If your chimney stack is in poor condition and a rebuild has been booked, knowing what to do in the meantime - and what to leave strictly alone - can prevent a difficult situation from becoming a dangerous one.
A chimney stack that is losing mortar, shedding bricks, or showing movement is not just a cosmetic concern. The stack sits at the highest point of the roof, and once the weatherproofing fails - whether through eroded pointing, cracked flaunching, or failed lead work at the roof junction - water enters at the top and works downward. It travels through the stack, into the roof space, and eventually appears as staining on the chimney breast or damp patches on the ceiling below.
Where the chimney serves an active fire or stove, the risks extend beyond damp. A compromised liner, or mortar joints in an unlined stack that have eroded enough to open gaps between the flue and the surrounding brickwork, can allow combustion gases including carbon monoxide to enter the roof space or the rooms below. This is not a situation that improves by itself.
A full chimney rebuild - stripping back to a sound course of brickwork and rebuilding above with correct mortar and matching brick, replacing the flaunching, re-bedding the pot, and attending to the lead flashings at the roof junction - is the right response when the damage is extensive. But in North Walsham, as anywhere, there is often a gap between identifying the problem and getting a contractor on site with scaffold. What you do in that gap matters.
Stop immediately if you notice any of the following, and do not restart until the stack has been properly inspected at scaffold level:
Carbon monoxide is odourless. A CO alarm in any room with an appliance or an adjacent chimney breast is a sensible precaution regardless of the condition of the stack. If the alarm sounds, evacuate the property and call the gas emergency service or fire brigade before calling a roofer.
Once the appliance is off and the flue is not in use, the main priority is limiting further water ingress until the work can be done. There are a few things that genuinely help.
Place a bucket or absorbent material below the fireplace opening if you are seeing water drip into the grate. This prevents water from spreading across flooring or soaking into the hearth surround, which can cause further damage to plasterwork and timbers nearby. It is also a useful way to gauge how much water is coming through, which is helpful information for the contractor.
If there is a chimney cover or cowl in reasonable condition, confirm it is in place. A correctly fitted cowl does not eliminate water entry through failed joints or flaunching, but it reduces the volume of direct rainfall entering the pot. A loose or missing cowl should not be replaced by a homeowner from a ladder - accessing the stack safely requires a proper scaffold or working platform.
Document what you can see from ground level. Photographs of any visible cracks in the flaunching, spalled bricks, or mortar loss are useful reference material for the contractor and may help clarify the scope of work before the scaffold goes up. Binoculars help considerably on taller stacks.
Tell your contractor about any recent changes you have noticed - when the damp appeared, whether the problem has worsened over a particular winter, and whether a sweep has been done recently. A picture of how long the deterioration has been developing helps them understand the likely extent of the damage before they get to scaffold level.
Do not attempt to access the stack from a ladder to apply any sealant, mortar, or filler. Working at chimney height from a ladder is not safe, and temporary repairs applied to failing brickwork rarely last more than one season. Brush-applied waterproof coatings on the outside of a stack can actually trap moisture inside the brickwork rather than excluding it, which accelerates freeze-thaw damage to the bricks rather than preventing it.
Do not apply expanding foam or temporary sealant around the base of the pot or in the flaunching cracks. This blocks the detail that the contractor needs to assess properly and can complicate the job unnecessarily.
Do not use the fire or stove to try to dry out a damp chimney breast. Lighting a fire in a flue that may be compromised or partially blocked is a serious risk, and heat cycling a saturated stack accelerates the deterioration of the brickwork and any remaining mortar.
Do not assume that because the problem is only a damp patch it can wait indefinitely. Water that enters a stack at flaunching or pointing level works downward through every course of brickwork. Each frost cycle opens the joints further. What is a damp patch on the breast in October can be a structurally compromised upper section of stack by the following spring.
Once the scaffold is in place, the contractor can assess the full extent of the damage at close range. The upper section of the stack - and sometimes the full height above the lead line - is taken down course by course until a section of sound brickwork is reached. New brickwork is built up from that point using brick that matches the original as closely as possible, in a mortar mix appropriate to the brick type. Soft, older bricks need a lime-based mortar; harder machine-made bricks can take a stiffer mix. Using a mortar that is harder than the bricks will cause spalling over time.
The flaunching around the pot is replaced in full. The pot is inspected and either re-bedded in the new flaunching or replaced if it is cracked. Step flashings and the back gutter at the base of the stack are inspected and made good - the lead is dressed back where it has pulled away, and mortar joints around the flashing edges are raked out and repointed.
If the flue needs relining, this is the point at which that work is done - before the scaffold comes down. A flexible stainless steel liner is the most common retrofit solution for both solid fuel and gas appliances, run down through the stack from pot to appliance and connected at each end. Clay liners in older stacks can be replaced section by section if only part of the liner has failed, but a full reline is usually more reliable and may be required if the appliance is being upgraded or replaced.
Not every chimney that needs attention needs a full rebuild. Repointing alone is appropriate where the brickwork is structurally sound and the joints have simply eroded. A partial rebuild - taking down the upper courses and rebuilding above a sound section - suits stacks where damage is concentrated high up. A full rebuild from the lead line is the right approach where damage extends down to the roof junction, or where the original mortar has caused widespread spalling throughout the stack.
The decision should be made at scaffold level, with the contractor able to assess each brick and joint. Any quote produced from ground level is an estimate, not a specification.
If you have a stack that needs work and want to know what to do before we can get to you, call us and we will talk you through it plainly. If there is an immediate safety concern, tell us and we will advise on the right next step.
No obligation · We usually respond within 2 hours
Storm damage, active leak, damaged ridge - we aim to be on-site within 24 hours.
