Ely Roofers carries out chimney rebuilds in Willingham, taking a failed stack safely down to roof level and building it back up properly, step by step.
A chimney rebuild is a sequence of distinct stages. Each one depends on the last being done correctly. When a homeowner understands what should happen at each stage, they are in a much better position to judge whether a contractor is cutting corners. Here is what a proper rebuild looks like, from the first inspection through to clearing up.
A proper assessment has to be done from the roof, not from the pavement. Ground-level observations can flag obvious problems such as a lean or large gaps in the mortar, but they cannot tell you the condition of the individual bricks, the state of the DPC, whether the mortar behind the pointing is sound, or the exact condition of the lead flashings at the base of the stack.
From the roof, a roofer should be able to tell you which courses need to come down, whether the stack below that point is sound, what condition the flashings are in, and whether the lead has already been cut short or previously repaired with inappropriate products. All of this shapes the scope of the job and the quote. If a roofer gives a fixed price for a chimney rebuild without getting on the roof first, treat that cautiously.
Chimney work at roof height requires safe access. For most two-storey houses, this means a scaffold tower or a section of tube-and-fitting scaffold erected against the wall and over the relevant roof slope. Some contractors use a cherry picker where access and ground conditions allow, but scaffolding is generally more practical for a rebuild because materials need to be moved up and rubble moved down safely over the course of the job.
The scaffold should be positioned to allow safe working on all four faces of the stack, not just the front. A rebuild that can only be accessed from one side will not be done properly on the others. Ask the contractor how access is being arranged before work starts.
The existing stack is carefully dismantled from the top down, course by course. This is not a case of pushing it over - loose bricks falling onto a roof can cause serious tile damage, and pieces falling from height are a safety hazard. Each course is worked loose with a bolster and hammer, and the bricks are lowered or passed down in a hod or bucket to avoid any impact on the roof covering below.
The demolition continues until the roofer reaches sound, stable brickwork that can serve as the base for the new build. On older stacks, this is sometimes lower than expected. If there is a chimney breast inside the property, the internal structure is not affected by a standard stack rebuild above roofline level.
The old lead flashings are removed at this point. If they are in reasonable condition and the correct Code specification, they can sometimes be re-used, but new flashings are generally the better option when a full rebuild is being carried out.
Before any new brickwork goes up, a new damp-proof course tray is installed at the base of the stack, above the flashing level. This is formed in Code 4 lead sheet, dressed carefully around the inside perimeter of the stack to create a tray that catches any moisture getting into the stack from above and directs it outward over the flashings.
The DPC tray must have proper stop-ends at each corner to prevent water from running sideways into the wall. It should protrude slightly beyond the face of the stack on the lower courses to allow water to drip clear. A DPC that has been folded roughly, left without stop-ends, or omitted entirely is one of the most common reasons a rebuilt chimney continues to cause damp problems inside the property.
The new stack is built up from the sound base, course by course, using bricks that match the existing stack as closely as possible in size, colour and texture. The mortar mix is chosen to suit the brick type - a mix that is too hard will crack the brick faces over time rather than allowing slight movement to be absorbed in the joints.
Each course is checked for level and plumb as it goes up. The stack has to be vertical. Even a slight lean built into the new work will worsen as the mortar sets and can be difficult to correct later. The joints are finished to match the profile of the original pointing - usually a slightly recessed or flush joint rather than a projecting ribbon of mortar, which traps water.
Any chimney pots are re-bedded or replaced at this stage. If the flue is no longer in use, a ventilated capping terminal is fitted rather than leaving the pot open.
New lead flashings are cut, dressed and fixed once the brickwork has set sufficiently. The flashings seal the junction between the stack and the roof slope on all four sides: a stepped flashing up each side, an apron at the front and a back gutter at the rear. Mortar joints in the brickwork are raked out to receive the top edge of the flashing, which is then pointed back in with mortar and dressed tight to the face of the stack.
Properly installed lead flashings, in the correct Code specification, will outlast the rest of the roof if left undisturbed. The most common cause of early flashing failure is insufficient depth in the mortar chase, or relying on sealant rather than mortar to hold the lead in place. Silicone and other sealants shrink and crack; mortar does not.
Once the leadwork is complete, the scaffold is cleared and the roof covering around the base of the stack is checked. Any tiles disturbed during the work are re-laid and any mortar splashes on the tiles are cleaned off. Rubble from the demolished stack is removed from site.
Before the scaffold comes down, the finished stack should be inspected from roof level - checking that the pointing is complete on all four faces, the flashings are tight, the DPC tray is not visible below the first course, and the pots are properly bedded.
We work in Willingham and the surrounding area. If you are unsure whether your chimney needs a full rebuild or a repair, call us and we will carry out a proper roof-level inspection rather than guessing from the ground.
Call Ely Roofers to arrange an inspection and get a clear account of what needs doing and why.
No obligation · We usually respond within 2 hours
Storm damage, active leak, damaged ridge - we aim to be on-site within 24 hours.
