Chimney, Fireplace & Woodstove inspection & troubleshooting questions & answers.

These frequently-asked questions (FAQs) about chimneys & flues assists in diagnosing problems with chimneys, chimney draft, heating appliance performance and building fire or flue gas safety.

Guide to chimney inspections: this series of detailed chimney articles provides detailed suggestions describing how to perform a thorough visual inspection of chimneys for safety and other defects. Chimney inspection methods and chimney repair methods are also discussed.

Troubleshooting Chimneys and Flues: FAQs

These questions & answers about inspeting, diagnosing, building or repairing chimneys were posted originally at CHIMNEY INSPECTION DIAGNOSIS REPAIR - be sure to review that page.

On 2019-10-10 by (mod) - Can I just stack up flue tiles to create a temporary chimney ?

Justin

In somewhat of a stick-in-the-mud reply I must emphasize that ANY makeshift chimney that is therefore not UL listed and approved is a potential catastrophe: burning down the house or killing its occupants with CO.

Therefore my suggestion would be to look into

1. a direct-vent system that is designed to work with and ok'd by your particular heating boiler or furnace brand and model (check the IO manual or check with the manufacturer)

2. a metal chimney of the proper type for your fuel (gas or oil) - that is a listed, approved product. Such a chimney can be put up far more quickly than a masonry chimney and flue.

On 2019-10-10 by Justin

My chimney flue is deteriorating and i've decided to rebuild my entire chimney; however, it is starting to get into cold season and i will likely need to run my boiler heater during chimney repairs.

Can i stack up flues to create a temporary chimney to keep the boiler active or what can i use as a temporary chimney?

On 2018-03-24 by (mod) -

I'm very doubtful that you could, Barry, since I'd worry that when the power vent is running we might get back-drafting out of the draft hood on the natural gas furnace.

On 2018-03-23 by BarryS

Can you safely share a natural gas furnace vent and a powered natural gas water heater vent?

On 2017-08-27 by (mod) - chimney has been blocked by chimney brush entangled

Linda

At WELL PIPE RETRIEVAL TOOLS https://inspectapedia.com/water/Well_Pipe_Grabbers.php are some devices, including home made or expedient ones, that can retrieve items from a chimney. In any event your worker will want to take care

1. not to fall off of the roof

2. to avoid breaking more of the chimney flue

Following retrieval your chimney needs to be inspected by a certified chimney sweep who can tell you the extent of repairs needed to assure that the chimney is safe to use. Otherwise you'd risk a building fire or even fatal carbon monoxide poisoning.

On 2017-08-27 by Linda

Our chimney has been blocked by chimney brush entangled in broken flue liners shards. How can it be cleared?

On 2016-03-17 by (mod) -

Good grief, Lyn. A damaged chimney is unsafe, risking fire, or death from carbon monoxide hazards.

I cannot comment on the "repair" you describe as I don't have a clear idea what was done but it does not sound safe nor proper to me.

Start with a safety inspection by your fire inspector, fire department, building inspector, or a certified chimney sweep. Document the findings in writing.
Do NOT waste time waiting for an insurance claim if the chimney can cause a fire or kill you. Fix the hazard immediately or stop using the chimney and anything connected to it.

On 2016-03-09 y Lyn

My neighbours builder has knocked down half my chimney stack and attached some kind of board to the exposed face. He said spot bracket board I think? He said the bricks were too poor to point. I expect this is because they are meant to be internal and not external! He didn't get permission and didn't erect scaffold or use a ladder. The council aren't bothered as he didn't need planning for this removal. Is the use of spot board ok on an external stack? I have asked for the builders name in case I need it for an insurance claim but the neighbour says he doesn't know his builders name!!!!!! I am not sure what to do now?

On 2015-10-14 by (mod) -

The building codes can't anticipate all of the unique things that building owners, builders, contractors, or repairpeople can invent so I doubt you'll find an explicit prohibition. "Code" is not the fundamental issue here: building codes describe good building practices not how to fix as snafu from decades ago or a deterioriated or unsafe condition.

