Chimney Flaunching Repair

The flaunching sits on the last course of brickwork and is shaped to fall outwards from the base of each pot. That slope is what keeps rainwater moving off the stack rather than soaking into the brick below or running down the inside of the flue. It is the most exposed mortar on the house, taking wind, rain and frost from every direction with nothing above it.

Over time the mortar shrinks, crazes and then cracks through. Older flaunchings were often laid flat or too thin, so they hold water instead of shedding it. Once a crack opens, water freezes inside it and pushes the pieces apart. Eventually sections come loose, the pots lose their support and debris can fall onto the roof slopes below.

From the ground you may see a dark band of damp brickwork near the top of the stack, a pot that is leaning, or pieces of mortar in the gutter or on the tiles. Inside, staining on a chimney breast in a top-floor room or loft, or damp patches near a fireplace after rain, can point to water entering at the top.

Those symptoms can also come from failed lead flashing or perished pointing lower down the stack, so the cause needs confirming before anything is quoted. A chimney can need one repair or several, and recasting the crown will not cure water coming in at the flashing.

With safe access in place, the old cracked mortar is broken out carefully around the pots. Each pot is checked; sound ones are kept and re-bedded, while cracked or unused pots can be replaced, removed or capped. A new flaunching is then cast in fresh mortar, built up around the base of each pot and trowelled to a clear outward fall so water runs off the edge of the stack.

This is a good time to look at the rest of the chimney while access is already arranged. Loose top courses, perished pointing and lead flashings can be assessed in the same visit, and anything else that needs doing is listed separately on the written quote so you can see each part of the job.

Pots and cowls are part of the same top-of-stack work. A pot that serves a fire or boiler stays open but can take a cowl to keep rain and birds out while letting the flue draw. The right cowl depends on what the flue serves, so ventilation is always kept where a working appliance needs it.

On a redundant flue, a ventilated cap stops rain getting in while still letting a little air move through, which helps the masonry dry out. Chimney cowl fitting is often carried out alongside new flaunching, because the pots are already being re-bedded and the access is in place.

If the top courses of brickwork are loose, the stack is leaning, or the brick has broken down badly, recasting the flaunching alone is not a lasting answer. Part of the stack may need rebuilding before a new crown goes on. Where the chimney is no longer used, capping or removal can be compared with repair, and we explain those options on our chimney repairs and chimney removal pages.