Replacing a Single Chimney Pot in a Row of Pots

Deciding whether one pot is enough

Replacing one pot is reasonable when the damage really is confined to that pot: a split rim, a crack running down the barrel, or a section that has dropped away. It is a poor idea when the same fault is showing in several, because swapping one pot in a failing row just moves the problem along. Look at the others first. If the mortar around their bases is cracked, if they are leaning even slightly, or if the glaze is flaking in the same way, the head probably wants dealing with as a whole. Bedding a Row of Chimney Pots in One Flaunching sets out what that involves.

There is also the question of what the pot is doing. A pot over a flue that is in use has a different job from a pot sitting over a flue that nobody has lit for decades. Either way the outside work is the same, but the replacement may differ: a working flue needs an open pot, while a redundant one can take a pot with a cap or a guard, as covered in Capping a Flue You No Longer Use, and Why Sealing It Solid Causes Damp. Anything that changes how a flue draws, such as terminals, linings or appliance connections, belongs to a HETAS or Gas Safe registered installer or a sweep, not to the person doing the outside work.

Matching what is already there

A row is read as a set, so a mismatch is the first thing the eye lands on. The measurements that matter are height above the flaunching, diameter across the base and at the rim, the shape of the barrel and the rim moulding, and the colour and finish of the clay. Pots that look identical from the pavement can differ by a few centimetres in diameter, and that is enough to leave a visible gap or a poor fit against the next one along.

Overall height is the figure people usually quote, and it is the wrong one to rely on. A pot is bedded to a certain depth, and the depth varies from one to the next. What counts is how much stands proud of the mortar, because that is what the eye compares along the row. Measure the neighbours from the surface of the bed to the top of the rim and match that, then allow for the depth the new pot will be set into the mortar.

Finding an exact twin is not always possible. Reclaimed pots turn up through salvage yards, and a few makers still produce traditional patterns, but colour and weathering will rarely be a perfect match. Where there is no twin, the sensible compromise is to match the profile and height first and the colour second, then accept that a new pot will look slightly cleaner until it weathers. Our notes on Chimney Pots, Cowls and Bird Guards: Which Do You Actually Need? cover the usual patterns and what suits which stack.

Cutting out the old pot without shaking the rest

The pots in a row are braced by the mortar between them, so every blow to one is felt by its neighbours. A cracked pot is therefore not simply knocked off. The mortar around its base is cut back with small tools to free it, working away from the pots that are staying, and the pot is eased out in pieces if need be. Hammering and levering are what loosen sound pots, so patience at this stage protects the rest of the row.

Once the pot is out, the seat is cleared back to sound material. The top of the brickwork or the flue liner is checked for damage, and any loose mortar from the neighbouring beds is removed. If the head under the old pot turns out to be crumbling, that is a different conversation: it may be time to look at Repoint, Rebuild or Remove? How the Decision Gets Made. What matters is that the new pot sits on something firm, not on a layer of rubble.

Disposal is part of the job as well, and so is protecting the slates, which are easy to crack when heavy clay is moved across them. Broken clay is heavy and sharp, and it should be lowered or bagged and taken down rather than dropped, because the area below a stack is usually a path or drive. This is also one reason a ladder-and-bucket approach is not suited to tall stacks, and why the ground below should be kept clear while work is going on.

Bedding the new pot and blending it in

The new pot is dry-fitted first against a straight edge and against its neighbours, checking it is upright, at the right height and square to the row. It is then bedded on fresh mortar, pressed down until the base seats fully with no gaps beneath, and the mortar is formed around it with a proper fall and a clean junction against the existing bed.

That junction is where replacements often go wrong. If the new collar is a different mix, a different colour or simply laid over dusty old mortar, it will separate at the join within a season or two. The edges of the old bed need to be cleaned back and wetted so the new material bonds, and the colour and texture should sit comfortably with what is there. A new collar that is much stronger than the old bed will crack the weaker mortar around it, so the mix needs thought, as covered in Repointing a Chimney: Why the Mortar Mix Matters More Than the Finish.

We deal with the outside of chimneys only, and this is exactly the kind of work that suits it. If you have a row with one damaged pot, our chimney repairs in Wallasey page explains the stacks we see in Wallasey, and you can describe what you see from the garden or send us a photograph for a free written quotation. Please do not climb up to look.