Height & Clearance Requirements for Chimneys
     

Chimney height & horizontal clearance specifications: this article describes the height requirements for chimneys, including rooftop clearances and overall chimney height necessary for proper chimney draft and function and for fire safety. We describe what can go wrong with chimneys that are not built to proper height or with proper clearances from other building features, including improper or unsafe heating appliance or fireplace or woodstove operation, odors, soot, draft issues, etc. These articles on chimneys and chimney safety provide detailed suggestions describing how to perform a thorough visual inspection of chimneys as well as chimney construction & repair methods. A variation on a "too short" metal or masonry chimney is a chimney that may look tall-enough to some folks but which lacks adequate clearance from a nearby roof slope, as we illustrate and explain in the text below.

Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.

Outdoor Chimney Height & Clearance Requirements

Chimney to Roof Clearance: from the ground you can guess and from on-roof access you can measure to determine if a chimney is simply too short for fire safety and code compliance. The length of a horizontal line drawn from the top of the opening of the chimney flue to the point at which that line touches the roof surface should be ten feet or more (the blue line in our photo). In our photo, our measuring tape is pulled to about 4 1/2 Ft. And the height of the chimney above the roof surface should be at least three feet - the green line in our photo. (This is a bit of an odd measurement and chimney clearance case because the chimney side is actually about 8" away from the roof edge. But the chimney-to-roof clearance rules still apply.) This measuring tape location shown in this photo is slightly incorrect (I didn't want to lose my tape down the flue while taking the picture). Measure from the edge of the chimney flue closest to the roof, horizontally, until you touch the roof surface to check the ten-foot clearance rule distance. That's the light blue line in our photo.

Check the chimney top for damaged masonry (or rusted metal), a missing cap, damaged, cracked, or missing top seal or crown on the top of a masonry flue, and here, an important discovery (at least in some jurisdictions) is whether or not the chimney is single wythe or thicker masonry and whether or not the chimney has (or perhaps needs) a chimney liner.

Chimneys Too Short - What is "too short" and What Problems Occur?

A chimney that is too short is unlikely to vent properly and it may also be a serious fire hazard to the building, risking setting the roof on fire. The photo at above left is a too-short masonry chimney (with no cap and other worries). A horizontal line (blue in our photo) drawn from the chimney top to where it would touch the roof surface was just about one foot instead of the required ten feet OR two feet above the ridge.

A "Hidden" "too-short" Chimney Specification: Distance Above the Flue Collar - can lead to inadequate draft

NFPA-211 1-8.2 specifies that

Natural draft chimneys and vents shall not terminate at an elevation less than 5 ft (1.53m) above the flue collar or the highest connected draft hood outlet.

Inspecting from outdoors you may not be sure if a chimney violates this rule or not - you'll also need to look inside at the heating equipment and at the building structure, ceiling height distances etc. to make an actual measurement.

Too-Short Heating Flue Can Mean Sooty Oil Burners and Puffbacks or Dangerous CO Poisoning Hazards

This height requirement is to assure that the chimney will develop adequate draft. A "too short" chimney in this case won't have a tall-enough column of rising hot gases inside to develop a safe, adequate draft. Our photograph below shows a "too short" chimney through a flat roof on a one-story home. This too-short chimney is more than a fire hazard. It can mean that heating equipment venting into the chimney won't work properly, is unsafe, or is "forced" to work by settings that waste your heating money. The vertical distance from the top of this chimney to the top of the oil fired heating boiler it serves is less than six feet. Our vertical red line shows that we measured about 24" of chimney above the flat roof. This seems to meet the "two foot chimney rule" but it fails the three-foot rule and also the whole chimney height was just too short to produce adequate draft. The oil fired boiler has blown soot into the utility room and garage throughout its' life, a constant source of annoyance that probably stems from inadequate total draft even when the oil burner, boiler, and chimney flue are up to full operating temperature. Because a short chimney can mean bad draft and sooty oil burner operation, also see OIL BURNERS and OIL BURNER NOISE SMOKE ODORS. The draft regulator on this installation was removed by an earlier service tech in an effort to improve draft in the flue. But even that step was not enough, and of course now the oil burner can never be properly tuned.

In response to owner pleas that no one had been able to fix this trouble, an oil company's service technician who worked on this flue in 2010 "solved" the long standing oil burner soot problem by setting the draft up as high as he could at the oil burner. That slowed but did not stop the sooting problem, and for sure it increased the heating cost for this building. Stack temperature was 600 degF (photo at left) - minus room temperature, making it about 530 - a bit high. We could have addressed this short chimney with a draft inducer fan, but a taller flue would be smart anyway, to get the chimney top higher than the roof surface. We discuss examples of extending chimney height to improve draft, performance, and fire safety separately at Chimney Height Extensions. We discuss draft inducer or "draft boosting" fans for heating systems (and maybe for some fireplaces) in detail at Draft Inducer Fans. Just how short is "too short" - we discuss chimney height and roof clearance requirements beginning below.

Carbon Monoxide Poisoning Hazards from Too-Short Chimneys

Particularly with gas fired appliances, the lack of adequate draft for any reason, including a chimney flue that is too short, can result in improper combustion and the production of dangerous, potentially fatal carbon monoxide gases. And the same inadequate draft that affects combustion in the heater can increase the risk that the gas backdrafts out into the buildings.

