Whether your insurer asked for it or you are buying a house with a wood stove, a WETT inspection follows a defined checklist drawn from the Ontario Building Code, the CSA B365 installation code, and the manufacturer’s listing. This guide sets out what a WETT-certified inspector looks at, in the order we look at it, and the items that most often come back as deficiencies.
Written by John Hansen, Registered Home Inspector, Past President of the Ontario Association of Home Inspectors, WETT certified, BCIN qualified for septic systems. Inspecting since 2011.
At a glance
- Confirm the scope: the appliance type and the level of inspection your insurer, lender, or purchase requires.
- Identify the appliance and find its certification label and listed clearances.
- Measure clearances from the appliance and connector to every combustible surface, with and without shields.
- Check the floor protection in front of, beside, and under the appliance.
- Inspect the connector pipe: material, gauge, joints, length, slope, and support.
- Inspect the chimney from the appliance to the cap: type, liner, condition, height, and termination.
- Check combustion air, dampers, and the signs of overfiring or improper use.
- Confirm smoke and carbon monoxide alarms where the Ontario Fire Code requires them.
- Issue the written report listing each item as compliant or deficient, with photographs.
The three levels of WETT inspection
WETT defines three inspection levels. A Level 1 inspection is a visual check of the readily accessible parts of the system, and it is what most insurers and real estate transactions ask for. A Level 2 inspection adds access to areas that need tools or ladders, such as the attic pass-through and the roof, and is used when a Level 1 raises questions or when a property changes hands with a system that has had work done. A Level 3 inspection is invasive, opening walls or ceilings, and is rare outside fire investigations. Our standard pre-purchase and insurance inspection is a Level 1 with Level 2 access wherever it can be done safely on the day.
Identifying the appliance
Everything else depends on this step. A certified appliance carries a label from a testing agency such as ULC, CSA, Warnock Hersey, or Intertek that gives the model, the tested clearances to combustibles, the floor protection required, and the chimney type it was tested with. We photograph the label and use its numbers. An uncertified appliance, which includes many older stoves, homemade stoves, and barrel stoves, has no label and is assessed against the much larger default clearances in CSA B365, which most installations do not meet without shielding. The report will say which path applied.
Appliance checklist
- Certification label present and legible, or appliance documented as uncertified.
- Firebox: cracks, warped plates, burned-through baffles, deteriorated firebrick.
- Door, hinges, latch, gasket, and glass seal.
- Catalytic combustor or secondary air tubes present and intact where the design has them.
- Signs of overfiring: discoloured steel, warped top, cracked castings.
- Modifications to the appliance that are not part of its listing.
Clearances to combustibles
This is where the most deficiencies are found. We measure from the appliance body and from the connector pipe to walls, ceilings, mantels, trim, cabinets, and furniture that could be left in place, and compare each with the listed clearance or the code default. Clearances can be reduced with a properly built heat shield, which is a non-combustible panel spaced off the wall on non-combustible spacers with an air gap open at the top and bottom. A sheet of tile glued flat to drywall is not a shield and does not reduce anything, which is one of the most common misunderstandings we see.
Floor protection
The hearth or floor pad must be non-combustible and must extend the listed distance in front of the loading door and to each side, with a minimum thickness or an insulating value set by the listing or the code. We measure the pad, check what it is made of and what is under it, and look for combustible flooring that has crept under the edge of the stove during a renovation.
The connector pipe
Connector (stove pipe) checklist
- Single-wall black pipe of adequate gauge, or a listed double-wall connector. Galvanized pipe and dryer-vent style flex are not permitted.
- Clearance from single-wall pipe to combustibles, which is larger than most people expect, or the reduced clearance that a listed double-wall connector allows.
- Joints overlapped the right way, with the male end toward the stove so creosote drips back into the firebox, and secured with three screws per joint.
- Total length and number of elbows within the limits; long horizontal runs and more than two elbows hurt draft and collect creosote.
