Hearth News

Learn Helpful Tips & Tricks from the Community

DON’T Just “Do it” - Placing a wood stove into an existing masonry chimney could be hazardous to your health and house. Read this to learn more.

One of our biggest problems occurs when a customer enters the shop and states “I have an existing woodstove into a masonry chimney - I’d like to replace the stove with a more modern one”.

In the old days, we thought this was a gravy job…these days I wonder if I should send them packing….why? because:

1. 90%+ or more of existing masonry wall-pass throughs are wrong

2. It is often difficult confirming or repairing these installations.

What to do? Most customers state “well, it’s worked for 10 years”. and look at us like we’re trying to take advantage of them by being concerned about their safety. However, I can assure the public that these “wall pass-throughs” are responsible for a LARGE percentage of house fires resulting from woodstoves. Let’s talk about the right ways and wrong ways to pass through a wall into an outside chimney. Most important - DO NOT ASSUME THAT YOUR WALL PASS-THRU IS OK - MOST ARE NOT.

The Problems:

1. Many masons and building inspectors are not aware of the current standards.

2. Most existing wall pass-throughs do not meet these standards.

3. It is difficult to inspect these installations, since the pass-through is often covered by the brick veneer on the inside of the fireplace.

Discussion of the solutions:

Most older chimneys use a “crock” , which is simply a piece of round terra cotta tile (similar to your chimney liner) which is cemented into the wall. The material that this crock is made from has little or no insulation value, which means the heat from the stovepipe is passed through to adjacent wall materials such as 2x4’s, paneling and the kraft paper on wall insulation. Our installation crew has found wood studs as close as 2” away from this crock - many times they are charred! The only reason that the wall didn’t catch...
Relining a Masonry Chimney

Introduction to the Basics

Chimney relining is often the best way to assure safety and proper performance with solid fuel (wood, coal, pellet) appliances. In fact, chimney lining has become almost mandatory in order to bring existing chimneys up to present codes.

Reasons for lining or relining your chimney include:

1. Properly sizing (by reducing) the chimney flue. Proper sizing assures better draft, less creosote and other advantages

2. Upgrading the safety quotient - having a liner inside your chimney assures that the fire will stay in a tightly sealed tube - and also transfer less heat through the wall of the chimney to nearby framing and combustible material.

3. Some older chimneys were built of brick with no liner - and some newer chimneys have cracked and deteriorated clay liners. Either of these pose safety hazards.

Rigid Stainless

There are three basic material types used in masonry chimney lining:

1. Stainless Steel rigid pipe - is often the best material to use when the chimney run is straight. Rigid pipe is quite a bit thicker than flex pipe and the smoother interior wall will help with draft and cut down on soot and creosote formation.

2. Stainless Steel Flexible pipe - is available in various grades and thicknesses and can make relining relatively easy since it is often pulled down in one piece. It is easy to snake around bends and can even be slightly flattened (ovalized) to fit through difficult spots like dampers, etc.

3. Cast in Place liners - are made of a cement slurry which is poured down the chimney around a round bladder - after the cement has hardened, the bladder is deflated and removed, leaving a round flue of your specified size. Another method uses a nose cone which is pulled up through the wet cement to form the flue passage. Cast in place liners can help strengthen older chimneys because the cement fills in gaps from the inside-out. One popular vendor of...
Installing an insulated HT chimney up through another floor is often the best way to run a chimney in a multi-story situation. This scenario might include the basement of a ranch house for a furnace or finished basement stove, or a first story of a typical colonial house. This straight up technique will result in better draft than a chimney which goes out and up (Tee installation) and also may cost less in materials for the DIYer.

As with any chimney installation, planning is the key. Study the layout of your house and the proposed location of the stove. It may be that there is a large closet or the unused corner of an upstairs room that the chimney can extend through.

The sketch in figure 2 shows a typical manufacturers drawing on how to accomplish such an installation. However, your real world layout may differ in some ways. There is a good chance that some of your floor joints, ceiling joists and rafters may not line up verticually, which might call for the use of 15 degree elbo offsets in the second floor or attic. Once again, careful planning BEFORE you cut too many holes is the key!

