· 6 min read · by the Remarkable team
7 warning signs your chimney needs attention
Chimneys rarely fail loudly. They hint — a smell here, a stain there — and the hints are easy to explain away. Here are the seven we hear about most on the phone, ranked roughly from "book a sweep soon" to "stop burning tonight."
1. A campfire smell — especially in summer
That cozy odor on a foggy July day is creosote absorbing moisture and drafting down into the room. It means there's enough buildup to smell, which is enough to sweep. Common all over SF; a cleaning plus a top-sealing damper usually ends it for good.
2. Oily black flakes in the firebox
Shiny, tar-like flakes that look like burnt cornflakes are pieces of glazed creosote shedding off the flue walls. Glaze is the most flammable stage of buildup and won't come off with a light brushing — it needs professional attention promptly.
3. Smoke that hesitates or backs up
A healthy flue pulls smoke up within seconds of lighting. Smoke that curls into the room points to a narrowed or blocked flue, a closed or seized damper, or a draft problem. Along with the nuisance, whatever's blocking smoke is blocking carbon monoxide. Stop burning until it's checked.
4. White stains on exterior brick
The chalky bloom is efflorescence — minerals carried to the surface by water moving through masonry. The stain is cosmetic; the water is not. Left alone it becomes spalling brick and interior leaks. This is a masonry repair conversation, not a cleaning one.
5. Bits of brick, mortar, or tile in the firebox
Debris raining down the flue means something above is coming apart — crumbling mortar joints, a cracked crown, or (most seriously) broken flue tiles. Curved shards of orange clay are flue tile. Don't burn until a Level 2 camera inspection finds the source.
6. Scratching, chirping, or cooing
Birds and raccoons love an uncapped SF flue. Beyond the noise, nests block airflow and are extremely flammable. We remove wildlife humanely, clear the nest, and cap the chimney so it doesn't happen again.
7. A roaring or rumbling you didn't light
A low freight-train rumble from the chimney during a fire is the signature of a chimney fire — creosote igniting in the flue. Get everyone out and call 911 first. Afterward, the flue must be inspected before it's ever used again; fires crack liners in ways that only a camera can see.
Many chimney fires are quieter — a homeowner never notices, and we find the puffy, honeycombed evidence during a routine sweep. That's the strongest argument for the annual look.
Seeing one of these?
Signs 1–2 mean book a sweep soon. Signs 3–7 mean stop burning and have it looked at. Either way, call (650) 722-5502 — describing what you see costs nothing, any hour of the day.