Most people install wood stove chimneys through the roof. So, unless you’re dealing with obstructions and limitations that only permit wall installation, you should always go for roof chimney installations.
The best part is that installing a wood stove chimney through the roof is a straightforward process that you can easily do yourself (DIY). The only stumbling block is local codes. Heating ventilation that breaches existing codes can attract penalties and make it difficult to sell your home.
To this end, we’ve created a detailed guide to help DIY enthusiasts and professional HVAC technicians better understand what it takes to install a wood stove flue through the roof successfully.
The guide includes standard codes, pipe selection, installation requirements, the step-by-step installation process, and best practices. Let’s go.
Does a Wood Stove Need a Chimney?
Yes, wood stoves require chimneys. This requirement is captured in National Fire Protection Agency (NFPA) 211, which addresses chimneys, fireplaces, and venting systems for heat-producing appliances. The agency says that the proper installation of chimneys and other venting systems are critical as they help with the “removal of waste gases and reduction of fire hazards associated with the construction and installation of chimneys, fireplaces, and venting systems.”
What Kind of Chimney Do I Need for a Wood Stove?
Wood stoves typically use either masonry chimneys or prefabricated/manufactured chimneys, while others are freestanding stoves that don’t require a chimney.
The masonry chimney is the most common type of chimney. It is made from brick, concrete, or stone and serves as the traditional smokestack for conventional fireplaces.
Masonry chimneys are the heaviest part of the house and must be constructed on a concrete footing heavy enough to support the weight without settling.
Typical masonry chimney footings extend at least six feet beyond the edge of the chimney on all sides and are 8-15 inches thick, depending on the type of house.
Masonry chimneys stand out for longevity and durability. The chimneys can last more than 100 years with good maintenance. However, they are high-maintenance and are prone to freezing.
On the other hand, prefabricated chimneys, also known as factory-built chimneys, are metal chimneys typically made in a factory with stainless steel. The chimneys are double or triple-walled.
Double-walled pre-fan chimneys, the most common prefabricated models, introduce cool air into the chimney pipe outer wall just above the fireplace and expel warm exhaust fumes below the chimney cap at the top of the chimney outside the house.
Pre-fab chimneys stand out for cost-effectiveness. They are also easier to install and replace. Above all, it’s the only chimney type you can use for manufactured wood stoves. However, they aren’t as durable as masonry chimneys.
Can I Use My Furnace Chimney for a Wood Stove?
The short answer is no, as it’s too dangerous. However, technically, you can vent a wood stove and gas furnace through the same chimney or even slide your wood stove into the fireplace opening to vent through the furnace chimney. The most important thing is to keep the inherent differences and risks in mind.
For one, wood stoves produce more toxic exhaust fumes, which require a lined flue. You must never vent a wood stove through a chimney that lacks flue lining. Additionally, furnace chimneys are typically larger than woodstove flues because they handle more heat output. Unfortunately, a larger flue can result in faster exhaust cooling, causing reduced exhaust velocity, creosote formation, and condensation.
Therefore, if you must use the furnace chimney to vent your wood stove, then you should begin by modifying it. This guide from the University of Idaho explains how to modify your furnace chimney for woodstove venting.
How to Install a Wood Stove Chimney Through the Roof
Now, let’s discuss how to install a wood stove chimney through the roof. Remember that you can also vent your wood stove through the wall. However, roof venting is more natural as it takes advantage of the stack effect, thus eliminating the risk of backdraft and odors.
- A chimney pipe
- A ceiling support box
- A plumb bob
- An adjustable flushing
- A storm collar
- A chimney rain cap
How to Install Wood Stove Pipe Through the Ceiling: Step-by-Step
You need first to install the wood stove pipe to the ceiling before installing it through the roof. Proceed as follows;
- Locate the center point for the chimney pipe: The most important rule here is to leave at least 18 inches of clearance from combustibles when using a single-wall black stove pipe.
- Mark where to cut: After identifying the perfect location, use the ceiling support box to make where to cut. Trace the outside of the support box onto the ceiling using a pencil.
- Cut out the opening in the ceiling: We recommend a Sawzall for this process. Cut along the lines traced in step #2 above. Then remove the cut piece of ceiling.
- Slide the support box into place: Ceiling support boxes have two brackets to make this step a breeze. Slide the support box through the opening from the attic and mount the brackets to the ceiling joists.
How to Install the Wood Burning Stove Chimney Through the Roof
Now that we’ve penetrated the ceiling, the next step is to make the hole to send the chimney through the roof then cut the section.
- Mark the exit location on the roof from inside the house: Slide a single wall stove pipe section through the support box with a level attached to it for balance. Then extend this section to the roof to the point where the chimney will pass through. Mark this section with a pencil. Then drive a screw through the roof deck to easily identify the location from outside.
- Mark the roof from outside: Move onto the roof and center the adjustable roof flashing around the screw you drove into the marketed location. Then mark the area for cutting. The easiest way to mark the area is to spray paint on the roof inside the adjustable flashing.