Tools needed - ideally a cut-saw (reciprocating saw), circular saw and drill - as well as common carpentry tools such as hammer, caulk gun, plumb bob, level and measuring tape.

The series of pictures below are courtesy of Hearth.com forum member Pagey, who was good enough to share them with all of us. The basic steps can be described as:

1. Make your Plan - measure, use a plumb bob to determine exactly where your holes will go and whether you will need 15 or 30 degree offsets in your insulated chimney. Also plan the setting of your stove and the chimney connector (the pipe from the stove to the ceiling) type and layoout. Chimney connector can also be offet using adjustable or fixed els.

2. Purchase all needed chimney and material. In the case of a straight up chimney, this would usually include...
Note: This article will guide you though the selection of materials and parts to complete a typical chimney lining job. With this information and your measurements, you should be able to price out the complete kit that will suit your particular installation.

Figuring out the cost can be overwhelming when deciding to reline your chimney with a stainless steel chimney liner. This step-by-step guide will help you determine what is included in a chimney liner kit and how to buy the right size. Getting educated about venting is important to vent your appliances safely and efficiently. Chimneys are made unique to each home. There are various applications and styles of stainless steel chimney liners that can be used to vent the appliance correctly. Choosing the least expensive option can cause various problems such as inadequate draft and smokiness entering your home. Look at all the options and choose the best option that suites your chimney. For more information on the benefits of using a chimney liner, please visit another article: Benefits of Chimney Liners

To begin, you will determine which size chimney liner is needed. Next, you will need to figure out which connection adapter and top plate are required. All of these factors determine how much your specific chimney liner kit will cost.

Chimney Liner

To determine the cost of the stainless steel chimney liner, you will first need to figure out the appropriate diameter and length of the liner. Round, corrugated chimney liners are the least expensive and, if at all possible, should be used. Round chimney liners draft better than rectangle and oval liners. Rectangle and oval liners have corners that can cool the flue and produce more creosote. Measuring the size of the exhaust hole of the appliance is a great place to determine the diameter of the chimney liner. Once the diameter is established, measuring the height of the chimney is the next step. Make sure to measure the entire length of the...
Hint #1 The plate does not fit it up at the damper area, but lower than that - about 2” above the fireplace opening…this has many advantages….

Materials needed
Sheet metal - 24 or 26 gauge galvanized metal is ideal for this application - available at many plumbing and heating supply houses
Masonry or cut nails - approx 1.5”
Silicone sealant
Furnace Cement

First, remove the fireplace damper. This usually involves removing a cotter pin and lifting the damper out. Store damper in a safe place in case you ever want to restore the fireplace to original.

Now, study the picture showing the side view of a fireplace (cutaway).
The plate which you are going to make is shown in red. The front edge of it will fit against the back of the steel lintel (#4 in diagram). For an example, we will use a level area approx. 2” higher than fireplace opening (#1 in diagram).

Now, you take only three measurements…as shown in the measuring diagram

#1 The front (at a level plane about 2” above fireplace opening)
#2 The rear (at same height approx.)
#3 The front to back in the center…..

Hint #2 - Take these measurements SHORT. In other words, if the actual measurement of the front is 36 3/4”, use 36” for your measurements.

Note: for this example, we will pretend that our “short” measurements are 36 along the front, 28 along the rear and 15 front to rear (back of angle iron lintel to read wall of fireplace) - AND we will be bringing a 6” pipe through it.

With these three measurements, the side angles will work out correctly. The key is this - Work from the center!
If your piece of sheet metal is square or rectangular, here are the steps.

1. Measure back 1” from the straight edge and draw a line.
2. Then measure from...
The various claims made by chimney sweeps, cap manufacturers and fireplace retailers can often confuse the issue. In this article we'll take an in-depth look at the different types of chimney caps and answer this burning question once and for all.

Metal Chimneys
Vacu-Stak: http://www.chimneycaps.com/

Please check with the manufacturers and your chimney professional to determine if these devices will work on your metal chimney.