For what you describe there are *potential" fire and carbon monoxide (fatal gas) exposure hazards and possibly flue performance problems that could affect the performance of applian ces venting into the flue. I don't assume that there are really "no problems at all" when problems can be subtle, can increase over time, or may not have been noticed but may still be important.

I'd ask for help from a certified chimney sweep / repair company (National Chimney Sweeps Guild) on

1. assessing the safety and condition of the flue

2. proposing necessary repairs

On 2015-10-14 by Anonymous

Hello,
I was recently informed that my fireplace is missing flue tiles on the inside. It appears that when my chimney was installed and braced, the brace ran right through the chimney and where it goes inside the chimney there are no flue tiles. This had to be done 50 or more years ago and it has posed no problems at all, however upon recent inspection we are being told that it could be a safety hazard.

Does anyone know if this is a new code issue, something that we need to worry about? Thanks!

On 2015-07-21 by marion

hello, we live in an old house which has 4 fireplaces and we have never been able to light a fire as we get smoke throughout the house. We have not been able to find a person/expert who can help diagnose the problem (to be honest I don't even know where to start). Any advice? We live in Melbourne close to the cbd.
Thanks

On 2015-07-16 by Anonymous (mod)

Anon:

If the cracks are in concrete and are hairline and due to shrinkage of the concrete then I'd re-seal the surface with a masonry sealer. If the chimney is moving or frost damage more investigation for hidden (and dangerous) other cracks should be made before doing any cover-up repair.

On 2015-07-15 by Anonymous

Chimney crown show cracks. Can crowns be removed and replaced with copper covered crown

Question: how do we measure the draft at a chimney?

How are chimney draft inspected. - Louie

Reply: we use a draft gauge, instruments ranging from simple and inexpensive to more sophisticated; measuring draft vs "inspecting" chimney draft - how to measure Chimney Draft

We use a draft gauge - a sensitive instrument that compares relative pressures at two locations - such as in the room and in the chimney.We can actually measure the draft in a chimney using a draft gauge - heating service technicians have this equipment. Draft can be measured at just about any chimney, but is discussed in detail where we explain the draft regulators used on heating equipment -

see DRAFT MEASUREMENT, CHIMNEYS & FLUES.

It makes sense to also perform a visual inspection of a chimney for draft problem sources such as an open or missing cleanout door, missing or improper chimney cap, or damage and leaks in the chimney itself.

"Inspecting Chimney Draft"

Because chimney draft is a number, we can't actually "see" draft. But an experienced home inspector, heating service technician, or chimney installer may indeed spot serious, even dangerous trouble, including chimney draft problems just "by eye" when inspecting heating equipment, fireplaces, building roofs, and chimneys themselves.

That's because lots of serious chimney defects that involve chimney draft can be caused by visible building conditions - such as a heating appliance installed in a tiny closet with no combustion air supply and an airtight door to that room, or a visibly cracked or damaged chimney, or a missing chimney cleanout door, leaving the chimney bottom open.

Other chimney draft problems might be "inspected" or I should say inferred by visual clues that telltale heating equipment operating trouble often traced to inadequate or even excessive draft - such as chronically sooty oil burner operation or an oil burner that keeps burning off the front of the appliance.

Question: how to deal with birds invading the chimney

I have birds that built nests in the inner wall of my 3 wall liner. The inspector said the nests have pushed down the pipe and that the flue will need to be removed and cleaned and then reinstalled. He estimated it could be around $1,800

! I have access to the back of my fireplace and asked if the flue can be disconnected from the fireplace and then raised enough to push the nesting down while someone pushes from the top. Has anyone ran into this or have a suggestion on how I should fix this so I can use this fireplace? Thanks Terry

Reply:

Terry I too have been absolutely stunned by recent quotes from chimney installation and repair companies. I don't have a full nor accurate picture of your chimney design and installation, but it's reasonable for you to

- not use the flue until it is repaired or replaced - a blocked flue or nests between flue or chimney walls are dangerous

- consider that a triple-wall metal chimney is probably not designed for easy cleaning of the interstitial space between the various walls, making removal, disassembly, cleaning, and replacement or reassembly and certification important for safety

Question: An orange powdery material is leaching through the flue of an old unused chimney - what is it?