NFPA 211 1.7.1 specifies:

... A chimney or vent shall be designed and constructed to develop a flow sufficient to completely remove all flue or vent gases to the outside atmosphere. The venting system shall satisfy the draft requirements of the connected appliance(s) in accordance with the equipment manufacturer's instructions or the chapter on Chimney, Gas Vent, and Fireplace Systems of the Equipment Volume of the ASHRAE Handbook.

Draft-Fixes for "Too Short" Chimneys

An obvious fix for a chimney that is too short to meet the fire safety clearances mentioned earlier is that must be extended above the roof for fire safety.

But in some installations, such as a heating appliance installed in a one story low ceiling structure, the chimney may meet the fire clearance specifications (NFPA 211 1-8: Termination Heights) but it not be tall enough to develop adequate draft (NFPA 211 1-7). In this case it is permitted (NFPA 211 1-7-2.) to use a draft inducer fan ("a mechanical draft system of either forced or induced draft design") to meet the draft requirements.

Watch out: if you use a draft inducer system the installation must assure that the heating appliance won't run if the draft inducer is not running. Most if not all modern mechanical draft or draft inducer systems include this safety feature as do direct-vent or side-wall vented appliances that use no chimney at all (another solution to some chimney problems). Also see COMBUSTION AIR for TIGHT buildings.

Bachrach, Field, & Tjernlund are examples of companies providing draft inducing or mechanical draft boosting equipment and direct-venting equipment that skips use of a chimney altogether. [14[15[16]

Required Chimney Height Above Roof Surfaces or Ridges

Roof Clearances for Chimneys 10 Ft. or more distant from the Ridge

Roof Clearances for Chimneys Less than 10 Ft. (3.1m) from the Ridge

The photo at above right is a too-short metal chimney that is less than two feet above the ridge. This chimney fails both the ten-foot rule (the blue line) and the two foot rule (the red line). A horizontal line drawn from the chimney top just touches the roof ridge.

For chimneys that are LESS than 10 feet from the roof ridge (measured at the up-roof side of the chimney)

We edited the short chimney photo to extend it up to meet the following roof clearance requirements (see edited photo at left):

- The top of the chimney should be at least 2 Ft (0.61m) above the ridge (the vertical red line at the left of our photo)

and

- The top of the chimney should be at least 3 Ft (0.92 m) above the roof surface. (This specification makes sure steep roof slopes are cleared.) For gas vents or a type L vent this distance must be at least 2 Ft (0.61m). (Vertical blue line along the left side of the chimney in our photo).

Watch out: We also notice that the chimney cap is discolored on this metal flue - possibly indicating an overheated appliance or other unsafe condition. Did you also notice that the sides of the chimney flashing are on top of rather than under the roof shingles?

Where to Make Measurements When Checking Chimney Clearances

Another question that has come up is "do we have to measure from the chimney cap or from the (lower) opening at the top of the flue? In specifying clearances the NFPA 211 refers to the "Highest Point" of the chimney.

Our reading of the NFPA and codes is that

• Vertical chimney to roof measurements are made from the top of the chimney flue opening, not the top of the chimney cap - reasoning that it is from the flue opening that an ash or spark might exit the chimney, making that the point of concern. Otherwise we could end up with an unsafe (too short) clearance of a low chimney on which someone stood a ridiculously tall "cap".
• Horizontal chimney clearance distance measurements are made between the building surface (roof or nearby wall or other nearby roof surface) and the nearest facing surface of the chimney side.

Roof Clearances for Wood Burning Fireplaces

Clearance specifications between Adjacent Metal Chimneys

B-Vent Rooftop Clearance Specifications for Gas Fired Appliances & Heaters

ROOF PITCH -  rise/run in inches
MINIMUM HEIGHT*
Flat to 7/12   - 1.0 foot above the roof surface
7/12 to 8/12   - 1.5 feet above the roof surface
8/12 to 9/12   - 2.0 feet above the roof surface
9/12 to 10/12  - 2.5 feet above the roof surface
10/12 to 11/12 - 3.25 feet above the roof surface
11/12 to 12/12 - 4.0 feet above the roof surface
*  Continues to 21/12 pitch at 8.0 feet

More Reading

• CHIMNEY HEIGHT for Types L & Type B Vents - separate article
• CHIMNEY HEIGHT EXTENSIONS - separate article
• FIRE CLEARANCE for MASONRY Chimneys - separate article
• FIRE CLEARANCE for Metal Chimneys - separate article
• FIRE CLEARANCES, Single-Wall Metal Flues - separate article
• Also see Chimney Height Extensions
• US CPSC warnings at CHIMNEY CLEARANCE & CONDITION SAFETY.
• Additional chimney clearance and safety information is at
  CREOSOTE FIRE HAZARDS
  Fire Clearances for Masonry Chimneys
  Fire Clearances for Metal Chimneys
  Fire Clearances, Single-Wall Metal Flues
• If you are using a conventional fireplace, also see FIREPLACES & HEARTHS

...

