Before I Grab the Hammer Drill .......

[SOH]

Hi everyone!

Thanks to everyone here (and some NFPA and other docs), I'm making progress on my installation. The next consideration:

I need to decide how high my thimble will be (so that I can begin creating that hole through the exterior wall and into the existing chimney and liner). I will use temporary heat shields this year, but ultimately I'll be building a raised hearth, so let's assume a stove connection point of about 36" off the floor.

My understanding is that I should have at least 1/4" of rise per foot of run. Even though we are talking less than 20" here, is there any reason to pitch it more steeply than that?

I have two choices: 1. Go straight up from the stove to within 14" of the ceiling and then run two 45s into the thimble (with the appropriate horizontal pitch); or 2. Run two 45s right from the stove into the thimble (again, pitched upward).

Is one better than the other in terms of draft? Do I want to maximize the vertical pipe from the stove before making the necessary bends? My instinct says to do that in order to get a good draft started.

Any and all thoughts and advice welcome. Thank you!

 

[AmbDrvr253]

I would make the vertical run as long as I could. Use plain old black pipe(single wall). Puts more heat into the living space. And draft is, usually, more of an overall height than anything else.

 

[SOH]

I would make the vertical run as long as I could. Use plain old black pipe(single wall). Puts more heat into the living space. And draft is, usually, more of an overall height than anything else.

Thanks for the reply! I've got 25 feet of overall height, so I'm hoping things will draft well. Do I have it right that the single-wall stove pipe can't be closer than 14" to the combustible ceiling? I've also seen reference to 18", so I'm not sure which is correct. More than likely I will err on the side of caution and center the pipe leading out to the chimney (through a thimble) at about 20" down from the ceiling.

 

[SOH]

Rather than compromising the integrity of the chimney by putting another 6"+ hole just below the existing one ... is there any scenario in which I could use the existing thimble hole? The top of the hole is 9" below the ceiling drywall. With some sort of insulated interior pipe and/or heat shields, is this acceptable? More important than code ... could it be made safe? Thanks.

 

[Jo191145]

Single wall pipe is a minimum of 18" away from the ceiling.

You say existing chimney and liner?
Are you referring to existing masonry chimney and clay flue liner or is there a stainless liner with a thimble hole already cut into it at 9" from the ceiling?

If your existing high thimble is entirely masonry that's easy enough to plug up and start new. If there's already a stainless liner with a hole cut into IMO that's not as easy to fix. I'm not an expert on metal tho.

Yes, I'm sure insulated pipe can be brought to within 9". Once again, you'll need to get more expert advice on that.
I use this litmus test on metal liners. When bholler says it's good its good.

 

[begreen]

I would keep the thimble at least 18" from the ceiling. Even more is better. The stove pipe will get hottest where it makes the turn into the thimble.

Questions: How tall is the chimney that is being connected to? How tall is the ceiling in this room?

 

[SOH]

Single wall pipe is a minimum of 18" away from the ceiling.

You say existing chimney and liner?
Are you referring to existing masonry chimney and clay flue liner or is there a stainless liner with a thimble hole already cut into it at 9" from the ceiling?

If your existing high thimble is entirely masonry that's easy enough to plug up and start new. If there's already a stainless liner with a hole cut into IMO that's not as easy to fix. I'm not an expert on metal tho.

Yes, I'm sure insulated pipe can be brought to within 9". Once again, you'll need to get more expert advice on that.
I use this litmus test on metal liners. When bholler says it's good its good.

Yes, it's an existing masonry chimney with a clay flue liner / no stainless steel. I could certainly plug that hole with refractory cement and create a new, lower thimble entry point. I like the litmus test! It's a good one.

 

[SOH]

I would keep the thimble at least 18" from the ceiling. Even more is better. The stove pipe will get hottest where it makes the turn into the thimble.

Questions: How tall is the chimney that is being connected to? How tall is the ceiling in this room?

Yeah, 9" seems VERY close. The ceilings are standard 8 feet and the chimney is about 25' from grade to top. I do want to have a vertical run from the stove, but I agree. 18"+ it is. Thanks.

