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Posted: 1/27/2011 4:09:57 PM EDT
[Last Edit: 1/27/2011 4:11:37 PM EDT by NAM]
I'm looking over a past chimney report of my place (level 2, from Aug 2010) It states everything is in great shape, with 4 minor issues.

1. chimney flashing in need of repair (we fixed this since...had a new roof put on)
2. Flue Liner: he lists it is 7.5 clay in good shape, but mentioned that there are 2 thimbles. Is two thimbles really that bad, if one is closed?
3. moisure resistance. Not sure what this means, as there is no explanation other than a checkbox by "unsat".
4. Combustible material within 2" of chimney. This is a farmhouse build ~75-100 years ago. The chimney has been fixed/rebuild since, but there's no way to put a chimney in a house, and keep flammable material more than 2" away. Is this more less a code issue on new installations, or is this really a major issue in my case?

As mentioned, my only real quesition is with #4. #1 has been fixed. in #2, one of the thimbles will be closed off, and is below where the stove will be, near the cleanout. as for #3, i have no clue what this is in reference to.

We have trees for firewood, and would really like to use a wood stove to supplement propane. A new Class 3 or masonry chimney won't be cheap, but if it's a must, we'll do what we have to. I just am looking over the report, and everything looks in great shape except for that #4. Any recommendations/suggestions?
Link Posted: 1/27/2011 5:38:16 PM EDT
Link Posted: 1/28/2011 4:11:33 AM EDT
Originally Posted By thebeekeeper1:
Even triple wall stainless must have 2" clearance to combustibles, so I would not use a tile flue that didn't have adequate clearance.


I think masonry chimneys are a an entirely different animal from metal chimneys though. There are several places where my brick chimney with 3 tiled flues doesn't have 2" of clearance to framing. I would think you would need a heck of a chimney fire to get the brick hot enough to ignite wood.

The "moisture resistance" part sounds like you may have spalling brick that needs to be sealed. It could also just be they want to sell you a sealant .
Link Posted: 1/28/2011 4:35:42 AM EDT
Originally Posted By prov:
It could also just be they want to sell you a sealant .


And that is my biggest concern. I am having doubts about whether this was a true inspection, or a sham...trying to get me to buy more shit. The moisture resistance could have been related to flashing/roofing near the chimney, which has been replaced. My roof was in bad shape, but is now new metal.

Everything I've been reading says an internal chimney is far better than an external or Class A type. Right now, our boiler and water heater vent through the chimney, via thimble in the basement. There is another thimble in our living room that would be where I'd like to put the wood stove. I understand I would have to reroute the boiler/water heater if I use it for a wood stove.

So...my options are:

Use existing chimney, reroute boiler/water heater.

or

Install external masonry or stainless class A chimney.
Link Posted: 1/28/2011 5:25:11 AM EDT
I don't know what the best option is but you are right about the upsell. I had some work done last year and 2 big companies wanted to do 15k worth of work. I then had a couple smaller family owned companies come and look and they were a lot more straight with what actually needed to be done and what the options were.


Link Posted: 1/28/2011 7:17:38 AM EDT
[Last Edit: 1/28/2011 7:18:45 AM EDT by brickeyee]
Originally Posted By prov:
Originally Posted By thebeekeeper1:
Even triple wall stainless must have 2" clearance to combustibles, so I would not use a tile flue that didn't have adequate clearance.


I think masonry chimneys are a an entirely different animal from metal chimneys though. There are several places where my brick chimney with 3 tiled flues doesn't have 2" of clearance to framing. I would think you would need a heck of a chimney fire to get the brick hot enough to ignite wood.

The "moisture resistance" part sounds like you may have spalling brick that needs to be sealed. It could also just be they want to sell you a sealant .


Clearance to combustibles depend on how thick the chimney is from flue liners to outer brick facing.

Two wythes usually can get to zero clearance IIRC.


Brick sealants can be a BAD idea.

They can trap moisture inside the brick and lead to spalling if the water freezes.
Link Posted: 1/29/2011 7:31:55 AM EDT
[Last Edit: 1/29/2011 7:33:43 AM EDT by ZW17]
Link Posted: 1/31/2011 4:49:49 AM EDT
You are fine unless the sweep told you it was a major issue and not to use the flue. As for the moisture, he was trying to sell you a sealant, likely chimney saver. It is really good stuff, and breathable. You may also have some damage on your crown, which is where water first starts to destroy a chimney. Chimney's ARE much more vulnerable to water damage than regular brick walls due to their exposed nature and the fact that they go through much more dramatic heating/cooling and freeze/thaw cycles.

You will be more than OK if you install a modern stove with a stainless steel liner that is insulated. At that point, clearance becomes a non-issue except for the books. This will also ensure the best draft and least amount of creosote build-up. A liner is not necessary in your installation, but would truly be the best way to go. While you are up top doing the work, you can seal any cracks in your chimney crown and maybe apply a product called "crown-oat" that does a great job keeping this weak point in good shape.

