If you’ve chosen to install a wood-burning stove in your home, a chimney liner is one of the most essential accessories you’ll need. A chimney liner is a pipe that runs from the stove up through the chimney. It serves several crucial functions:

  • Protects the masonry chimney from heat damage and corrosion
  • Provides a smooth surface for proper ventilation and draughting 
  • Reduces build-up of creosote and improves stove performance 

Choosing the right chimney liner and correctly measuring your chimney is key to safely and effectively operating your wood-burning stove. Follow this guide to learn everything you need to know about selecting and sizing a chimney liner. 

Never buy a cheap chimney liner 

When shopping for a chimney liner, you’ll find options ranging widely in price. While it may be tempting to choose a cheaper liner to save money, don’t! Cheap liners are not worth the risk. 

Low-quality liners can unfurl as they’re being installed, and their sharp edges are dangerous to work with. A cheap liner may also get stuck partway down your chimney. 

The materials in bargain liners are prone to breaking down. This creates ledges inside the liner that disrupt airflow and allow creosote to accumulate. 

You’ll often see cheap liners advertised online with persuasive claims about quality and guarantees. Don’t believe them. Proper chimney liners will cost more upfront but save you trouble and money in the long run. 

Determine the correct diameter

Chimney liners usually have diameters between 5 and 9 inches. So, how do you determine what size you need?

The first rule is to follow the stove manufacturer’s guidelines. They will specify a minimum flue diameter for proper operation. 

If the stove is not approved for smoke control areas, the minimum is 6 inches, regardless of location. 5-inch

Manufacturer instructions override general rules if they require a larger diameter. For example, the stove may have a 5-inch collar, but the manufacturer recommends a 7-inch liner. Always follow the manufacturer's specs in cases like this.

The liner diameter should never decrease as it runs up the chimney. Otherwise, smoke backups would occur. So, if your stove collar is 6 inches, don’t use any liner less than 6 inches along the route. 

It’s okay to use a larger diameter liner than the minimum required. For example, a 6-inch liner can be used even if 5 inches is allowed. But it’s best to match the stove collar diameter for optimal performance. 

Some reasons you may opt for a larger liner:

  • Accommodate heavy use
  • Allow for build-up of soot over time 
  • Work with an oversized chimney

A 5- or 6-inch liner is perfect for most stoves. According to experts, 5-inch liners hardly get stuck during installation, while 6-inch liners are more prone to problems. 

Choose between 316 and 904 grade 

Chimney liners come in different grades, depending on the type of stainless steel used. The two main options are:

  • 316 grade: The budget-friendly choice suits light to medium stoves using only seasoned wood. 
  • 904 grade: Made from a higher grade stainless steel that resists corrosion better under heavy use and wetter, dirtier fuel. 

904-grade steel contains more chromium and nickel than 316-grade steel. This makes it more resistant to acids and corrosion on the inside of the liner over many years of use. 

It’s a good idea to upgrade to 904 grade if:

  • You anticipate burning coal or smokeless fuels in addition to wood 
  • You consider yourself a “heavy” stove user 
  • You plan to install a boiler stove that may slumber overnight 

Lower overnight temperatures can cause condensation and corrosion with a boiler stove. The 904 grade will hold up better. 

Slumbering or smouldering also creates more creosote and incomplete combustion by-products that a 904 liner will withstand better. 

Though 904 grade costs more upfront, it’s a wise investment if you expect to push your stove and liner to work hard. 

Measure your chimney height 

Once you’ve selected a liner, you need to determine its length. It’s best to measure from the stove location up to the top of the chimney. 

Make sure your measurement includes:

  • Height of the room with the stove 
  • Height of any floors above 
  • Height from the upper floor to the roof apex 
  • Any chimney stack above the roof 

Allow for around 50cm per floor thickness in your calculations. 

Some installers simply count the bricks for gable wall chimneys. You can also measure interior room heights and add them together. 

A typical measurement might be:

  • Downstairs room height: 2.4m
  • Upstairs room height: 2.4m 
  • Loft height to roof apex: 2m
  • Chimney stack above roof: 1m

Total = 7.8 metres of chimney liner required.

It’s wise to add at least an extra metre beyond your measurements. This provides a margin of error if your chimney has tight bends or you accidentally measured slightly short. 

It is challenging to get an exact measurement with a clay or brick chimney. The generous extra length helps ensure the liner can be fully extended when installed. 

Now you’re ready to install your chimney liner 

Installing a chimney liner requires special skills and tools. If you’re not confident doing it yourself, have the work completed by a certified chimney sweep to ensure safety and compliance with building codes. 

Learn more: DIY Guides: How to Fit a Chimney Liner

With the right chimney liner adequately installed, your wood-burning stove will burn safely and efficiently for years of cosy winter nights. Selecting quality materials suited to your needs will save you money and trouble. 

Follow the tips in this guide to determine the type, diameter, grade, and length of chimney liner that’s right for your stove and chimney setup. Though it’s an investment, a proper chimney liner is one of the most essential accessories for your hearth. Stay warm!