Building a chimney ?mortar between flue tiles?

Joe.G

I am useing it for coal and I guess coal is corrsive, so even a SS liner that is meant for caol will not last as long as a masonary chimmeny. If there is no mortar put between what kind of problem are you looking at?

Joe.G

Hi, I am having a masonry chimney put up soon, I have heard different views on weather you should put mortar in between each clay flue section, some say yes some say no, they state that with the mortar they will break due to the constant temp change the tile moving. I know that the outside block will have to be cemented in place. The chimney is going to be outside the house and hooked to a coal boiler. Thanks

Chris S

masonry chimney

Best to check with your local code enforcement officer. Each mason will have his own opinion, which you've already heard, now find out what is required. I know of one municipality that we work in where the inspector looks for a refractory cement to be used between the flue tiles- the masons hate this.

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Bob Harper

flue linings

You must build the chimney per your codes. Even in the absence of codes, you should then default to NFPA 211, which is the national standard and is referenced for heater flues by virtually all model building codes. Once your community votes a code into law then it is just like any other law, which you must obey. No code on the planet allows for no mortar btw flue tiles.

If you are under the IRC, then flue tiles must be set per ASTM C-1283 using a refractory mortar that meets ASTM C-199 with the thinnest joint that joins and stabilizes the flue with the joints struck inside and out. NFPA 211 calls for a medium duty non-water soluble calcium aluminate refractory cement mixture. Most masons hate to use anything other than ordinary mortars because:
-they are lazy
-they are uniformed
-they are too cheap to use the specified mortar

I have never met a mason who owned a copy of the building code. I strongly recommend a factory built chimney over any masonry chimney.

Unknown

i'd consider a ss liner insulated with vermiculite if needed instead of clay tiles

Jack

Size of liner

You are correct that coal is very aggressive. One thing that iwll make it slightly less aggressive is to properly size the chimney flue. What is the breech diameter of your coal stove? Make your chimney liner the same size. I pretty much say that a masonry chimney is a marvelous architectural device but a terrible mechanical device. That has been my experience and I feel more strongly on it as time goes by.

NFPA is the proper reference for you. You should have an airspace around the indder tile or SS liner The tile should be cemented with a refractory cement. Portland cement melts there, not from temperature but from acidic condensation.

I would suggest a good quality CO detector for your coal unit.

Joe.G

I have co2 detectors though out teh house. the outlet of the stove is 8 inch, I am going with 8 ib =nch square flue tiles. If you just sit the clay flues in there with no mortar what could happen or will happen. it is a outside chimmney.

Unknown

Failure to seal

the tiles on an inside chimney will endanger occupants to Carbon monoxide poisioning. On an outside three sides exposed chimney you have heat loss to deal with already. When you fail to seal the tiles you will lose heat thru the un sealed liner which increases the likely hood of poor draft and the acidity from the coal products of combustion will affect the integrity of the chimney and shorten its life.

The coal stove manufacturer will probably recommend a factory built chimney system for their unit so I would go with that.

Being a good old boy from southwestern PA I know a little bit about coal and protection of the vent system.

Bob Harper

won't listen to advice

Joe G., why do you still keep asking about a masonry chimney without mortar btw flue tiles? You asked and were answered. You were told it is not optional but REQUIRED. Yet, you continue to talk about leaving out the mortar. You also ASSume that terra cotta and mortar will last longer than any stainless steel liner. Fact is, regardless of which chimney you go with, they all will suffer some level of degredation. If your stainless liner rots out before the warranty period, you have a mfr. to go after for replacement. What is the warranty on a masonry chimney liner? Cold exterior high mass oversized chimneys do not perform as well as warm interior insulated properly sized factory built stainless steel chimneys.

Since you have already made up your mind, why do you still keep asking us here?

Joe.G

Some people say no mortar I am just asking ? to hear diffrent opions, I want the job done right. I hate the way steel looks and don't want it stuck to the side on my home that I just had re done. Going though my floor and out of the roof is not a option either. When I added my additon last year I should have added a chimmney then but did not plan on adding a coal stove.

