Checking the Chimney After a Storm

While the storm is still going

Nothing about a chimney is worth a trip onto a wet, windy roof. During the storm itself:

• Keep clear of the fall zone. If you hear masonry hit the roof or see the chimney move, keep people, pets and cars away from the area below it and on the side it leans toward.
• Leave a struck or damaged chimney alone. If a tree limb hits the chimney or you suspect lightning struck the house, do not light a fire or run the appliances on that chimney until it has been checked.
• Catch the water. If water is coming into the firebox or through a ceiling, put down buckets and towels, and keep water away from light fixtures and outlets.
• Run generators outside only. The Consumer Product Safety Commission says never to run a portable generator inside a home or garage, even with doors and windows open, and to keep it at least 20 feet from the house with the exhaust pointed away.

If you are relying on a fireplace or stove for heat during an outage, use it only if it was in good working order before the storm and nothing about it has changed since. A carbon monoxide alarm, or headache, dizziness or nausea in anyone in the house, means everyone goes outside and someone calls 911.

The first look, from the ground

Once the weather clears, walk all the way around the house with binoculars or a phone camera on zoom. Photograph each face of the chimney from the same spots you would use for a before-and-after comparison.

1. The topIs the cap still there, sitting straight and fully seated? Is the crown intact, or are there missing chunks? On a factory-built chimney, is the chase cover flat and the storm collar in place?
2. The stackCompare the chimney with the roofline and with older photos. Look for a lean, new cracks, missing bricks, or a chimney that has started to pull away from the siding.
3. The rooflineCheck whether flashing has lifted or peeled back, and whether shingles around the chimney are missing.
4. The ground and guttersPieces of brick, crown, flue tile or cap on the roof, in the gutters or on the ground tell you something came off the top.
5. Attachments and treesAntenna straps, satellite dishes, and limbs resting on or near the stack can all be pulled loose or pry at the masonry.

If you see a lean, a gap or loose masonry at the top, treat the area below as off limits and stop using the fireplace and connected appliances.

Inside the house, the same day

Some storm damage shows up only indoors. Check:

• The firebox and smoke shelf. With a flashlight and the fireplace cold, look for fresh debris: brick, tile fragments, mortar, leaves or pieces of the cap. Rusty water on the firebox floor means water came down the flue.
• The attic beside the chimney. Where there is safe footing, look for wet roof boards, water on the chimney masonry or daylight around it.
• Ceilings and walls near the chimney. Mark any new stain with a pencil and the date. See stains on walls and ceilings near the chimney.
• The base of each flue. At the cleanout door or where a furnace or water heater vent enters the chimney, look for water, sand or debris that was not there before.

What each kind of storm tends to hit

High wind

Wind works on everything attached to the top of a chimney: caps, the lids of top-sealing dampers, chase covers, and the edges of flashing. It also brings down limbs. A cap that has shifted but stayed on is easy to miss and may let go in the next storm. See chimney cap types compared.

Wind-driven rain

Storms that drive rain sideways push water into joints, crowns and flashing seams that shed ordinary rain without trouble, and leaks may show only on the face that took the wind. See wind-driven rain and chimney leaks.

Flooding

A flooded basement brings the heating appliances into the picture, along with the chimney or vent they use. CPSC warns that gas control valves on furnaces, water heaters and other gas appliances that have been under water must be replaced, and that other submerged parts, including venting systems, should be evaluated by a qualified technician before continued use. Silt and water can also collect at the base of a flue and around the cleanout.

Snow and ice

Heavy snow can bury a cap or a short chimney, and meltwater can back up behind the chimney when ice forms lower on the roof. See ice dams and chimneys.

Lightning and falling trees

Both can damage parts of a chimney that look fine from below, including the flue liner. This is one reason CSIA lists weather events, along with building fires, chimney fires and seismic events, among the situations that call for a Level 2 inspection with a video scan of the flue.

Before the next fire or heating cycle

Use this as a simple gate. Hold off on using the fireplace, stove or connected appliance until it has been checked if any of these apply:

• You found new debris in the firebox or at the base of a flue.
• The cap, crown or top courses are damaged or missing pieces.
• The chimney leans, has new cracks, or has pulled away from the house.
• A tree, limb or lightning struck the chimney or the roof near it.
• A furnace, boiler or water heater on that chimney sat in floodwater.
• Water came down the flue or into the house around the chimney.
• A carbon monoxide alarm sounded, or there is a new smoke or exhaust smell.

If none apply and everything looks as it did before, keep to the usual yearly schedule; the annual inspection that NFPA 211 calls for, as CSIA's FAQ explains, still covers what a storm might have done.

Damage that shows up later

Some storm effects take weeks or months to appear:

• Stains that appear after the storm has passed. Masonry soaked in a long storm can keep releasing water as it dries.
• Flaking brick the following winter. Masonry that went into a hard freeze while still wet is more prone to spalling; see why chimney brick flakes.
• White salt deposits weeks later. Water moving out through the brick leaves salts behind; see white staining on brick.
• A cap or flashing piece that finally lets go. Parts loosened in one storm often fail in the next.

Take a second set of photos from the same spots after the next hard freeze and compare them with the first set.

Keeping a record

Date-stamped photos from the first look, the indoor checks and the follow-up give you a clear before-and-after. Add the date and type of storm, what you heard or saw, and any temporary measures, such as a tarp, with receipts. If you think an insurance claim may be involved, our guide to chimney damage and homeowner's insurance covers what to gather and what to ask your insurer. We describe what we find; we do not determine coverage.

What a post-storm assessment covers

CSIA's Level 2 procedure for masonry chimneys includes a video scan of the flue, a look at the crown, flashing and any cricket, a check of the rain cap for obstruction, an attic inspection for water damage and clearances, and attention to signs of water entry and structural irregularities on the exterior.

When we check a chimney after a storm, the visit starts with an assessment. We inspect from the roof when it is safe and accessible, run a camera up the flue when it allows, check the attic side where we can reach it, and use controlled water testing if a leak source is unclear. Our photos and notes come to you first, and repairs are scheduled only after that. See chimney inspection and, if a cap is damaged or gone, chimney caps.

Questions homeowners ask

Sources

1. CSIA: The three levels of chimney inspections
2. CSIA: Level 2 inspection procedure for masonry chimneys (PDF)
3. CSIA: Frequently Asked Questions
4. U.S. Consumer Product Safety Commission: Warning to flood victims, replace gas control valves and other components that have been under water
5. U.S. Consumer Product Safety Commission: Carbon Monoxide Information Center

This guide is general information. It can't diagnose a specific chimney; an inspection can.