Thread: 100%+ Corbeled Chimney

1915 house. The roof structure has done a good job of holding up this chimney for over 90 years. There is no way it could have supported itself.

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Now, that's a great picture.

Rich

Yup, great shot. Sooner or later, gravity works....

The flashing topside was in bad shape and needed to be repaired or counterflashing installed. Some repointing was also needed. The chimney is unlined and the boiler and water heater (both natural gas) vent through the chimney.

I recommended that the chimney be taken down to the ceiling joists and a metal chimney installed.

Here in Chicago, I frequently see older chimneys corbelled far in excess of modern standards. When they have been constructed with a good mortar bond they can be successfully self-supporting to a surprising (to me, anyway) extent - when doing my own rehabs I've been amazed at how strong such a bond can be, sometimes it's hard to knock them apart with a sledge. And I've never seen one which appeared to be in good conditions fail inside an attic, or talked to anyone who has.
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So while I don't know the extent to which this one has deteriorated, FWIW if such a chimney appears to be in good condition I would not automatically recommend immediate replacement. Rather I would point out that while the chimney currently appears structurally functional on visual inspection of its exterior (and whatever interior inspection is possible from the roof) it's corbelled far in excess of modern standards, that I can't determine the extent to which the masonry and/or mortar bond has deteriorated, that these might fail in the future, and that the buyers should consider replacement at the next re-roofing, or sooner if evidence if distress is observed. And that if they are concerned about it's integrity in the meantime, they should consult a mason with experience in building and repairing fireplaces and chimneys.

First, using the term 'corbeled' for that is incorrect.

Corbeled brick is where the face brick extends outward like that, but where the brick behind it continues to go up vertically, with the brick wall thickness increasing as the brick is corbeled out(see attached drawing from BIA).

That is just an 'offset' chimney.

Michael, I don't know of anything which, when offset more than 100% of its width can be considered 'self-supporting'. Unless that item is a single, continuous, member which is also firmly secured to a suitable foundation, such as a metal pole either embedded in, or anchored to, a suitable foundation (such as a heavy counter-weighting concrete footing/piling which can sustain the cantilevered load forces of the metal pole.

A brick chimney, on the other hand, is a discontinuous element constructed of smaller pieces held together with an adhesive (the mortar). The support for that offset chimney is provided by the roof framing around the chimney. The roof framing should not be touching the chimney (minimum 2" clearance), thus, the roof structure should not be providing any support for the chimney.

I'm guessing that if the roof framing was removed from around that chimney, it (the chimney) would come tumbling down into the attic and into the living space below.

I agree with Bruce - that thing needs to come down and be replaced with something which is properly constructed. Regardless how nice it looks at this time and regardless how long it has managed to stay up there without falling.

If you look closely you will see the brace at the left side, which is the reason the chimney is still standing.

'I'm guessing that if the roof framing was removed from around that chimney, it (the chimney) would come tumbling down into the attic and into the living space below...'

Likely, you would be guessing wrong - if you inspect in Chicago you learn from experience that masonry chimneys are able survive a lot of "offset"; when I rehab buildings with such chimneys it's a sometimes a considerable effort to demolish them down to the joists once the roof is gone. If my blanket recommendation was replacement, I would be recommending immediate replacement of probably a third of the chimneys withing a mile of where I'm sitting at the moment - all of which have lasted 80-100 years, and most of which, unless the roof flashing fails or condensing appliances are connected to them, will probably last as long again - I've yet to see one failing structurally in the attic other than as a secondary result of water damage, and I've not talked to anyone else who has.

(I suspect those prone to fail, failed in the first few years).

Are these chimneys inherently unstable?

Of course.

And so is every 100 year old masonry foundation I inspect ... the surrounding soil really, really wants to return to that empty space and it's only the structural integrity of the walls that prevents if from doing so.

Inspecting such foundations I know that I would not be allowed to build one today, that the fact that "a foundation still keeping the soil out today only means it has not failed yet") , that a mason familiar with such foundations can give the client a better idea than I of its condition and expected life (especially if he trenches a bit on the exterior), and the only way to insure that this foundation is stable is to jack up the house and pour an new one.

Never the less, I don't tell my clients to immediately replace every such masonry foundation I inspect - it's been my experience that a 100 year old brick foundation, unless such a wall is experiencing water damage or the soil surrounding it has become unstable, will likely last a considerable additional period of time.

And unless I see evidence of such problems, I instead stress the importance of keeping water away from the foundation and vigilance for evidence of developing problems - explaining that while I cannot predict what will happen to this foundation, based on my experience of similar foundations, there is no present visible evidence of impending failure.

Similarly, looking at a typical offset chimney, absent evidence of past or current failure I can't know the probability it will fail tomorrow - all I know is that I've seen a lot of similar chimneys which have not, and that I've heard no accounts of any that have. Nor an I aware of such concerns expressed by any local AHJ, or any blanket advice elsewhere (for example, in the masonry industry) that these chimneys be proactively replaced in my area. (I can imagine that there might be greater concern in seismically active areas).

