Whether you share a chimney with a neighbor or have multiple fireplaces in your home, you may be wondering if the fireplaces can be connected to one chimney. A chimney takes up a considerable amount of space, and sharing one chimney may help save space.
Multiple fireplaces can share a chimney, granted that certain standards are met. If the fireplace is double-sided, then it shares one firebox and one chimney. When the fireplaces are on the same level but opposite sides of the wall, they have their own firebox and can share the chimney—in some cases, they may even share a flue.
The logistics of how fireplaces can share a chimney is tricky, especially if the fireplaces burn two different fuel types or share a flue. Answers to your questions regarding multiple fireplaces connected to one chimney can be found below—so read on!
Can You Use The Same Chimney For Two Fireplaces?
The same chimney can be used for two or more fireplaces. A fireplace can also share a chimney with an appliance that also uses a chimney (like a furnace or water heater). Typically, each portion has its own flue while the chimney breast and chimney stack are shared.
However, two fireplaces of similar type (i.e., two wood-burning fireplaces) on different levels can share both a chimney and a flue. A chimney can be shared in most other layouts, but separate flues are required for safe use.
Shared Chimney And Shared Flue
A chimney and flue can be shared if 1) the fireplaces burn the same fuel and are on different levels, and 2) if the fireplace is double-sided. Although this layout occurs, there are building codes to follow which ensure that the flue properly exhausts smoke and fumes.
- Same type of fireplace on different levels. A fireplace on the main level can share a chimney and a flue with a fireplace located on an upper level. An example of this arrangement is a fireplace is on the main floor in, let’s say, a living room, and directly above the living room is a fireplace in a bedroom. The chimney and flue are shared, but a flue divider is used. This divider blocks an upstairs fireplace from leaking smoke coming from the downstairs fireplace.
- A double-sided fireplace. A double-sided fireplace has two open sides. It uses one firebox, flue and chimney.
Shared Chimney And Separate Flue
Oftentimes, a chimney is shared while the flues are separate. This occurs when 1) there are different fuel types (i.e., a gas fireplace plus a wood-burning fireplace), 2) a fireplace and an appliance (like a furnace) use a shared chimney, and 3) the fireplaces are the same type but are back-to-back on the same level.
- Different fuel fireplaces. Fireplaces on separate levels that burn different fuels can share a chimney but not a flue.
- A fireplace and an appliance. Some appliances utilize a flue and chimney. Water heaters, furnaces, and boilers are all examples of this. They can share a chimney with a fireplace, but not a flue.
- Back-to-back fireplaces. Fireplaces that burn the same fuel type, but are located on the same level will share a chimney but not a flue. For example, let’s say a home is one story and the living room has a fireplace in it. The bedroom on the other side of the wall could also have a fireplace in it. The firebox is usually offset to avoid a thick chimney breast. In this case the chimney is shared but there are two flues.
Does Every Fireplace Have Its Own Chimney?
Each fireplace does not need to have its own chimney. When the fireplaces align with a shared wall or a shared vertical space (on different levels), they can easily share a chimney.
A fireplace will not share a chimney when the two fireplaces are not located in the same area. A chimney breast and stack go straight up, so they won’t share a chimney when the two are not aligned.
Does Every Fireplace Have Its Own Flue?
Typically, each fireplace will have its own flue. When a flue is shared with multiple fireplaces or with an appliance, there is a risk of leaking combustion gases or exhaust inside the home. At times, a flue can be shared for very specific reasons.
A flue can be shared if:
- Two similar-fuel appliances are connected to one flue
- The fireplaces are on different levels
Two similar appliances may share a flue if done with proper installation and following local building codes. They usually will not share a flue with a fireplace, but they likely share a chimney.
If the fireplaces are on different levels of a home, both the chimney and flue can be shared. A flue divider is installed to prevent exhaust from the lower-level fireplace escaping inside through an upper-level fireplace.
Who Is Responsible For A Shared Chimney?
In rowhomes, the chimney is shared between the two homeowners, and chimney repairs are shared. In condos and townhomes, the chimney is considered a common area and is covered by the master HOA (homeowner’s association), which homeowners pay monthly.
Rowhomes are owned individually but share a common wall with neighbors on either side. In these situations, a chimney breast and chimney stack are a shared portion of the structure. Each fireplace or appliance will have its own flue. Therefore, the homeowner is responsible for the portion they use—their flue, fire box, and part of the chimney breast that extends into their home.
A deteriorating chimney stack is a shared portion of the home, so the repairs should be shared between neighbors.
Condos and Townhomes
Each condo and townhome association will have its own rules and regulations, but typically, the condo or townhome owner is responsible for what’s called “the walls in.” Meaning, everything from the walls to inside their unit is the owner’s responsibility.
‘Walls out’ is considered shared space. This includes siding, attics, crawlspace, roof, and chimneys. The association pays for damages to shared spaces which each owner in the association funds.
What Does A Shared Chimney Look Like From The Inside?
From the outside, the chimney stack will look like one solid unit. On the inside, the chimney is divided by multiple flues or flue liners when the chimney is shared. A brick divider separates the flues, and the flue liner is made of fire-resistant material.
Here is an example of a top-down view of a divided chimney.