- Slope rising toward the chimney and the pipe supported so it cannot sag or separate.
- The pipe does not pass through a wall, ceiling, or closet. Where it must pass through a wall to reach a chimney, a listed thimble or an approved pass-through is used.
- Proper connection into the chimney: a flue collar or listed adapter, not a pipe pushed into a hole in the masonry.
The chimney
A wood-burning appliance needs a chimney rated for it: a factory-built chimney listed to ULC S629 for solid fuel, or a masonry chimney with an intact flue liner. We confirm the type, check the liner for cracks, gaps, and missing mortar, and look at the exterior for spalling brick, a deteriorated crown, and water damage. A fireplace insert needs a continuous stainless liner from the insert to the top of the chimney; a slammer installation, where the insert simply sits in the firebox and vents into the open fireplace flue, is a deficiency that insurers will not accept.
Height and termination are checked against the familiar rule: the chimney must extend at least 900 mm above the highest point where it passes through the roof and at least 600 mm above any part of the roof or structure within 3 m of it. A rain cap and, on a factory-built chimney, the listed cap for that system are required. We also check the clearance of a factory-built chimney where it passes through floors, ceilings, and the attic, including the radiation shield and the attic insulation shield, because insulation piled against a chimney is a fire waiting for a cold night.
Combustion air, alarms, and use
Modern airtight houses can starve a stove of air and pull exhaust back into the room, so we look at combustion air provisions and ask about smoke spillage. We check that dampers operate and that a fireplace has a working screen or doors. Finally, the Ontario Fire Code requires carbon monoxide alarms near sleeping areas in any home with a fuel-burning appliance and smoke alarms on every storey; we confirm they are present and note where they are not.
The most common deficiencies
- Clearance to combustibles short at the back or side of the appliance, usually by a wall that was finished after the stove went in.
- Single-wall connector too close to a ceiling or passing through a wall without a thimble.
- Floor protection too small in front of the door or made of a combustible material with tile on top.
- Uncertified appliance installed at certified clearances.
- Insert without a full liner, or a liner that stops short of the top.
- Chimney too short for the roof, missing cap, or a deteriorated masonry crown.
- Factory-built chimney with insulation in contact in the attic or missing the attic insulation shield.
- Creosote too heavy to inspect the liner, which means a sweep before the inspection can be completed.
How to prepare
Before the WETT inspection
- Let the appliance go cold and remove the ash so the firebox can be examined.
- Have the chimney swept if it has not been done this season. A heavily creosoted flue cannot be inspected and the report will say so.
- Find the owner’s manual or the model number, and any receipts or permits from the installation.
- Clear furniture and stored items away from the appliance and the connector so clearances can be measured.
- Provide safe access to the attic hatch and, where practical, the roof. If the roof cannot be reached safely, the exterior is assessed from the ground and from a ladder.
- Tell us about any changes: a new liner, a replaced stove, a wall that was finished, or a problem with smoke.
Book a WETT inspection
Certified inspections of wood-burning appliances to verify safety, compliance, and proper installation for homes and commercial properties.
FAQs
Does a WETT inspection include sweeping the chimney?
No. An inspection and a sweep are separate services. If the flue is too dirty to see the liner, the inspection cannot be completed until it has been swept, so a sweep ahead of the appointment saves a second visit.
Are pellet stoves and gas fireplaces covered?
Pellet appliances are solid-fuel appliances and are inspected under WETT. Gas fireplaces and gas inserts are not; they fall under the gas code and a licensed gas technician.
How long is a WETT inspection report valid?
There is no fixed expiry. Insurers usually want a report that reflects the current installation, so a recent report is accepted until something changes: a new appliance, a renovation around it, or a change of owner.
What happens if the installation fails?
The report lists each deficiency with what would bring it into compliance. Many are simple: a heat shield, a larger hearth pad, a section of double-wall connector, a chimney extension. Once the work is done we can re-inspect and issue an updated report for the insurer.