I will certainly point out to my client that this arrangement is unacceptable by current standards, I that I can't predict when it will fail (and that, someday, it will), that if it fails it could crash onto a sleeper below, that the best way of determining the likelihood of impending failure is the opinion of a mason experienced with fireplaces and chimneys, and that the only way to completely avoid eventual failure due to the offset is to rebuild from the base of the offset on up.

But a lot of stuff can happen, and based on my experience, and the lack of concern (that I'm aware of) by "authorities" over such chimneys, I can't see a blanket recommendation to replace immediately, in this case my opinion (similar, for instance, to asbestos insulation on pipes) is that that once I have stated these concerns what if anything to do about such a risk is a judgment call to be made by my client, and that based on their individual concerns and circumstances it's up to them to decide if this should be further investigated and/or corrected.

Now, show me an authoritative source for such concern (as for example in the case of fires due to defective and/or incorrect dryer venting) that I can cite in a report, and I'll have reason and grounds to change my advice.

Wayne,

That "brace" was likely placed there by the mason to assist in building the chimney.

See attached pics

Bob,

I know we can't build them that way today.

The problem is what to do with all the ones we have (at least in Chicago).

If I want to tell people to start spending thousands of dollars to tear out a common design of functioning chimney, and I want my words to have effect rather than it just being CYA boilerplate, I need some better reason than "Can't do that under current standards" - I need to be able to demonstrate the adverse effects of continued use.

I'm a safety conscious inspector, and I'll take the heat any day for (for example), recommending Level II at every change of ownership.

But there is a reason I can do that - the documented occurrence of fire and toxic gas as the result of fireplace and flue defects, and my experience of the fact that it is beyond the scope of a home inspection to adequately determine the condition of many flues, and that I can't always know which these are.

In these situations I want to be able to say - truthfully - that "Often when I point out the dangers of incorrect glazing in doors, someone at the inspection will roll up their sleeve, and show me their scar", or "According the the CPSC, there are around 15K dryer related fires every year", or "I've seen flues that look OK from the top and bottom, but when inspected with a cameras had serious problems", or even "I've been told by an experienced chimney sweep, who's opinions I trust, that it's quite possible there will be problems with a custom built three-sided fireplace this close to an exterior door".

That's the justification I don't have for recommending tearing out and replacing a sort of chimney I've never seen experience a structural failure as a result of this design feature, when I haven't talked to anyone who has.

If this is is a problem, someone here must have a picture, or can point time to a newspaper account, or a technical bulletin, or something, illustrating this failure.

If so, once I have it believe me, I'll load in on my handheld, show it to the client right there at the inspection, and reference it in the report.

Michael, I hope you aren't waiting for the other shoe (or chimney as it were) to drop. Regardless if this standard was in force at the time of construction, we know now that is is clearly a violation. The question then becomes, does it pose a hazard to life or property? With all that leverage against the roof framing, brace, and ceiling, yes, there is the potential for a catastrophich collapse. Even if it doesn't fall, it may open up a leak and cause water problems, which, as you know, can lead to health problem, too. Then, there is the performance question. This chimney is unlined and, by code must be relined if it is to be used. All liner mfrs. require the chimney to be structurally sound, which this chimney clearly is not. In fact, when the contractor leans on this chimney while installing the liner, there is a good chance of total collapse. It is unsafe for the contractor to be up there of in the attic under it.

A chimney with such an offset presents an undue resistance to flow. That's one of the main reasons corbelling is limited. Even with a liner, this represents an unacceptable restriction. I agree this should be torn down and factory chimney or B-vent run from a liner through the roof directly above it. What is the reason for this offset?
I would not hesitate to call out this chimney.

Bob,

I can call out anything I want.

At this point all I can give for a reason in this case is:

1) It does not look like this is a stable design

2) It's not allowed by modern standards

3) It may restrict the flow of exhaust gases

4) Likely, it cannot be upgraded with a liner

Against this, I have the fact that tens - perhaps hundreds - of thousands of such chimneys are currently operating in Chicago, and no one yet has be able to give me instance of a single injury or financial loss due to this design.

On this basis I should recommend immediate replacement of such chimneys, knowing that if my clients actually did so it would be often be at the cost of deferring or forgoing other repairs and upgrades that I know will actually save lives and preserve property?

This when I have no actual evidence that this will prevent injury or property loss?

We can recommend replacement of anything and everything that might go wrong, and there is a powerful legal incentive to do so.

And often we tell ourselves that when doing so we are serving our clients interests as well - probably the more conscientious we are, the more often we tell ourselves that.

But on this basis - objectively - would I not be more justified in calling for the replacement of every GFAF I see more than 10 years old because if might develop a defective heat exchanger in the next 12 months?

Because as far as I can tell, statistically I would be on firmer ground recommend that those furnaces get trashed than I would recommending wholesale replacement of these chimneys, because at least I can cite (a handful) of illness and deaths due to defective HEs.

Usually the only leverage we have if we are really concerned about out clients welfare is out credibility.