Frequently Asked Questions (FAQs) about chimney height & fire safety clearance requirements specified by building codes and best construction practices

Question: how to diagnose a smoky fireplace & chimney

Why would my fireplace smoke up the house during the time I have a fire. It's a masonry chimney. Also, my chimney is not 2 foot higher than the peek of the roof. - George Angell

I get smoke in my basement when I first light my fireplace. Both my fireplace flue and furnace flue are at the same height. I also had my co detector go off the other day. Is the flue height being the same, be the reason for those 2 problems? TKS - Dom 4/11/12

Reply: "Why would my fireplace smoke up the house during the time I have a fire. It's a masonry chimney."

Dom and George:

If your flue is cold it can take a while for the chimney to heat up enough to establish a good draft over a fireplace. To help things get going we often

• Make sure the damper is fully opened and that the chimney is not blocked and not damaged - hire a certified chimney sweep to inspect the flue for safety and to clean it if necessary.
• Light some newspaper placed at the back of the logs in the fireplace to help establish draft when you're first getting your fire going
• Make sure the ash pit door for your fireplace is closed = if the ash pit door is open air entering at that location will reduce draft seen in the fireplace. There may be ash pit doors both in the floor of the fireplace and also in the basement below the fireplace.
• Be sure that the chimney cap is properly installed and is the right type - a bad or missing chimney cap can cause bad draft as well as allowing downdrafts.
• Open a window or door near the fireplace so that there is plenty of good air flow into the room when you are lighting the fire - you can close this opening again once the fire is established.
• Best practice: after correcting chimney height, making sure the chimney flue is sound and not blocked or dirty, provide outside combustion air for your fireplace

RE: "my chimney is not 2 foot higher than the peek of the roof."

The chimney should be extended to be at least 2 feet above the ridge if the chimney is at or close to the ridge, or it should meet the height requirements shown in the sketch at page top.

If your chimney is too short it may not only result in inadequate draft (and improper heating system operation) but it can also be a fire hazard to the structure.

Question: Do we have to comply with chimney height clearance requirements for a 12/12 pitch roof? Does a power-vent flue excuse chimney height requirements?

We gave a 12/12 pitched roof and want to put a wood burning stove near the outside edge of the house (not near the peak) - is there ANY configuration of chimney that will not have 12 feet (or more) of pipe sticking out of the roof line?

Routing the chimney flue pipe toward the peak is not really an option it would basically have to come up near the outside eaves - clearing 2 feet any roof surface within 10 feet means at least 12 feet of pipe as far as I can tell. Are powered chimney vents an option? - Matt

Reply:

Matt: a line drawn horizontally from the top of the chimney to a point where that line would touch the roof surface needs to give you ten feet in distance for fire safety. If your roof pitches up steeply that may mean you need a rather high woodstove chimney to be safe. And you may need bracing.

I've not found references to power vent exhausts for woodstoves. Certainly it is not at all likely that a power-vented chimney would be more fire safe and thus would not need the same fire clearances as other chimneys and flues.

Question: What is the chimney clearance from the chimney pipe to a second story window?

i have a two story home. i just built a single story room off this home with a wood stove. what is the clearance from the chimney pipe to 2nd story window? it is already 2 feet above the ridge and 12 feet from the 2nd story windows - Charlie

Reply:

Charlie I'm not sure I understand the picture and measurements of the addition you describe. If your chimney is two feet above the ridge of the upper roof it would certainly not be too close to any windows.

If your chimney is two feet above the ridge of a roof over the one story addition, if you can't get more than 12 feet of horizontal distance between chimney and windows of the upper floor, you probably need to extend the chimney above the upper roof, following the ten-foot horizontal line rule we describe above.

Otherwise in at least some conditions, someone is going to open an upper floor window and find smoke blowing into the room.

Question: We're adding a roof whose ridge will abut the existing chimney. How does that affect chimney height clearance requirements?

I want to add a pitched roof to an existing home for a screened in porch. The point of the gable would go up against the existing chimney. Is that acceptable as long as the point of the gable (the highest point of the addition) is still 3.5 feet below the top of the chimney?

Reply:

Dave that sounds OK to me, just be sure to properly flash against the chimney or you'll have leaks. That is, if the ridge of the lower roof, where it abuts the existing chimney, is three feet or more below the chimney top, you've met that clearance requirement (the three-foot chimney clearance rule).

Question: My masonry chimney extend 2' above the top of the pitch. Does it have to be extended to 3'

My masonry chimney extend 2' above the top of the pitch. Does it have to be extended to 3' above to comply with the NBC? - Frank

Reply: here is a summary of chimney code and fire clearance rules: the two-foot, three-foot, ten-foot rule for chimney heights:

Frank,

Some building code officials, builders, and chimney professionals call this simple chimney fire clearance code the
"two-foot, three-foot, ten-foot rule for chimney heights" - which we explain as follows:

Your chimney top to roof clearance (for fire safety) is correct if the chimney height extends:

• The two-foot chimney rule: The chimney top must be two feet above the ridge of the roof (If the chimney is at or very close to the ridge) This is the red line at the right side of our chimney height sketch above.
• The three-foot chimney rule: The chimney top must be three feet (or more) above the roof surface (measured right next to the chimney, at the up-slope side of the chimney). This is the vertical green line in our chimney clearance sketch above.
• The ten-foot chimney rule: The chimney top must be high enough above the roof surface such that a horizontal (level) line drawn from the chimney top to the nearest roof surface will run ten feet or more before that line touches the nearest (up-slope) roof surface. The ten foot chimney height rule is illustrated by the blue line in our sketch above.

