Lightning strike on a house: damage and what to check

How you know it hit

A direct strike is hard to miss: a deafening bang at the same instant as the flash, sometimes with the house shaking, the power going out, or a smell of burning or ozone. Afterwards you may find:

• Scorch marks or a hole in the roof, chimney or siding
• Shingles, bricks or pieces of chimney on the ground
• A split tree nearby
• Tripped breakers, dead outlets or burned cover plates
• Electronics that no longer work

A strike does not have to hit the house. Lightning that hits a tree, the ground or a utility line nearby sends a surge through wiring, phone and cable lines and metal pipes.

The first hour

1. If you see flames or smoke, or smell burning, get out and call 911.
2. Call the fire department even without visible fire if you believe the house took a direct strike. Lightning can ignite framing or insulation inside a wall or attic, where it smoulders and breaks out hours later. Firefighters can check with a thermal camera.
3. Check on everyone. Anyone who was shocked or struck needs medical attention.
4. Stay away from downed wires and report them to your electricity distributor.
5. Do not touch scorched outlets, switches or the panel.
6. Walk through the house, including the attic if it is safe, and look and sniff for smoke. Repeat over the next several hours.

What lightning damages

Fire

Lightning carries enormous current and heat. It can set fire to roof framing, attic insulation, wall cavities and anything along the path it takes through the building, including gas piping.

The building

• Holes blown in roofing and sheathing
• Chimneys cracked or knocked apart, because moisture in the masonry flashes to steam
• Split rafters and studs
• Shattered plaster, drywall and concrete
• Broken windows from the shock wave

Electrical system

• Melted or vaporised wiring inside walls
• A damaged service panel, breakers and meter base
• Burned outlets, switches and light fittings
• Damage that leaves a circuit working today and failing later, when weakened insulation breaks down

Appliances and electronics

• Televisions, computers, routers, modems and phones
• Furnace and air conditioner control boards
• Appliance electronics: fridge, stove, washer, dryer, dishwasher
• Sump pumps, well pumps and garage door openers
• Security systems, smoke alarms and thermostats
• Electric vehicle chargers and solar equipment

Plumbing and gas

• Pinholes in copper water lines, which show up as leaks days later
• Damage to corrugated stainless steel gas tubing. If you smell gas, leave and call your gas utility’s emergency line from outside.
• A damaged well pump or pressure switch

What to have inspected

• The electrical system, by a Licensed Electrical Contractor. This is the most important check. Hidden wiring damage is a fire risk. Repairs are filed with the Electrical Safety Authority.
• The roof and chimney, by a roofer and, for a chimney serving a fuel-burning appliance, a qualified chimney professional.
• Heating, cooling and gas appliances, by a licensed technician.
• Plumbing, for new leaks, over the following days.
• The structure, by an engineer, if framing or masonry is visibly damaged.

Until the electrical inspection, limit use of the affected circuits and keep working smoke alarms on every level. Replace any alarm that may have been damaged by the surge.

Temporary protection

• Tarp any hole in the roof to keep rain out
• Board broken windows
• Keep people away from loose masonry
• If water came in, start drying within a day or two

Insurance

Lightning is a standard named peril in Canadian home insurance, so damage from a strike and from any fire it causes is generally covered. Points to know:

• Surge damage. Damage to electronics and appliances from a lightning-related surge is commonly covered, though some policies distinguish between lightning and other power surges, such as those from the utility grid. Read the wording or ask your broker.
• Proof. Insurers may ask for a technician’s report stating that the damage is consistent with lightning or a surge. Keep the damaged items until the adjuster says otherwise.
• Trees. Removal of a tree is generally covered only where it has damaged an insured structure.
• Food spoilage after a power cut may have its own limit.
• Deductible. Small electronics losses may fall below it.

List every item that stopped working, with make, model and age, and photograph the damage.

Protecting a house

Surge protection

• A whole-home surge protective device at the electrical panel, installed by a licensed electrical contractor, reduces surges arriving on the power lines
• Point-of-use surge protectors for electronics add a second layer
• Neither will stop a direct strike, but they prevent a great deal of damage from nearby ones
• Unplugging valuable electronics before a storm is the surest protection

Lightning protection systems

A system of air terminals, conductors and ground rods gives a strike a controlled path to earth. It is most worth considering for houses on high or exposed ground, with tall trees close by, or with a history of strikes. Installation should follow the recognised Canadian standard and be done by a specialist.

During a thunderstorm

• Stay indoors, away from windows
• Avoid corded phones, plumbing and anything plugged into the wall
• Do not shower or bathe
• Wait 30 minutes after the last thunder before going back out

More: storm damage restoration.