Questions on chimney liner for 1950's brick chimney (length & opening size)

[RickBlaine]

Modifying my 1950's fireplace with brick chimney to accept a wood stove and want to tackle issues one at a time. I need your advice please.....

I removed the old iron throat damper today, but left the damper's structure in place. The removal of the swiveling throat- which never really "sealed" very well, left a space 28 inches wide by 6 1/4 inches.

In anticipation of a liner and block-off plate:

1) If I will purchase a stove with a 6" flue, how large do I have to make the throat's opening for the liner to fit through? Please note that:
a) My chimney is only 10 feet from the throat to the top of the square clay tile exhaust, so from reading here, I will need to ensure a liner that will give me the best draft.
b) It will be a Class A liner- but should it be solid double-walled, or flexible with insulation? I have been saving my pennies and will spend whatever is best for my situation.
c) I assume I will have to "extend" the chimney to at least 12+ feet if I want to install either an Englander 30 or the Drolet (both fine stoves and I will be buying one of them).

2) If I have to enlarge the opening from 6 1/4 inches to 8 or 9 inches, I can do that by busting up some of the mortar used to secure the damper structure to the brick fireplace. I will then remove the entire iron "base" structure that the throat swiveled from. Can I still secure a block off plate without any damper "structure" remaining?

3) I like the idea of a solid chimney liner, but the throat opening of my existing 1950's brick fireplace is a full 8 inches forward of the center of the clay flue opening (12" x 12", by the way) at the top of my chimney. Is there any advantage to using solid liner above the throat opening, and transitioning to flexible liner for a gentle bend to meet the top of the stove? Or am I over-thinking (never happened before )?

I thank you all for this site- the pros and the "newbies", and the moderators. I am half watching the Super Bowl and half reading thread after thread here!

I will start a "build thread" this week....step by step, inch by inch, mile by mile.....thank you!

 

[begreen]

Sounds like it could be a problem installation. Most inserts are designed around a 15-16ft. chimney. I think you are going to need an easy breathing insert and a few feet of extension plus insulated liner.

 

[webbie]

I don't think you have to bust out anything at all - or, at the very worst, do some grinding in one spot only to get it to about 7".

Everyone has their own preferences, but your situation may fit well to line it with double wall rigid which could extend a couple feet out the top - something like:
http://www.efireplacestore.com/simpson-duraliner-chimney-liners.html

You could use the round rigid sections and then a flex for the bottom 5 feet or so......

Or, you could DIY your own together and insulate the upper portion yourself - and still use flex at the bottom:
(broken link removed to http://www.rockfordchimneysupply.com/rigid_liners.php)

Total chimney height is usually figured from either the floor or the top of the stove, so if your pipe comes 2-3 ft out the top and is insulated, you should have plenty of draft (15-17 ft ground to top of chimney) for most stoves.

 

[mstoelton]

I would cut out the damper before I started breaking brick. You can cut the damper with a 4 1/2 inch angle grinder and cutting wheels (about $25 at harbor freight).

There is a tutorial on this site to make a Block-off plate. it is not connected to the damper structure. It is nailed into the brick mortar (I used tapcons) and I sealed mine with fireplace mortar.

 

[RickBlaine]

webbie: Thank you for the fast reply and especially for the explanation of how chimney "length" is measured. With a 3 foot extension out of the top, I should have 15-16 feet of chimney "length" when all is said and done. Can you please tell me what this extension is called? Or is it simply called a "chimney extension"? At what length point do you recommend external bracing for a chimney extension?

begreen: Thank you again for responding to my question. Please note it is a stove I would like to put in, not an insert (unless the term "insert" is used if I fit a stove into a masonry fireplace). I have no problem with an insulated liner- what type would you recommend to give the best draft in my situation? Again, I could grind down or knock out some mortar to enlarge the current 6 1/4 inch opening to accommodate a circumference of up to 9 inches without too much work or damage.

Gents: When the flexible liner goes through the existing opening and soon-to-be block off plate, would I need a "T" connection for a clean-out or not? I could make the liner almost straight, but it would have one very gentle bend- perhaps no more than a 23 degree bend to get to the top of the stove's flue.

 

[RickBlaine]

@mstoelton: Thank you- I saw the plans for the block off plate. I don't know why I kept thinking I could just secure it to the already embedded iron damper structure. If I removed that structure, it looks like I can get about 8 1/2 inches to 8 3/4 inches of opening before I hit actual brick.

I have an angle grinder with cut-off wheels that I got at Menards! Had it since Christmas (one of those sales) and knew I would need it someday.

I guess I need to know what the circumference of the flexible liner (with insulation wrapping or not??) coming through the block off plate will be. If it is 6 1/4 inches, I am in business. If I need more room- I start cutting/grinding/cold chisel hammering.

My goal is to have it done by March 1.

 

[mstoelton]

RickBlane: When you get your chimney liner kit, it should come with an appliance adaptor. Use the appliance adaptor collar to mark your block-off plate with a majic marker to make the hole (use the big end). Make sure you have the liner in place and measure where the liner comes through the space where the block-off plate goes. You will need to measure the distance from the back wall of the fireplace and from each end to locate the hole. You want the liner bare at this point (insulation should only be above the block-off plate). You can use tin snips to cut the hole, use a hammer to blunt the sharp endes slightly and then use stove cement to seal the space between the block-off plate and the liner once the block-off plate is in place with the liner through it. Use the stove cement to seal the edges of the block-off plate against the masonary walls as well.

I suggest this order of assembly: get the insulated liner in place with the end of the liner to go through the block-off plate uninsulated (you will need to measure this or just remove enought insulation to get the block-off plate where you want it). Install the insert and get all the connections where you want them. Do not finish the top of the chimney until the block-off plate, and the insert are installed. Once the liner is attached to the insert, and the block-off plate is in and attached, then go back up on the roof and cut the liner to length and install chimney top plate. This will keep you from cutting your liner too short.