Wood Burining Fireplace

How Deep Should a Wood Burning Fireplace Be?

In Technical Details by Giovanni ValleLeave a Comment

Wood-burning fireplaces are a relatively simple way of heating your home and have been around for centuries. Still, one common mistake homeowners often make is not building them deep enough to keep all the smoke inside. This can lead to smoke escaping into the room, which isn’t too pleasant. So, how deep should a wood-burning fireplace be?

A wood-burning fireplace should be at least 16 inches (40.64 cm) deep, as standard, unless the opening is over 48 inches (121.92 cm) wide, according to the Brick Industry Association. At most, the depth of a wood-burning fireplace should be 20 inches (50.9 cm) to allow for ample heat distribution.

This article will discuss the dimensions needed for a wood-burning fireplace and why they’re essential for your safety.

The Average Depth of Wood Burning Fireplaces

Wood burning fireplaces should be built based on the data from the Brick Industry Association, as all regulations set by them are engineered to reduce smoke emissions. Their guidelines are the best way to avoid any smoke inhalation and should be followed down to the millimeter to prevent potential health risks.

When measuring the fireplace, it’s crucial you don’t include the thickness of the materials. For example, the average brick is at least 3 inches (7.62 cm) thick, so if you start measuring your fireplace on the outside of this, you will lose at least 6 inches (15.24 cm) of depth to the materials.

Instead, start by measuring on the inside so the full depth of the fireplace is accurate.

Per the Brick Industry Association, you should be following the below sizes when building a fireplace:

Opening WidthFirebox DimensionsDepth
24 inches (60.96 cm)11 x 14 inches (27.94 x 35.56 cm)16 inches (40.64 cm)
32 inches (81.28 cm)19 x 14 inches(48.26 x 35.56 cm)16 inches (40.64 cm)
42 inches (106.68 cm)29 x 16 inches(73.66 x 40.64 cm)16 inches (40.64 cm)
48 inches (121.92 cm)33 x 16 inches (83.82 x 40.64 cm)18 inches (45.72 cm)

These are just a few of the dimensions provided – check out this table for more.

As you can see, the average fireplace requires a 16 inch (40.64 cm) deep cavity. It’s not until the opening reaches 48 inches (121.92 cm) wide that the depth needs to change.

Why Wood Burning Fireplace Depth Is Important

A wood-burning fireplace is made of standard heat-resistant materials, such as brick or stone. To create heat, you can burn dry firewood, wood bricks, or pellets.

To ensure there are no risks, the fireplace is constructed with a firebox of appropriate size and a hollow flue that connects to a chimney. This flue funnels harmful fumes out of the fireplace and your home by filtering in fresh air.

A fireplace that is built incorrectly is very dangerous because it can allow these harmful fumes into your home. That’s why your fireplace must meet specific regulations. Fireplaces that don’t could damage your health in the long run and also ruin your home.

According to the American Lung Association, smoke emissions can cause a whole host of health issues, including:

  • Coughing
  • Wheezing
  • Asthma attacks
  • Heart attacks
  • Lung cancer
  • Death

Even the slightest design flaw can impact the amount of smoke you inhale. While it’s infrequent for wood-burning fireplaces to be built incorrectly, accidents do happen. However, if you follow the guidelines provided above by the Brick Industry Association, you should be more than safe.

Choosing the Right Size Fireplace

Although the average-sized fireplace requires the dimensions mentioned above, the size of your wood-burning fireplace will depend on the size of your room.

For example, your home may not be big enough to fit the average fireplace, meaning you will need to make the firebox a lot smaller. On the other hand, you may have a more significant, open space that needs heating, which will undoubtedly mean a larger firebox.

Unfortunately, wood-burning fireplaces are some of the least efficient, which means you will need something larger than you might think to properly heat your space. The good news is that larger fireplaces are often more aesthetically pleasing, even in smaller areas.

When looking at the efficiency of your fireplace and how well it will heat your space, you need to consider the amount of British Thermal Unit (BTU) it can produce. This is a measurement of heat by which all fireplaces – gas, electric, etc. – are measured.