I've got an orange powdery material leaching through the flue of a chimney that was seal off about 1-1/2 years ago. Any ideas as to what the substance might be? - Dan

Reply: check out efflorescence and look for a chimney leak

Dan
It sounds like efflorescence from moisture leaks.

at EFFLORESCENCE SALTS & WHITE DEPOSITS take a look at our photos of efflorescence, a mineral salt left behind when water penetrates a masonry wall (or chimney) and evaporates. There we also discuss causes, cures, and implications of efflorescence for building care and maintenance.

Question: noises coming from inside the chimney when it's windy - like a tennis ball?

i have a strange noise coming from inside my house chimney when the wind gets strong something like a tennis ball rattling around what could it be - Steve

Reply:

Steve, I don't know, but some guesses include

- chimney mounted components like antennas (not recommended)

- a chimney top damper that has become loose

- downdrafts rattling a loose damper at chimney bottom

- a rattling barometric damper on one of the heating appliances connected to the chimney

Is the chimney in use for venting heating equipment? If so I'd get a chimney sweep out promptly to take a look, since the flue could be unsafe. If it's just for a fireplace, you might be ok doing some further detective work.

Also check out our diagnostic guide to house noises

at NOISE / SOUND DIAGNOSIS & CURE and be sure also to

see CHIMNEY NOISE DIAGNOSIS and

see WIND NOISES at BUILDINGS

Question: Is it safe to remove asbestos chimney parts?

is it safe to remove a asbestos chimney pot, if it can be removed without touching it. ie taking the mortar from around it carefully lifting it out straight into a asbestos bag - Aharri 12/16/11

Reply:

I'm not sure I've got an exactly clear picture of what you're facing. A "chimney pot" in my parlance is a ceramic chimney top fixture that extends chimney height, can also form a cap, and is usually molded for architectural or aesthetic reasons.

I've not found one of those made of asbestos. Perhaps you could send us some sharp photos (use the CONTACT link on our pages).

In general, if you are referring to nonfriable material such as a transite flue section in good condition, that can be simply lifted free and bagged, that sounds reasonable to me. The ancillary fiber release outdoors one would expect to be below detection.

But beware that no one can accurately assess an asbestos hazard by a one line question.

For example there may be friable asbestos materials involved that deserve greater care, and there may be more asbestos-containing-materials that need attention than just a chimney top extension (if that's what you are referring to.)

Question: water leaks through our chimney during rain

There has been a lot of rain recently and our chimney was blocked off 3yrs ago and water has started to drip down onto where I have my electricals.

When the rain stopped, it stopped coming in. Could it be a damaged flue? The plaster board was soaking as if it had been happening for a while but we only noticed yesterday. - Ruth 4/30/12

Reply:

Ruth,

Leaks at a chimney can be water running down the flue interior - a missing or rusted out chimney cap could be a cause. On occasion water running down in a chimney flue can exit the chimney at a crack or defect and show up elsewhere in the house.

But leaks also occur at the chimney exterior - for example due to a leak at the roof flashing.

And water often enters an electrical panel through the service entry cable.

I suggest that you need a competent expert not only to track down the leak source but also to inspect the safety of the electrical panel.

If you like, try the EXPERTS DIRECTORY link at the top of this page - we have no business/financial connection with anyone listed there.

Question: our chimney liner is intact but not straight - the cleaner says I need to replace the liner due to backpressure.

I had my chimney inspected,the liner is in tact but it is not in straight alignment. The chimney cleaner said I need to replace the liner because it is creating back pressure. Am I being scammed? I called them because them because I had a blow back, which I believe came from a dirty nozzle - Joe B 4/6/12

Reply:

Joe I can't second guess your chimney cleaner with so little information - we and you need some clear specifics, maybe a chim-scan video of the chimney interior. A chimney does not have to be dead straight to function properly.

