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FAQs
Chimney Liners
Beware! Chimney sweeps may be selling dangerous repairs!
The chimney liner of a fireplace is one of the most critical components of the operating system. The chimney liner is design to safely expel hot flue gases to the exterior atmosphere. The proper sizing of these liners is very important. If the liner is too small, the gases will back into the home and cause smoking issues. If the liner is sized too large, the smoke will travel slowly up the chimney and large amounts of creosote will form on the liner. Creosote build-up is one of the major causes of chimney fires.
Types of liners
If you have read other pages on our website, you have likely been informed there are basically two types of fireplaces. The first is masonry (brick construction top down) and the second is a prefabricated chimney which is sometimes called a “fake fireplace.” The chimney liner of a masonry fireplace is usually constructed with terra-cotta flue tiles and acks as a heatshield. These flue tiles are an excellent material to contain and shield heat but are prone to crack during thermal shock of a chimney fire. The National Fire Protection Association 211 Standards for Chimney, Fireplaces, Vents and Solid Fuel Burning Appliances section 13.9 state that cracked flue liners should be either repaired, removed and replaced or relined with a UL listed chimney liner. This is a very important recommendation and should be discussed in detail. There are three options mentioned which are repair, remove and replace, and reline.
Repairing chimney liners: This is a very heated issue in the chimney industry. Currently, it is the opinion of A Step in Time that there is NO system that can properly repair a damaged chimney liner. See our detailed explaination regarding chimney liner repair located at the bottom of this page. Basically, UL has withdrawn it's 2425 standard for repairing chimney liners.
Replacing chimney liners: When a person talks about replacing a chimney flue liner, they are likely talking about breaking out an existing terra cotta flue tile and reinstalling another terra cotta flue tile. This operation is a little difficult because you need to properly apply mortar between flue tiles joints. The terra cotta flue tiles are very heavy and stand 24 inches tall. Unless you are going to tear down a chimney and rebuild it, a technician can only replace the top two flue tiles. The reason why he can only replace the top two flue tiles is that he will need to reach down 48 inches inside the chimney to place the mortar joint.
Relining chimney liners: If a chimney liner is damaged farther than 48 inches, the best repair is to reline the system. It is the opinion of A Step in Time that relining with stainless steel liners is the best solution. There are many reasons why we feel this system is the best way to reline a system but the strongest reason is that it is easy to inspect the condition of the liner after it has been installed. The draft of the chimney appears to follow the coils of stainless steel liners. Basically, smoke travels up a chimney flue in circular spiral cones which follow the groves of a stainless steel chimney liner. Many stainless steel chimney liner manufactures offer a lifetime manufacturer warrantee on their relining products.
Chimney liner repair – is it possible?- by Raymond Gessner, P.E.
There has been a flurry of discussion regarding new ways of repairing damaged terra cotta flue tiles with chimney liner repair and resurfacing systems. They claim to seal your chimney liner as a flue sealant. Unfortunately, there has been very limited written discussion regarding this issue. Our industry should thoroughly research these topics when they surface. NFPA 211 section 13.9 might suggest chimney liners can be repaired instead of replaced or relined. It is my opinion that cracked terra cotta flue tiles can not be successfully repaired and the reasons are noted below:
1) The UL 2425 Standard for chimney liner repair is a withdrawn standard. (http://ulstandardsinfonet.ul.com/tocs/tocs.asp?doc=o&fn=o2425.toc)
The reasons why this standard has been withdrawn should be discussed with UL but some of the reasons why I feel it should be withdrawn are listed below.
2) Part 4 of the withdrawn UL 2425 standard is a 100 stroke steel wire test. This test is designed to simulate how the product would handle typical cleanings of a chimney. A normal chimney is routinely cleaned with a steel wire chimney brush. The problem with this test is that if the chimney has experienced a chimney fire, it likely has a design issue. The chimney might draft too slow and produces more than normal amounts of creosote. When the chimney produces more than normal amounts of creosote, sometimes level three or glazed creosote is formed. To clean these flues, chimney technicians will employ motorized glazed creosote removers which are designed to scour the interiors of chimney flues and smoke chambers. The 2002 reference manual for the Certified Chimney Sweep Program of the Chimney Safety Institute of America chapter 4 state “this method of cleaning is far more aggressive than conventional means of chimney cleaning and is normally used when a heavy glaze exists.” Basically, the withdrawn standard was testing products to a very light standard.
