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Size Of Flue Needed For 30 Fireplace Chimney Liner Calculator Selection




This can cause smoke to pour out of the stove and it can also cause gas and oil appliances to fail. Two general requirements of the 211 standard are that chimneys be at least 3 feet (90 centimeters) taller than the highest point where it goes through the roof of a single structure and 2 feet (60 centimeters) taller than any portion of the building or any adjacent building within 10 feet (3 meters) of the chimney.

Masonry chimneys are usually required to have walls at least 4-inches (10-centimeters) thick. For appliances, the flue starts no less than 8 inches below where the appliance hooks into the flue.
Flue liners need to line up flush at the joints to form a smooth interior surface with no ledges or other obstructions where creosote and debris can accumulate.

The flue liner must be allowed to freely expand and contract and not be bonded to the surrounding masonry.
A chimney may contain more than one flue. If a flue must be angled or offset, the angle can be no more than 30 degrees from vertical. Popular outdoor options include man-made stone or sliced natural stone. Execute this 3 seconds after onload.
The chimney diameter should never be less than the diameter on the appliance flue outlet. In many cases, 8” x 12” flue tiles were used by the mason constructing the fireplace instead of 13” x 13” flue tiles which are now the minimum size required by building codes.

Generally the smoke does not move quickly up the flue in a straight line, but moves up in a turbulent/rolling manor very slowly. Fireplaces that have this problem have smoke stains above the fireplace opening from the smoke escaping at the top edge of the fireplace opening.

Many drafting problems can be solved with very reasonable expense. Additionally, the fact that furnaces and stoves of 2011 require a more capable chimney to support them makes unimproved, older chimneys more or less obsolete.

If used for gas, modern appliances have such low-temperature flue gasses that they produce huge amounts of condensation. This ruins wall paper in the house, and the freeze-thaw cycles in the winter slowly demolish the masonry chimney.
If you try that you’ll end up with a very tall chimney outside the building and providing stability will be difficult if not impossible.

That will keep the venting system mostly inside the building where it will stay reasonably warm and will provide the most stable, least ugly chimney installation.

Is ther anything short of actually buying a new furnace?

Canada they are banned outright because of the hazard they represent. Arguably the best installation option is installing a stainless steel liner from the top of the stove to the top of the chimney.  The best installation option is the installation a stainless steel liner from the top of the stove to the top of the chimney. 

This method provides the most efficiency and is the easiest to sweep and inspect.   This new chimney liner when sized correctly for the wood stove or insert is less likely to be a problem. Confirm factory-built chimney termination height using the manufacturer’s installation instructions.
A cricket is not required if the chimney intersects the roof ridge line. Provide a caulked bond break between the cap and flue liners.
Smoke has to push the heavy, cold air up and out of the chimney. If the problem is just in the opening and firebox, the repairs can be made by reconstructing the fireplace from inside the house.


Masons install the throat and flue for the Rumford fireplace in the Lifespan House.Indoor Conventional Fireplace – Size Of Flue Needed For 30 Masonry Fireplace


For fireplaces, the flue is constructed directly over the fireplace. For appliances, the flue starts no less than 8 inches below where the appliance hooks into the flue.
Flue liners are installed by neatly embedding one on top of the other in non-water soluble refractory mortar using a 1/16 to 1/8 inch mortar joint.

Flue liners need to line up flush at the joints to form a smooth interior surface with no ledges or other obstructions where creosote and debris can accumulate.

When constructing the chimney around the flue liner, an air space must be maintained between the chimney wall and the flue liner of not more than the thickness of the flue liner wall.

A chimney may contain more than one flue. If a flue must be angled or offset, the angle can be no more than 30 degrees from vertical. When required, flue liners may be cut with a masonry saw.
Appliances are attached to a chimney by way of a metal or clay thimble that is inserted into an appropriate sized hole into the side of the chimney flue.

The connection thimble is inserted so that it is flush with the inside flue liner surface and does not protrude into the flue.
Alternatively, the thimble may also butt flush against the outside of the flue. The joint between the flue and thimble must be attached using refractory mortar. All masonry chimneys must be terminated with a cap that is 2 inches thick (minimum), extending 1½ inches away from the chimney wall with a drip edge.