Take a look at the chimney height clearance requirements sketch at the top of this page. The only confusing detail in that sketch is that the "ten foot chimney height rule" horizontal line was shown as drawn mid way down the chimney - really that line is drawn from the chimney TOP to the nearest roof surface.

Question: My A-Frame chimney is just one foot above the roof if measured at the ridge - do I need to extend it

I have an "A" frame cottage with a new metal roof. The woodstove has a 10" insulated metal chimney which extends above the roof line by approximately 7 ft. and is above the peak by maybe 1 ft.

Reply: details of the ten-foot rule for chimney distances from nearby roof surfaces

Bruce:

Ok, so technically your flue is one foot short; perhaps given the very steep roof and that it's metal, I'm not as worried as I'd be otherwise, but it's possible that the chimney is not fire safety and code compliant for a second reason: if you were to draw a horizontal line from your chimney top towards the ridge, and if the horizontal distance from the top to the ridge is less than 10 feet, then properly your chimney needs to go up another foot.

On the other hand if the horizontal distance from your chimney to the ridge is ten feet or more, you're ok as is.

At CHIMNEY HEIGHT & CLEARANCE CODE you can find articles on required chimney heights above the roof line.

Question: Exactly where do we measure chimney roof clearances?

Refer to the sketch titled "Masonry Chimney Roof Clearance Requirements".
The line that is drawn that illustrates the 10 feet run is placed in the middle of the chimney. Depending on where you place this line has a HUGE impact on how high the chimney needs to be. If this line were drawn on the top of the chimney it would need to be substantially taller. Where am I supposed to take the measurement from?? - Jason Vetter 3/11/12

Reply:

Jason, you are dead right - the page top chimney to roof clearance sketch has long bothered me too, leading to other photos and sketches on this page that showed the required distances correctly. We have reviewed, edited, and adjusted all of the chimney clearance measurement drawings and photos in the article above to clarify these distances.

The original NFPA-211 drawings on which the page top sketch was based were equally confusing.

For chimneys that are 10 Ft (3.1 m) or MORE away from the roof ridge (measured at the up-roof side of the chimney):

• The top of the flue opening should be at least 10 Ft (3.1 m) away from any roof surface as measured by a horizontal line drawn from the top of the chimney flue opening to where it would touch the roof surface.
• The top of the flue opening should be 3 Ft (0.92 m) above any roof surface. I.e. a vertical line drawn along the up-roof side of the chimney, from the roof surface to the top of the chimney flue opening shall be at least 3 Ft in height. This is for masonry chimneys. For a gas vent or Type L vent this height must be 2 Ft (0.61m) or more.

Notice that I use the words "any roof surface" in this explanation. That means that if there are other nearby structures, say a dormer, the same clearance rules apply,

For chimneys that are LESS than 10 feet from the roof ridge (measured at the up-roof side of the chimney)

• The top of the chimney should be at least 2 Ft (0.61m) above the ridge

and

• The top of the chimney should be at least 3 Ft (0.92 m) above the roof surface. (This specification makes sure steep roof slopes are cleared.) For gas vents or a type L vent this distance must be at least 2 Ft (0.61m).

Another question that has come up is "do we have to measure from the chimney cap or from the (lower) opening at the top of the flue? In specifying clearances the NFPA 211 refers to the "Highest Point" of the chimney.

• My opinion of the NFPA and codes is measurements are made from the top of the chimney flue opening, not the top of the chimney cap - reasoning that it is from the flue opening that an ash or spark might exit the chimney, making that the point of concern. Otherwise we could end up with an unsafe (too short) clearance of a low chimney on which someone stood a ridiculously tall "cap".

Thanks so much again for the reminder to fix this, Jason. We welcome reader questions and comments. We are dedicated to making our information as accurate, complete, useful, and unbiased as possible: we very much welcome critique, questions, or content suggestions for our web articles. Working together and exchanging information makes us better informed than any individual can be working alone.

Question: can I fix my own chimney?

I just had a home inspection done and the inspector said that my furnace pipe that goes through the roof needs to be extended (metal pipe) is that something I can do myself - Rusty 4/18/12

Reply:

Sorry Rusty but not to be glib, i don't know your capability. The chim materials and extension need to meet code, be secure and od correct materials. You could get a bid from a chi net person who is certified.

Question: We had a chimney fire and a WETT inspection

I live in a Cape Cod style home. We recently had a chimney fire and a subsequent WETT inspection. I was told that the chimney does not meet code and is not 2 feet taller than the nearest structure. I am wondering what the code was in 1990 when the house was built? We live in southern Ontario. - Sara 1/10/12

Hi, I've found an answer for the "what was the code 21 years ago" question. Now I'm wondering what I can do re. the chimney that is apparently 8" below code. Do I have to pay to have it fixed even though it's not my fault? No one has ever mentioned the 2' rule before and I worry that we've had a chimney that is unsafe for 21 years. The inspection cost $339 and I need to know how I can fix this situation. I can't use the fireplace now. Sara 1/12/12

Reply:

Sara the risk of a house fire is deadly serious and deserves a proper and safe chimney. The fact that no one mentioned chimney safety to you is a bit cloudy to me - unless you had a professional inspection or service performed on the home I'm not sure who was on site before a chimney fire or related problem to examine the home and and inform you.