IMO, that credibility is enhanced when we can provide an objective basis for our opinions when they are challenged, and it's reduced when we can't.

Of course, we can always fall back on "in my experience and opinion" - we get a certain amount of slack from everyone involved if we appear authoritative, but that authority is also reduced a bit every time we fall back on such opinion to support a recommendation absent objective evidence.

And if that opinion is that an system or technique in wide use should be replaced every time we encounter it, and we haven't personally seen examples of that failure, and we haven't talked to someone who seen an example, and we can't find an example on the net (I just spent 15 min looking for one), and no one here (and that's tens of thousands of inspections) has come up with an example, then maybe - just maybe - whatever problem this is in principle, it's not in fact a significant problem compared to many other things we encounter, and we should revisit our reasoning for the recommendation.

I'm open the possibility that every time I see a chimney not meeting current standards in this regard I should unequivocally recommend immediate replacement.... I've just not seen the objective evidence to support it.

Michael, forgive me but it sounds to me as if you won't call something out unless you have personally seen evidence of failures or problems. Is there one specific reporting system to which you subscribe? I'm not trying to give you a hard time here. The incidence rate has been and probably will for the forseeable future, be shrouded in mystery and buried in court vaults and graveyards. Nobody is anxious to publish a chimney collapsing into a home unless it kills someone. There was a case a few years ago where a chimney collapsed on a girl killing her as she walked by. As for performance problems, these get swept under the rug as DavidR, our HVAC expert will tell you. Again, who is reporting it and where whenever an unlined chimney causes water damage to a home or the CO injures someone. The reporting systems in this country are virtually non-existent. Bottom line is, if you're waiting to read about it in the papers, better get a good chair.

As for calling them out or not, that is your call, of course. Just understand that inspite of the high incidence rate of these installations in your service area and what you perceive as a non-existent failure rate, I want you to understand that you (and these chimneys) don't have a leg to stand on. Let me play the devil's advocate: you inspect a home and fail to call out such an installation. There is a personal injury or property loss. You admit in the deposition you are aware this construction is no longer allowed in the code or NFPA 211, the national standard for chimneys. You admit you are aware such a hard offset may have adverse effect on proper chimney performance such as condensation, CO leakage, or even spillage. You recognize all these perils yet you failed to warn your client.

See my point? I advise you help your client make an educated decision.
Bob

That chimney wouldn't last very long out here in California. Please explain to me why folks still believe they need fireplaces in their homes along with those really dumb masonry chimneys?
Founder/President: “Fireplaces Must Go Society.”

The June Issue of the ASHI Reporter Magazine has an article on this very issue. The Author was hired by disgruntled Home Owner mad at inspector for calling out his offset chimney in attic. The chimney in this case had an offset
of an inch per foot or about 8 inches so it would exit alongside ridge board. The ridge board was not in contact with chimney. (Not as severe as pic by Bruce)
Basically the Author says the HI should not have called this chimney out as the mortar joints were level, chimney in good condition with no pressure or contact with ridge board. He says calling this out hurts our profession.
Between reading this article and responses on this forum I guess it would be a judgment call on the severity of the offset, condition of chimney, contact with wood roof structure etc.

Where can I get a copy of this article? I'm not a member of ASHI so I don't get this magazine.

So, what you're telling me is this guy, who was paid by the seller to dispute the home inspector, disagreed with the home inspector. Wow, that's a shock. What are his credentials? Is is a licensed PE? Did he conduct compression tests on the mortar? Run calculations? Measure to see if out of plumb? Did he push on the chimney laterally as wind does? Did he climb up and stand on the chimney? How much weight was calculated to be above the point of offset in total and how much of that is calculated to be past the centerline of the flue? Was the flue in question lined?

As a chimney is corbelled out of column with the chimney proper, the loads change. As the dead weight of the top presses down, the cantilever exerts tremendous crushing on the side closest to centerline while the opposite side starts to see a tensile or lifting force. Some chimneys were built with high psi mortars with a really good bond and tend to withstand these forces better than others. However, this is wholly unpredictable. I still say your best bet is to point out the hazard and let them make an educated decision what to do.

BTW, any of these chimneys without proper clearances or a liner should be called out anyway. I see you having more trouble making a case it can stay than proving it should go.

Just my opinion.
Bob

Waiting for proof that that is a 'problem' is a bit like standing a drunk by the side of the road and waiting for a car to run over him.

May take a loooonnnnngggg time for that to happen, and, what to heck, you are only killing one drunk just so you can get your 'evidence'.

I really do not understand your position, Michael ... waiting for a known 'bad thing' to happen just so you can then use that documentation for the next 'bad thing' to happen??

Jerry,

Nobody can seem to produce evidence that these chimneys are failing in my area.

I know (or at least I've read) that after 10 years the incidence of heat exchanger failure starts to steadily increase.

I know (or at least I've read) that in some cases a defective heat exchanger can cause illness or death.

If I would call out the first for replacement every time I see it, isn't the case for calling out the second even stronger?