Lastly, make certain the other thimble is air tight, as well as the clean out. At least if you are not using a stainless liner. Those leak point will reduce the draft through your stove and cause one or all of the following problems: Smoke entering the house when stove is opened, creosote build-up, hard lighting, difficulty maintaining the fire, and smoke build-up on the door glass even if it has an air wash.

Link Posted: 1/31/2011 4:55:00 AM EDT
Originally Posted By BustinCaps:
You are fine unless the sweep told you it was a major issue and not to use the flue. I was not around when he did the inspection, but he stated that combustible material was flush with the masonry/brick (i.e. studs, ceiling, plaster, etc) As for the moisture, he was trying to sell you a sealant, likely chimney saver. It is really good stuff, and breathable. You may also have some damage on your crown, which is where water first starts to destroy a chimney. Crown is brand new...upper portion of chimney was rebuilt within the last year or so. It was marked as satisfactory Chimney's ARE much more vulnerable to water damage than regular brick walls due to their exposed nature and the fact that they go through much more dramatic heating/cooling and freeze/thaw cycles.

You will be more than OK if you install a modern stove with a stainless steel liner that is insulated. At that point, clearance becomes a non-issue except for the books. This will also ensure the best draft and least amount of creosote build-up. A liner is not necessary in your installation, but would truly be the best way to go. While you are up top doing the work, you can seal any cracks in your chimney crown and maybe apply a product called "crown-oat" that does a great job keeping this weak point in good shape.

Lastly, make certain the other thimble is air tight, as well as the clean out. At least if you are not using a stainless liner. Those leak point will reduce the draft through your stove and cause one or all of the following problems: Smoke entering the house when stove is opened, creosote build-up, hard lighting, difficulty maintaining the fire, and smoke build-up on the door glass even if it has an air wash.



Link Posted: 1/31/2011 7:30:06 AM EDT
Originally Posted By NAM:
Originally Posted By BustinCaps:
You are fine unless the sweep told you it was a major issue and not to use the flue. I was not around when he did the inspection, but he stated that combustible material was flush with the masonry/brick (i.e. studs, ceiling, plaster, etc) As for the moisture, he was trying to sell you a sealant, likely chimney saver. It is really good stuff, and breathable. You may also have some damage on your crown, which is where water first starts to destroy a chimney. Crown is brand new...upper portion of chimney was rebuilt within the last year or so. It was marked as satisfactory Chimney's ARE much more vulnerable to water damage than regular brick walls due to their exposed nature and the fact that they go through much more dramatic heating/cooling and freeze/thaw cycles.

You will be more than OK if you install a modern stove with a stainless steel liner that is insulated. At that point, clearance becomes a non-issue except for the books. This will also ensure the best draft and least amount of creosote build-up. A liner is not necessary in your installation, but would truly be the best way to go. While you are up top doing the work, you can seal any cracks in your chimney crown and maybe apply a product called "crown-oat" that does a great job keeping this weak point in good shape.

Lastly, make certain the other thimble is air tight, as well as the clean out. At least if you are not using a stainless liner. Those leak point will reduce the draft through your stove and cause one or all of the following problems: Smoke entering the house when stove is opened, creosote build-up, hard lighting, difficulty maintaining the fire, and smoke build-up on the door glass even if it has an air wash.





Believe it or not, that situation is extremely common with the clearance. If you go the route of an insulated stainless liner you will not need to worry, even though it is out of spec. Without the insulated liner, you have a slightly elevated risk should you have a chimney fire. At that point, it is all about the condition of the flue tiles themselves, as well as how they were installed. MANY if not MOST masons DO NOT leave the required airspace between the tiles and the chimney brick. The void that is supposed to be there is often filled with mortar. That airspace is the best protection from the high heat of a chimney fire being conducted through to the structure. I know this to be a fact because 75% of the local clay tiles i remove around here are a total bitch to get out for that reason.

As far as an insulated liner goes, I have no idea what the standards for flues are in your area, but around here a chimney that you describe would tend to have an 8x13 flue tile with the internal dimensions being even tighter. (The exact dimensions vary widely by manufacturer.) Even with the tiles being removed, it will be a stretch to get an 8" liner in there, which is what is typically used by older stoves. A newer stove will require a 6" liner and even that will be difficult with the tiles removed if you use the typical wrap-around insulation. Your best bet would be a 6" liner with loose-fill insulation.

I would honestly have a sweep experienced in installation look at it again and give you advice specific to the installation. But from what you describe, you should be OK as long as the flue is in decent shape, even without a new liner. Just use dry wood, and sweep it frequently. The key is to avoid a chimney fire. DON'T damp the fire down to make it burn forever. Adjust the burn by adjusting the fire itself, not the damper.

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