The question of who pays for repairs is one to discuss with your attorney.

Question: my chimney extends 2 ft not 3 ft up above the roof surface. Does it comply?

My masonry chimney extend 2' above the top of the pitch. Does it have to be extended to 3' above to comply with the NBC? - Frank 9/6/11

Reply:

Some building code officials, builders, and chimney professionals call this simple chimney fire clearance code the
"two-foot, three-foot, ten-foot rule for chimney heights" - which we explain as follows:

Your chimney top to roof clearance (for fire safety) is correct if the chimney height extends:

• The chimney top must be two feet above the ridge of the roof (If the chimney is at or very close to the ridge)
• The chimney top must be three feet (or more) above the roof surface (measured right next to the chimney, at the up-slope side of the chimney - see our sketch above)
• The chimney top must be high enough above the roof surface such that a horizontal (level) line drawn from the chimney top to the nearest roof surface will run ten feet or more before that line touches the nearest (up-slope) roof surface.

Take a look at the chimney height clearance requirements sketch at the top of this page. The only confusing detail in that sketch is that the "ten foot chimney height rule" horizontal line was shown as drawn mid way down the chimney - really that line is drawn from the chimney TOP to the nearest roof surface.

Question: Can I put in my own chimney using a single wall and triple wall?

if i install an older stove in my shop , will i suffer any code violations if putting in everything myself , using new single wall below and triple out the metal roof with one inch space between wall and durarock used as a heat spacer ? - Mike 1/5/12

Reply:

Mike, possibly yes.

In many U.S. & Canadian jurisdictions a building permit and approval inspection are required for the installation of woodstoves and other heating appliances.

Question: smoky fireplace on first lighting a fire

I get smoke in my basement when I first light my fireplace. Both my fireplace flue and furnace flue are at the same height. I also had my co detector go off the other day. Is the flue height being the same, be the reason for those 2 problems? TKS - Dom 4/11/12

Reply: how to improve fireplace draft on initial ignition of a fire

Dom,

There are plenty of reasons for backdrafting when first lighting a fire, including a chimney that is blocked, too short, has an open cleanout door, and more. Here are some things to check in order to improve fireplace draft when first lighting a fire:

1. Watch out: Have your chimney checked for safety and blockage and it's clear, and have the chimney cleaned of creosote and soot; depending on the amount of usage and type of fuel burned in a fireplace, chimney cleaning may need to be performed more or less often than annually.
2. If your fireplace and chimney are older and do not include an outdoor combustion air supply, then try opening a nearby window or door to assure very good air supply and no negative air pressure when first lighting the fireplace. Once the fire is going well you should be able to close the window or door; of course this will draw some cool air into the house and result in a net heat loss, but, then, operating a conventional fireplace (without glass doors or other features) will pretty much always result in a net heat loss to the building.
3. Because the fireplace chimney and air in the chimney are cold when you first light a fire in a fireplace, the initial warm smoky air can face inadequate draft - it has trouble pushing up that column of cold air. You can improve the initial draft by lighting some newspaper placed at the back of the fireplace.

Question: how do I find sizes and dimensions for a fireplace box?

Is there somewhere I can find standard fire box sizes for a masonry fireplace? - Lou 4/25/2012

Reply:

Lou - certainly - just search InspectApedia for "fireplace dimensions" and you'll find the article. Or go directly to FIREPLACES & HEARTHS

Question: is 25 feet to a nearby roof ridge sufficient chimney clearance distance?

We built a one and a half story garage next to a breezeway that separates the house by an additional 12 feet making the ridge of the garage 25 feet from the top of the chimney to the top of the ridge,the ridge is even with the top of chimney which is 25 feet away is this a safe distance between them? - Paul F. 4/29/12

Reply:

Paul,

if you've checked the sketches on chimney clearance distances shown on this page (10 ft. from a roof, 3 feet above the roof, etc) I'm unclear on the question in your note. If you are saying your chimney top is 15 feet away from a ridge that is at the same height, it's certainly past any clearance issue. Keep in mind however that wind effects on a chimney can indeed be affected by more distant site conditions, even a hill, or trees. So if there is a draft issue changes could be needed.

Question: Objection to neighbor's chimney fumes

I wonder if you could advise me - a neighbour some thirty years ago put on a side extension and wanted to put a chimney in. I put in an objection to this due to the fact that the smoke would come into my garden and across the front of my home. He wrote to me assuring me that his intention was to use a gas fire and not a wood or coal burning stove/fire and he would never extend his chimney. Recently he has extended his chimney by approximately one meter? I am now getting fumes from the fire both in the front and rear of the house and if I open the windows the fumes come in. I live in the Barnet area North London. - Gordon 5/6/2012

I should have mentioned that it was a single storey extension with a flat roof. Look forward to hearing from you.

Reply:

Gordon, I'm a bit puzzled by this description, but you didn't give any chimney clearance distances. Indeed a gas fireplace won't produce smoke, and if properly adjusted shouldn't be producing strong fumes that bother a neighbor, but the real answer to the question includes knowing the distances involved. The same clearance distances that apply to building a chimney on an individual home would certainly provide minimum clearance distances between neighbors. Did your neighbor obtain a building permit and approvals for his construction?