Bob,

David's example is exactly what I'm talking about: without objective evidence of the prevalence of such problems, in the presence if a chimney which is not in visually apparent distress, from a structural standpoint, as a generalist, how can I defend my call to recommend replacement?

OTOH, if I state this this might be a concern, this opinion grounded (for example) in the the fact that this method of construction is no longer allowed, state that in my opinion the best way to evaluate this chimney would be 1) a Level II inspection of the interior of the flue by a qualified chimney technician and 2) inspection of the chimney structure by a mason experience in chimney construction, then it appears to me that I am addressing a possible concern (the only concern I can legitimately have), and recommending a reasonable way to address it if the client desires.

Now, I will certainly tell the client that the changes of direction in this chimney may affect it's performance, that it likely can't be relined, and that it was not designed for the appliances connected to it, and so on.

But all I know is that the ones I see like it appear to be performing properly as regards the offset.

So I'll *strongly* suggest that when you come out to look at it, they discuss these issues with you.

And if you, as an expert in this area, are convinced that this chimney ought to be replaced, and they ask me what I think, I'm going to say "Bob Harper is the expert here - he's forgotten more about fireplaces than I will ever know - and I would give his opinion serious consideration".

But that's because you have the experience and knowledge to look at the totality of the situation and make that judgment for that individual chimney, irrespective of how the "average" similar chimney I see performs.

Michael,

Nobody can produce definitive evidence that, if a large asteroid hits planet earth, people will die.

That does not, however, stop sane people from realizing that people will die if a large asteroid does strike planet earth.

And no one needs to see that proof before understanding what would likely happen.

You see that chimney is offset approximately 45 degrees. You KNOW that is not a good thing (by your own statements, it is obvious that you KNOW that). Yet you insist on standing on the premise that it is a harmful thing to point out to your clients that any chimney offset that far has a chance of failure at any time.

'Passing the test of time' *IS NOT* a safety device. To the contrary, all which has been shown is that it has not fallen *YET*. 'Time' is ticking away and running out. When the clock will stop, no one knows, but you stand there defending not reporting it.

That is not, in my opinion, and, apparently many others here, 'having your clients best interests' as your goal.

It seems you are more concerned with protecting your 'integrity', whatever that is and whatever good that does, and protecting yourself from being called 'an alarmist deal killer' for reporting *THE FACT* that any chimney offset that far 'is not inherently safe', and that its demise could lead to injury.

Why do you think so much time and money as been spent on keeping the Leaning Tower of Pisa from leaning further? Answer: Because it will fall over.

I just don't get it (your position).

Jerry,

On the objective evidence, a ten year old furnace is a greater risk that a typical Chicago offset chimney.

Do you suggest we call out every ten year old furnace for replacement?

If not, why?

"A Buffalo firefighter is clinging to life this morning after he was seriously injured on the job.

Firefighter Mark Reed of Engine 31 is in intensive care at Erie County Medical Center after fellow firefighters say a chimney collapsed on him.

It happened as Reed and fellow firefighters were battling flames inside a house at 120 Wende Street. Investigators say the empty house quickly became unstable. Then about ten minutes after crews got to work, disaster struck.

Witness Maria Redd-Moss says "I was standing on the porch, I actually seen the chimney began to collapse and fall. Then I heard a big crashing. I didn't think anyone could have been below it but then they started yelling and screaming and paramedics and everybody were running in the backyard."

Now we have a statistic and a reason to call it out. If the house has a fire reach the attic or the framing the chimney WILL collapse and likely kill an unsuspecting fireman.

Jim,

But ... Michael can only use that after the fire starts.

Sorry, Michael, but you set yourself up for that one.

(I can see Michael's response: BUT ... did that chimney collapse *because* of an offset like the one in the photo? Maybe the offset would have saved the chimney from collapsing.)

Originally Posted by Bob Harper

.... Let me play the devil's advocate: you inspect a home and fail to call out such an installation. There is a personal injury or property loss.

You admit in the deposition you are aware this construction is no longer allowed in the code or NFPA 211, the national standard for chimneys.
You admit you are aware such a hard offset may have adverse effect on proper chimney performance such as condensation, CO leakage, or even spillage.
You recognize all these perils yet you failed to warn your client.

See my point? I advise you help your client make an educated decision.

Bob

Agreed.

I notice that no one here seems willing to address the question asked above:

"What is the logic of calling out every over-offset (by current standards) chimney we encounter for immediate replacement because we suspect it might be increasingly prone to failure, but not doing the same for every 10 year GFAF heat exchanger we encounter because we know it's increasingly prone to failure?"

Unless someone can justify that decision (or they recommend blanket replacement of older GFAFs) IMO they have not really thought through the logic of their decisions about what to recommend, and why.

(And, yeah, that chimney in that fist picture is a really extreme example, and by virtue of it''s construction IMO is more that usually suspect. My concern is the more typical Chicago chimney, with 6-12" inches of offset in 5-6' of rise.)

"You recognize all these perils yet you failed to warn your client."

(Turning to page 17 of the report).