P.S this is how you learn by asking ? and hearing diffrent opions and facts.

realolman

I can't see why

you couldn't build a masonry chimney with a stainless steel liner.

I'm no expert by any means, but I would expect the SS liner to last longer than you will.

FWIW.... 2003 International Building Code R1001.9

... Fireclay flueliners shall be laid in medium duty refractory mortar conforming to ASTM C 199 with tight mortar joints left smooth on the inside and installed to maintain an airspace or insulation not to exceed the thickness of the flue liner seperating the flue liners from the interior face of the chimney masonry walls. Flue liners shall be supported on all sides. Only enough mortar shall be placed to make the joint and hold the liners in position.

I understand the part about the mortar beteen the liner, but anyone care to translate the part about the "Only enough mortar..."?

Does that mean you would fill the space with something (what?) to hold the "Only enough mortar" and keep it from falling to the bottom?

As I recall in my extremely limited experience with chimneys that there ia a fair amount of space between the liner and the block if you use chimney blocks.

I believe I had heard that you don't fill it up with mortar and the IRBC would seem to imply that as well. Maybe that's where the OP is hanging up.

Jeff Lawrence_25

You don't need opinions

You need to follow the codes. Period.

As Bob Harper said, in absence of local codes, you need to follow the NFPA 211.

Easy, huh?

Bob Harper

space confuision

Don't confuse the space btw the flue tile joints with the joints themselves.

When you install flue tiles, you must use the proper refractory mortar btw the tiles themselves. this joint is about 5/8-1" wide but only 1/16-1/8" thick per ASTM E-1283. Outside of the flue tiles, there must be a space to allow for thermal expansion. This space is allowed to be 1/2-4". In Calif., they have required this space be filled with mortar and vertical rebar for seismic concerns. They crack a lot of flues there. Some people try to insulate this outer space with vermiculite, perlite or listed chimney insulation such as Thermix but the code does not allow this. This space provides a thermal break so as the flue tile heats up, it does not conduct heat to the adjoining masonry. Instead, the flue stays warmer. If you backfill the space, heat continues to wick away thus hindering draft. Also, as moisure hits the outside of the chimney, it is driven inwards by vapor diffusion. If you have the requisite space, it acts as a drainage plane so the flue joints do not saturate (if you have a rain cap). If the masonry is in contact, the moisture saturates the mortat joint leading to joint erosion as the flue itself becomes the drainage plane. We see this all the time with sweating flues where they were mortared in tight. Also, if you ever go to bust out the old tiles, it is 100x harder to remove cement encased tiles. If you have a chimney fire or overfire the flue where it is mortar encased, you could crack the entire chimney from hoop stress or steam cracking.

If you like the look of masonry, you can build a masonry chase that houses factory chimney or you can build a masonry chimney but line it with a listed stainless steel liner. There are listed liners with lifetime warranties even for coal. What's that warranty again for terra cotta tile? What's that listing for terra cotta tile? What's the minimu size liner for terra cotta tile and is it properly sized for your appliance? What does the listing of this coal appliance say?
Joe, I suggest you get a local chimey pro to consult with you on this. Note, that typically excludes most guys who call themselves 'masons'. There is a whole industry out there making a living off correcting the mistakes these masons entomb in chimneys.

I realize you are collecting information Joe G. but asking the same questions once they have already been answered gets you nowhere and becomes a waste of our time. A little acknowledgement on your part might help.

bob young

all bases covered

great treatise on chimneys , bob thanks

Joe.G

BOB HARPER thanks for the explnation.What is all the talk about pre built chimneys? How much is a stainless steel one tha tI could put inside of the block instead of the clay flue?

John Pilger

Building a chimney ?mortar between flue tiles?

Bob Harper is right on in his explaination. If you like the looks of a masonry chimney, I would recommend that you line it with a 316L stainless steel insulated lining system. Make sure you have it swept as soon as you stop using it for the season. Call a CSIA (Chimney Safety Institute of America) Certified Sweep in your area (www.csia.org) Coal leaves very corrosive sulphur deposits that will corrode even stainless steel if not properly maintained. Annual maintence of the chimney is the key to keeping your chimney in good shape.

