching around the base of the pot.
 

 
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