"I stated that the offset of the chimney did not meet current standards, and that while I did not observe visual evidence of structural distress to the chimney that 1) it's design might present a hazard and also that 2) I could not visually determine the condition of the flue, and thus possible internal damage to the chimney.

Therefor, I recommend 1) a Level II (video camera) inspection of the chimney by a qualified person to determine it's internal condition, and 2) evaluation of the structure of the chimney by a mason experienced with chimneys and flues, as in my opinion these specialists could determine more accurately than myself if the offset of this chimney was likely hazardous."

------

The reality is, if I inspected that chimney, and it went straight up and down, and it was in perfect condition at the time of inspection, and the next day it fell immediately after a lightning strike and killed or injured someone, my name is going to be on a lawsuit.

Bob if you want I can mail you a copy of the ASHI article or fax.
Send me an e-mail if so.

"and protecting yourself from being called 'an alarmist deal killer"

Jerry,

Any RE agent who knows me, and reads that, would be going "IF ONLY!..."

"Tough but fair" is the policy in my sector, and many is the time I've come home, told my wife: "Oh well, that's the last time I'm on that office's list" and sat down, wrote the report, and sent it off without a second thought for the "marketing" consequences.

Originally Posted by Michael Thomas

"Tough but fair" is the policy in my sector,

"fair" ???


To whom? Your client? The house? The seller?

Michael, again, I am not busting on you but I just want you to ponder something. In your first post you said,"Here in Chicago, I frequently see older chimneys corbelled far in excess of modern standards. When they have been constructed with a good mortar bond they can be successfully self-supporting to a surprising (to me, anyway) extent - when doing my own rehabs I've been amazed at how strong such a bond can be, sometimes it's hard to knock them apart with a sledge. And I've never seen one which appeared to be in good conditions fail inside an attic, or talked to anyone who has."

What constitutes a good mortar bond? Is this based on your visual inspection or some ASTM test criteria?
"which appeared to be in good condition"--again, based on what?
"fail inside and attic"--the problems with such chimneys are not limited to a collapse of the upper section. The flow resistance can cause condensation, premature heat exchanger failure, rusted out connector pipes, rotting flue, which can lead to blockages, condensation rotting the chimney top faster than freeze-thaw damage alone, etc.,etc.
Who have you talked to? Do you maintain a record of who you talked to and what their credentials are? I mean, afterall, if there is a lawsuit, this will become important information because its what you say you are basing your opinion on.

Michael, I would suggest to you that you need to re-examine your criteria for reporting defects and potential defects.

I have another question for you--if you feel such offsets are acceptable and not reportable, what amount of offset is unacceptable? Do you have some yardstick or can they offset 20 feet? How do you draw the line? I hope you see that you are substituting your own standards for national standards here. Many states will accept an opinion from an engineer or architect over the codes and standards. Are you a licensed professional engineer or AIA architect? If not, then I would suggest both you and these chimneys are hanging in the breeze.

Just trying to help,
Bob

Bob,

"I hope you see that you are substituting your own standards for national standards here."

Please note that I'm calling out the chimney as over-corbelled (or "offset", if you prefer), and stating that it may be potentially unstable.

It appears to me that the bone of contention is the correct recommendation; some feel the recommendation should be for immediate replacement, some (for example the "expert" cited in the ASHI article cited above) don't.

Originally Posted by Michael Thomas

It appears to me that the bone of contention is the correct recommendation; some feel the recommendation should be for immediate replacement, some (for example the "expert" cited in the ASHI article cited above) don't.

Michael,

Who do you believe is the 'greater' "expert", Bob or that one in the ASHI article?

Your call, of course. I just doubt that there are many here who would agree with you, except maybe TM.

Thanks Jerry,
I read the ASHI article with great interest. I would like to try to put that article into perspective of our original discussion and chimney shown here:
-the author is a home inspector- not a licensed professional engineer. No slight intended but when you get into "opinions" versus 'observations", this becomes important.
-The chimney shown in the article has an offset only a fraction of the one posed here. Not apples to apples.
-The chimney shown in the article has an offset right at the limit allowed by NFPA 211.
-The mortar joint(s) are NOT all level--just the one he picked out. Look at the joint btw his hands. It looks like a roller coaster. You cannot take one joint and make that generalization
-What is up with all those dark stains on the chimney? Creosote or soot?
-What are those whit-ish stains along the sides? Water marks?
-What is that big round mortar patch below his elbow?
-No contact with ridge board is not listed in the codes. Clearances to combustibles are, which he failed to state.
-There is combustible blown insulation piled up indirect contact with the chimney.
-There is some smaller wood packed out btw the rafter and chimney. Appears to be at zero clearance.
-there appears to be a cut rafter to the left. Did they cut out two rafters without doubling and heading off?
-The photo is tilted.

