Kit for a Chimney Through a Garage

The diameter is measured on the inside of the (inner) pipe. Common sizes are 4", 6", and 8", depending on your appliance. A 4" liner is typically used for gas appliances and some pellet stoves. Most wood stoves use a 6" internal outlet, while larger stoves or open fireplaces may need 8". Check your appliance manual or look at the round collar where the flue connects.

Determine the Height of the Stove pipes

Take a measurement from the ceiling to the floor.

Now subtract the total height of the stove (measured from the bottom of the stove to the top of the flue collar) from the ceiling height.  Don't forget to subtract any hearth or hearth pad that the stove will sit on.

You also need to subtract the distance that the ceiling support box will extend down into the home. The support box must extend a minimum of 2" below the ceiling to meet clearances.

You only need to be close with your measurements here, not exact. Our black stove pipes cannot be cut to size so you will need one of our telescoping lengths to complete your installation. This gives you lots of "play" in your measurement.

Height of the Class A Pipes

That is : 

Distance from the attic floor to the roof 

              + 

Height on the roof

 

Calculate the required height on the roof

The termination of a chimney above a roof must comply with NFPA 211 and/or CAN/CSA-A405. These codes require the chimney to terminate at least 3 feet above the point it penetrates the roof and 2 feet higher than any part of the building within a 10-foot radius. A UL- or ULC-listed chimney cap must be installed.

What is the 3-2-10 Rule for Chimney Height?

If your chimney is too short, it won't draft properly. Smoke may enter your living space instead of venting outside. But if the chimney is too tall, the flue gases can cool excessively, reducing draft and potentially creating backdraft.

To avoid these problems, use the 3-2-10 rule:

• The chimney must be at least 3 feet higher than the point where it exits the roof.
• It must also be 2 feet taller than any part of the building within a 10-foot radius.

This ensures a safe and effective draft, even with sloped or pitched roofs.

How to Calculate the Correct Chimney Height

Knowing your roof pitch helps determine how high the chimney must extend. Roof pitch is the vertical rise per 12 inches of horizontal run. For example, a 7/12 pitch means the roof rises 7 inches for every 12 inches of run.

Step-by-Step Calculation:

1. Measure Roof Pitch: Identify the pitch (e.g., 7/12).

2. Measure Horizontal Distance from Ridge: Use the actual distance or 10 feet (whichever applies).

3. Calculate Height: Multiply pitch rise by horizontal distance, then add 24 inches.

Example 1: Chimney More Than 10 Feet from Ridge

• Pitch: 7/12

• Distance: 10 feet

• Height: 7 x 10 = 70 inches

• Final chimney height = 70 + 24 = 94 inches above roof

Example 2: Chimney 4 Feet from Ridge

• Pitch: 7/12

• Distance: 4 feet

• Height: 7 x 4 = 28 inches

• Final chimney height = 28 + 24 = 52 inches above roof

Why Proper Clearance Matters

The 3-2-10 rule isn’t just about smoke control. It helps prevent fire risks by keeping hot embers away from the roof and ensures compliance with building codes. Always double-check your local building codes before installation, and consult a professional if in doubt.

How much chimney is above the last support (roof edge or wall band)? 

You need to support the flue if the free end becomes too long and requires additional support. We recommend using a telescopic support if the free end From last wall strap to the cap) is between 5 and 10 feet.