DO NOT Install a Chimney Liner UNTIL Reading 10 Most Asked Questions

Q. Are Rock-Flex Chimney Liners Approved?

A. The quality and workmanship of the Rock-Flex chimney liner is reflected in the recognition Underwriters Laboratories has given these products. Our liners are UL and ULC Listed and meet all UL1777 and ULC-S640 code specifications. The rigorous UL testing and listing requirements is your assurance of consistent quality in materials and manufacturing standards used for these lining systems. In addition, the industry leading forever Lifetime and transferable Warranty on Rock-Flex is a further indication of our confidence in the quality of this product.

Q. Do I need to reline my chimney?

A. Most masonry chimneys starting in the 1940's were made with clay tiles, that line the inside of the chimney. Over time these tiles deteriorate or crack. This will leave gaps, allowing toxic carbon monoxide and possibly chimney fire sparks to escape through the cracks into the home, igniting a fire. When this happens, the chimney is no longer safe, and needs to be relined. Even the furnace and water heater will vent better and no more condensation issues.

Q. What are the benefits to relining my chimney?

A. Having peace of mind, knowing your family, house and belongings are better protected from dangerous carbon monoxide and potential chimney fires, by the installation of a stainless flue liner. Whether it is a furnace, hot water heater, wood-burning insert or stove, and even existing fireplace, by adding insulation you have also increased the protection, and added extra to the value of your home.
Now days when homes are sold many new buyers and realtors are asking for chimney inspections, and if you do not have a liner, they will ask to have one installed before purchasing. Since our liner warranties are transferable, they too will be covered should they ever have a problem.

Safety, knowing the gases and sparks won't enter into your home.
Increased efficiency through a better draft, and reduced creosote build up.
An affordable alternative to repairing or rebuilding the chimney and much easier to clean.
Lifetime Warranty because the stainless steel liner is a corrosion resistant liner you can expect the liner to last a lifetime, virtually maintenance free.

Q. Is this a DIY project?

A. Typically yes, you need to stand on the roof and reach the top of the chimney, and being somewhat handy with household tools will help. We also have knowledgable Certified Chimney Sweeps, that can walk you through even the toughest situation, we are just a phone call away 866-708-2446, even email us your pictures and we can troubleshoot right on the spot.

Q. Is a stainless liner my best option?

A. Stainless will always be the best option when it comes to performance, durability, safety and cost.

A stainless steel chimney liner that is properly sized, for the stove, furnace, or fireplace will maintain or improve the venting performance (draft). If going to a Smooth Wall liner, it will additionally improve your draft by up to 20% for gas and up to 15% for oil burning appliances.

Our stainless chimney liners are primarily used to upgrade and repair existing chimneys. These liner systems are U.L. tested and listed, and if properly installed and maintained are extremely safe and durable. Stainless steel is suitable for wood burning, gas, or oil applications. The liner protects the house from heat transfer to combustibles while being installed in a masonry chimney. In the NBS tests, unlined chimneys allowed heat to move through the chimney so rapidly that the adjacent woodwork caught fire in only 3 1/2 hours.

Q. I have a Rectangle Flue, do I use a Rectangle Liner?

A. Probably not, most everything can be installed with a Round liner, with the exception of some liners for fireplaces. Larger is not necessarily better when it comes to your flue liner. Too large will give you a slow draft and poor performance, and too small will restrict the draft.

If you are connecting this to a gas furnace, boiler, or water heater then you will need to know the total amount of BTU's. If you are connecting an oil system, it would be GPH (gallons per hour) which is listed on the unit. Also knowing the height of the chimney will help. With this information we can calculate the liner diameter needed. If this is for your stove or insert, then it would be the same as the inner diameter of the exhaust of the unit. Keep in mind that all round liners are 1/4" larger on the outside than the inside, so a 6" liner will be 6.25" on the OD. Try our handy Liner Size Calculator or give us a call for sizing help!

Q. How much liner will I need?

A. This will depend on what you are connecting. A stainless liner going through a thimble hole, will be measured from the center of the hole to the top of the chimney. A liner going to an insert or stove in the fireplace will be measured from the top of the chimney to the top of the insert or stove or the center of the hole on the back of the stove. Please remember these liners are sold in 5' increments, 15', 20', 25' for instance an 18' chimney will need a 20' liner.

Q. Does my liner need to be insulated?

A. It is always a good idea to insulate your flexible chimney liner. The insulation will enable the flue to heat up more quickly and this increases your draft, reduces creosote, making it easier to clean and makes your system more efficient & safer. Having 1/2" thick insulation will maintain your liner to the UL1777 standard.

Q. How do I get the TEE down my chimney?

A. Not all installations require a Tee Connector, but if yours does, it doesn't get any easier than this. When a Tee is needed and the masonry chimney has little or no offsets, connect the Tee Body to the bottom of the liner with the attached clamp, the Tee Cap should be attached to the bottom of Tee Body. Before lowering the flex liner and tee body down the chimney, insert the Tee Snout (pipe coming off the tee that goes through the wall) into the opening in your masonry chimney. Now lower the flex liner assembly down through chimney, it is recommended to use two people when installing the liner through the chimney. The Tee Body will need to pass through the clamp that is attached to the Snout, and then tighten the clamp using the attaching screw on the inside of the snout to secure them together. Watch a quick video here.

Q. How do I cut my stainless liner?

A. Carefully... is the best answer. The liner ends will be very sharp so take precaution. Wear gloves for protection. We have cut these liners with many tools but the quickest, cleanest, and straightest is with an angle grinder with an abrasive wheel. For those who want to use a Hacksaw, Tin Snips, Sawzall, or other device, that is perfectly fine, it may not look pretty when you're finished cutting, but it does get covered up with the Top Plate and Rain Cap, and no one can see it when you finish.

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Our 316Ti flexible chimney liner and chimney liner components have passed the rigorous testing at the Underwriters Laboratories with best in class status and are UL Listed. So if you are looking for UL listed chimney liner sold directly to homeowners, then look no further than Rockford Chimney

Customer Testimonials

Back in July you gave me excellent advice re. sizing/purchasing a flue liner for the chimney associated with my wood stove. I'd like to thank you once agai... More

—AE Northfield, MN

A few weeks ago I ordered a chimney liner system for my fireplace insert. Your salesman recommended the liner system plus the insulating blanket. I just wa... More

—AH Happy customer

Just got around to installing my new smooth flexible liner and deluxe terra cotta cap (wow). The quality of your product is second to none. Very pleased an... More

—B.B. from Massachusetts

Thanks so much for the great tech service from Dennis, very knowledgable, friendly and proffessional.Your website is the best, beats your competition by fa... More

—Bill in Knoxville

Sue and Dennis, I received the final part of my order yesterday (the chimney cap that actually fits over the chimney chase). It looks wonderfu... More


Hello, I was shopping for an fireplace insert and called RCS to ask why they were so much cheaper than my local guy, the reply was " we sell thousand of th... More

—Chris, PA.