extending flexible flu liner above chimney crown

[Joern]

Hi,

I have a 36 year old house with a double flu chimney where the chimney crown is only 14in above the roof top, the flue tiles maybe 18in.
There are two wood burning fireplaces, one in the basement and one first floor using this outside chimney.

After cleaning and inspection the chimney sweep discoved that one of the flues has cracks in it from a previous chimney fire.

I bought a fireplace insert and want to reline the cracked flu (myself) with a 6in flexible liner kit but also extend
the liner above the chimney crown in order to have enough clearance.

I plan to use the extend-a-flue product for the other intact flu and put a damper-cap on it.

Now I have a couple of questions:

What kind of (rigid) pipe can I use for the 2ft section between the flashing adapter and the rain cap?
Would the flexible pipe go all the way up to the rain-cap, or do I need to put a piece if double walled chimney pipe up?

Since I only have 7x11.5 in inside clearance of my flu tile I would rather not insulate the flex liner -
would this be against code having cracks in the tiles?

How is the 2-3-10 clearance measured, from the chimney crown or from the flue opening?

Please share your ideas with me,

Thanks,

Joern

BTW: I was quoted prices for re-lining the flue $8000 and rebuilding the chimney from rooftop up 3 feet for $5000

 

[elkimmeg]

Since I only have 7x11.5 in inside clearance of my flu tile I would rather not insulate the flex liner -
would this be against code having cracks in the tiles?

How is the 2-3-10 clearance measured, from the chimney crown or from the flue opening?

2-3-10 code adresses the actual chimney not the extended flueliner height as the extended flue liner height is only one component of a chimney make up and not the actual complete chimney. Acccording to NFPA-211 the flue liner can only extend 2" beyond the cap.
I know masons extended the bare unprotected liners to gain height this is called a cheat, which will not pass inspections in my town.

Now it you use a product like extenda flue designed and tested to achieve extention,
I have no problem approving such an installation

PM our webmaster concerning it he the guy than knows the most about them

Second part of your question liner. Commonly there are various liners that pass UL listings the cheaper 304 composit stainless steel,
which requires insulation to achieve the Ul listing. And the stronger better blend stainless steel 316 ti HT-2100, also cost more. By its self, it passes code without being insulated providing insulation is not a manufacturer listed spec. Some manufactures may list their liner to require it being insulated in an exposed to exterior wall location regardless of the stainless steel make up.

There is also one other factor to consider the lessed grade liner can be used in a chimney in good condition. I doubt it can be substuted in a compromised chimney. the 316ti can

You can run you liner and attach a 2' section of class A chimney pipe extending beyond you flue to achieve the required height.
You are running a chimney pipe designed to do so.



PS. you made no mention of a damper block off plate???

 

[Joern]

Thank you very much for the quick response.
I will try to go with the higher quality 316ti liner and no insulation and a grade A 2foot pipe for extending the cracked flu.

...
PS. you made no mention of a damper block off plate???

Regarding the damper block-off plate, I though I can remove the (currently shot) dampers in both flues and put a chimney top damper-cap on the intact flue after extending with extend-aflue.
For the lined flue I thought I don't need a damper anymore because it will be sealed off by the fireplace insert?! Please correct me if I am wrong with this assumption.

Thanks,
Joern

 

[elkimmeg]

The existing un damaged flue is not the concern


Lets deal with the fireplace flue and location of your new stove,

Many remove the damper plate then use oval to round pipe to pass threw the damper opening to the new flue liner,
that is an acepted practice but not the best condition to promote a good draft. If the damper is shot, the best solution is to cut out enough so that the pass threw that area round. Straight runs and round flues are optium for the best draft preformance.

Code also addresses sealing that damper area from the dilusion of room air. This is where there is no substitution of a decently sealed damper block off plate.. Many members have preformed this task and can help advise how to go about cutting you damper, running your liner, and damper plate make up

 

[webbie]

Hi,

I have a 36 year old house with a double flu chimney where the chimney crown is only 14in above the roof top, the flue tiles maybe 18in.
There are two wood burning fireplaces, one in the basement and one first floor using this outside chimney.

After cleaning and inspection the chimney sweep discoved that one of the flues has cracks in it from a previous chimney fire.

I bought a fireplace insert and want to reline the cracked flu (myself) with a 6in flexible liner kit but also extend
the liner above the chimney crown in order to have enough clearance.

I plan to use the extend-a-flue product for the other intact flu and put a damper-cap on it.
Please share your ideas with me,


BTW: I was quoted prices for re-lining the flue $8000 and rebuilding the chimney from rooftop up 3 feet for $5000

You can purchase the "castings only" of any of the three Cast Classic extendaflue models and then run your liner up through them...that can give you from 2 1/2 to 4 feet total extra height above the top of the flue. Extendaflue can provide top adapters so that your liner can attach to a stainless ring at the top of the castings.

 

[Joern]

Sounds great - this will solve my chimney problems. I will search the forum what to do with the damper block off plate.

Joern

 

[BrotherBart]

Craig's article on making a damper block-off is at:

https://www.hearth.com/econtent/index.php/articles/making_a_block_off_plate/

 

[Joern]

...
Second part of your question liner. Commonly there are various liners that pass UL listings the cheaper 304 composit stainless steel,
which requires insulation to achieve the Ul listing. And the stronger better blend stainless steel 316 ti HT-2100, also cost more. By its self, it passes code without being insulated providing insulation is not a manufacturer listed spec. Some manufactures may list their liner to require it being insulated in an exposed to exterior wall location regardless of the stainless steel make up.

There is also one other factor to consider the lessed grade liner can be used in a chimney in good condition. I doubt it can be substuted in a compromised chimney. the 316ti can

Follow up question: I called the Mfg of the flex liner and they sell a 316L flex liner with a UL1777 rating. Can I use this instead of the 316ti HT-2100 ?

 

[elkimmeg]

Yes you can. The ss is 316 and the UL approval is the correct refference. It is probably HT 2100 also thought he did not mention it
All 316 SS I have reviewed are HT 2100 listed. HT 2100 is the amount of degrees it can withstand a certaint amount of time exposed to a chimney fire before it looses its properties. Most chimney fires do not reach 2100 degrees but around 1800 and most are of short duration

 

[BrotherBart]

Follow up question: I called the Mfg of the flex liner and they sell a 316L flex liner with a UL1777 rating. Can I use this instead of the 316ti HT-2100 ?

The key difference between 316l and 316ti is resistence to "sensitization". Sensitization is where the stainless reaches a temperature where the anti-corrosive chromium in the alloy precipitates (between 1100 and 1600 degrees) and you lose the anti-corrosive properties added by the chromium to the stainless. While a 316l chimney will withstand a chimney fire, it is less likely to come out of the experience with the ability to continue use. 316ti, with the stabilization that the Titanium gives the alloy, has a better chance of continued use after a chimney fire.

In other words, if they are both the same price buy the 316ti.