John Pilger
Chief Chimney Services
CSIA Certified #1780
FIRE Certified #126
NFI Certified
C-Det Certified

Bob Harper

look what the cat drug in!

Hey John, how are things up in New Yawk? Say hi to Di for me.

Yes, maint. esp. with coal and oil. If burning coal, you need to shop around for a low ash hard anthracite whenever possible. Softer, lower grades of coal have higher sulfur content.

You need to contact your local chimney pro for pricing and options.
Bob
Certified Fireplace Inspector, NFI Master Hearth Professional,IAFCI Eastern Regional Director, HPBA Board of Directors, UL Standards Technical Panel 103

Joe.G

I just want to make the best choice, are round and square clay tile the same price?, Round seems to be better do they both fit in the same size block? If you use round they interlock and there is no need for mortar inbetween them, from what I understand.

realolman

As a practical matter

How do you do this?

Flue liners shall be supported on all sides. Only enough mortar shall be placed to make the joint and hold the liners in position.

It's kinda hard for me to imagine the integrity of 3 stories of flue liners with a little mortar(refractory ) in between them, sitting inside a space that is 4" larger than the tiles. I can understand why someone would want to fill it up, but I understand that that is not a good idea.

I am sincerely asking: What is the appropriate way of supporting them on all sides?

John Pilger

Joe, you are talking about round flue tile that interlock, they are called bell and spicket or ship lap tiles. They are rare and you may have to special order them. Like regular round flue tiles they must be joined with non-water solubile refractory cement as per code. Bob Harper already told you that. If you chose to use round flue tiles over a listed stainless steel chimney lining system make sure the size tiles you use match the flue outlet of the coal stove. Remember yearly maintenance is the key to the chimney lasting.

John Pilger
Certified Chimney Sweep


Date: September 17, 2008 01:43 PM
Author: JOE.G
I just want to make the best choice, are round and square clay tile the same price?, Round seems to be better do they both fit in the same size block? If you use round they interlock and there is no need for mortar inbetween them, from what I understand.

John Pilger

Hi Realolman, they are talking about the first flue tile in a fireplace where the smoke chamber meets the flue tile. In a oil or gas masonry chimney the tiles are placed on the foundation or just below the breech, if it is just below the breech the brick should be corbelled (just like the fireplace)to support the clay flue tile. HTH

John Pilger
Chief Chimney Services
Smithtown, NY
CSIA Certified #1780

Date: September 17, 2008 07:10 PM
Author: realolman
Subject: As a practical matter

How do you do this?

Flue liners shall be supported on all sides. Only enough mortar shall be placed to make the joint and hold the liners in position.
It's kinda hard for me to imagine the integrity of 3 stories of flue liners with a little mortar(refractory ) in between them, sitting inside a space that is 4" larger than the tiles. I can understand why someone would want to fill it up, but I understand that that is not a good idea.

I am sincerely asking: What is the appropriate way of supporting them on all sides?

realolman

I'm sorry,

but I still don't understand. I am not talking about fireplaces, but a chimney that would be used with maybe a coal boiler. I am wondering about all the tiles from top to bottom and how it is to be capped off.

You put mortar between the tiles, smooth inside and out, but leave a space between the tiles and the chimney blocks or bricks?

How are the tiles supported, and how is this structurally sound? Why would the tiles not become mis-aligned after a few years of expansion and contraction?

Certainly filling everything between the liners and the blocks or bricks with mortar would hold everything in place, but it seems that is undesirable as well.

I'm sorry, but I don't get it. I truly would like to get it. I am no mason, obviously, but I do have some construction experience. I just can't see how a structurally sound chimney can be built like this.