 

[begreen]

You should get decent draft with an equal sized stainless liner in the chimney. Sounds like there is plenty of wiggle room to drop the thimble height to at least 18" from the ceiling. 24" or 6' off the floor is common. That would give you at least 3' rise off the stove depending on the hearth height.

 

[SOH]

You should get decent draft with an equal sized stainless liner in the chimney. Sounds like there is plenty of wiggle room to drop the thimble height to at least 18" from the ceiling. 24" or 6' off the floor is common. That would give you at least 3' rise off the stove depending on the hearth height.

Thanks, begreen. I was thinking that centering the hole at 24" down from ceiling drywall sounds about right; and yes, that would leave me with about 3' vertical pipe out of the stove. Honestly, I'm trying to avoid lining the chimney with stainless steel (if the clay liner proves to be in good shape -- need to find a pro to check that out). Do you think that NOT lining with SS is a mistake? Horror stories / cautionary tales? The SS liner kits seem to run about $500 for 25' and that sorta makes me want to curl up in a corner and sob. I'm already looking at $200+ for the thimble unless I do a masonry version myself .....

I appreciate your input, as always!

 

[begreen]

I appreciate the concerns about cost, but think of it as a permanent safety insurance policy that not only greatly increases safety but also helps the stove perform optimally and cleanly. Using the chimney flue might work with some important caveats like:
• nothing else is connected to this flue
• the clean out is sealed
• the flue is clay tile lined and has a cross sectional area not more than twice that of the stove flue (~28" for 6" round)
• the chimney has the correct spacing throughout the house and roof from combustibles
• the chimney is in proper physical condition

 

[SOH]

Ah, begreen. The voice of reason.

I'm sure it's well worth the price for the peace of mind it would offer.
-- nothing else connected to this flue
-- the cleanout is not well sealed, and is also at grade / would need to be redone at NFPA height
-- the clay tile liner appears to be in good shape, but I would never make that call. I am shopping around for a pro I trust (cross sectional area is less than twice that of stove flue)
-- spacing of the chimney structure is correct -- exterior with 1" space, no contact at soffit/eave. Appears to be solid and on a good independent masonry bed.
-- The block exterior condition is fair (mortar beds are solid and well done). Some spalling because the chimney was not flashed (at ALL) and the eave gutters were long ago ripped off. I am in the process of repairing that now with mason's mix.

I'm sure the reality will be that I will go with a liner. I'm certainly not going to skimp on safety in order to save a few bucks. Too bad it's so hard to find a pro around here. The guy I called out didn't even peek into the chimney -- just quoted me something in the 3K range and seemed offput that I was considering a used stove. I am a capable builder, but I also know there are times to let a project go to a specialist.

This is a straight shot of about 25' with a standard tee. Flexible or rigid?

Sorry for the tome. Not enough coffee yet.

THANK YOU for the thoughtful reply.

 

[SOH]

I appreciate the concerns about cost, but think of it as a permanent safety insurance policy that not only greatly increases safety but also helps the stove perform optimally and cleanly. Using the chimney flue might work with some important caveats like:
• nothing else is connected to this flue
• the clean out is sealed
• the flue is clay tile lined and has a cross sectional area not more than twice that of the stove flue (~28" for 6" round)
• the chimney has the correct spacing throughout the house and roof from combustibles
• the chimney is in proper physical condition

I meant for that message to be a reply directly to you. Thanks again.

 

[begreen]

It can be hard in some areas to find a good installer. To locate a certified sweep have you tried www.csia.org and typed in your zip code?

 

[NVHunter]

It can be hard in some areas to find a good installer. To locate a certified sweep have you tried www.csia.org and typed in your zip code?

This is very true. I did this search and there are NO certified sweeps in my area within the state... County of 400,000 plus people and not a one that's CSIA certified.

To the OP. Our installs sound similar. My thimble is 12" from the ceiling in solid block. I'm going to install a Stainless Steel Liner (oval 5"x8.15") and use a double wall masonry adapter to connect to double wall black stove pipe. I can't find anyone in my area who is willing to install the liner without purchasing a stove from them. So, I'm gonna do it my self. Already pulled the permit and cleaned the chimney. Ordering parts in the morning.

Hammer drill next day off to open the thimble hole a little more.

Good luck!