Here is exactly what happens during a chimney rebuild in Lakenheath, from the first inspection on the ground to the final clear-up, so you know what to expect at each stage.
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The process starts before any scaffold goes up. A good assessment begins from the ground, using binoculars if needed, to look at the overall lean of the stack, the condition of the pointing, visible cracks, and the state of the flaunching and pots. This gives a first indication of how serious the deterioration is and whether a partial or full rebuild is likely to be needed.
The roof-level inspection comes once access is in place. From close up, we check each element: the condition of individual bricks, how far the mortar has receded in the joints, whether the bricks themselves are spalling or just surface-stained, how the flaunching sits, and the full condition of all the lead flashings at the roof junction. This is also when we check the back gutter behind the stack, which is often the part in worst condition and the least visible from anywhere else.
The roof-level inspection determines exactly where sound brickwork starts. That is the level from which the rebuild begins. There is no benefit in taking the stack lower than necessary, but equally there is no point rebuilding from a course that is itself on the way out.
Chimney work cannot be done safely from a ladder. Scaffold or a properly set-up tower is required to give a stable working platform at stack height, to allow materials to be brought up and debris brought down safely, and to protect the roof surface below. The type of access depends on the height of the stack, the pitch of the roof, and the layout of the property.
On most two-storey properties, a scaffold tower or a low scaffold lift is sufficient. On taller or more complex properties, a fuller scaffold frame may be needed. The cost of access equipment is part of the overall job cost and should be included in any quote you receive. A quote that does not mention access is worth questioning.
Demolition of a chimney stack has to be done by hand, brick by brick. Power tools cannot be used at roof level without creating vibration that damages the tiles or slates below, or risks dislodging the remaining structure. Bricks and mortar debris are lowered down or bagged and carried rather than dropped.
The tiles or slates immediately around the base of the stack are removed carefully and set aside before demolition starts. This protects them and gives access to the roof timber and flashing fixings beneath. Any bricks in reusable condition are set aside if there is a chance of using them for matching. The rest goes to skip or disposal.
Once the stack is down to the agreed course, the remaining brickwork is cleaned back to sound faces and the mortar beds are raked out ready for new work to start.
Rebuilding begins from the sound course of existing brickwork. New bricks are laid in the correct mortar mix for the property, with full mortar joints - not a thin spread that will crack and recede quickly. Each course is checked for level and plumb as the work goes up. A chimney stack that is built slightly out of plumb will be more prone to movement and more susceptible to water running back towards the roof rather than away from it.
The bond pattern (the arrangement of the bricks) should match the original stack where possible. On most domestic stacks this is a simple English or Flemish bond. Getting the bond right is part of making the finished stack look correct, not just structurally sound.
Corbelling, where the top of the stack steps out slightly to shed water, should be maintained or reinstated as part of the rebuild. This detail is sometimes lost when stacks are rebuilt purely for speed rather than correctly.
Once the brickwork is up to height, the chimney pots are set in the new flaunching. Flaunching is laid in a sloped bed around and between the pots, angled to direct water away from the pot bases and off the top of the stack. It needs to be properly keyed to the brickwork underneath and built up in a single operation where possible, rather than added in layers, which are prone to splitting along the joints.
Pots are checked for condition. If the original pots are intact and undamaged, they can be re-set. If they are cracked or broken, new terracotta pots are fitted. For chimneys that are no longer in use, a capping pot or half-round cover can be fitted to keep rain out while allowing the flue to breathe.
The lead work is the most critical weathering detail on the whole job. The sequence is: front apron at the lowest face of the stack first, then stepped flashings up both sides, then the back gutter behind the stack. Each flashing is cut and dressed into a raked-out joint in the mortar, wedged with lead clips, and then pointed over with mortar to hold it permanently.
The back gutter is a formed lead channel that runs across the back of the stack and discharges water out to the sides. It needs a proper fall towards its discharge point. A flat or back-falling gutter holds water behind the stack, which will eventually find its way through. This is a detail that is sometimes done poorly, and it is worth asking specifically how the back gutter will be formed and discharged when you are agreeing the scope of work.
Soakers - small pieces of lead that tuck under individual slates or tiles at the sides of the stack - are used alongside the stepped flashings to give a two-layer seal at the most vulnerable point. On a full rebuild, soakers should be replaced along with all the other lead work.
The tiles or slates that were lifted around the base of the stack are relaid and checked. Any that were damaged during the work are replaced. The roof surface around the stack is left in the same condition it was found in, or better. Mortar droppings and debris are cleared from the roof slope and gutters below.
The scaffold or tower comes down once the work is signed off and the roof has been checked from ground level. Any debris at ground level is cleared and taken away.
A properly rebuilt chimney stack should sit straight and true. The brickwork should be clean and consistent, with full, slightly recessed mortar joints. The flaunching should be smooth and well-sloped. The lead flashings should be tight to the brickwork with no lifted edges or visible gaps. From inside the house, any damp on the chimney breast should dry out and not return once the stack is properly sealed.
Thetford Roofers carry out full chimney rebuilds for homeowners in Lakenheath and nearby, including Thetford. If your stack needs attention, call us to arrange a roof survey and we will walk you through exactly what the job involves before any work starts.
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