Lightning damage is not one of the more common reasons we inspect chimneys, but it does happen. This real inspection shows what can happen when a chimney, steel roof and metal flue liner are involved in a lightning event, and what should be checked before the heating appliance is used again.
In this case, the strike caused electrical damage throughout the house and left physical evidence around the chimney from the roof down to basement level. The main question was whether the metal chimney liner had also been damaged.
The starting point: a masonry chimney extending through a steel roof after a reported lightning strike.
The exact route of a lightning discharge can be difficult to prove after the fact. The useful part of the inspection is identifying what was affected and whether the chimney remains serviceable.
A damaged area was visible in the metal flashing at the base of the chimney where it passed through the steel roof. The homeowner had already made a temporary repair before the chimney inspection was carried out.
At basement level, the cleanout door had been displaced during the event. Nearby, localized cracking and damage were visible at the floor.
Electrical and communications equipment elsewhere in the home was also damaged, including telephone and alarm equipment.
Roof-level evidence: a small damaged area in the chimney flashing had been repaired before the inspection.
Damage at basement level and to communications equipment shows why a lightning event should not be judged only by what is visible outside.
At the chimney base: localized cracking and floor damage were visible near where the chimney reaches basement level.
Elsewhere in the house: telephone and alarm equipment also showed damage from the lightning event.
Metal chimney liners, flashing, steel roofing, plumbing, electrical wiring and other conductive components can all potentially carry part of a lightning discharge.
Under the voltages involved in a lightning event, current can arc between nearby conductive components. Masonry between two pieces of metal does not necessarily mean the components are electrically isolated during a strike.
A metal liner carrying part of a discharge does not automatically mean it will be perforated or destroyed. The result depends on the actual current path, connections, arcing points and available routes toward ground.
Rather than assuming a liner is either safe or ruined, inspect the accessible system for perforation, separation, obstruction, damaged connectors, displaced components and other evidence of the event.
That was the main question in this inspection.
The chimney cleanout was opened and cleaned so the lower portion of the flue could be examined. The metal liner was visually inspected from the accessible lower section.
No visible perforation or separation of the liner was identified. The flue remained clear and unobstructed, with a direct view through the liner to daylight at the chimney termination.
Based on the accessible visual inspection, no damage was identified that required repair or replacement of the liner. The liner remained serviceable.
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View through the liner: the flue remained clear and unobstructed through to daylight at the chimney termination.
Basement inspection: the accessible lower chimney, liner and appliance connection were examined as part of the assessment.
A post-lightning inspection is looking for evidence that the flue can no longer safely perform its job. Depending on the system and where the strike travelled, concerns could include:
None of these automatically follows from a lightning strike. The point of the inspection is to find out what actually happened.
While inspecting the chimney system, a portion of the heat shielding adjacent to the furnace flue connector elbow was noted to be missing.
This appeared separate from the lightning event. The homeowner was advised to extend the shielding appropriately before the heating appliance was used again.
It is a useful example of why an inspection should look at the accessible chimney connection as a system rather than focusing only on the one defect that prompted the visit.
At basement level: the cleanout and accessible lower chimney formed part of the inspection before the liner was assessed.
A chimney can look relatively normal from outside even when the event has affected components inside the building.
Check accessible portions for perforation, separation, distortion, heat damage and obstruction.
Look for displaced doors, damaged fittings, separated connections or evidence of arcing around metal components.
Check masonry, flashing, cap and termination for cracking, displacement, impact or localized damage.
Lightning can damage electrical and communications equipment well away from the visible strike point. These systems require assessment by the appropriate qualified trade.
If the building experienced a significant strike, the grounding and bonding arrangements may be worth reviewing as part of the broader post-event assessment.
Where the chimney serves a heating appliance, resolve any identified safety concerns before returning the appliance to normal operation.
A properly designed lightning protection system is intended to intercept a strike and provide a deliberate route for lightning current toward ground. That generally involves more than a single rod.
Depending on the building, a system can involve strike termination devices, down conductors, bonding of conductive components and suitable grounding arrangements.
Because this property had already experienced a substantial strike involving a steel roof and chimney area, adding a properly designed lightning protection system was raised as something worth considering.
Lightning protection design and electrical grounding are outside the scope of masonry work and should be assessed by an appropriately qualified lightning protection contractor or electrician.
Canadian lightning safety guidance notes that lightning current can follow metal pipes and wires through a building. Canadian lightning-protection design is addressed by CSA B72, while NFPA 780 also provides recognized technical guidance on bonding and side-flash prevention.
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Technical context: CSA B72, Installation code for lightning protection systems, and NFPA 780, Standard for the Installation of Lightning Protection Systems.
The liner remained clear and serviceable based on the accessible visual inspection.
This is the practical lesson from the case. A lightning strike near a chimney is a reason to inspect the system, not a reason to automatically condemn it.
In this instance, the building showed clear evidence of a substantial electrical event, including damage around the chimney, a displaced cleanout, localized floor damage and damaged electrical equipment. Yet the metal liner itself did not show visible damage requiring repair or replacement.
If lightning strikes your chimney, have the chimney checked before assuming either that it is ruined or that it is fine.
Yes. A metal liner is conductive and may become part of the current path during a lightning event. Possible damage can include perforation, pitting, separation, distortion or damage to connected components. However, a strike does not automatically mean the liner needs replacement.
If the chimney, roof or area around the chimney was involved in the strike, an inspection is advisable before continued use, particularly where the chimney contains a metal liner or serves a heating appliance.
It is possible. Lightning can arc between conductive components rather than requiring one continuous metal connection. Establishing the exact route after a strike is often difficult, so conclusions should be based on the pattern of physical damage and the condition of the components that can be inspected.
The more useful question is how a building manages lightning if it is struck. A metal roof is conductive, but by itself it is not a complete lightning protection system. A designed system provides a deliberate path to ground using appropriate strike termination, conductors, bonding and grounding.
Send clear exterior photos, any visible damage, and information about the appliance or chimney system involved. The first step is determining what actually needs to be inspected or repaired.
Prepared by Dean MacArthur, DinoMac Masonry Ltd., a third-generation mason with more than 20 years of hands-on masonry experience.
The inspection observations and photographs on this page come from the actual chimney assessment. Discussion of lightning behaviour is presented as general educational information and does not replace an electrical or lightning-protection assessment.
Reviewed September 1, 2026.
The case studies document real masonry conditions, repair decisions and field observations rather than generic before-and-after galleries.
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