If you're going to write such an article, he should have listed all these defects and included the other pertinent facts such as what fuel/ appliance(s) are using or have been using this chimney; what is the condition of the flue liner; Is there a rain cap; have there been any complaints of water damage in the living spaces or in the basement; What is the condition of any heating equipment serving these chimneys; has a chimney contractor been brought in to address these and any other defects or questions as noted in a Level II inspection. Note he never even mentioned Levels of inspection.

If this inspector who wrote this article is calling this chimney in "good condition" then he may well have just impugned himself. I could make a case that he did exactly what he was hired to do instead of being objective and reporting the facts as they are instead of offering opinions. Before slinging mud, he should have proofed his own work first. This alone makes him a hippocrite. He keeps coming back to the need for experience. Yet experience is not needed to make accurate observations--training and education are. This author, whom I have no prior knowledge of or beef with, is probably a great inspector. However, when writing authoratatively, you'd better proofread it and follow your own advice by getting a peer review. I'm sorry but this inspector's big point about your experience leading you should have lead him to get more opinions and do a little research before writing such an article. My impression of this article is that it reflects the author's attempt at asserting his own superiority and authority over lower less experienced inspectors. Quite frankly, he sounded a little arrogant.

If you stick to making observations and base your opinions on codes and standards, you present your client with an educated decision. Yes, these severely corbelled chimneys do not meet current codes. They may have met code when built or may not. I am not being paid to conduct research into the codes at the time of constuction but to share what we now know and present it with your home in context. We do recognize the following potential hazards with such offset chimneys: colllapse; exacerbated condensation; spillage and flow restriction, etc. If you are worried about it, repair options might include tearing the chimney down to plumb and sound then replacnig with factory chimney, which is allowed a maximum offset from vertical of 30 degrees or seal up the roof and rebuild the chimney plumb. If the flue is rotten or other condiions exist to where the chimney cannot perfom its intended function, then the offset may be the least of your worries. you must look at it holistically.

For future reference, it is much easier and more accurate to drop a plumb bob with a tape rule to the chimney and photograph the actual offset. To know the maximum allowable offset, you would need to know the flue dimensions and where they are located. For instance, if this chimney has an 8x13 flue, you would assume the center line of the flue to be about 11 inches in from the side or centerline. However, a roof top inspection revealed the mason installed the flue with the short side facing the camera, which thereby drastically shortens the allowable offset. Pretty shoddy article. Reads more like a fluff piece to inflate his ego. Just my personal opinion.

Bob and Jerry gave some great advice in this thread. I rarely sign my posts by putting my P.E. after my name but in this case it seems necessary.

A typical (without internal reinforcement) masonry chimney that is offset more than the limits in the diagram that Bob posted is not self-supporting, is unstable, and is not structurally sound. For it to remain standing, it needs to rely on the adhesive bond of the mortar or on an external support such as the roof framing or on a combination of both.

To say that such a situation is OK because "it has stood the test of time" or "I've seen a lot of these that are still standing" is foolhardy, when failure carries the high risk of causing personal injury or death. Can you personally guarantee that the circumstances in the past (that have not caused the chimney to fail) will not change in the future? Of course not.

The risks from failure of a chimney that is offset more than the limits in Bob's diagram include: property damage and injury from masonry falling inside and outside the home, fire hazard from contact to combustibles (external support framing), fire and/or life safety hazard from a shift in the chimney that damages the flue and allows combustion gasses to escape, and life safety hazard to firefighters.

The thing about heavy things that are (or become) structurally unstable is that they can appear to be fine right up to the moment of failure. Once the failure process begins, often times it progresses rapidly, in a chain-reaction manner. An example of this failure mode in action is the collapse of the Twin Towers on 9/11 or an explosive demolition of a building (boom, pause, collapse).

It's an accident waiting to happen: one that threatens the life of the occupants of the home, the child playing outside in the yard, the person walking by on the street, and the firefighter who might be fighting a fire at the home.

Brandon W. Chew, P.E.

The problem is the recommendation.

As noted above, as best I can tell from my reading a 10 year old gas forced air furnace represents a significantly greater risk to my client than most of the '"over-offset'" chimneys I see.

If the correct recommendation is immediate replacement of every chimney not meeting modern standards, should I also calling out every 10+ old heat exchanger for replacement?

If not, why?

I find it interesting that during this discussion I have repeatedly asked this question - which I really do think would move this discussion along to a new and potentially even more interesting and useful level - and not only has it never been answered, it's never even been acknowledged...

Why do you have to make the call on the spot on whether to replace or not? An inspector reports his findings--not opinions. Can you predict the date and time when that offset chimney will eventually collapse? You can state today it does not meet current codes and list the hazards discussed on this thread then let them make an informed decision how to proceed. For instance, what does this chimney serve? It may be more cost effective to decommission that chimney, raze it below the roof to where it is stable (approx. attic floor level), then relocate or do with the fireplace or attached heating appliances. If you have atmospherically vented heaters, it may pay to switch them to Cat. IV units and pvc them out the side of the home. Ditto for water heater. Even with a masonry fireplace, there might be enough room to install a gas direct vent in its place.