The cap must be separated from the flue by a bond break and sealed with a resilient sealant. Oil based sealants do not hold up well. The termination of the flue liner should not extend above the cap by more that 4 inches. The finished height of a chimney needs to be 3 feet above the highest point of the structure or 2 feet above any part of the structure within 10 feet of the chimney.

Masonry chimneys constructed in seismic areas require special reinforcement and alternate construction techniques. Please refer to local building code requirements for applicable seismic requirements for masonry construction. Please note that special rules apply to woodwork around fireplace openings (i.e. The flue liner required must have a minimum of 108 square inch cross-section. Check with your certified professional.  The excess air, usually below room temperature, may be forced into the room containing the fireplace. The maximum projection for an individual unit should not exceed either one-half (1/2) the height of the unit, or one-third (1/3) the bed depth.

Figure 4 shows a plan view of an air passageway and ashpit. The ashpit cleanout door should be metal and fit tightly to reduce air infiltration.
This is required since this forming is inaccessible for removal and is thus a permanent part of the fireplace. The blackouts that form the opening in the slab for the ash drop and air inlet should be set so that they extend approximately 1 in.

This will facilitate removal of the forms. This reinforcement is also beneficial in resisting the stresses induced by the high temperatures the slab will be subjected to. Similar results may be obtained by eliminating the concrete slab and supporting the hearth on masonry.

Chimney Liner Size Calculator and Selection Guide

The ash dump and air passageway are formed by the judicious use of corbeling.
The mortar joints need be only thick enough to provide for dimensional irregularities in the unit being laid.
The wall behind the firebrick at the rear of the firebox should be at least 8 in. A greater thickness may be required to support higher chimneys.
All lintels used in the fireplace should bear on the brick masonry at least 4 in. The damper should not be embedded in mortar, but merely seated on the thin setting bed.
This material provides space for thermal expansion and movement of the damper during fireplace operation.
The usual limitations for corbeling walls are not applicable in this area of the fireplace since the corbels are continuously laterally supported by adjacent masonry.

While small deviations from the dimensions and proportions given may have little or no effect on performance, larger magnitude changes should be carefully considered since they may have serious negative effects on the function of the fireplace.

Does a chimney flue have to have a bend in it? What should be the average cost to build a full brick chimney? Does predominant wind direction make a difference in fireplace location? Wherever the chimney crosses a wall, install metal flashing sealed with waterproof silicone caulk to keep water from leaking into the house around the chimney.

This is mostly determined by what appliance(s) the chimney is built to vent. Each type has different diameter requirements depending on what they are venting. If you are not building on an existing fireplace or base, you may need to pour a reinforced concrete pad for the chimney to be built upon.

The flue connects the top of the smoke chamber to the roof through the middle of the chimney. It should extend past the chimney wall by at least 2 inches (5 centimeters) and have a drip edge to channel water away from the chimney.

The term “make-up” air is normally used since it describes the volume of air that must be made up inside the building to replace the air passing up the chimney.

If the building has internal fans that exhaust air from the house, the problem is made worse. Changes in the air-tightness of a house may cause a drafting problem with the fireplace. Therefore, choose a window or door opening on the windward side of the house. If the problem is solved by opening a door or window, a fresh air intake needs to be installed in the back wall of the fireplace to allow adequate air for the fireplace on a regular basis.

If the temperature outside is relatively warm or the air is damp and “heavy”, the fireplace will not draw as well as with colder temperatures.

This technique can be used essentially with all trial and error procedures and the draft strength can be determined as these different procedures are tried.

This fact is correct since hot air rises and the more hot air that is contained within the chimney the stronger the draft. The additional height added to the chimney is proportional to the increase in draft. On the other hand, the same 2 feet added to a chimney that is 30 feet high is only 7%. If extremely cold temperatures are present, the temporary metal extension should be insulated. If the temporary extension seems to solve the problem, the chimney can be permanently increased in height at a later date.
If a chimney is located with a large portion of the flue area surrounded by cold air, the draft of the chimney is reduced because of the cold chimney.