If you don't have draft problems and just need a replacement cap, first try to find the same brand as the existing termination. If that fails, you can often use a cap from a similar brand, but make certain you confirm this with the store where you are purchasing. Another option is a "generic" metal chimney termination such as the WeatherShield at:

Note: Some metal chimneys are "air cooled" by venting that is on the top. If your chimney is of this type, be certain not to close off the venting slots on the top. A HOUSE FIRE COULD RESULT FROM CLOSING THESE VENTILATION SLOTS!
Special caps are available for these chimneys to assure proper cooling. Check the WeatherShield link above for information about a model (WSA TDW) with this feature.

Masonry Chimneys and Fireplaces

There are advantages and disadvantages of capping a masonry chimney or fireplace. Let's list negative and positive points and then we'll discuss the different models that are available.

Possible Disadvantages:
1. Draft Restriction - An improperly designed or installed chimney cap can possibly reduce the draft of a chimney.
2. Clogging of Screen in Cap - Some chimney caps have small screening which can become clogged with soot and creosote after heavy use. This will cause draft reductions and poor performance of your stove/fireplace.
3. Discoloration of chimney exterior - In some cases, creosote and tar can collect on the chimney cap and then run down the outside of the chimney...
Chimneys and fireplaces come in all different shapes and sizes. Following is a short discussion of varied flue and fireplace sizes and the things to keep in mind before venting your stove or fireplace. This article relates mostly to fireplaces and stoves that burn wood or coal as a fuel.

First, let's talk about chimney sizes. Chimneys can be broken down into two main categories; metal and masonry. Metal chimneys, also called prefab, class A and Double or triple wall are usually found in three diameters as show below. Larger diameters which may apply to prefab fireplaces. round flue tiles or single wall stainless chimney liner are also shown. Each diameter has a specific useable area, which is also called it's cross section. The capacity of a chimney to remove smoke and/or BTU's from an appliance is directly related to this area.

*only rare older stoves use 10" chimneys

One thing that we notice from this table is that a 6" flue is almost 1/2 the size of an 8" flue. The natural tendency might be to think that a 6" flue is "only" two inches smaller that an 8" one, but in truth you can see the difference is much larger.

This space for rent - contact webinfo@hearth.com


Effective Area
Since smoke rises in a circular fashion, only a certain area of a square flue tile is really being put to effective use. The listings in the table above refer to the usable area.

Venting a Freestanding Stove

In general, your should use the same size chimney diameter as the flue collar on your stove, i.e. a 6" stove should use a 6" chimney or a 7 1/2 X 7 1/2 flue tile. In most cases, you can also step up a size or two..for instance, a 6" stove could vent into an 8" insulated chimney. If your flue is over 3 times the size of your stove outlet ( i.e. a 6" stove into a 13 X 13 Flue tile), then you may have problems with excess cooling of the smoke, resulting in poor draft...
Chimneys—An unexact science !

Did You Know that a adequate chimney is actually more important for successful wood burning than a good stove or fireplace? In other words it would be better to have a good chimney and a poor stove than the opposite.

As the title implies, chimneys are an unexact science. The intent of this paper is to educate you so you can make the proper decisions concerning your wood burning systems. Problems with chimneys -If a stove smokes into the room , an inadequate chimney is the most likely cause. Creosote problems can often be lessened by good chimneys. Low heating efficiencies can also often be traced to poor chimney draft—In short, 90% of all wood burning problems (in our experience) can be traced to draft and chimneys.

Fundamentals- The function of a chimney is two-fold, first to carry the undesirable products of combustion (smoke) out of the home : secondly to supply the draft (pressure) to feed air to the fire. The draft of a chimney comes from the tendency of hot air to rise . This flow up the chimney is determined by many factors such as :
1. Chimney Height
2. Chimney Diameter
3. Chimney Location
4. Bends in the Chimney
5. Construction of Chimney
6. Tightness of House

Reversing Chimneys - a common problem Wind Related Downdrafts

By following some of the guidelines given in this paper you can learn which type of chimney to build or how to upgrade your present chimney to a higher standard.

Chimney Height- The taller the better ! A taller chimney will have more draft than a shorter chimney (all other things being equal). Its relatively easy to decrease the draft in a chimney which is too strong, but improving the draft on a short chimney can be more difficult.

Chimney Diameter- Chimney diameter also has an effect on the draft of your chimney. In this case, however, having a chimney that is too wide (as compared to the outlet on the stove) can be a problem since it allows the smoke to...