# Cinder Block  Chimney?



## Febronia (Nov 5, 2006)

Hello-newbie here with a  quick question.  We moved into our home a year ago, and decided to go with wood heat due to struggling with oil/gas/ and electric heat cost(yes all three-this was the existing lay out)  The owners before us installed an oil furnance with duct work through half of the house and had two of our four chimneys rebuilt with cinderblock.  One is for the exhaust, but the other, upon our inspection in the cellar, is not being used by the furnance.  There was a circle shape on the wall outside of the chimney in my dining room, and thinking it was the flue, I knocked the wall out around it only to find that there isn't one-yeah, you should of heard my husband.  So my father came over and seen the cinder block chimney and said it was a no go-that the wood heat would cause it to crack, and since it's going between walls, it will be a major fire hazard.  So, basically I was wondering if there is a way to use it, like lining to inside with proper pipe, or if I should go ahead and buy some drywall and replace the wall, and just forget about using wood heat??  Any help greatly appreciated!


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## saichele (Nov 5, 2006)

It is a major fire hazard as is.  Depending on what the internal dimensions are, you might be able to get a 6" liner with insulation in there.  You could also run a pellet or corn stove vent up it.


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## Roospike (Nov 5, 2006)

Does the Cinder Block Chimney(s) have a clay liner or is it just Cinder Blocks?


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## Febronia (Nov 5, 2006)

Yes, we were hoping to go with a pellet stove.  The chinmey measures 21"x21" in our attic, and our wall is 8 inches thick(the chimney sticks out the back wall in the kitchen).  Since this is an old house, the wall itself has horsehair and plaster, so I thought it would be safer to replace the wall any way, and if we do use a pellet stove, use a heat sheild.  Something else-I still can't find a flue. Can a chimney sweeper be able to tell, or is there any way for us to find it? Thanks!


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## Febronia (Nov 5, 2006)

Roospike- we haven't been up on the roof yet to see if it's lined or not. Maybe my husband can do that tomorrow.


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## elkimmeg (Nov 5, 2006)

the block chimney should have 4" of solid masonry if it is solid chimney block and the motar joints  there are good there possibilities for its use. The other part of the equasion  it has to be sound motar joints is. 2" clearance to any combustiables  including ceiling and floor penatrations.   As Roo mentioned what size liner if ther is any? and its general condition. 
 If we know that info wer can better give you educated advice /options As it stands now, like you we are guessing


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## Roospike (Nov 5, 2006)

block chimney / 8 X 8 clay liner * For wood stove use.


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## Febronia (Nov 5, 2006)

Thanks-I'll see if my husband and father can find the information you all need. Also, earlier I posted external measurements, I'll get the internal measurements.  These chimneys were put in new three years ago, and the one in question has never been used.  The other one has an exhaust pipe for furnance, so maybe there is a liner-I'll find out and post back tomorrow.


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## Roospike (Nov 5, 2006)

Block.


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## begreen (Nov 5, 2006)

Wait, she says she wants to use it for a pellet stove. With a 3 or 4" flex liner this should be no big deal right?  The fact that it is cinder block won't matter much. 

I'd get some quotes from the dealers and see what they say. What stoves are you looking at? Make sure pellets are easily available and at a reasonable price in your area at this time of year.  Best to check first or it may be a cold stove.


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## Roospike (Nov 5, 2006)

And this is our Ole' buddy Eagle Eye ELKer inspecting the chimney liner.


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## elkimmeg (Nov 5, 2006)

Roospike said:
			
		

> And this is our Ole' buddy Eagle Eye ELKer inspecting the chimney liner.



 Here  the code violations he sees 
Violation #1  chimney blocks are not 4" solid masonry but in many cases less than 3". 
 Violation #3  Picture #2 check out the NFPA 211 it calls for solid blocks not cored and again this is made wores with less than the 4" required 
Violation #3   one inch air space is required between the suposedly soild masonry and the flue liner.
Violation #4   the clay liner is anly allowed to extend 2" beyond the chimney
Violation #5  if the blocks are cored and less the the nominal 4" masonry units  bricks, which they are,
 then the pass threw the wood frame structure , also violates code  dealing with clearance issues


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## seaken (Nov 5, 2006)

By far - the majority of masonry block site built chimney are in violation of building codes. But there are ways to update the chimney using specialized materials that have been tested to UL standards for this purpose. You will need local help. There is no way we can tell from here what exactly needs to be done. You might start by going to www.csia.org and searching for a qualified sweep or two, or three, by your zipcode.

Once you get some local opinions we may be able to help sort out the options for you.

Good luck,


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## begreen (Nov 5, 2006)

Is there a code reason why they can't safely use the existing flue as a chase in which the pellet vent pipe (flex or rigid) is run?


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## elkimmeg (Nov 5, 2006)

Be green thanks for bringing it back to the original post. If the double wall pellet vent can be positioned in that chimney such that it affords 2" clearance to combustiables it will be allowed their on the pellet vent merits.  Consider the block masonry chimney a convient chase passage way to the roof. The chimney, if flue lined and mortar joints soild. will afford additional saftey margins. If not the pellet vent will have to stand on its own manufacture specs and merits.

 Concerning Rooskpke photos: I had considered just PM to him my observations and not air them out on the forum. But when he added  my inspector avtar  and snide remark  
 I posted my response. all of which can be clearly found in NFPA 211.  I can take being the butt of jokes, but there is no joke where safety is compromised. 

