What Measurements Do I Need For a Wood Stove Chimney Liner?

Chimney Liner Measurements

So the time has come to reline your chimney with a stainless steel chimney liner for your wood stove or boiler. Correctly preparing and getting the right information is crucial to the success of a chimney liner installation. Taking a little more time before you do the job will ensure the job is done correctly. 

The first measurement we need to determine is what size liner you need for the wood stove to properly function. Installing a chimney liner that is too small for a wood stove will make it difficult to light the stove and cause smoke to come into the room. No one wants that. The rule of thumb for wood burning stoves is that the area of the chimney liner must not be smaller than the area of the exhaust hole and not more than three times greater the area. This is the same rule if the exhaust hole is rectangle or oval (found on older stoves).

Now that we know what size liner we need, the second measurement we need is the INSIDE dimensions of the flue in which we are installing the liner. To be more clear, the EXACT inside flue dimensions. Just because we know what the correct size chimney liner is that we need, doesn't mean it is going to fit down any chimney flue. This is where a lot of people like to make assumptions as to what their flue size is. The commonly heard 8" x 13" Terra-Cotta clay flue could have an inside measurement of anywhere form 6" to 8" on the short side and anywhere from 11" to 13" on the long side. If the liner you need is an 8" diameter, you could run into some problems. Climbing to the top of the chimney to measure the flue will ensure that no problems will come up.

The third measurement you will need is the length of the chimney. The easiest way to do that is to climb up to the top of the chimney and drop a tape measure down the flue. For a fireplace insert you should measure to the top of the stove to the top of the chimney. For a freestanding stove going into a thimble, you should measure to the top of the thimble to the top of the chimney. You must add 3.5" to the exact length to accommodate the liner fitting into the top plate. If your flue has some bends, it is recommended that you add at least an extra foot or two to accommodate the radius of the bend. It is always best to make sure you have more than you need. However, if you come up short, you can use a liner to liner quick connector to couple two sections of liner together. 

The last measurement would be the damper for a fireplace insert or the thimble for a freestanding stove.

• A fireplace generally has a damper that is very narrow and usually causes a restriction for the chimney liner. You may have to ovalize a small section of the liner to get it through the damper. Don't worry, its easy to reshape back to a round shape in order to connect it to the stove. Note: Smooth Wall flex liners cannot be ovalized. The damper frame may need to be cut out.
• If you have a freestanding stove, knowing the depth of the thimble is a good thing to have on hand. Knowing this measurement will ensure that the horizontal tee snout is long enough to pass through the thimble. Tee snouts are offered in 10" and 22" length. Extensions are available when needed.

Measuring Forms

Having these measurements will help ensure a properly functioning wood stove or fireplace insert. Here is a link to our measuring form you can fill out and send back to us for a parts list! Any questions? We are here to help - Contact a Certified Tech at Rockford Chimney Supply.