A good rule of thumb to follow is:

  • Multiply the square footage by 10-15 in warm climates
  • Multiply the square footage by 20-30 in moderate climates.
  • Multiply the square footage by 30-40 in cold climates.

Below are some average numbers to keep in mind based on the size of the space and the quality of the insulation:

Good InsulationPoor Insulation
200 square feet (18.58 m2)4,000 BTU9,000 BTU
400 square feet (37.16 m2)8,000 BTU18,000 BTU
600 square feet (55.74 m2)12,000 BTU27,000 BTU

As you can see, the numbers change a great deal when you take away adequate insulation. So, if your home doesn’t have the best insulation and you have the space, it might be best to opt for a larger fireplace to make up the heat.

This could mean the depth of the fireplace will need to be larger than the average 16 inches.

To work out the size you need, check out the BTU calculator provided by We Love Fire.

Fireplace Design & Dimensions Checklist

As with any household appliance, it’s essential to make sure your fireplace is placed correctly. Aside from measurements, it’s also vital to get the right design.

Here is a checklist you can use to help determine if your fireplace meets the minimum requirements:

  • The walls of your fireplace should narrow towards the back.
  • The wall at the back needs at least 12 inches (30.48 cm) of a vertical surface.
  • Above this 12-inch vertical space, the rest of the wall needs to slope inwards towards the front.
  • The width and the height need to be very precise and taken from the guidelines given by the Brick Industry Association.
  • The smoke shelf – the area above the firebox and below the chimney used to collect rainwater or debris – must also be carefully measured to function correctly.

Along with following the guidelines set out by the Brick Industry Association, you must check your state regulations.

Each district will have its own set of rules that you’ll need to abide by, which may affect the depth of your wood-burning fireplace. Head to your local state website and search for property regulations.

If you live outside of the United States, check your standard country laws regarding building regulations. Although, it’s good to remember that each town will have different rules compared to overall state or country laws.

Here are other codes that you should be aware of:

  • The International Residential Code (IRC). The IRC is the most accepted code for building regulations. They update their laws every three years and provide recommended dimensions for one or two-family homes.
  • The National Fire Protection Association (NFPA). The NFPA provides chimneys, fireplaces, vents, and fuel-burning appliances. They also offer guidelines on gas codes and update their regulations every few years.


Can a Fireplace Be Too Deep?

Yes, a fireplace can be too deep as it will impact the fireplace’s ability to emit smoke properly.

A too deep fireplace can cause smoke to build up inside, defeating the design, as the smoke needs to travel high enough to disperse into the fresh air. When it’s cut off – due to being too deep and not having proper access to the flue – the smoke will linger, which can be deadly to you and your home.

Can a Fireplace Flue Be Too Big?

Yes, a fireplace flue can be too big as it will result in a cold chimney that won’t keep a lit fire.

Aside from that, mold can start to form due to the increased chance of condensation buildup. That’s why it’s vital to build the correct dimensions.

How Do You Know if a Fireplace Is Safe To Use?

There are a few steps you can take to determine if your fireplace is safe to use or not:

  1. Examine the firebox and check for cracks, gaps, or signs of damage.
  2. Look for smoke stains.
  3. Inspect the grate and make sure it’s appropriately sized.
  4. Inspect the chimney to see if it’s functioning correctly.
  5. Make sure your fire extinguisher is ready to use.
What Is the Minimum Depth of a Fireplace Hearth?

The minimum depth of a fireplace hearth is four inches and must be made from concrete, ceramic tile, or masonry.

Checking the American Legal Publishing Corporation can provide insight into wood-burning fireplace regulations.


A wood-burning fireplace is dangerous if it’s not built up to standard, and it can severely damage both your home and your health if not fixed. The average wood-burning fireplace depth is 16 inches (40.64 cm), but that will change if you look into building something more extensive.

Following regulations will guarantee that everything is safe and up to standard. It will also ensure you aren’t charged any fees if you’re inspected. All houses need to be up to regulation, so be sure to do your own research based upon your city and state.


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