Adding Class A Extension to Flex Liner

[BCC_Burner]

So in my effort to enhance my draft, I'm making some modifications to my setup. First up, removing the 90* in the stove pipe and replacing it with 2 45*s. This will shorten my horizontal run into the T from 24 to about 6 inches. I'm also limbing an adjacent tree to try to increase air movement across the top of the stack.

From the T up is about 11 feet of insulated 5.5 inch Flex King Pro HD liner that sits inside a terra cotta flue. This liner is affixed to a top plate on the chimney, with a cap above there. I am planning to add a 3 foot section of Class A to further enhance the draft. I am wondering about how to make the connection from the Flex King liner/top plate to the section of chimney pipe? It seems like the chimney will fit nicely over the top of the existing liner, but I'm not sure what the best method is to make that joint secure/smoke tight. Thanks for the help!

 

[MDFisherman]

You would need a stove pipe adapter that would lock into the chimney section. Not sure what your plans are for anchoring the pipe sticking out of the chimney.

I think building the chimney higher and replacing with a longer liner would be a more appropriate setup. More connections=more leaking

 

[webbie]

One question becomes how you are going to support the additional section....but connection should be fairly easy. Use a pipe adapter on the bottom of the piece of double wall, and then find another adapter from 6 to the 5.5 (probably stocked at various chimney companies.
This may involve taking the top plate off or modifying it...or making another one. Some insulated chimney companies offer "masonry adapters" which the insulated chimney locks into - you can probably fit an adapter to the bottom of that to receive your pipe.

Here is another option for you.
I had a business making chimney extensions - but sold it. I have some samples left over at a very good price.

They are two-piece cast aluminum and you run your flex or rigid right up through them and wrap it. It gives you a great chimney pot look too!

The CC88 sells for $395+, but $125 plus shipping takes one of these samples!

It's the one on the left in this booth pic.
(broken image removed)

 

[BCC_Burner]

From the reading I have done on here it seems like sections shorter than 4 feet or so generally don't need additional support. This needs to be done safely, but as inexpensively and easily as possible. This is a rental property and I am not interested in putting a lot of time and money into something I'm going to walk away from in a few years.

 

[webbie]

From the reading I have done on here it seems like sections shorter than 4 feet or so generally don't need additional support. This needs to be done safely, but as inexpensively and easily as possible. This is a rental property and I am not interested in putting a lot of time and money into something I'm going to walk away from in a few years.

When they talk about additional support, they are assuming that the bottom of said piece is rock-solid. In other words, you may be able to support 3-4 feet above where a roof brace or flashing is placed.

Not so with a piece just sitting on the chimney! If the chimney is large enough, you can get some support by dropping 8" or so of the insulated chimney into the flue and packing around it and having a sheet metal plate then cover the top with a hole for the pipe, etc.

 

[BCC_Burner]

Not an option, the existing flue is barely large enough for the 5.5 inch flex liner wrapped in insulation. Perhaps I will have to give up on the extension and just deal with it.

My landlord installed the flex liner himself a little over a month ago, and before doing that had a list of other stove related things he agreed to do (including extending the chimney height), but he had so much trouble getting the liner down that he hasn't done anything else and won't return my calls. Class act, but I've just decided that I need to be proactive and try to improve the draft as much as possible.