But if you had an oil burner puffback then it's possible that the chimney was damaged. It's not something to take a chance-on. Look for a chimney sweep who is a member of a professional certifying association, ask for a complete safety inspection, and a written report of the results.

Also see CHIMNEY FLUE INSPECTION CAMERA for a discussion of chimney inspection camera systems.

Question: smoke problems from a neighbor's chimney

I am wondering if there is some law about smoke from neighbors chimney. I have COPD and cant hardly breathe in my own home. The smoke rolls in sometimes and it makes me very sick then I have to go pay a doctor. Thats not fair to me. It may be costing them less but it is costing me almost $200. a month more now. Please help me breathe. What can I do? - J.C. 12/28/2012

Reply:

A competent onsite inspection by an expert usually finds additional clues that help accurately diagnose a problem with a chimney or venting problem. That said, here are some things to consider:

First: f your neighbor's chimney is smoking it may indicate conditions that are unsafe for those people as well, such as an unsafe or improperly-operating heating system.

Therefore it makes sense to be sure to tell your neighbors about the smoke and that there are possible safety concerns (as well as unnecessary heating costs) - the system and chimney should be inspected and cleaned/adjusted if appropriate.

Second, if a chimney is improperly constructed, such as wrong height or location, it may not provide proper draft - again potential safety or heating equipment operating problems, and as well it may be in violation of local building codes.

There are building code regulations and standards for chimney and heating appliance venting and chimney construction, but I'm not aware of specific rules about smoke intrusion. Rather a chimney, properly installed an designed, should not discharge smoke where it may enter its own building nor another one nearby.

By no means do I encourage an argument with a neighbor, but if your neighbor is simply uncooperative, you may be forced to ask your local building inspector to take a look and to advise both you and the property owners if there are unsafe or improper conditions.

Question: Does California’s Code allow that fire place vent be together with other exhaust ducts? Installation specification details for chimneys / vents when installing a gas fireplace

I am mechanical engineer with 15 years of experience in Serbian and Russian market. I have been working for American market for a couple of month and I would like to ask you to help me with my problem. I apologize in advance about my English but I hope you will be able to understand essence of my question.

[Click the image at left to see the complete architectural drawing of fireplace vent and kitchen bathroom vent and vent shaft drawing]

In some non-residential building in Oakland CA, I have units with fire place at living room.

Architect wants that fire place vent be in shaft up to roof. In that shaft are also toilet exhaust duct and kitchen hood exhaust duct (sub-ducts within metal duct which will be conjoined at the roof with common fan). I tried to find if that option is permit and what will be demands for that but I couldn’t.

• Does California’s Code allow that fire place vent be together with other exhaust ducts?
• If it does not, what will be thickness of separations within the shaft?
• Is it possible to join two fire places vent into one common duct?
• What I have to know about their roof exit?

I am sending you also drawings for easier understanding.

I am looking forward to your answer. Thank you in advance.

Best regards, - S.V. 8/14/2013

Reply:

Thank you for the questions S.V.

You won't find any code that permits using a fireplace chimney vent also for venting other exhaust ducts thorugh its interior. Such an effort would be very dangerous, risking a building fire as well as causing improper operation of all of the appliances or vents being so-joined.

For example, we do not run wires, gas lines, and certainly not a chimney within the interior of a heating or cooling air duct or similar building feature.

Depending on the chimney materials and type and the size of an existing passage through a building, it may be permitted to route a UL listed metal chimney through a larger chaseway inside of which other vertical vents or air ducts are also routed provided proper fire clearances are respected and that proper construction prevents any possible leaks or interference.

Using such a chaseway for multiple purposes must consider the number of bends, turns, slope, overall dimensions, height, and fire clearances, and certainly the plans for such a structure need to be submitted, approved, and inspected by local building officials.

