Can a cracked chimney pot be replaced?

A chimney pot is a clay or concrete cylinder standing on top of the stack, extending the flue upward. It is not just placed on the brickwork. It is bedded in mortar, and a sloping collar of mortar, the flaunching, is built up around its foot to grip it and carry rain away from the flue. So the pot is held in two ways, by the bed beneath and by the crown around.

That arrangement explains most failures. Wind pushes on the pot, frost splits the clay, and the crown shrinks and cracks until rain finds a path in. A cracked pot can drop fragments into the flue, let water run down the stack, or topple in a gale. It is the highest and smallest part of the chimney and often the first to give trouble, partly because nobody looks at it from one year to the next. Our page on chimney pots and cowls shows the choices.

The old pot is lifted off, loose mortar is chipped away, and the stack top is then inspected. If the brick beneath is sound, the new pot is stood on a fresh bed of mortar and a new flaunching is formed around its foot, sloping outward so that water runs off. Where several pots share one stack, each is checked in turn, since one that looks fine may be loose underneath. A pot that rocks when tapped has lost its bed and is not safe to leave, so it is better dealt with before the next gale than after it.

Pots come in many shapes and heights, and matching matters on a terrace where the line of stacks forms part of the street. We can usually source a clay pot in the same style, and where an exact match is hard to find, you see the options before anything is ordered. The new pot must also suit the use of the flue. A live flue needs an open pot that lets smoke out. A dead one can take a capped or vented pot, which our page on capping a chimney discusses.

Swapping the pot and leaving a cracked crown is half a job. The new pot would stand on a weak base, and rain would still find its way into the flue beside it. So the crown is cut back to sound mortar and rebuilt as part of the replacement. It is a small amount of material doing an important job, keeping water out of the top courses of brick.

If the top of the stack is itself loose, or the pointing nearby has opened up, those get repaired in the same visit, since the access is already in place. Our guide to chimney flaunching describes the crown in more detail. We photograph the pot, the crown and the top courses before and after, so the survey record shows exactly what changed. You receive one written price for the whole repair, fixed after we have seen the stack.

Before the pot comes off we look for signs of nesting. A pot with birds using it has to wait until they have finished, as protected nests must be left alone. Tell us if you have watched birds going in and out of the top of the stack.

If the flue serves a fire, a stove or a boiler, tell us that too. A cracked or loose pot above a live flue affects safety as well as weather-tightness, and the flue should be swept and checked for blockage before use. A roofer deals with the pot and the stack, and a sweep deals with the inside of the flue. Our page on sweep or roofer explains how the two jobs divide, which helps you decide whom to ring first.

A pot sits at the very top, so safe access is required, which usually means scaffold. Scaffold over the pavement calls for a highway licence, and scaffolding for chimney repairs covers the notice period. Swapping a pot is a modest piece of work, yet access can account for a good share of the price, so check whether a quote includes scaffold and VAT.

On a listed building, altering the look of a chimney can need listed building consent, and a like-for-like pot is the easiest case to make. In conservation areas the council may control work on chimney stacks, as Portsmouth does in Old Portsmouth with an Article 4 direction. Check with the council's planning team if your house is protected. The main chimney repairs page lists the work that goes alongside a pot.