A short while ago I was contacted by a homeowner who had installed a wood stove in his work shop. He had a used wood stove which was in fine shape in spite of being an uncertified appliance. If you recall my previous blog post on WETT Inspections (of course you read it, right? RIGHT?) you’ll remember that to call something an uncertified appliance doesn’t mean it’s unacceptable. It simply means that it does not have a certification sticker and must be installed to the standards of CSA B365. Overall their installation was pretty good but did need some adjustment to meet the clearance requirements.
During the inspection they mentioned that they had a very difficult time finding information about how to install the wood stove. Since it was a second-hand stove, it did not have a manual. The Ontario building code does not describe the proper way to install a wood stove since it’s a standalone appliance with a separate installation standard.
I always encourage people to contact me before they install their wood stove to ensure that it meets compliance upon inspection. I can review the location and advise on the installation from the start rather than having to advise on changes after the fact. I mentioned that and said that he had hoped to find even a basic overview of wood stove installation.
So what follows in this article is a very general description of an overview of a wood stove installation.
HUGE DISCLAIMER: This post does should not be construed as a definite guideline for installation. Installation requirements are not exhaustively detailed. The lack of description of a requirement does not indicate a lack of that requirement. As this is merely an overview, many details and requirements are omitted. Every installation is unique with different structure, layout, and components to take into consideration. As mentioned above, it’s best to contact me or another WETT Certified professional prior to installation in order to ensure proper installation. I assume no liability for any actions taken based on what is written in this article.
Installation of a wood stove
For the purposes of this post, we are going to discuss a free-standing uncertified wood stove. There are various types of appliances (wood-burning inserts, hearth-mounted stoves, indoor or outdoor wood-burning furnaces/boilers, etc.), but we are going to keep it simple here.
There are three main components: wood stove, flue pipe, and chimney.
If a wood stove has a sticker on the body, it is considered certified. This is the source of installation information. The manual will also have this information. For this hypothetical installation, it is an uncertified appliance which must be installed as per CSA B365. This standard requires that there be a clearance between the stove and the adjacent walls of no less than 48 inches to combustible walls if proper shielding is not provided. A certified appliance will have a clearance of much less than this listed on the sticker.
Note: a non-combustible wall must be made of non-combustible materials throughout the wall assembly. E.g.: a concrete wall with tile or brick surround. A wood-frame wall with a brick surround is still considered a combustible wall.
A properly installed shielding can reduce the clearance to combustible walls. The side clearances can be reduced by 67% with a shield constructed of 28 gauge sheet metal or by 50% with a shield constructed of brick/tile.
The shielding must be installed with noncombustible supports which provide an airspace of at least 7/8” between the sheilding material and the wall. There must be clear air space of 1-3” at the bottom and at least 3” at the top of the shield. Air must be allowed to to travel vertically so if furring strips are used, they must be installed vertically.
The purpose of the shielding is to prevent radiated heat from heating the combustible walls. The shield will reflect some and absorb some. As it heats up, an air draft will occur behind it. Cool air will enter in the space below, rise up between the shield and the wall and exit out the top, which keeps the combustible wall from overheating.
Combustible floors must be protected from heat and embers. A floor that is constructed of concrete which does not sit on combustible structure does not require additional protection.
Ember protection - The ember pad must extend at least 18” horizontally from any side equipped with a door and 8” on all other sides. This material can be 28 gauge sheet metal or a grouted tile.
Radiant heat protection - For uncertified appliances, with a clearance of less than 7” between the bottom of the stove and the combustible floor surface, it be a bit complicated to satisfy the installation requirements. Contact Cherry Home Inspections to discuss.
There must be a clearance of at least 60” from the top of the stove to the ceiling.
Flue pipes direct the smoke and combustion gases from the fireplace to the chimney. Flue pipes may not pass through any wall or ceiling space. At the point that the flue meets a wall or ceiling, it must connect to a thimble which in turn connects to a chimney.
Flue pipes can be single-walled or doubled-walled. In general, single-walled are uncertified and double-walled flue pipe may be certified. As with wood stoves, a certified flue pipe will have a sticker that indicates installation requirements. For this discussion we will talk about uncertified single-wall flue pipe.
There are many details in the installation requirements. They key ones are as follows:
Clearance to walls and ceilings must be at least 18” (can be reduced by 50% with appropriate sheet metal shield)
Flue pipe must me made of mild steel with a thickness appropriate to the diameter of the pipe. Galvanized steel is not permitted.
Horizontal runs must be supported at intervals no more than 36”.
Pipe run is not to exceed 10 feet in length, including elbows.
Elbows used must not exceed a total 180 degrees.
Horizontal areas must slope to allow condensed liquids to drain back to the stove
Joints are to be connected with three screws
Joints must have the male end oriented in the direction of the stove.
Pipe seams should not be on the bottom side of the pipe installation.
I will not go into too much detail about chimneys in this article. There are many things to consider when installing a chimney such as the 3-2-10 rule and keeping the chimney to the interior of the house as much as possible so it drafts better, but these are details that a DIYer is not likely to deal with when simply replacing a wood stove on an existing chimney.
Chimneys are either constructed with factory-built stainless steel units or are site-built masonry structures. If you are using a factory-built chimney, it must be installed as per manufacturer instructions. Ensure that it is compatible with the flue pipe and wood stove it will be connected to. When connecting to a site-built fireplace it is important to make sure that the connection of the flue pipe to the thimble is properly done. Prior to connecting anything ensure that the condition of the chimney is sound. It’s a good idea to have a WETT inspector or a chimney sweep inspect it to make sure it doesn’t need repair or upgrading, such as a new flue liner.
Wood stoves seem like simple devices, but there is a level of complexity to their installation and operation. It’s important that it be installed properly to avoid the variety of issues that could occur. These could result in anything ranging from a poorly drafting wood-burning system to a house fire. If in doubt, consult with a WETT Certified inspector during the planning stage, or just hire a WETT Certified installer to put the device in. It will cost you a bit of money, but what it may save could be priceless.
Once you have your wood stove properly installed, you’ll certainly be eager to fire it up. Make sure to burn clean, dry hardwood and ensure a proper burning cycle to ensure secondary combustion takes place. If you you aren’t sure what that is, make sure to find out before starting your next fire. It will help you get more heat from less wood and it will keep your chimney much cleaner. Perhaps it will be the subject of a future blog post.