- Cut the roof: Use the Sawzall to cut out the marked section of the shingle Accuracy is critical here. Then cut the nails on the top half of the circle. This is important because you need to slide the flashing underneath the shingles. Use tinsnips to cut the shingles two inches back on the top half of the circle.
- Slide the flashing into place: Apply sufficient high-temperature silicone to the back of the chimney pipe flashing, then slide the flashing under the top half of the roof shingles in the area you cut.
- Screw the flashing: Using a screwdriver, drive stainless steel screws through the flashing to fix it onto the roof. Then apply silicon over the screws to create a weatherproof surface.
How to Install the Class A Flue Pipe
You now have the setup ready for flue pipe installation. Get your Class A flue pipe and proceed as follows;
- Attach the pipe adapter to the pipe: Locate the male end of the Class A pipe. The male end is the side with insulation recessed down. You need to install a universal adapter to this end to safely transition from the Class A pipe to the black stove pipe.
- Lower the chimney pipe through the roof: Get back onto the roof and lower the section where you just installed the universal connector down the flashing, through the support box installed earlier, and into the room below. Ensure the chimney pipe protrudes roughly two feet above the shingles and is at least ten feet away from the roofline.
- Install the storm collar and rain cap: While still on the roof, install the storm collar on the chimney pipe, then apply silicon over the joint to create a weatherproof bond. Then install the rain cap to the top piece of the chimney using a 1/16 nut driver.
- Connect the chimney pipe to the stove pipe: Attach the female end of the stovepipe to the male end of the pipe adapter dangling from the support box using the provided hardware.
- Complete the pipe length and connect the line to the stove: This should be a straightforward process. Connect the final pipe to the woodstove collar once you’re done connecting the remaining pipe pieces.
- Install the support box trim: Installing the trim should also be easy. Make sure to drive it against the ceiling, then use the provided hardware to secure it to the ceiling.
That’s it! Congratulations, you’ve just installed a wood stove vent through the roof. Feel free to test it to see if it’s working as intended.
How to Install Wood Stove Pipe Through a Cathedral Ceiling
Installing a wood stove pipe through a cathedral ceiling is slightly different from a standard (flat) ceiling. Remember that cathedral ceilings feature two equal sloping sides that meet at an “apex” in the middle and typically conform to the shape of the room.
So, you cannot install the vent pipe as in standard ceilings. However, it’s still a fairly straightforward DIY job. Here’s how to proceed.
- Install the woodstove: Do so per the manufacturer’s guidelines, paying particular attention to clearance and footing support.
- Locate the venting point: Again, observe local codes and the manufacturer’s guidelines, especially on clearance.
- Cut a hole in the ceiling: Make sure the hole is large enough for the piping to go through. About two inches should be good. You can confirm that you’re on track by inserting a piece of the piping through the hole.
- Cut a hole on the flue pipe: Use a hacksaw to cut a small hole on the side of the flue pipe, making sure the hole is about an inch below the hole on the ceiling.
- Insert the flue pipe: Fit the pipe into the two holes cut in steps #c and #d. Then use a hammer to align the area around the two pipes gently.
- Attach flue to the exterior wall: Use standard metal connectors for this process. Feel free to run the flue over a cowl top r top plate fitting.
- Attach the bottom pipe to the stove pipe outlet: This is a straightforward process. Make sure the connection is sufficiently airtight.
- Cover the pipes and finish up: Exposing the vent pipes can create a bad sight. So, hide them away with drapes or even foam board insulation.
How Do I Install Wood Stove Pipe Through a Metal Roof? The same way you would install a wood stove vent pipe through shingle roofing. You need to cut through the roof and the ceiling and lower the vent pipe to the stove.
Does a Wood Stove Pipe Have to Go Above the Roof? Yes, the wood stove pipe must go above the roof to vent correctly. Otherwise, the exhaust fumes may cause a backdraft into the house.
How Far Above the Roof Does the Wood Stove Pipe Need to Be? The NFPA recommends installing your wood stove vent at least three feet above the roof and two feet higher than anything within two feet. This is known as the 3-2-10 Rule.
Does a Wood Burning Stove Chimney Have to Be Straight? Yes, ideally. The wood stove chimney needs to run straight up and out of the house makes as few bends and turns as possible for the free flow of exhaust gases out of the furnace.
How far does a woodstove need to be away from the wall? A wood stove should be at least 36 inches away from the wall. However, you can have it as close as two inches from the wall if wall protection is used.
What do you put on the wall behind the woodstove? Most people put type X drywall. Type X drywall is gypsum-based drywall that’s 5/8 inches thick, installed on each side of a 2×4-inch wood stud. Type X drywall has special core additives that allow it to be used in fire-rated designs.
That’s all you need to know about installing a wood stove chimney through the roof. Remember that you can vent the wood stove through a furnace chimney, albeit with a few modifications to the chimney. However, it’s best to build a new chimney for the woodstove. Good luck!