Brandon Roofers carries out full chimney rebuilds for homeowners in Thetford, and this page walks you through every stage of the job so you know exactly what to expect.
A chimney rebuild is not a small job. It involves scaffolding, several days of work on a high, exposed part of your property, and decisions about materials that affect how long the finished stack lasts. Understanding what happens at each stage means you can ask the right questions before work starts, check progress as it happens, and know what a properly finished job looks like when the scaffold comes down.
We carry out full chimney rebuilds across Thetford and the wider area from our base in Brandon. Here is what the process looks like from beginning to end.
The first step is getting a proper look at the chimney. A ground-level inspection through binoculars can identify obvious problems - a visible lean, large cracks, missing pots, or clearly failed flaunching - but it cannot tell you the full picture. The back face of the stack, the condition of the mortar joints at the base, and the state of the flashing can only be assessed properly from scaffold level.
A roofer who quotes for a rebuild without getting close to the stack is guessing at the scope of work. When we assess a chimney, we do so from the scaffold or at minimum from the roof slope, so we can inspect all four faces and the flashing junction before giving you a recommendation.
At this stage we are looking at: the extent of brick or mortar damage, whether the stack has moved or is plumb, the condition of the flashing, the state of the flaunching and pots, and whether the flue liner (if in use) needs attention. All of this feeds into the specification for the rebuild.
Safe access is essential on chimney work. A chimney stack sits above the roofline, often on the ridge or towards the top of a roof slope, and working from a ladder is neither safe nor practical for a rebuild. Scaffold is erected to give a stable working platform at chimney height, with edge protection on the roof slope below.
On a typical two-storey house, scaffold for a chimney rebuild usually takes half a day to erect and the same to strike at the end of the job. The scaffold hire period is factored into the overall cost of the rebuild. If your property has restricted access or sits close to a boundary, the scaffold design may need to be adapted accordingly.
It is best to arrange scaffold as part of the job rather than leaving it to the homeowner to organise separately. This avoids the risk of a scaffold being built to a specification that does not suit the roofing work.
Once the scaffold is in place and checked, the rebuild begins with carefully taking down the existing brickwork. This is done by hand, working from the top of the stack down to the point where the brickwork is structurally sound - typically at or just below the roofline, though on a severely deteriorated stack it may be lower.
The old flashing is also removed at this stage. The flashing groove (the channel cut into the mortar joints to receive the lead) is cleaned out ready for the new flashing. The existing chimney pot is carefully removed and checked - if it is undamaged and the homeowner wants it retained, it can be reused. If it is cracked or the wrong type for the rebuilt stack, a replacement is sourced.
All debris - old brick, mortar, and lead - is brought down from the roof using bags or a chute and removed from site. We do not drop material off the roof or leave debris in the guttering.
Before any new brickwork goes up, the top course of the remaining original stack is cleaned back to sound, clean masonry. Any loose or hollow brickwork at the base of the rebuild area is taken out and replaced. The surface needs to be level and free of dust or loose material so the new courses bond properly.
If the flue is in use and requires a new liner, the liner is installed at this stage - before the new brickwork is built up around it. A flexible stainless steel liner is fed down from the top of the existing flue and fixed at the register plate level inside the house. This is much easier to do before the new stack is in place than after.
New bricks are laid in courses using a mortar mix appropriate to the property and the original brickwork type. On older properties, this typically means a lime-based mortar rather than ordinary Portland cement. On modern properties, a standard sand-and-cement mix to the correct ratio is used. Getting the mortar specification right is one of the details that separates a rebuild that lasts from one that starts failing within a few years.
Bricks are sourced to match the existing stack as closely as possible in colour and texture. This is not always straightforward - older handmade bricks can be difficult to match exactly - but a good roofer will source reclaimed or period-compatible stock rather than using whatever is cheapest.
Each course is checked for level and the joints are kept consistent in width and profile. The stack is checked for plumb as it rises. Any corbelling or decorative detailing that was present on the original stack is replicated where practical.
Lead flashing is fitted once the new brickwork has been laid. On a chimney, there are typically several pieces of flashing to fit: the apron (front), the back gutter, and the step flashings on each side. Each piece is cut and dressed individually. The step flashings are tucked into the mortar joints as the brickwork progresses, or let into cut grooves where the brickwork is complete.
The lead is dressed firmly into all surfaces and the joints are pointed in to hold it securely. The overlap at each junction is sufficient to prevent wind lifting the flashing edge. Code 4 or code 5 lead is used, depending on the size of the flashing piece and its exposure.
Flashing is one of the most important elements of a chimney rebuild. A new stack with poorly fitted flashing will leak just as surely as the old one did.
Once the brickwork and flashing are complete, the chimney pot is set in fresh mortar flaunching. The flaunching is built up as a firm, sloped collar around the base of the pot, shaped so that water runs away from the flue opening and off the top of the stack. A smooth finish is important - any hollows or cracks in the flaunching will hold water and fail within a winter or two.
If the pot is being capped because the flue is out of use, a vented cap is fitted at this stage instead. The flue must be able to breathe even when not in use, so a solid cap is not appropriate.
Before the scaffold comes down, we inspect the completed stack from all sides: checking the pointing, the flashing, the flaunching, and the plumb of the stack. Any minor finishing is done at this stage while access is still available.
The scaffold is then struck. Any debris from the strike is cleared from the site. Guttering is checked and cleared of any dust or grit that has come down during the work. The work area around the base of the property is swept and left tidy.
What you should be left with is a plumb, fully pointed stack with sound lead flashing, a solid flaunching, and no loose material on the roof or in the gutters.
How long a straightforward single-flue stack rebuild takes depends on the property and the stack, so it is worth asking for a timescale specific to your job, not including scaffold erection and strike. Larger or more complex stacks take longer. Weather can also affect the programme - new mortar should not be laid in freezing conditions.
Lead flashing fails when the lead oxidises and cracks, when the mortar joints holding it erode away, or when it was never correctly fixed in the first place. Surface-applied mastic or tape repairs on flashing are temporary and will fail again. A rebuild is the right time to fit new, correctly installed lead flashing throughout.
Yes. A disused chimney still needs to be weathertight and structurally sound. During the rebuild the pots can be removed and the stack capped with a vented terminal, which prevents water ingress while allowing the flue to breathe.
If your chimney in Thetford needs assessing, call Brandon Roofers to arrange a survey from scaffold level. We will tell you exactly what needs doing, explain the process, and give you a clear quote before any work starts.
No obligation · We usually respond within 2 hours
Storm damage, active leak, damaged ridge - we aim to be on-site within 24 hours.