The thickness of separations within shaft depend on the type of appliance being vented and thus the chimney requirements. There are different types of chimneys - I have no idea from your question which type is needed - see CHIMNEY TYPES & MATERIALS. Also see
FIRE CLEARANCES INDOORS.

For example gas-appliances vent through a B-vent and operate at much lower temperatures than oil fired equipment or wood fired equipment.

See FLUE SEPARATION REQUIREMENTS

Roof exit requirements too depend on the type of vent: chimney clearances from rooftops are specified in articles at InspectApedia.com

See CHIMNEY HEIGHT & CLEARANCE CODE

No you cannot vent two fireplaces into a common "duct" and to be clear, duct is the wrong word. A "duct" is for movement of building air in a heating or cooling system or perhaps for venting kitchen or bathroom air as an exhaust fan; A fireplace vents through a chimney. The fire resistance, temperature properties, clearances etc are quite different.

See SHARED CHIMNEY & FLUE Hazards

At the rooftop, in addition to meeting fire clearance requirements, the chimney must be properly flashed so as not to leak into the roof structure;

and in some locations where nearby buildings, prevailing winds, nearby hills, etc. could cause chimney draft problems, the chimney height might need to be increased above the minimum; in addition the chimney must terminate in a UL listed and approved chimney cap or top to protect the flue (chimney interior) from damage and to protect against downdrafts.

With respect, even though you are a mechanical engineer, your questions suggest  you are not familiar with chimeys, flues, and vents, which inturn raises life-threatening questions about the work you are trying to perform - my advice is that you do NOT undertake this project without employing someone who is expert in chimneys, flues, venting, etc.

Beginning at CHIMNEY INSPECTION DIAGNOSIS REPAIR - home you will find our library of chimney and vent inspection, hazards, design, installation, etc.

Reader follow-up:

You made me speechless with your answer! Thank you very much. The architect didn’t want to put other exhaust ducts into the chimney; he said "Please vent the fireplaces in Units C1 & C2 to the roof through the adjacent bathroom vent shaft as drawn."

It sounded like bad solution to me, that is the reason why I asked you for help. If that isn't to much I will send you pdf file as well. The fire place is Heat&Glo type SL-550 TR-E, natural gas. Yes, I don't have any expirience in fire place ventilations - that is a reason I want to learn it! ( I have been working for american market since January.) Thank you so much once again, I will read all that for sure

Reply:

I appreciate the discussion - working together makes us smarter;

The first image I enclose, cut from your pdf, looks to me like a gas fireplace direct side vented out through a wall and over a stairwell which, if the vent is actually in or close to the walking path of people, something that to mee seems improper.

That same unit ... has a vent for kitchen and bath nowhere near the fireplace.

Seems to me the architect has got himself into a tight spot here and just "tossed the probelm over the wall to you saying "fix it" - asking you to do his job. I'd be careful about working with whomever that is. I'm not sure what s/he had in mind when these plans were drawn.

Indeed there are direct-vent gas fireplaces that can avoid the need for a chimney; some of these can vent horizontally OR vertically but have to terminate at an acceptable location which I doubt to be along a stairway.

In theReferences or Citations section of this article you'll find some key codes & texts you'll want to review for chimney and fireplace installation and safety.

Reader follow-up:

You made me speechless with your answer! Thank you very much. The architect didn’t want to put other exhaust ducts into the chimney; he said "Please vent the fireplaces in Units C1 & C2 to the roof through the adjacent bathroom vent shaft as drawn."

It sounded like bad solution to me, that is the reason why I asked you for help. If that isn't to much I will send you pdf file as well. The fire place is Heat&Glo type SL-550 TR-E, natural gas. Yes, I don't have any expirience in fire place ventilations - that is a reason I want to learn it! ( I have been working for american market since January.) Thank you so much once again, I will read all that for sure.