Question: Can I vent a gas fireplace into a masonry chimney in bad shape?

I would like to vent gas fireplace insert into masonry chimney. The chimney is in bad shape, but the portion 3 ft above the rooftop is good. Will venting to 3 ft height be sufficient with appropriate manufacturers specified metal liner? Do I need to concern myself with lateral 10 ft dimensions? - Roman, 5/27/12

Reply:

Roman,

Usually if a chimney is structurally sound it is relined or a liner is run up thorough it. For a gas fireplace that'd be a B-vent of sufficient diameter. In fact, a chimney that is too large in diameter for the appliance it vents may never work properly as a small appliance can't heat the chimney enough to establish a good draft;

If you line the entire chimney to the top, and better, use an insulated liner or insulate around the liner, the design should work.

And yes you still need to apply proper chimney clearance rules for gas vented appliances or B-vents.

Watch out: DO NOT just terminate a vent up inside the chimney - you're asking for dangerous carbon monoxide hazards and other problems. The height of the chimney above the roof surface depends on where it exits - and is shown, explained, and illustrated ad nauseam in the article above.

Question: chimney fumes bothersome on adjacent roof deck

I have an old masonry chimney that extends about 5 feet above the flat roof in an old four story townhouse (brownstone).

The problem is I have a roof deck on that flat roof and recently I've noticed fumes frequently if not constantly coming out of the chimney. There were always some fumes but not to this extent. Since it's June, the fumes would be from heating of the hot water which is heated by the year 2001 oil burner.

1) I think we need our boiler adjusted, do you agree?

2) Can we extend our chimney to vent the fumes higher? Do we need to extend the chimney using masonry and how much higher would you recommend? - Judy, 6/10/12

Reply:

Judy, I'm not sure there is a single correct answer to your question because local and site conditions (wind direction, downdrafts, other obstructions, as well as condition of the oil fired heating equipment) all affect the production of odors and downdrafts that may send chimney fumes down onto an adjacent area. But certainly I agree that

1. the heating system should be cleaned and adjusted annually; if after your service tech leaves the chimney is showing smoke then something is still wrong and you need to talk with the service manager for your oil heating company. See OIL BURNER INSPECTION & REPAIR for a complete guide to oil burner troubleshooting & tuneup.

2. the chimney height of five feet is certainly inadequate clearance above an occupied deck; you may need to at least double that, as well as providing bracing.

Question: outdoor wood fired oven with a metal flue and a canopy

Building an outdoor wood-fired oven that will have a metal flue. Plan on a permanent canopy in front of it with a metal roof. Roof of oven will be hardiboard (cement product). What kind of clearance will I need between the roof of the flue-top and the oven. Between the flue-top and the roof of the canopy? - Frank, 7/7/2012

Reply:

See the chimney clearance specifications above as a starting point, but because your oven (of unspecified use) may be in service for long periods or at unusual temperatures, it makes sense to also check with your local fire inspector.

Question: outdoor wood fired boiler chimney clearance to building - ending below roof

With a 2 story walkout basement can I put an outdoor wood boiler with the chimney 10'+ from the wall/gutter even though the top of the chimney would not reach the roofline? - John Henry, 7/23/12

Reply:

I'm doubtful, John; a chimney ending below the roof line of a two story house may meet the ten-foot distance rule correctly, but I suspect that in at least some conditions you'll be blowing smoke at nearby windows and walls.

Question: three adjacent chimneys

I came across a house today that has three chimneys right next to each other. The first two is a wood burning fireplace and the second is for three gas appliances: a boiler, water heater and a gas free standing stove. Just above these two chimneys is a steel plate and above the plate is a third chimney for a free standing wood stove. I know its wrong in so many ways but can't fine a reference. - Kelly Moore 8/27/12

Reply:

Kelly, send us some photos or sketches and we might have a clear enough understanding of the situation you describe to offer some comment.

Question: installing a wood stove through a one story roof

Greetings; I am considering installing a wood stove on the back end of a single story kitchen addition which has a low pitch roof. The kitchen addition is about.18 feet away from where it joins on to a story and a half main part of the house. The second story has one window about 18'. away from the proposed stove pipe which will be a Selkirk.SS type. Question: How far does the chimney need to be from the second story portion of the house to be safe from sparks and smoke? Thanks- from someone who does not want to freeze another winter because he cannot afford oil. QC - Rev. Quincy Collins, 9/2/12

Reply:

Rev. Collins,

The answer is in the text above - the same rule for structures applies as for adjacent roof surfaces. See "Roof Clearances for Chimneys 10 Ft. or more distant from the Ridge"

Question: what is the minimum chimney height up through a flat roof near two windows?

What is the minimum height clearance needed for a wood burning stove pipe when exiting a flat roof. the roof is in front of two 1st floor windows
thanks - Paula Moss 10/2/12

Reply:

Paula:

The minimum chimney heights above roof are in the article above. For the case you describe, there are other distances like from windows, and depending on the total chimney height, even meeting the above-roof minimum distance (3 ft. on a flat roof) may not be tall enough.

