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Chimney Relining Methods

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Unread 10-10-2019, 07:24 AM   #1
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Chimney Relining Methods


Could use some advice on hiring a contractor to reline a chimney due to cracked terra cotta liner and missing a few chunks... In this case with two adjacent flues, fireplace and boiler/HWH. Two story cape cod, circa 1947.

Just got an estimate (yikes) for busting out the terra cotta of both liners, they are close to each other, and then installing stainless flex, etc. Is the preferred method? The clay dimensions are on the smaller side, maybe 8" x 12" for the fireplace, to give an idea.

As an alternative, I just read about adding a heat shield product to coat and seal the existing terra cotta. Any knowledge of that? Supposedly done in europe, and I do like the idea of not vibrating the the heck out of the brickwork. We're calling that company next.

Thanks.
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Unread 10-10-2019, 07:41 AM   #2
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Re: Chimney Relining Methods


Why do they have to remove the terrain cotta? Around here, when they re-line a chimney, they drop down a stainless steel flex tube, and then attach that to the vent pipe from the appliance.

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Unread 10-10-2019, 07:45 AM   #3
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Re: Chimney Relining Methods


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Originally Posted by jeffmattero76 View Post
Why do they have to remove the terrain cotta? Around here, when they re-line a chimney, they drop down a stainless steel flex tube, and then attach that to the vent pipe from the appliance.

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Good question. Size of flue, apparently. I was wondering about this, too.

And they are recommending doing both flues, since busting one is going to probably break the combustion gas one if it's not already.
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Unread 10-10-2019, 07:47 AM   #4
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Re: Chimney Relining Methods


Not an expert, but you may want to get more than one estimate.

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Unread 10-10-2019, 08:36 AM   #5
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Re: Chimney Relining Methods


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Originally Posted by jeffmattero76 View Post
Why do they have to remove the terrain cotta? Around here, when they re-line a chimney, they drop down a stainless steel flex tube, and then attach that to the vent pipe from the appliance.

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That's what I did with my fireplace insert. Installation was easy and it works great.
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Unread 10-10-2019, 08:46 AM   #6
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Re: Chimney Relining Methods


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Originally Posted by MarkJames View Post
Good question. Size of flue, apparently. I was wondering about this, too.

And they are recommending doing both flues, since busting one is going to probably break the combustion gas one if it's not already.
You are being taken for a ride.......again
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Unread 10-10-2019, 08:47 AM   #7
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Re: Chimney Relining Methods


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You are being taken for a ride.......again
I sense that. Please elaborate. Thanks.
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Unread 10-10-2019, 01:08 PM   #8
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Re: Chimney Relining Methods


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Originally Posted by MarkJames View Post
I sense that. Please elaborate. Thanks.
There is no need to bust up the liner, not many chimneys that need liner would survive breaking the existing liner. A stainless steel line will easily fin inside it and depending on the appliance connected may or may not need to be grouted in place.

I had a customer who had a ungrouted one 6" with a blower that starts before the furnace starts and shuts off after. There is a Tee just before it goes into the chimney with a baffle that automatically opens and closes so that just the correct amount of air is being pulled through the furnace before, during and after firing.

HVAC guy said condensation was an issue since he had a tall chimney. They did it in 5 hrs including blower

I think they did put some type of insulation around the liner from the top, not sure what it was.
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Unread 10-10-2019, 01:41 PM   #9
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Re: Chimney Relining Methods


How about the re-lineing where they use a bladder ?
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Unread 10-10-2019, 01:54 PM   #10
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Re: Chimney Relining Methods


This is a wood-burning fireplace, btw. After having a closer look myself, this is an issue of missing mortar in a couple spots, like chunks that have fallen out.

Anyway, first guy recommends a bust it out for air flow sizing with the liner.

Second guy says he doesn't bust out 9 x 13's, since it's too much risk of extra damage, and you don't know what debris/if any is part of the fill behind the liner. There's a chance of knocking out an exterior brick with the hum-dinger (liner buster), etc. Also, he says the firebox would need to become a little smaller to meet the flow calculation, if a flex liner is installed into the existing flue.
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Unread 10-10-2019, 05:14 PM   #11
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Re: Chimney Relining Methods


Quote:
Originally Posted by MarkJames View Post
This is a wood-burning fireplace, btw. After having a closer look myself, this is an issue of missing mortar in a couple spots, like chunks that have fallen out.

Anyway, first guy recommends a bust it out for air flow sizing with the liner.

Second guy says he doesn't bust out 9 x 13's, since it's too much risk of extra damage, and you don't know what debris/if any is part of the fill behind the liner. There's a chance of knocking out an exterior brick with the hum-dinger (liner buster), etc. Also, he says the firebox would need to become a little smaller to meet the flow calculation, if a flex liner is installed into the existing flue.