Reply:

The first image I enclose, cut from your pdf, looks to me like a gas fireplace direct side vented out through a wall and over a stairwell which, if the vent is actually in or close to the walking path of people, would be flat crazy. That same unit #205 has a vent for kitchen and bath nowhere near the fireplace. Seems to me the architect has got himself into a tight spot here and just "tossed the probelm over the wall to you saying "fix it" - asking you to do his job

. I'd be careful about working with whomever that is. I'm not sure he's doing what he was paid for. Indeed there are direct-vent gas fireplaces that can avoid the need for a chimney; some of these can vent horizontally OR vertically but have to terminate at an acceptable location which I doubt to be along a stairway.

Also it occurs to me that if you contact the fireplace manufacturer they will probably be glad to help with a more detailed spec on how their unit can be safely vented.

Also see the citations I offer at https://InspectAPedia.com/chimneys/Chimney_Inspection_Repair.php#reviewers (click to show) for some key chimney and fireplace codes and specs sources.

Reader remark: Well yes...It seems that everyone chase for form only, not for essence. That vent over a stairwell is ok, I check in Installer Guide.

Reply: I think you can vent over an exterior stairway PROVIDED there is adequate overhead clearance from the walking space. Otherwise you will or may run into stair code violations such as intrusions into the walking space or stairway headroom. We publish stair clearances too if you need to check that.

Reader comment: In installer guide is written - 7ft clearance from public property and the architect provide that. Anyway, when I told to my menager my doubts she didn't have answers on them and the result is that project is postpone till next week.

I wrote to the manufacturer and I won a coupon for fire place!(?!). It will be much easier next year when I move to America! Right knoow I just want to find out is it possible to put vent pipe into the same shaft or into the drop ceiling with others exhaust ducts.

Reply: "the vent pipe" is just too vauge. There are multi-wall insulated chimney materials typically described as "zero clearance" that can be put typically 1" from combustibles; B-vents have different clearance requirements. You are also not adequately addressing issues of chimney venting design: angles, bends, lengths of run, horizontal distances, and as a result possible code violations as well as fireplace draft hazards.

I would BE VERY CAREFUL to review the design against the manufacturer's specifications and also national model codes as well as local codes because especially with a gas fireplace it is very easy to produce fatal carbon monoxide gas (and kill the occupants) if a gas fired appliance does not vent properly.

Reader comment: I agree with you completely.That is the reason why I insist on codes or regulations. Firstly, the architect wanted to go with that pipe thru whole bedroom ( from one side to another) and I avoid that. Can you recommend me which codes will that be? As I said, I typed every possible solutions of the words, but I couldn't find anything.

Reply: In the citations to my chimney articles you can find good details in the US national fuel gas code, and also there are NFPA specs on chimneys. But to really cover yourself a checkmwith the technical representative for the gas fireplace company is important too - they want their product to be safe.

Reader comment: I tried to get in contact with Heat & Glo but only I did is to get a coupon of 100$ for a fire place!

Reply: contact information & manuals, architect's guides & CAD drawings for Heat & Glow Gas Fireplaces

at http://www.heatnglo.com/ I found this contact information

Heat & Glo A Brand of Hearth & Home Technologies Inc. Corporate Office 7571 215th Street West Lakeville, MN 55044 Phone: 1 (888) 427-3973 Email: hnginfo@hearthnhome.com

and at the same website the company offers some installation manuals for professionals

at http://www.heatnglo.com/For-Professionals.aspx?tab=2#tools

as an example I looked at the PDF installation manual for their LUX fireplace series - on p. 26 are specifications for fireplace venting for this natural gas fired model. There you will see the rules for allowable chimney vent runs for horizontal, angled, and vertical lengths and probably fire clearances as well.

There are some important restrictions; here are two examples (th examples are incomplete and thus NOT a complete and safe installation specification)

LUX36 requires a minimum of 36 inches of vertical venting before attaching any elbow to the appliance for the venting configuration (in an example fiture 4)

LUX42 requires a minimum of 48 inches of vertical venting beforeattaching any elbow to the appliance.

Try contacting the Heat & Glo Fireplace company by email at the address I gave above. Also - once you've identified the specific gas fireplace model to be installed, you will want to look at ALL of the installation manuals and guides.