John Pilger

Better explaination

Even thought you are not talking about a fireplace the code for masonry chimneys are the same. As I explained, if you have a single flue masonry chimney for gas, oil or solid fuels the liner must be supported on all sides. The first flue tile at the bottom will either sit on the foundation base or on corbel brick.
The flue tiles expansion and contraction rate are the same from top to bottom. They will expand vertically. The problem occurs when the chimney crown (the cement on the top of the chimney)is cemented to the top flue tile and has no bond break. The tiles and the chimney crown have different rates of expansion and contraction. When there is no bond break something has to give, either the top flue tile or the chimney crown.This may also cause tile misalignment.
When the chimney is build the mason generally will support the flue tiles on the sides with rubble. This really don't meet the letter of the code which stated between 1/2" and 4" air space, but it works. If the flue tiles are mortared correctly with the proper mortar then you don't have to worry about the bond breaking,tiles being misaligned or putting rubble to vertically suport it.. Remember the expansion rate of all the flue tiles are the same and they move as a unit instead individually. The brick or block on the exterior is only a chimney chase but properly built is structurally sound. HTH

John Pilger
Chief Chimney Serv.
Smithtown, NY


Date: September 18, 2008 04:26 PM
Author: realolman
Subject: I'm sorry,



but I still don't understand. I am not talking about fireplaces, but a chimney that would be used with maybe a coal boiler. I am wondering about all the tiles from top to bottom and how it is to be capped off.

You put mortar between the tiles, smooth inside and out, but leave a space between the tiles and the chimney blocks or bricks?

How are the tiles supported, and how is this structurally sound? Why would the tiles not become mis-aligned after a few years of expansion and contraction?

Certainly filling everything between the liners and the blocks or bricks with mortar would hold everything in place, but it seems that is undesirable as well.

I'm sorry, but I don't get it. I truly would like to get it. I am no mason, obviously, but I do have some construction experience. I just can't see how a structurally sound chimney can be built like this.

realolman

thank you

There were a few places I was getting hung up.

• I was thinking expansion horizontally, not vertically.
  
  
• I would not have considered a space filled with rubble to be an air space. Is there any minimum size rubble? I suppose sand wouldn't do?
  
  
• Of course it needs to be supported on the bottom... I would have thought that went without saying.
  
  

One more question if you wouldn't mind... how do you cap it off to allow for vertical expansion? with a precast piece or what?

Thanks for you patience.... believe it or not, this was something I had wondered about many times, but never found a good answer from somebody knowlegeable ... till now.... thanks

John Pilger

Chimney question

I would never advise anyone using sand as a back file. If stuff happens it could leak into the chimney blocking the flue gases. There is no size for the rubble the masons use, remember it is not code, air space is.

After the chimney is constructed there should be a bond break between the last brick or block and the chimney cap/or crown. Another words the crown should be floating and there should be space around the flue tile for vertical expantion and contraction. This space can be filled in with sicicone to keep it water tight. You can also use a precast crown but don't cement it to the brick or block. Check with the Brick Institute of America for the proper construction of a chimney cap/crown. HTH

John Pilger
Chief Chimney Services

MikeyB

John, Bob - Thanks for your detailed explanations. I learned a lot from them.

- Rod

Unknown

what i did

u get stove mortar from plastic container ,grab handfull & rub into tilejoint from interior of tile as each tile is installed

scrook_2

NFPA is authoritative, \"some guys say...\" isn't!

NFPA 211 says refractory cement...'nuf said!

Note: you can line a masonry chimney w/ a stainless liner w/o the ugly look of an exposed or boxed in metal chimney.

John Pilger

Building a chimney ?mortar between flue tiles?

pook, I will respectfully disagree with your response. As per the IRC and NFPA Codes you must use non-water soluble refractory cement. The proper way to join the flue tiles is to use a trowel and butter the ends of the tiles. After they are install you wipe the surface clean of any motor protrusions.

Bob Harper

The stove cement Pook referred to may actually comply with the IRC requirements as an acceptable material but his technique certainly would not: Per the IRC, it only has to be a medium duty refractory mortar that meets ASTM C199 and laid to ASTM C-1283. The joints must be tight with the inner walls struck smooth. The space btw the tiles and chimney walls cannot exceed the flue tile thickness, while NFPA 211 allows for 1/2-4" air space. Tiles should be laid ahead of the surrounding masonry, which would preclude relining with tile flues.


You need to know what the codes are in your area as you can see it does vary.