The damper in my fireplace is stuck

Likely causes, most common first

Here is what jams a damper, from the everyday to the one that means the flue gets a camera before another fire.

1. Most common

   Rust and creosote have seized the plate on its pins

   The sign: The handle moves a little and binds, orange flakes drop when you jiggle it, and the plate looks scaled rather than smooth.

   The fix: The plate is lifted off its pins, the frame and pins are wire-brushed clean, and it is reset with a dry graphite lubricant that will not smoke. Damper Repair and Replacement, from $149

2. Common

   Debris is lying on the plate

   The sign: It closes most of the way and stops with a crunch, grit or leaves fall when you move it, and it began after a windy week.

   The fix: A sweep clears the shelf and the flue above the plate, and a cap keeps the next load of leaves and mortar crumbs out. Chimney Sweep, from $249

3. Common

   The handle, rod or rotary gear has broken or slipped

   The sign: The handle spins or flops with no resistance, a poker handle will not catch its notches, or the rotary knob turns with nothing happening.

   The fix: The handle, rod or worm gear is replaced or re-pinned to match the frame, a short job once the right part is in hand. Damper Repair and Replacement, from $149

4. Less common

   The plate warped in a chimney fire

   The sign: The plate rocks on its frame, light shows around its edge when closed, the surface is blistered or rainbow-colored, and the creosote above it is puffy.

   The fix: No fires until a Level 2 camera run has checked the flue; then a new plate or a top-sealing damper takes the warped one's place. Chimney Inspection, from $129

5. Less common

   The frame has rusted through or the plate never fit

   The sign: The plate closes freely but a steady cold draft comes down anyway, and the frame crumbles when touched.

   The fix: A top-sealing damper at the flue top, closed by a cable from the firebox, takes over from a frame that cannot be rebuilt. Damper Repair and Replacement, from $149

Two minutes of safe checks

Four things to look at from the hearth, with the fireplace cold and nothing more than a flashlight in your hand.

• Work out which damper you have: a poker handle that swings into a notch, a rotary knob on the fireplace face, or a chain in the firebox, which means a top-sealing damper with its own fix.
• Look at the plate itself: flat and gray with rust flakes is a cleaning, while bowed, blistered or rainbow-colored means heat it was not built for, and the flue needs a camera before another fire.
• Jiggle the handle gently instead of forcing it; if grit, leaves or mortar crumbs fall onto the hearth, debris is the jam.
• Confirm a carbon monoxide alarm is working on this floor, because a damper that will not open sends combustion gases into the room rather than up the chimney.

Nothing on this list needs a ladder, the roof or a lit fire. Leave those to the visit.

Why a damper stuck shut matters more than one stuck open

A damper stuck shut or half shut turns the first fire into a room full of smoke and carbon monoxide, which is why the fireplace stays cold until it is freed. A damper stuck open costs heat and nothing else.

Carbon monoxide has no smell, and the early signs, a headache, dizziness, an upset stomach, are easy to blame on something else. Oregon law counts a wood or gas fireplace as a carbon monoxide source, and an alarm on the same floor is the one thing that notices a half-open plate before you do.

Vented gas logs are the exception: they are installed with a clamp that holds the damper open, and the clamp stays. If a gas log set sits in the firebox, a damper that will not close is on purpose, and glass doors are the answer to the heat loss.

Rain, rust and the cold mornings that freeze a damper

Water is what seizes a damper in Portland. Rain down an uncapped flue lands on the plate and the smoke shelf, and a cast iron plate left wet between fires rusts to its frame in time.

Portland averages about 32 freezing nights a year, and on those nights water sitting on the plate and in the frame can lock a damper shut until the house warms it. Wait rather than pry; by afternoon it moves, and the lasting fix is a cap.

Creosote adds to it. A flue burned with wet wood leaves tar on the plate and the frame, and a damper that has not been moved all summer glues itself in place by the first cold evening.

What freeing or replacing the damper involves

The visit runs from the simplest fix to the most involved, and stops where the damper works.

1. Freeing a seized plate

   After a flashlight look at the plate, frame, pins and handle, the plate comes off its pins, rust and creosote are wire-brushed off the frame, and the plate is reset and run from fully open to fully closed. Dry graphite goes on the pins; oils smoke and bake on.

2. Replacing what has broken

   A broken handle, rod or worm gear is replaced to match the frame. A plate that has cracked or warped is replaced where a matching plate exists, and where it does not, a top-sealing damper at the flue top takes over, closed by a cable that hangs in the firebox.

3. After a chimney fire

   A warped or discolored plate is treated as a fire sign. If you ever hear a roar in the flue with a fire lit, get everyone out the door, then call 911, before touching the damper. Otherwise the Level 2 camera inspection comes first, the flue is repaired as the camera finds, and the damper is replaced last.

Related pages

Services, symptoms, fireplace types and guides that connect to this page.