Installation Guide for Home Owners
Check your Installation before calling for a WETT Inspection
Is Your Appliance Certified?
The first item you want to know is if your stove is certified by an accredited laboratory. The most common labs are CSA, Underwriters Laboratory (ULC), Warnock Hersey, and OMNI testing Laboratories. They will have a sticker on the appliance (usually on the back) that specifies the required clearances around the stove. This is important because if there is no sticker then your unit is uncertified.
If you have an insert that was installed by a previous home owner, you probably can’t see the sticker without removing the insert from the fireplace – a bit more work than most homeowners are willing to tackle. If the manual is available, the installation specifications will be included. If the manual is not available you can always use Google to find a picture of your unit and then from there find the manual.
There are two aspects to floor protection: thermal protection – protecting the floor from radiant heat from the bottom of the stove – and ember protection.
For ember protection, you need to have continuous, non-combustible flooring under your appliance, extending 8” beyond it at the rear and sides and extending 18” in front of the wood loading door. When I say “continuous” it means there can be no cracks where embers could get down to combustible material. So, patio stones won’t work unless you grout between them.
If you have a certified appliance, you don’t need to worry about thermal protection. The legs are designed to be long enough to keep the firebox far enough from the floor that the floor won’t get too hot. If you have an uncertified appliance, you will need to have additional thermal protection under the stove. This gets complicated (different requirements for different leg lengths). My WETT Code book has all the different requirements if your stuck.
Clearances around the appliance seem pretty straightforward…until they get complicated. Look at the sticker on the appliance to tell you how much space you need between the appliance and any combustible construction.
Define combustible construction? Combustible means anything that is capable of catching fire and burning. This includes drywall. And a wood framed wall with brick in front of it is still combustible. So, unless you’ve got a solid masonry wall, you will have to comply with the required clearances.
The sticker likely won’t tell you what the clearance to the ceiling needs to be. You have to calculate this by measuring the height of the stove in inches and subtracting that from 82”. That is:
Top clearance = 82” – height of stove
If you have an uncertified stove, don’t rush off and measure its height. The clearance to the ceiling is required to be 60”.
If you have a wood burning furnace, the sticker will likely give you a clearance from the top of the plenum and the first six feet of duct.
The sticker will tell you the required clearance from the back, sides and corners of the appliance. The clearance from the front or wood loading door is always 48”. So, it’s simple, right? Just measure from the stove to the nearest combustible items (walls, ceilings, furniture). If you have less than the required distance, you have to move the stove, move the combustible item or install shielding to reduce the required clearance (see “Clearance Reduction” below).
The flue pipe is the pipe (usually black) that connects the appliance to the chimney. Measure the distance between the pipe and any combustible construction. Required clearance around the standard single wall flue pipe is 18”. Double wall flue pipes have a sticker stating the required clearance (usually 6”). The flue pipe needs to be fastened at each connection with at least 3 screws and its elbows may not exceed 180 degrees (i.e. no more than two 90 degree elbows). Also the flue pipe has to be inserted inside the low pipe so that any creosote will not leak outside pipe joint when heated.
The chimney must be appropriate for wood burning. This means it should be a masonry chimney or a listed 650 C chimney. Type A chimneys used to be approved for wood burning, but have been found to be unacceptable and should be replaced. If you have a factory built chimney that was installed before 1990, chances are it’s a Type A. If the appliance and chimney are original equipment and in good condition they are “Grandfather Protected”, but if you upgrade your appliance the chimney has to be upgraded also.
A masonry chimney requires 2” clearance to combustibles unless it’s an exterior chimney which only requires 1” clearance. The subfloor may also come as close as 1” from a masonry chimney. I rarely see masonry chimneys that comply with the required clearance. So, if you’ve got a wood stove venting up a masonry chimney, chances are you’ve got some work to do. You can remove the combustible material or you can put an insulated liner in the chimney. All (at least every one I’ve ever seen) factory built 650C chimneys require 2” clearance to combustibles. Follow the path of the chimney and make sure you’ve got 2” clearance the whole way.
I often see chimneys exposed as they pass through portions of the house. They meet clearance to combustible construction, but they are required to be enclosed so that combustible materials (e.g., boxes or clothes in a closet) don’t come in contact with the chimney.
A masonry chimney should be supported on a foundation (i.e. masonry extending to a footing). In older homes they are sometimes supported on a wood frame. This is not an acceptable arrangement.
Factory built chimneys are often installed using a makeshift support. I’m often impressed with the ingenuity of some people (as well as their thriftiness). However, anything other than an approved support supplied by the manufacturer is not acceptable.
The clearances around the appliance, flue pipe and, in theory, the chimney may be reduced by installing shielding as described in A Guide to Residential Wood Heating.
It is generally not recommended to have a wood burning appliance in a shop or garage where there may be gasoline or solvent fumes. However, it is permissible as long as the appliance is raised 18” off the floor. In addition, if it’s in a garage, it must be protected from impact. The regulations are vague here, but one or two steel posts well anchored to the floor will meet requirements.