There is merit to what he said about firebox sizing. Also,in a square or rectangular liner,the corners don't figure into the formula,they are considered dead airspace. So,for example,in a 12 x 12 liner you do not get 144 sq. inches of volume. You get the area contained in a circle that can fit in that square.
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Unread 10-10-2019, 07:20 PM   #12
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Re: Chimney Relining Methods


I never heard that the corners of a square flue dont count. hmmmm....

You have to get your chimney certified anytime you upgrade your appliance efficiency. They were pushing the flues on everything here in NJ before the state pulled back on HOT WATER heaters.

The logic is as less heat is lost up the flue, acidic condensation erodes the clay flues which can drop shards down and block flue gas. CARBON MONOXIDE. Since all new furnaces are higher efficiency its a mandate to reduce the flue size to keep the temps up. 6" covers most all of these cape single family homes. Specially when the chimney runs up on the outside.

They laid off on HOT Water heaters because of two fold. One was these water tanks have not changed in efficiency in years and the other problem was people were avoiding permits to avoid paying for liner. Hustler/Salesman So if its clear some will certify it as is.

With a firebox its size cant be reduced. So repair it as is. They make some kind of coating that they use to line flue-less chimneys (just brick) It spins/splatters up the walls but it wont fill a chink of missing clay
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Unread 10-11-2019, 10:02 AM   #13
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Re: Chimney Relining Methods


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I never heard that the corners of a square flue dont count. hmmmm....
y



A round, insulated flue is the most efficient design for venting exhausts because of the way flue gases spiral in the chimney. This spiraling of flue gases in round flues eliminates the cold corners found in square and rectangle flues and allows the use of a smaller flue size which increases flue gas velocity. For instance square or rectangle flues are required to be 1/10 the size of the fireplace opening. Or, even as big as 1/8 the size of the fireplace opening, when a rectangle flue has a high aspect ratio. Cast in place liners only require between 1/12 and 1/18 the size of the fireplace opening for the flue size (depending upon the height of the chimney). Insulated metal round flues must always be at the 1/12 size regardless of chimney height, one reason being that metal flues heat up and cool down rapidly and are highly affected by cold outside temperatures.
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Unread Today, 11:05 AM   #14
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Re: Chimney Relining Methods


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Originally Posted by rrk View Post

I think they did put some type of insulation around the liner from the top, not sure what it was.
Normally vermiculite over here.
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Unread Today, 11:11 AM   #15
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Re: Chimney Relining Methods


I've been having second thoughts on the necessity of this job.

Yes, some mortar is missing in a couple places (between liner pieces), but it turned out that their mention of a crack never showed up in the pics they sent.

I'm probably going buy a boroscope and have a closer look myself. Chimney is mostly external to the structure, and only used a few times a year for wintery ambiance.
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Unread Today, 11:29 AM   #16
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Re: Chimney Relining Methods


Quote:
Originally Posted by MarkJames View Post
I've been having second thoughts on the necessity of this job.

Yes, some mortar is missing in a couple places (between liner pieces), but it turned out that their mention of a crack never showed up in the pics they sent.

I'm probably going buy a boroscope and have a closer look myself. Chimney is mostly external to the structure, and only used a few times a year for wintery ambiance.
Ever see a chimney fire? It only takes one time
Just get another opinion
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Unread Today, 11:44 AM   #17
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Re: Chimney Relining Methods


Quote:
Originally Posted by MarkJames View Post
I've been having second thoughts on the necessity of this job.

Yes, some mortar is missing in a couple places (between liner pieces), but it turned out that their mention of a crack never showed up in the pics they sent.

I'm probably going buy a boroscope and have a closer look myself. Chimney is mostly external to the structure, and only used a few times a year for wintery ambiance.
Maybe just start your cell videoing and dangle it down the chimney.

I've tried scopes, and by the time you get the picture quality with a narrow scope, there are usually tons of other options.
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Unread Today, 11:49 AM   #18
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Re: Chimney Relining Methods


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Originally Posted by rrk View Post
Ever see a chimney fire? It only takes one time
Just get another opinion
I've seen more than one. How bad they are depends on a few things, including how hot you run your fire and for how long.

They're no fun, and a gap in the liner system would be catastrophic if it isn't in a masonry chimney.
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Unread Today, 11:53 AM   #19
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Re: Chimney Relining Methods


BTW, small fires lead to faster build up. The key to reducing build up is avoid wet wood, most soft wood, and cooler fires. The very first fire you build should get very hot very fast to heat up the chimney and reduce deposits.
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Unread Today, 12:51 PM   #20
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Re: Chimney Relining Methods


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Originally Posted by hdavis View Post
BTW, small fires lead to faster build up. The key to reducing build up is avoid wet wood, most soft wood, and cooler fires. The very first fire you build should get very hot very fast to heat up the chimney and reduce deposits.
Really good advice. I've seen S/S liners wrecked in a few years by people burning wet wood, especially leaving the woodburners on a slow burn overnight.

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