All you need to support your points are two simple facts:
1) masonry chimneys do erode over time and will eventually need repointing or rebuilding and
2) gravity works

I could add wind pressure, too along with performance issues but you get the point.

Bob

Originally Posted by Bob Harper

Why do you have to make the call on the spot on whether to replace or not? You can state today it does not meet current codes and list the hazards discussed on this thread then let them make an informed decision how to proceed...

Bob, as noted in my posts above, starting with post #5 - my first post to his topic - and repeated in post # 8 and reiterated in post # 27, that is what I currently do.

My sin in the eyes of some posters here - as best I can determine it - is that I do not issue a blanket recommendation of immediate replacement for every "off-set" chimney I encounter which does not meet current standards, based on the fact that it will fail at some point in the future, and likely sooner that a chimney meeting the current standards.

I tell clients this is the case.

I point out the possibility of significant property damage and/or personal injury or death if the chimney falls.

I inform them that for these and other reasons - such as reclaiming of interior space and the elimination of a roof penetrations prone to leaks - I have removed all such chimneys at my own projects, including my own home.

I recommend that if they wish additional information about the condition of the chimney that they obtain a level II inspection to determine its interior condition, and the advice of a masonry contractor familiar with chimney design, installation and maintenance to assess the chimney's condition and stability and the possible requirement for and means of reinforcement when deciding how to proceed.

What I have never said, here or to a client, that "such offsets are acceptable and not reportable", nor have I "substituted my own standards for national standards".

What I have said is that if someone believes that I am obliged to call for immediate replacement of every such such chimney I see, because failing to do so puts me the position of "waiting for a known 'bad thing' to happen just so you can then use that documentation for the next 'bad thing' to happen", they also need to explain why I should not also be condemning every 10 year old heat exchanger I encounter, as these appear to me to objectively create a greater hazard if "having my clients best interests" is my goal.

And I'd really like some answers to that question, as it goes to the heart of determining how we should approach our responsibilities to our clients.

Michael,

When you find something wrong, do you:

- tell them what is wrong

- tell them what can happen if not corrected

- tell them it should be corrected

- tell them it is okay to leave in service as it is

The first two you have covered in your posts above, which of the last two do you do?

Jerry,

It seems to me there is an entire missing step there, and it's what I trying to get at with my (still unanswered) heat exchanger question: when the result of a condition is some (often relativity low) probability of a disastrous event in the future, how do we decide whether the correct recommendation is "it should be corrected" or ''left in leave in service as it is").

Why is it we don't we just recommend replacing heat exchangers after 10 years, as these are more likely to kill people than chimney falls in attics?

Originally Posted by Michael Thomas

It seems to me there is an entire missing step there,

There is no step missing in my above post.

You report what is found, then make a recommendation based on your personal and business decisions you have established for yourself/your business.

and it's what I trying to get at with my (still unanswered) heat exchanger question: when the result of a condition is some (often relativity low) probability of a disastrous event in the future, how do we decide whether the correct recommendation is "it should be corrected" or ''left in leave in service as it is").

Answer my question in my post above and I believe you will find your answer.

Today, the master speaks in koans - it's all too deep for me.

Perhaps tomorrow he will condescend to answer the question in a form better adapted to the merger capacity of my intelligence, which basely suspects that answering a question with a question is a way to avoid an answer.

Like the old saying "Seek and ye shall find."

That's not saying "Go out and look and it will be right there."

No, what that is saying is "IF YOU DON'T GO OUT AND LOOK, you shall not find."

And, "When you go out and look, you will find where it is not, until, eventually, and after many findings of 'where it is not', you will find 'where it is not where it is not'."

Now, if that is too deep for you ...

I asked:

When you find something wrong, do you:

- tell them what is wrong (and I stated "The first two you have covered in your posts above")

- tell them what can happen if not corrected (and I stated "The first two you have covered in your posts above")

- tell them it should be corrected (here, I expected you to answer "sometimes")

- tell them it is okay to leave in service as it is (here, I expected you to answer "sometimes")

Now, think Grasshopper, think ... under what conditions do you "sometimes" do each of those?

Apply those answers to your question ... and you shall find what you are seeking.

While we are discussing “offset ” and ”corbelling”, here’s an interesting page from a site referenced by Raymond Ward in another thread here:

http://www.ibstock.com/pdfs/architec...corbelling.pdf

Originally Posted by Michael Thomas

The problem is the recommendation.

As noted above, as best I can tell from my reading a 10 year old gas forced air furnace represents a significantly greater risk to my client than most of the '"over-offset'" chimneys I see.

If the correct recommendation is immediate replacement of every chimney not meeting modern standards, should I also calling out every 10+ old heat exchanger for replacement?

If not, why?

I find it interesting that during this discussion I have repeatedly asked this question - which I really do think would move this discussion along to a new and potentially even more interesting and useful level - and not only has it never been answered, it's never even been acknowledged...

I've come late into this thread, but I'll bite and take a shot at it.

I assume we are comparing a chimney with an excessive offset and that has no visible signs of failure in progress, with a 10 year old heat exchanger that has no visible signs of either actual cracks or conditions that would lead to cracking or rusting through. You ask why recommend the chimney be replaced and not the heat exchanger.