Properly installed insulated stainless steel lining systems usually always increase the draft of the fireplace. At least 1” of insulation needs to surround the stainless steel liner tube.
Another procedure that can be used while using this procedure is to also block off the bottom of the fireplace opening by installing bricks across the opening.

If the fireplace is too deep as referenced in the attached chart, simply construct a new back wall of the firebox by dry stacking refractory brick to test the effect of reducing the firebox depth.

This dryer wood produces less smoke than wet wood. It is also a good idea to keep the glass doors tightly against one another when they are fully opened. This “miniature chimney” will allow smoke to be drawn from the fireplace to escape into the room.
You can also see smoke or have smoke smell at the ground level at the base of the chimney if this is the problem.

Some trees grow very quickly and can therefore create a new problem as the new growth interferes with the draft.
A licensed electrician is needed to run power through a rheostat switch (usually located near the fireplace) to the fan on top of the chimney.

This problem is brought about by the smoke either transferring at the top of the flue tiles or internally. If the primary fireplace is used and the problem doesn’t reappear with the use of several fires, the problem is with smoke transferring at the top.

If closing off the secondary flue at the top does not solve the smoke transfer problem, the problem is an internal smoke transfer problem.

If the liner diameter is too large, the fireplace or heating appliance will lose its efficiency and must of your heat will go up and out of the chimney.

In most states, insulating your chimney liner is required by code.
Keeping the chimney warm will greatly enhance its draft ability.
Inuslated chimneys greatly reduce condensation, which ages metal chimneys and must be drained.
A warm, less condensing chimney would create less creosote built-up and/or corrosive material build-up. Figure 1001.1, which shows examples of typical construction.
This table does not cover all requirements, nor does it cover all aspects of the indicated requirements. The total minimum thickness of front, back and side walls shall be 8 inches (203 mm) of solid masonry. The inside surface of the smoke chamber shall not be inclined more than 45 degrees ( 0.79 rad) from vertical when prefabricated smoke chamber linings are used or when the smoke chamber walls are rolled or sloped rather than corbeled.

Where the fireplace opening is 6 square feet ( 0.6 m2) or larger, the hearth extension shall extend at least 20 inches (508 mm) in front of and at least 12 inches (305 mm) beyond each side of the fireplace opening.

Two such ties shall be installed at each bend in the vertical bars. Straps shall be hooked around the outer bars and extend 6 inches (152 mm) beyond the bend. The projection of a single course shall not exceed one-half the unit height or one-third of the unit bed depth, whichever is less. Where the chimney offset is supported by masonry below the offset in an approved manner, the maximum offset limitations shall not apply.

Construction of masonry chimneys as part of the masonry walls or reinforced concrete walls of the building shall be permitted.
The net free area of the arrestor shall not be less than four times the net free area of the outlet of the chimney flue it serves.

The arrestor screen shall have heat and corrosion resistance equivalent to 19-gage galvanized steel or 24-gage stainless steel. Openings shall not permit the passage of spheres having a diameter greater than 1/2 inch (13 mm) nor block the passage of spheres having a diameter less than 3/8 inch (10 mm).

The spark arrestor shall be accessible for cleaning and the screen or chimney cap shall be removable to allow for cleaning of the chimney flue.

Residential-type appliances (general).
Factory-built chimneys or chimney units listed for installation within masonry chimneys. Flue linings for specific appliances.
Pellet vents listed for installation within masonry chimneys. Section 1003.11.1, the chimney shall be plainly and permanently identified by a label attached to a wall, ceiling or other conspicuous location adjacent to where the connector enters the chimney.

Only enough mortar shall be placed to make the joint and hold the liners in position. The masonry wythes shall be at least 4 inches (102 mm) thick and bonded into the walls of the chimney. Square chimney flues shall have a minimum net cross-sectional area of 1/10 of the fireplace opening. Rectangular chimney flues with an aspect ratio of 2 to 1 or more shall have a minimum net cross-sectional area of 1/8 of the fireplace opening.

