Creosote buildup stages 1–3
Typical published planning values — NOT a certified spec or professional advice. The 1/10–1/12 flue rule, the 3-2-10 height rule, creosote stages, NFPA 211 inspection levels, clearances and cost bands vary by chimney and appliance; confirm your exact dimensions and follow the manufacturer’s instructions and local code. Creosote, chimney fire, carbon monoxide, structural and code judgment are a CSIA-certified sweep / licensed mason / NFPA 211 / local-code matter — have a certified professional inspect; never a step-by-step procedure or medical advice here.
Creosote is unburned wood smoke condensed on the flue. It builds in three stages, and Stage 3 glaze is the dangerous one that fuels chimney fires. These are LABELED planning typicals; the stage and the response are a CSIA-certified sweep’s call, never a DIY procedure or medical advice here. Use them with the creosote-removal cost tool and the creosote-stages reference.
| Stage | What it looks like | Cleaning effort |
|---|---|---|
| Stage 1 — loose soot | Loose, sooty, powdery — brushes off easily. | ×1.00 |
| Stage 2 — flaky | Hard, flaky black buildup — needs a rotary brush. | ×1.50 |
| Stage 3 — glazed | Shiny, tar-like glaze — the highest chimney-fire risk; special tools or chemical treatment. | ×2.00 |
LABELED planning typicals — the stage and the response are a CSIA-certified sweep’s judgment, not a DIY procedure or medical advice. Stage 3 glaze is the highest chimney-fire risk. Snapshot: 2026-07-14.
Sources
These are LABELED planning conventions that follow published primary sources; confirm the current text with each body and with your local code.
- Chimney Safety Institute of America — creosote formation, the buildup stages and chimney-fire risk.
- NFPA — NFPA 211, on cleaning and the condition that requires it.