 I also know if he lived near me, he would be the one I could count on, to helped me with yesterday's install.


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## Dave_1 (Nov 5, 2006)

Roospike said:
			
		

> And this is our Ole' buddy Eagle Eye ELKer inspecting the chimney liner.



 :lol:  Love it 

Got a brother-in-law I'm trying to get to abandon his & put in a class A. 

Some people are a hard sell.

So I taking your pic, blowning it up, adding Elk's comments, & giving him an early thanksgiving postcard with the info inside.  :lol: 

Dave


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## Roospike (Nov 5, 2006)

Just to note , I was not making ole' buddy ELKer the butt of any joke but he did end make the out come of the chimney the butt of the joke. :lol: Its all good fun. 

If you look closely at the chimney you can see it was freshly build. This is my brothers and he went to the local masonry shop and this is all the stuff he was sold to build a chimney.
Right or wrong he was / is none the wiser as this is what items he was sold for the job as per building a new wood stove chimney.


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## Roospike (Nov 5, 2006)

Some others if anybody is interested ...........


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## Roospike (Nov 5, 2006)

Took the siding off the house to build and will be resided . last one.


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## jabush (Nov 6, 2006)

That's exactly how my setup looks right down to the 18" or so of flu tile extending past the top of the block.  I don't think the block is vented on my chimney, unless the builder just used one un-vented block for the top.  Hopefully the full liner plus thermix insulation brought me up to/within code...


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## saichele (Nov 6, 2006)

How does the cost of a exterior block chimney (with liner) compare to the cost of just a standard metal Class A?

Steve


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## joshuaviktor (Nov 6, 2006)

ditto what steve asked.  Plus, what if you build a double flue?  Gonna need two flues in a couple of years, thinking either block or class A exterior (pair of).  Which is cheaper/better?

Joshua


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## Harley (Nov 6, 2006)

Roospike said:
			
		

> Block.



Hey... That's not Block... This is


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## joshuaviktor (Nov 6, 2006)

Hard to stack.  But definitely cute.


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## Roospike (Nov 6, 2006)

The building of the block chimney ( not Block the dog ) w/ the clay tile liner ended up costing about the same as my class A SS chimney and 66' black double wall pipe. The self built block chimney was a hair cheaper then you add his single wall interior pipe , so again , about the same.

Now add a stainless steel liner and the cost goes up what ever the cost of the liner.


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## elkimmeg (Nov 6, 2006)

ok time to back a step up I own a chimney block chimney that my Intrepid attaches to. Truth is one with some skill can install them.
 and one cah form a double chimney block chimney to carry two flues.

 Aslo truth being almost all  other inspectors would never come up with what I pointed out and they are probably passable in their jurisdiction.
 Ac ctually quite easy to build one could build them then make the choice of either clay or stainsess steel liner  the liner does not have to be clay

 Wife yapping at me  



 to be continued


 lets compare cost each chimney block 8/8 cost $7.75 16' requires 24 blocks and $ 186 Hidden cost mortar  wall ties and possibly the need 
 for a decent footing re rod pined to the existing foundation.  
 If installing 8/8 clay liners, each 2' section cost about $9 add about $15 for ash clean out door.

 Cost for  clay lined chimney 16'
24 blocks blocks     $186
8 Clay flue liners      $72
5 80 LBs Mortar        $36
wall ties and 
Ash door                  $25
 Lead flashing            40
 Labor could be done one weekend

 Total materials cost $360 you milage may vary depending on height, removing siding, building a cricket, and possibly a footing Plus masonry tools

 and some hard labor possibly a deliver charge 
And some companies do ASTME certify the blocks


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## BurningIsLove (Nov 7, 2006)

I have a recently installed cinder block chimney w/ 2 flues, one for my Dutchwest non-cat and the other for my oil furnace (guess which one is cold and lonely!).  There is a 6" clay liner in both which satisfies local building codes.  My only complaint is not any firehazard, but that the stack takes over an hour to get up to temp when started from cold, even though it's an internal chimney.  My masonry blocks are solid and the fire inspector had no issues with the setup.

pics attached for reference.....


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## begreen (Nov 8, 2006)

A lot of stoves take  an hour to come up to temp. An hour to get that amount of mass warm is not unusual. 

What is meant by - get up to temp? Is there a draft issue, does the stove smoke alot?

Can't see from the photo, but is there a difference in height between the two flues at the top?


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## elkimmeg (Nov 8, 2006)

> Can’t see from the photo, but is there a difference in height between the two flues at the top?



 Good point let me take it further: one cap servicing two flues is not a good idea. It acts as a channel to direct wood stove smoke down the other burner flue


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## BurningIsLove (Nov 8, 2006)

They are the same height exactly, neither has a cap for the reasons I mentioned in the other thread about water in the chimney.  both of mine cleanouts are bone dry even after a rainstorm, and no overhanging trees so no critters or debris to worry about.  The clay liner does stick up a few inches about the masonry block, but like 2-3" at the outside (so little you cant even see it in the attached pics).

As for the draft, I do notice a difference in the reburner behavior when the stack is cold vs. warm.  I get significant smoke/particulates coming out the top of the stack when it's cold vs. hot.  I know it takes a while to warm that much mass up to temp, my posting was more of an advisory that one has to be more patient w/ thick masonry vs. a steel chimey before engaging a cat/reburner.


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