When the tested product is installed, the product will typically coat the liner. Since the general configuration of the system is not changed, the performance of the system will not change and the issues which caused the liner to crack will continue. Typically cracked flue tiles are caused by chimney fires which are usually caused by ignition of excessive creosote build up. The “repaired” system will likely continue to form excessive creosote build up. This glaze creosote will coat the tested repair product. A chimney technician will see the glaze creosote and will “normally” clean the chimney by mechanical cleaning which is “far more aggressive.” If the chimney liner repair product was not tested to situation which might be encountered in the field, the mechanical cleaning might remove the chimney liner repair product from the chimney liner. The chimney technician might not even realize the product was installed and assume the chimney is in good condition. If the original damaged is not discovered after the chimney technician cleans the chimney, the home owner might be living with a false sense of security.
3) Chimney liner repair would have a variety of field control issues. This is a little difficult to explain. If the chimney liner repair product coats the existing terra cotta flue tiles, then the product is designed to repair cracks and voids in chimney liners. Let’s assume it is a void and the void is 1 inch. The product is installed and successfully bonds and transitions the damaged liner for 1 inch. Now let’s assume the void is 2 inches and it successfully transitions the repair. There will be a point when the transition will not set. The repair technician will attempt this repair and the bond will not hold. At this point, the technician might recommend relining with stainless steel. The issue which should be considered is repairs which are on the edge of success. The repair barely makes the void transition. It appears to the product installer that the bond was successful but might be on the verge of failure. This repair might be weak and may be easily damaged during a later chimney cleaning process.
4) The UL 2425 standard which has been withdrawn, did not consider important issues regarding product adhesion. The UL 2425 standard requires tested products to be applied to a clean terra cotta flue tile. Flue tiles which require repair may have situations which may prevent product adhesion. These situations might include flaking tiles which occur when oil flues are converted to natural gas and light acid deteriorates the interior skin of the flue tile. Other circumstances might include glaze creosote deposited which may not be removed with even thorough mechanical cleanings. The UL 2425 test does not account for these situations.
Finally, the ultimate decision whether chimney liners can be repaired will fall on the home owners. A product might offer long warrantees, but verify if it is a manufacture's or a installer's warrantee. If a resurfaced liner repair peels off the chimney liner and closes the flue, is that considered a product failure or an application error. Our industry should educate our clients with as much information as possible. If we inform our customers with testimonials and concerns from every point of view, than they will be more informed to consider this matter for themselves.
Tips regarding chimney liner facts
1) How do you know that you need a chimney liner?
Many homeowners may have had a chimney sweep recommend to have a chimney liner installed. The truth to the matter is that sometimes, chimney sweeps push liners on home owners. They may use scare tactics or automatically perform video inspections on every chimney. NFPA 211 recommends video inspections if the chimney has experienced chimney malfunctions (chimney fire), changing of appliances or on the sale of the home. There have been cases where chimney sweeps have manipulate cameras to illuminate "water marks" to look like cracked flue tiles. Make sure that you are watching the chimney camera monitor while the sweep is performing the inspection. The inspection of a chimney is common sense. If it looks like a crack, it's likely a crack.
Most recent video inspection scam!
Here is the most recent trick that chimney companies are using to sell chimney liners. The chimney technician video inspects your chimney. While he's out there, he takes "still photos" of your chimney liners. The technician returns to his office and they send you a report that states you have severe chimney liner damage. The problem is that the photograph they send you may be from a completely different chimney! A good chimney sweep company will discuss your chimney problems with you while they are performing the inspection. Buyer beware!
Beware Limited Warranty
Products that offer material warranty - even if it is a long period, usually only cover the cost of the product and not the labor installation cost. The product usually on makes up 10% of the total repair cost. Always insist on warrantees that include material and labor.