Question: Large masonry flue, extension fell off, reduced use, draft worries

We live in a smaller 3 flat with an oversized chimney (used to exhaust a boiler) opening directly adjacent to a much taller mid-rise. Until recently, there was a metal extension terminating above the taller structure and the chimney now only handles 3 water heaters instead of a boiler. As a section of the extension fall off, we need to do something to avoid back drafts. Do you know if it's legal and safe in Chicago to terminate lower than the mid rise's roof line, if we use a properly sized liner in our stack and install a draft inducer? There are no windows that would be affected. James. - 5/1/3013

Reply: dealing with a reduction in use of a large masonry flue

There are general chimney height rules that we document in the article above and that we also discuss at

FLUE SIZE SPECIFICATIONS

But at any specific site there can be nearby structures that, even if they meet the distance requirements, interfere with draft or cause a downdraft.

When you vent just a few small heating appliances into a large chimney there is a good chance draft will be inadequate and thus the systems unsafe ( a potentially fatal CO poisoning hazard).

I can't say what's legal (vs. safe) for your specific chimney just from your email, but the fact that you describe a chimney part as having fallen off is itself a concern and an indication that the chimneys and flues need inspection and repair by an expert. Indeed you may need to line the flue or install a draft inducer.

You could check for backdrafting just at the water heaters, but an individual test is not reliable as site conditions vary. For example draft will be different at different outdoor and chimney temperatures and will vary depending on how many heaters are running, indoor combustion air supply, and other variables.

...

Ask a Question or Search InspectApedia

Questions & answers or comments about chimney height & clearance requirements to comply with building codes and fire safety.

Technical Reviewers & References

Related Topics, found near the top of this page suggest articles closely related to this one.

• Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides:
  • Commercial Building Inspection Courses - protocol ASTM Standard E 2018-08 for Property Condition Assessments
  • Home Inspection Education Courses including home study & live classes at eleven colleges & universities.
  • Home Inspection Education Home Study Courses - ASHI@Home Training 10-course program.
    Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
  • The Home Reference Book, a reference & inspection report product for building owners & inspectors.
    Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
  • The Home Reference eBook, an electronic version for PCs, the iPad, iPhone, & Android smart phones.
    Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter inspectaehrb in the order payment page "Promo/Redemption" space.
  • The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors.
    Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
  • The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones.
• Thanks to Luke Barnes for suggesting that we add text regarding the hazards of shared chimney flues. USMA - Sept. 2008.
• [2] Arlene Puentes, an ASHI member and a licensed home inspector in Kingston, NY, and has served on ASHI national committees as well as HVASHI Chapter President. Ms. Puentes can be contacted at ap@octoberhome.com
• [3] Roger Hankey is principal of Hankey and Brown home inspectors, Eden Prairie, MN, technical review by Roger Hankey, prior chairman, Standards Committee, American Society of Home Inspectors - ASHI. 952 829-0044 - hankeyandbrown.com
• [4] G. Howard suggested text clarification on proper chimney height and roof clearances, August 2009.
• [5] NFPA 211 - Standards for Chimneys & Fireplaces, NFPA 211: Standard for Chimneys, Fireplaces, Vents, and Solid Fuel-Burning Appliances, 2006 Edition (older editions and standards are found at the same bookstore)
• [6] NFPA #211-3.1 1988 - Specific to chimneys, fireplaces, vents and solid fuel burning appliances.
• [7] NFPA # 54-7.1 1992 - Specific to venting of equipment with fan-assisted combustion systems.
  • NFPA 211 - 3-1.10 - Relining guide for chimneys
  • NFPA 211 - 3-2 - Construction of Masonry Chimneys
  • NFPA 211 - 3-3 - Termination Height for chimneys
  • NFPA 211 - 3-4 - Clearance from Combustible Material
  • NFPA 54 - 7-1 - Venting of Equipment into chimneys
• [8] GAMA - Gas Appliance Manufacturers' Association has prepared venting tables for Category I draft hood equipped central furnaces as well as fan-assisted combustion system central furnaces.
• [9] National Fuel Gas Code, an American National Standard, 4th ed. 1988 (newer edition is available) Secretariats, American Gas Association (AGA), 1515 Wilson Blvd., Arlington VA22209, and National Fire Protection Association (NFPA), Batterymarch Park, Quincy MA 02269. ANSI Z223.1-1988 - NFPA 54-1988. WARNING: be sure to check clearances and other safety guidelines in the latest edition of these standards.
• [10] Fire Inspector Guidebook, A Correlation of Fire Safety Requirements Contained in the 1987 BOCA National Codes, (newer edition available), Building Officials and Code Administrators International, Inc. (BOCA), Country Club HIlls, IL 60478 312-799-2300 4th ed. Note: this document is reissued every four years. Be sure to obtain the latest edition.
• [12] New York 1984 Uniform Fire Prevention and Building Code, Article 10, Heating, Ventilating, and Air Conditioning Requirements
• [13] New York 1979 Uniform Fire Prevention & Building Code, The "requirement" for 8" of solid masonry OR for use of a flue liner was listed in the One and Two Family Dwelling Code for New York, in 1979, in Chapter 9, Chimneys and Fireplaces, New York 1979 Building and Fire Prevention Code:
• [14] Field Controls provides instructions for the installation of LP and Natural Gas spill sensor switches, for example for their Gas Spillage Sensing Kit Model GSK-3, GSK-4, GSK-250M switches. Contact your heating service technician directly, or contact Field controls at fieldcontrols.com for more information. These switch models include a manual reset switch. Field Controls, Kingston NC 28504 - Tel 252-522-3031.
• [15] Tjernlund Products provides instructions for the installation and use of their controls, including the WHKE Millivolt Interlock Kit for use with their UC1 Universal Control, MAC1E or MAC4E auxiliary controls for gas fired equipment. This document also describes Tjernlund's recommended combustion air safety check which we recommended in this article. Contact Tjernlund Products at tjernlund.com or at 800-255-4208.
• [16] Bachrach Corporation, www.bachrach-training.com provides education for HVAC technicians. We found their web pages hanging during loading -01/2009. Readers may want to contact the company directly at: bacharach-inc.com or at 800-736-4666.
• "Top Ten Chimney (and related) Problems Encountered by One Chimney Sweep," Hudson Valley ASHI education seminar, 3 January 2000, contributed by Bob Hansen, ASHI
• Chimney Inspection Checklist, Carson Dunlop, Associates, Toronto, Ontario
• "Rooftop View Turns to Darkness," Martine Costello, Josh Kovner, New Haven Register, 12 May 1992 p. 11: Catherine Murphy was sunning on a building roof when a chimney collapsed; she fell into and was trapped inside the chimney until rescued by emergency workers.
• "Chimneys and Vents," Mark J. Reinmiller, P.E., ASHI Technical Journal, Vol. 1 No. 2 July 1991 p. 34-38.
• "Chimney Inspection Procedures & Codes," Donald V. Cohen was to be published in the first volume of the 1994 ASHI Technical Journal by D. Friedman, then editor/publisher of that publication. The production of the ASHI Technical Journal and future editions was cancelled by ASHI President Patrick Porzio. Some of the content of Mr. Cohen's original submission has been included in this more complete chimney inspection article: InspectAPedia.com/chimneys/chimneys.htm. Copies of earlier editions of the ASHI Technical Journal are available from ASHI, the American Society of Home Inspectors.
• Natural Gas Weekly Update: http://tonto.eia.doe.gov/oog/info/ngw/ngupdate.asp Official Energy Statistics from the U.S. Government
• US Energy Administration: Electrical Energy Costs http://www.eia.doe.gov/fuelelectric.html
• Brick Institute of America - Flashing Chimneys
  Brick Institute of America - Proper Chimney Crowns
  Brick Institute of America - Moisture Resistance of Brick
• American Gas Association - New Vent Sizing Tables
• Chimney Safety Institute of America - Chimney Fires: Causes, Effects, Evaluation
• National Chimney Sweep Guild - Yellow Pages of Suppliers
• Fireplace & Chimney Design, Repair Books - Fireplaces, Chimneys: design, repair
• Fireplace & Chimney Inspection Books - Inspecting and diagnosing chimney problems, fireplace problems, chimney & fireplace standards
• Ceramic Roofware, Hans Van Lemmen, Shire Library, 2008, ISBN-13: 978-0747805694 - Brick chimneys, chimney-pots and roof and ridge tiles have been a feature of the roofs of a wide range of buildings since the late Middle Ages. In the first instance this ceramic roofware was functional - to make the roof weatherproof and to provide an outlet for smoke - but it could also be very decorative.
  The practical and ornamental aspects of ceramic roofware can still be seen throughout Britain, particularly on buildings of the Victorian and Edwardian periods. Not only do these often have ornate chimneys and roof tiles but they may also feature ornamental sculptures or highly decorative gable ends. This book charts the history of ceramic roofware from the Middle Ages to the present day, highlighting both practical and decorative applications, and giving information about manufacturers and on the styles and techniques of production and decoration.
  Hans van Lemmen is an established author on the history of tiles and has lectured on the subject in Britain and elsewhere. He is founder member and presently publications editor of the British Tiles and Architectural Ceramics Society. Available at the InspectAPedia Bookstore.
• Chimney Inspection Checklist, Carson Dunlop, Associates, Toronto, Ontario
• Chimney & Stack Inspection Guidelines, American Society of Civil Engineers, 2003 - These guidelines address the inspection of chimneys and stacks. Each guideline assists owners in determining what level of inspection is appropriate to a particular chimney and provides common criteria so that all parties involved have a clear understanding of the scope of the inspection and the end product required. Each chimney or stack is a unique structure, subject to both aggressive operating and natural environments, and degradation over time. Such degradation may be managed via a prudent inspection program followed by maintenance work on any equipment or structure determined to be in need of attention. 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. This book provides a valuable guidance tool for chimney and stack inspections and also offers a set of references for these particular inspections.
• Fireplaces, a Practical Design Guide, Jane Gitlin
• Fireplaces, Friend or Foe, Robert D. Mayo
• NFPA 211 - Standards for Chimneys & Fireplaces, NFPA 211: Standard for Chimneys, Fireplaces, Vents, and Solid Fuel-Burning Appliances, 2006 Edition (older editions and standards are found at the same bookstore)
• Principles of Home Inspection: Chimneys & Wood Heating (Principles of Home Inspection), Carson Dunlop
• ...

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

• Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.

• Carson Dunlop, Associates, Toronto, have provided us with (and we recommend) Carson Dunlop Weldon & Associates' Technical Reference Guide to manufacturer's model and serial number information for heating and cooling equipment
  Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.
  
• ...