I notice there are installation instructions and also an "Architect's Guide" for using these gas fireplaces. There are also some CAD drawings. Among these key documents you will find rather detailed specifications of the constraints that must be respected in framing, installing, and venting the gas fireplace.

Question: styrofoam falling out of a gas fireplace chimney?

(Jan 28, 2014) Anonymous said:
I'm finding small styrofoam pieces on the ground near a vented gas fireplace chimney. Where could they be coming from?

Reply:

Anon,

Styrofoam may have been used in any of quite a few building locations but hopefully not exposed (it's a fire and smoke hazard) and nowhere near combustibles. I'd look in the attic, basement, building exterior, and I'd look at the pattern and location of the fragments to see

- if these came from your building or somewhere else

- if from your building, from its exterior

Question:

(July 3, 2014) Mrs. K said:
I had gas coming out of the keyhole for the turnkey. I wasn't sure if it was from the gas pipe leading into the chimney or what: gas man who came out said gasket might be loose in the keyhole--that is where leak is. "Do not break the wall, just get a plumber to use a tool to install a new gasket."

Plumber said one had to open the wall to take out the casing for turnkey (cemented in), and he couldn't do that. Another said over the phone it might just be tightening the nut. Before I pay again, is this an issue a chimney repair man can do?

Reply:

(July 3, 2014) (mod) said:
Sorry Mrs. K I'm not clear what we're talking about. "keyhole" and "turnkey" are not terms I understand when talking about chimneys. Explain a bit more and we'll be glad to research the question.

Question: inserting the flue vent connector too far into the chimney flue

(Aug 9, 2014) Stan said:
I saw your comments on the dangers of a sheet metal appliance vent extending to far into a masonry chimney and possibly affecting draft. I am replacing a water heater sheet metal vent into a masonry chimney that is only used to vent the gas-fired water heater and gas-fired furnace.

The old water heater vent pipe goes probably 8-9 inches into the clay flue of the chimney. This did not seem right to me, as this is probably 3/4 of the distance into the flue. How far should the vent go into the chimney?

Reply:

Stan

Putting aside for a moment other serious hazards such as cold chimneys not adequately venting a gas appliance (fatal carbon monoxide hazards) and draft interference between the two appliances, generally the metal thimble that inserts the flue vent connector to the chimney protrudes just a very short distance past the interior face of the chimnney flue - perhaps 1/2" to be sure it's connected - and of course sealed at the penetration.

Question: how to seal off an unused chimney

May 1, 2015) Anonymous said:
Does completely Sealing off an unused chimney, all three flues at the top of the chimney above the rooftop with aluminum flashing sealed with roof cement cause any problems considering moisture escape, air exchange during the winter freeze, or humid summer - for the brick or mortar integrity over time?

Does the chimney flue even if they will never be used for venting a fireplace, or venting gas - need to breath, have an air exchange at the top chimney above the roof line?

Reply:

Interesting question, Anon. I suspect a reliable answer is dependent on the individual building and its condition, maintenance history, possible leak sources. For example leaks into an abandoned chimney invite trouble.

Keep in mind that not just water, but also air leaks into and out of a chimney can bring moisture into that structure.

If the unused flue remains dry and is sealed it's probably fine.

Question: relocating a fireplace

(May 20, 2015) Anonymous said:
I am purchasing an older home and want to move the fireplace to the center of the room. How expensive is it to move the flue and do I need to? Have heard that I could run duct work to the flue and keep it in the same place?

Reply:

Anon

Moving a fireplace from a wall to room center would be a costly proposition in most cases - particulary if we're talking about a masonry unit. Think thousands of dollars. To support the weight of the fireplace as well as to make it fire-safe you're likely to have to build a masonry foundation as well as to interrupt the floor framing.

Then you'll need a fire-safe chimney. While we may see a wood-stove whose flue has a horizontal run to a chimney, I'm doubtful that you'd like living with the size and clearance requirements for an in-room flue connecting a central masonry fireplace whose chimney was not above the unit.

...

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