The height of the chimney shall be measured from the firebox floor to the top of the chimney flue. Cleanout openings shall be provided within 6 inches (152 mm) of the base of each flue within every masonry chimney. The height of the opening shall be at least 6 inches (152 mm). Chimneys located entirely outside the exterior walls of the building, including chimneys that pass through the soffit or cornice, shall have a minimum air space clearance of 1 inch (25 mm).

The intersection of the cricket and the chimney shall be flashed and counterflashed in the same manner as normal roof-chimney intersections. A quick and easy test is to take a piece of aluminum foil, pull out enough to span the width of your fireplace, fold it to a 4” high x however wide your fireplace is, and tape it up to the opening of your fireplace.

In other cases your chimney just isn’t high enough. I have an oval opening on my wood stove. Pro is preferred by professional installers and is our top selling pellet vent pipe. You can always increase a 3″ pellet stove for use with a 4″ system but you should never reduce the size. You are not required to install a cleanout opening if a masonry fireplace can be cleaned through the fireplace opening.
Structural loads include roof and floor framing and attachments such as antennas.
Vertical reinforcing usually consists of four number 4 reinforcing bars. Anchor chimneys to the building if any part of the chimney is outside of building’s exterior walls.3. Viewer experience will not be affected by the lack of data // if the video is not actively playing.
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Transportation, more than 47, 000 bridges around the nation are in poor condition. There is no rise to the coal boiler’s stove pipe, it enters straight into the chimney and runs slightly down hill. Do you think this alternate piping might make an improvement?

At the start of the article above we give some help choosing which tables to use to answer chimney questions.
Your chimney cross section area is 8 x 13″ = 104 sq.in. Adding about outdoor chimney temperatures vs. Assuming that the connection can be made safely between the different chimney diameters and materials, and that the above-roof height is just a few feet, that may be ok.

Be sure to obtain the latest edition.
Each chimney or stack is a unique structure, subject to both aggressive operating and natural environments, and degradation over time. Sample inspection report specifications, sample field inspection data forms, and an example of a developed plan of a concrete chimney are included in the guidelines.

The unscientific definition of that is that the ignition temperature of wood gets lower over time. Old oil furnaces may have released sulfuric acid in the chimney for years and worn the chimney out from the inside. Be sure to have this checked, and especially if you or your family have a lot of colds or headaches because this could very well be carbon monoxide poisoning.

With regards to that debris in the chimney, many older homes are “finer homes” that are surround by trees or perhaps in a semi-rural setting with lots of animals and leaves.

My problem, there are a couple of sections that are about 4 courses of brick where it appears to be shifting out at the corner or edges of the fireplace.

My suggestion is to get at least two quotes, three if you feel you still need it after the second. A decent job is more important than the last dollar, and generally does cost more than the hack job. You can’t use made-up information or stuff “you heard” to build a business with. Instead lay off the bull and get out and do some hard work. I have a oil furnace and a woodstove vented into it and both work fine. The chimney sweeps around here shrug thier shoulders and help me clean it every year. We aren’t dumb someone you think because you have a business you have an education?

Apparently you had an encounter with a chimney guy that didn’t go well. They’ve just forked over money to presumably make them safer and they want to know what the sweep has to say about their systems.

Most folks understand that a chimney man makes his living fixing chimneys so are not surprised if he proposes some repair or improvement. They listen to what the sweep has to say and evaluate it against a battery of things, such as trust, budget and money.

Secondly, about whether or not a chimney should be lined. Appliances are engineered to work best with specified venting systems. and modern appliances, either wood stoves or gas/oil furnaces/boilers, are all much more efficient than they were many years ago. These appliances all put vastly more stress on chimney than in the past. What they think should matter to us, whether we like it or not. In our litigious society and it would be foolhardy for a professional sweep to sanction an unlined chimney. It sounds like your chimney has been working for 90 years, and that’s great. They don’t last forever and they do require some maintenance. Cracks and loose bricks are expected after 90 years, yes. That is absolutely against most written codes or standard (including in our area), and for good reason. I over reacted because the tone of the original article, intended to be helpful and properly authoritative came across as forceful and condescending. Emphasizing each word lays down a particular emphasis. You say the same information in both methods but the first method that you used makes it sound like you are the nations expert and everyone ought to listen to you.