In the case of the chimney, the defect is already present and is in the plain sight of the inspector. The defect is the excess offset. The defect is not a condition that "may be potentially unstable" (your words); it is one that is unstable by design and construction. The backup for that is the diagram Bob posted from NFPA 211. It is, literally, a house of cards just waiting for the right set of circumstances to occur that will cause the onset of failure, and when failure occurs it will most likely progress rapidly with dire consequences to life and property. The circumstances could be something as simple as the highway department disturbing the road surface near the house and now street traffic hitting the bump sends a small but repeating vibration up the chimney.

I make it quite clear to the client in plain English that this defect could result in a situation that could easily kill them and if it occurred while a fire was burning it could result in loss of the home. I do not soft-sell its significance with inspector-speak like "doesn't meet current standards" (the client has no idea what that means) or add comments like "I've seen plenty of chimneys with excessive offset and they are still standing" or "this one has been here x number of years and it doesn't look like it has started to fail". I'm not saying that you say these things to the client, Michael, but any inspector that does say them needs to think hard and ask themselves whose interests are those comments are serving.

After I have explained to the client the consequences of the defect, my recommendation is not to "replace" the chimney, but to immediately take steps to eliminate the known defect (excessive offset) and the hazards it presents. I advise the client to consult with a chimney and venting specialist to discuss methods and determine the costs of correcting the problem. And because of the potential hazard and cost to correct it, I encourage them to do so before they take title to the home.

Now, your case with the heat exchanger is an apples and oranges situation when compared to the chimney. Because there is no visible crack or evidence of conditions that would lead to cracking or perforation of the exchanger, there is currently no present defect. Also, since a good portion of the exchanger is not visible to an inspector during the course of a typical home inspection, the ability to determine whether or not such a defect is currently present is not in plain sight of the inspector. Recommending replacement of an exchanger simply because it is 10 or more years old is simply the opinion of the inspector that it is prudent to do so. The inspector may have many good reasons to support that opinion but it is not based on a present defect that is in plain sight of the inspector.

What I do when I find a heat exchanger that is 10 or more years old (with no cracks or conditions that would lead to them that are visible to me), is inform the client of the potential risk, explain that I cannot do a proper inspection of the exchanger within the scope of our contracted services and there could be cracks that I cannot see, and recommend that they have a HVAC specialist come out, pull the exchanger, inspect it, and make a recommendation about whether or not it should be replaced. And because of the potential hazard and cost to correct it, I encourage them to do so before they take title to the home.


Now, an apples to apples comparison to the situation with the chimney would be one with a current defect in plain sight of the inspector. The first example that pops into my mind is finding a breaker in a panel that is too large for the wiring on the circuit it is protecting. It might have been that way for twenty years without a causing problem. That could be because the right set of circumstances hasn't occurred yet to overload the circuit. Do you tell the client things like "I've seen this a lot and the house hasn't burnt down" or "it's been this way for 20 years so you can wait to get it fixed"? Of course not. Do you hand it off to an electrician for further evaluation? No. You tell the client to have an electrician fix it (remove the defect).

Now, back again to the heat exchanger. If the defect (crack) is currently present and in plain sight of the inspector, do you recommend replacement of the exchanger, or further evaluation by a HVAC tech?

For your entertainment.

This stub is actually freestanding, the board at left leaning on the underside of the roof and provides no support to the chimney, the 2x4" material is nailed to to the chimney to support items on the hooks screwed into it.

Then, to top it off, they elbow out of it back to the right ...

What was that serving with the metal flue/vent?

The chimney is resting on a 2x.That 2x has been reclaimed from another job and is possibly not original when the house was built.See the marks from the old wood lathe and plaster.Also the brickwork looks like it might be cracked at the bottom right corner.and it it also looks like it has been repointed in spots.Just my opinion from looking at the picture.Any outside pictures?Great picture,your camera?

Originally Posted by Bruce Breedlove

1915 house. The roof structure has done a good job of holding up this chimney for over 90 years. There is no way it could have supported itself.

The older they become the sooner they may/will fail.
Document the implications and move on.

T.Neyedli CHI
BPCPA #47827
www.alphahomeinspections.ca

I was referring to the picture at the beginning of the thread and not the latest one

Originally Posted by Terry Neyedli

The older they become the sooner they may/will fail.
Document the implications and move on.

I hope that by "document the implication" you are saying to write them up for deconstruction and reconstruction, which is the correct way to address it.

And that why you say "and move on" you are not saying to mention it in the body of the report to cover your butt and let it go at that, because if you are you will one day be responsible for when it fails and should be included in the lawsuit which follows.

Originally Posted by Jerry Peck

Then, to top it off, they elbow out of it back to the right ... What was that serving with the metal flue/vent?

GFAF and WH. The single wall you can see transitions right above the top of the picture to B-Vent were it passes through the roof. No way to tell if there was a "chimney liner" below that "cap".