The short answer
A chimney sweep and a WETT inspection are separate services. Cleaning may be advisable before an inspection when deposits could hide surfaces or create a fire concern, but the right order depends on the system's condition and the requested inspection scope. Ask before booking.
If you are preparing for a real estate transaction or insurance request, document when the system was last swept or inspected and whether there have been smoke, draft, odour, or chimney-fire concerns.
The "Failure to Inspect" Trap: Auditor vs. Cleaner
A chimney sweep removes deposits; a WETT inspection documents the system within an agreed visual, technical, or invasive scope. One service does not automatically include the other.
When deposits cover a surface that matters to the requested scope, the report may record a limitation or the provider may recommend cleaning before completing further assessment. Ask about this before scheduling two separate visits.
The 3mm Rule: The Inspector’s Ethical Mandate
Ontario Fire Code Article 2.6.1.4 requires chimneys, flues, and flue pipes to be cleaned as often as necessary to keep them free from dangerous accumulations of combustible deposits and calls for removal when the accumulation exceeds 3 mm. This is maintenance guidance, not an automatic inspection result. Deposit type, location, system condition, accessibility, and the requested inspection scope still matter. Accumulation can also prevent parts of the venting system from being adequately observed.
Organize the likely sequence
Answer the maintenance-history questions and get a preliminary next-step suggestion before requesting provider contact.
What Soot is Hiding: The Danger of the Unseen
The primary reason you need a chimney sweep first is that soot and creosote are masters of disguise. A heavy layer of soot can easily hide severe structural defects, including:
- Cracked Flue Tiles: In masonry chimneys, clay liners develop splits due to thermal shock.
- Perforated Stainless Steel Liners: Acidic creosote can eat tiny holes through metal liners, allowing carbon monoxide to leak into your home.
- Damaged Baffles and Firebricks: Soot piles up on internal components, hiding cracks or warping that indicate the appliance is failing.
By hiring a sweep first, you clear the "diagnostic canvas," allowing the inspector to verify the actual structural integrity of the venting system.
Strategic sequencing: questions that can prevent repeat visits
Providers may charge for a scheduled visit even if the requested scope cannot be completed. Before booking, describe the maintenance history and ask whether cleaning, inspection, or a combined appointment is appropriate.
A common sequence when cleaning is needed is:
- Step 1 (The Sweep): Hire a professional to clean the venting, chimney system, and firebox.
- Step 2 (The Inspection): Once the system is clean, the inspector can perform a Level 1 or Level 2 SITE® inspection with a clear view of all components.
Use the free triage tool to organize your maintenance history and likely next step. It cannot determine whether deposits require cleaning or which inspection level is appropriate; a qualified provider must assess that.
Sweep first, inspection first, or ask?
| History or symptom | Useful next question |
|---|---|
| Recent sweep with records and no known concern | Can the requested inspection proceed using the current maintenance record? |
| More than three years or history unknown | Should a sweep be scheduled before or with the inspection? |
| Smoke spillage, strong odour, draft problem, or suspected chimney fire | Should use stop and a technical/specialist assessment be arranged? |
| Insurance or closing deadline | Which report level is accepted, and can cleaning/report delivery meet the deadline? |
Sources and limitations
Last reviewed: July 23, 2026. This page does not diagnose deposits, approve a system, or prescribe an inspection level.