The only other option is to continue the building more chimney below where it already rests in the basement floor. Or get rich and buy an instant flash hot water heater and do a direct vent out the side of the house. It’s not like there will be ash or creosote building up in there. The gasses just float around in there. So do you agree, a four walled chimney can be safe and might not need to be torn down just because it is against the house.

That part of the article really stuck me. Gas exhaust in a large flue often (always?) condenses and leaves the inside of the flue wet, at the very least. But all that black tar left in the flue is flammable, so you get a fire hazard to boot. The chimney physics are the same though, so it’s always appropriate to have the flue properly sized to the appliance regardless of the fuel being used.

When you line a chimney, especially an outside one, be sure to have it insulated. While that’s less important for and inside chimney, there are no liner manufacturers of listed chimney liners that do not require insulation for liners venting wood.

and it’s just a really smart idea for gas (and oil, but especially gas) flues because it’ll reduce condensation and/or spillage a great deal.

Is the brick structure sound?

My chimney does need to be replaced, it never had a chimney cap and has used coal heat, wood heat, gas heat and back to wood over 84 years.

My chimney has been tuck pointed several times in places many times before the cap and liner were installed, but now the mortar has so deteriorated bricks are falling out in some places.

One gave the option of applying mud, lathing, and two more coats of mud. You are right about the bricks being better in older homes, as well. Every workman has a different perspective on the problem and project. He did not suggest using the old brick which meant more expense and difficulty matching brick. You may or may not save much money because there could be considerable labor in cleaning it up enough to use. and if you’re caught in the middle with not having enough good ones to do that, the trick is to rob some bricks from a less visible place and replace those with your new bricks.

My chimney runs on the exterior of my house(if that makes a difference).
You need to make sure you have the proper size metal chimney there. For example, if it’s for a fireplace it will need a larger flue than a gas furnace. You might also consider lining the chimney down to the appliance (i.e. I need to worry about asbestos in the mortar or bricks?

Also, it looks like part of the brick is inside the wall in the house. Just raising the chimney is not likely to work. A theoretical alternative is to ‘trick’ the chimney into thinking it is inside the house and at the same time raise it to be taller than the house.

But your chimney is air-cooled, which means it will be cooling itself, whether you have a fire on or not. The only benefit of an air cooled chimney is that it is cheap. Filling the house with smoke in the middle of the night is just totally unacceptable, not to mention hazardous. The chimney has been rebuilt by a previous owner above the roofline once before. We have installed glass doors on the main floor fireplace to prevent smoke from escaping into the room. I am planning to have the chimney replaced above the roofline with matching bricks, new crown, rain cap and install a stainless steel chimney liner for the furnace.

I was wondering what we could do to make the fireplaces more functional?

Is it feasible to expect that we not need the glass doors, as they do not allow the heat to escape? By all means, install a liner for the gas furnace. The actual frequency and severity of cold backdrafts in any given system depends on a lot of factors, but the taller the system and the colder the weather, the stronger the backdraft and the harder it will be to correct.

I would investigate re-installing the system inside the house. On the other hand, if this is a cheap factory-built fireplace, then its poor performance wouldn’t likely justify the expense, even if it worked to its potential.

Taller chimneys make more draft, but chimneys exposed to outside cold don’t. The hearth/grate is 80 x 50 x 50 cm. Is there an equation to calculate height and size of flue needed?

It looks like you’ll need at least 2 metres of chimney projecting from the roof. The draft hoods on the gas appliances bleed off draft to the point where you could hardly get the stove to run at all, and it would smoke like crazy if you opened the door.

Wood stoves are space heaters and so should be installed in the space to be heated, not hidden away someplace in the basement.
If you value your house and your family’s safety, save up your money and buy a proper solid pack insulated metal chimney.

