Getting a chimney ready before hurricane season

Why spring is the time

NOAA's National Hurricane Center puts the Atlantic hurricane season at June 1 through November 30. To prepare a chimney for a hurricane, the checks below take a dry day on the roof, and materials such as a replacement cap or chase cover may need to be made or ordered, so the useful window is the spring before the season opens. Work that waits until a storm is forecast competes with every other house on the list.

The checklist is the same wherever in Florida you live, even though design wind speeds differ across the state. Wind and driven rain find the same weak points on a chimney whether it stands near the coast or well inland: whatever is loose at the top, whatever is cracked, and wherever metal meets masonry. Treat what follows as a hurricane season chimney checklist, in the order the wind finds weak points.

Cap and chase cover fasteners

A chimney cap is held to the flue tile or the crown by screws, clamps or a flange, and a chase cover is screwed down along the sides of a framed chimney. Those fasteners are small, they sit in the weather, and they corrode. A cap or cover that has worked loose is what wind lifts first, and a missing one leaves the flue or the whole chase open to rain.

Check that the cap does not rock when pushed, that its screen is intact, and that the fasteners are not rusted through. On a chase cover, look for lifted edges, missing screws, sealant that has cracked away and a storm collar that has slipped down the pipe. Loose parts are reset with new fasteners of a compatible metal, and a rusted-through cover is replaced before the season.

While you are looking at the top, check anything else attached to the chimney. A dish or antenna strapped to the stack adds wind load at the top of the stack, and its straps can cut into the brick. Check the mount, or move the equipment.

Cracks in the crown

A masonry chimney is normally topped by a crown, a slab of concrete or mortar poured or troweled around the flue. Section R1003.9.1 of Florida's residential code calls for a drip edge on it and a flexible, caulked joint where it meets the flue liner. Wind-driven rain pushes water into any crack in it, and from there into the brick and down the outside of the flue.

A sound crown with only hairline cracks can take a sealant designed for crowns. Cracks that run through the slab, broken edges, or a thin mortar wash without an overhang are better recast before the season than patched after a storm has driven water through them.

Flashing edges

Flashing seals the chimney to the roof, with step flashing woven into the roofing and counterflashing cut into the masonry above it. Driven rain gets under any edge that has lifted, any counterflashing that has pulled out of its joint, and any sealant that has cracked. From the ground, look for metal that stands away from the brick or shows gaps at the corners.

The flashing is chimney work. Damage to the shingles or tiles around it is roofing work, and both should be checked together, since a chimney with good flashing on a torn roof still leaks.

Loose masonry near the top

The courses above the roof take the most wind and the most water. Worn joints there loosen bricks, and a loose brick at the top of a chimney can come off in high wind and land on the roof, a car or a walkway. Crumbling joints, bricks that have shifted out of line and new cracks near the top all belong on the spring list.

Repointing or relaying the top courses is ordinary masonry work in calm weather and a hazard once a storm is coming. If the top of the chimney has visibly moved, keep people clear of the area below it pending an inspection.

Framed chimneys and chase tops

Behind a factory-built fireplace, the chimney is a metal pipe inside a framed chase, and the weak points there are different. The chase cover is the whole roof of the chase, the storm collar seals the gap where the pipe passes through it, and the termination cap on top belongs to the listed chimney system. Siding joints and trim on the chase are where driven rain gets in at the sides.

Before the season, check that the cover is fastened and sheds water, that the storm collar sits tight against the pipe, and that the termination cap is secure. Those top parts must be listed for that particular chimney under the code, so a replacement can take time to order.

Trees over the roof

A limb that hangs over the chimney can break a cap, crack a crown or knock loose bricks when it comes down. Tree work is for an arborist, not a chimney crew, but noting which limbs overhang the stack helps the arborist decide what to take first.

When a storm is on the way

Once a storm is forecast, the job is to close up and stay off the roof. A few steps help the chimney ride it out.

• Close the fireplace damper, and a top-sealing damper if you have one, so driven rain has a harder path into the firebox.
• Move rugs and furniture back from the hearth in case water comes down the flue.
• Do not climb onto the roof to secure anything once the wind has picked up.
• Plan to keep the fireplace cold after the storm until someone has looked the chimney over.

After it passes

Look from the ground first, with binoculars if you have them, and keep clear of the base of the chimney if anything at the top has moved. Among the events NFPA 211 treats as reasons for a more thorough chimney inspection is weather that may have caused damage. A missing cap, a lifted chase cover, pieces of crown on the roof or water in the firebox are all reasons to call before the next fire. Our storm damage chimney repair page covers what that check and repair involve.