Two Fireplaces One Chimney: Pros and Cons Homeowners Must Know

If you plan to add another fireplace to your home, you might wonder whether you’ll need another chimney. The two fireplaces one chimney system are feasible, but there are specific guidelines you need to follow. These guidelines ensure the safety and efficiency of your fireplaces.

Can Two Fireplaces Share One Chimney?

Homeowners can have a single chimney sharing two (or more) fireplaces. But each fireplace needs to have its separate chimney flue (liner.)

 Doing this minimizes the risk of a chimney fire. You can operate one of the fireplaces with a separate flue for each fireplace whenever you want, and you can also use different fuels for each fireplace.

You can connect two fireplaces to a single chimney even if they are on different floors of your home. But in this case, your chimney needs to extend from the lowest floor up to the rooftop.

Following the clearance and maintenance protocols is essential when connecting two fireplaces to a shared chimney. For example, having an 8″ masonry wythe between adjacent flues within the chimney is best. Single wythe brick (4″) between two flues is acceptable in Canada.

State building codes differ in the design requirements for a two fireplace and single or dual chimney system, which is why hiring a certified chimney sweep is important. Chimney experts know the different building codes and state laws and provide expert advice according to your requirements, chimney design, and locality.

Can Two Wood Stoves Share One Chimney?

Two wood stoves can share a single chimney, but it is important that each stove has its own chimney flue (liner.) Following the NFPA 211 standard is crucial to ensure the safety and well-being of your family. Before connecting two wood stoves to a single chimney , Here are a few things to consider:

• Size of your chimney – your chimney must be large enough to handle multiple flues
• Location of the stoves – The location of the stoves must be located close enough to the chimney to connect to it
• Proper Draft – It is important to ensure that the chimney has proper draft, If the draft is insufficient, it can cause smoke and gases to back up into the house.
• Safety codes – Installing two wood stoves in one chimney requires careful planning and installation by a qualified professional, This includes ensuring you are compliant with all the local building codes and regulations.

Can Two Gas Fireplaces Share the Same Chimney?

Installing multiple gas fireplaces to a single chimney and two gas appliances to share a chimney flue is possible. However, this may create potential health and safety hazards in specific scenarios.

Consider a boiler and water heater on different levels of your home. If both share a chimney, it increases the risk of Carbon Monoxide leakage and chimney fire. The fire or leakage can spread between floors and increase the damage because the appliances are on different floors.

That is why you can only have one gas appliance with a single chimney in various states.

How Do Multiple Fireplaces Work?

Multiple fireplaces connected to a single chimney come in different configurations. Let’s discuss each of these configurations in detail:

See-Through Fireplaces

A see-through fireplace can be an elegant addition if you’ve got an open layout house. The firebox of a see-through fireplace has more than one side open, and such a setup allows you to see the next room through the firebox.

Multi-Sided Fireplaces

Fireplaces with two or three sides typically have separate fireboxes that share a chimney. The specific configuration of such fireplaces can vary based on the homeowner’s preferences. For instance, it is possible to connect indoor and outdoor fireplaces to a single chimney, with the chimney between the main room and the outdoor fireplace.

You can add a third firebox in the main suite connected to the same chimney in the same setup. The result will be a popular setup of three-sided fireplaces.

Multi-Level Fireplaces

Multiple fireplaces located on different levels of a home can share a single chimney to vent out smoke. 

The chimney must be extended from the lowest floor to the roof to ensure proper ventilation. Additionally, it is possible to connect a one-story fireplace with a two-sided fireplace located on another level, allowing for three fireplaces to be connected to a single chimney.

Note: When two or more fireplaces share a chimney, it’s crucial to have separate flues for each fireplace. This allows homeowners to use different fireplaces whenever they want and use different types of fuel for each fireplace.

It is still possible to connect two fireplaces to a single flue and chimney, but only if they are the same type and use the same fuel. It is recommended to consult a chimney expert to ensure optimal design and clearances for such a setup. Additionally, it is advisable to have it inspected by local authorities for safety compliance.

Can You Add Another Fireplace to an Existing Chimney?

If your current fireplace is not providing enough heat for your home, you can add a fireplace. Various options are available, but state law and local building codes may restrict the fireplace type you can install, and there may also be limits on the allowed fireplace emissions.

It is best to check your local authorities for the applied restrictions.

How to Properly Maintain Two Fireplaces One Chimney?

Two fireplaces (with separate liners) sharing a chimney follow the same principle as a single fireplace and chimney system. So they need the same sort of maintenance.

For safe and efficient operation, you must schedule annual chimney inspections. Moreover, regular cleaning of your chimney is necessary because a certified chimney sweep will remove creosote buildup inside the chimney flues.

Doing so will also prevent clogging of the chimney through dust, debris, and small animals seeking shelter inside the chimney.

Sometimes homes with fireplaces on different stories have smoke problems. The smoke from the active fireplace enters the house through the unused fireplace flue.

This happens because when air (along with smoke) exits the house, an equal amount of air is pulled in to replace it. Since the unused fireplace flue is empty, it provides the optimal space for the incoming air to fill. The replacement air brings with it the smoke from the active fireplace.

You need to get a chimney expert to install air intakes on both fireplaces to prevent this problem. Also, cover both fireplaces with fireplace glass, and it will prevent smoke from entering the house.

A certified chimney sweep will also check all parts of your chimney, and he will inspect the chimney damper, flue, cap, crown, and other chimney parts. The chimney expert will also ensure that the parts are in proper working conditions.

Maintenance becomes even more critical if two fireplaces share the same chimney and flue. That’s because creosote produced by two fireplaces will be considerable. But with regular cleaning and inspection, you can avoid situations.

The Pros and Cons of Having a Chimney With Two Fireplaces

Let’s weigh the pros and cons of a chimney with two fireplaces to help you decide whether it is a good option for you:

Pros

• You won’t need an additional chimney
• It is a cost-effective
• It saves a lot of space that another chimney would occupy otherwise
• Aesthetically pleasing

Cons

• Need more maintenance
• Smoke enters the house through the unused flue

The Takeaway

Larger houses need more than one fireplace to provide adequate heat for the whole house. The good news is that you don’t need an additional chimney for the other fireplaces. You can connect multiple fireplaces to a single chimney, even on different floors.

But each fireplace will need a separate flue, and you must also follow the mandatory building codes and clearances.