I don’t want to put in a shiny new chimney that’s inappropriate for the present stove or a later stove acquisition. I suspect that if the size difference is too great, one eventually gets into trouble of a different kind.
That much more important not to close doors on myself.
 Also if clay liners have a tested operating temperature.
 There is no performance test for clay liners.  They tend to fail because of thermal shock caused by rapid temperature changes like those that happen during a chimney fire.
It had plenty of draft and is covered at the top with a chimney cap.
I want to know what the lifespan would be for an outside the house woodburning chimney made of block and tile as opposed to insulated stainless pipe.

The life span of a masonry chimney depends a lot on how it is used and maintained.  A severe chimney fire can blow the tile liner instantly and a failure to maintain the cap or crown every year or two can allow water in.

If you live in an area with freezing temperatures, this can lead to rapid deterioration.  Well built and maintained, a masonry chimney can last a long time. On balance, of all the chimneys that are acceptable under building codes, a concrete block chimney is the worst.  The fact that you intend to put it outside, which we strongly discourage, makes it a truly lousy option.
Metal chimneys are well proven and most have parts warranties. Massachusetts is entirely heated by wood.  We do normally burn with the choke pretty tight, so it’s not very hot in the chimney. I am surprised that such a young house would need that kind of repair. Masonry chimneys can fail in as little as three years, depending on how they are used. Choking down woodburning equipment is the main way to destroy chimneys, both by being the main cause of chimney fires, and also by permitting water condensation in the chimney, which is really destructive.

You should try to avoid smoldering fires because of the damage they do to your system and to the environment.  Chimney liners (not inserts) surround the flues.
In answer to your question, yes, you can connect a wood stove to the other flue, provided it meets code requirements.  You really need some local assistance to make sure the connection would be effective and safe.  Chimney sweeps are good at checking out existing chimneys.
 We have been awakened in the middle of the night to the heavy smell of creosote.  My husband has cleaned the flue and replaced the pipe from the stove to the flue.  We have had the stove for 3 years now and this is the first time we have had this problem.  It sounds like you are suffering a cold backdraft, normally linked to installations in which the stove is installed low in the house and the chimney runs up the outside wall.

If someone in your household likes to sleep with their bedroom window open a little for fresh air, this may be the problem.  Any leaks high in the house will make a cold backdraft more likely and more powerful. The air space around chimneys must be maintained or they will overheat. How tall is your house and chimney?

The really bad thing about outside chimneys is that the remedial measures are either ineffective or unappealing or expensive or all three, which is why we tend to be strident about not installing chimneys outside in the first place.

When it first happened last spring, we thought it was possibly because of a pressure inversion.  This winter, however, we seem to have a smoky house any time there is a wind.  Our chimney is straight, inside in a one story addition to a one and one half story house.  We clean the chimney frequently (approximately 5 or 6 times/winter).  Do you have any diagnosis for the problem, where we can get help, and how we can fix it?

We didn’t have this problem the first winter we were here.
 This may not be the main cause, but it weakens the chimneys ability to flow air and gas up under all conditions.
 If spillage happens when wind blows from the single storey side, you need to look for leaks on the downwind side of the house on the two storey side, especially high level leaks like open second floor bedroom windows or a leaky attic hatch.

Smoldering fires are a key cause of this type of failure.  The wood should be flaming until it is reduced to charcoal.
 Raising the chimney might help to get the top of it up out of a zone of positive pressure caused by a wind effect.

Check first with local chimney sweeps or long-time stove and fireplace retailers.
 We are working on a project where there are two existing fireplaces, roughly 75-80 years old.  The owner would like the fireplaces restored.  Can stainless steel liners be used on wood burning fireplaces?

In this case the liner is sized to the insert, not to the fireplace, and the connections can be secure and permanent.  This is the only environmentally responsible solution, in our opinion.
 This insulating cementatious material greatly improves the structural integrity of the chimney and improves performance by insulating it.
 One vents the heating system and air conditioning; that one is in the living room.  I would like to add a fireplace in the living room.

Masonry Fireplace Inspection





Category: General Masonry, Brick Walls, Chimney, Masonry Fireplace, Masonry Repair
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