Liner as Chimney Extension

[ColdNorCal]

Installing wood stove and the chimney is only 11' tall from top of stove. When the liner is installed, their will be about 3' feet extending above the crown. It seems like a waste to cut this off and not utilize it.

Does anyone know if their is a SS steel tube/pipe available that would slip over the remainder of the liner? What Im thinking is, the tube would slip over the "outside" of the top plate and into the "inside" of the cap, between the cap and liner. It could be secured with screws at top and bottom and have a small cut out for the clamp fastener on the top plate. Having the liner inside the tube would add some structural integrity to the flue extension. Also, their would be an insulation advantage since their would be an airspace between the liner and tube. It may even be possible to add insulation in the space between liner and tube.

I realize their are flue extenders available in 18" and 24" lengths designed for the flex liner systems. But, these are a little pricey when you want to extend more then 2 feet.

If this is not availbale, are their any fabricators that may be interested in making this?

 

[RobbieB]

Yeah, you can buy a 3 foot length of 7 inch dia rigid SS from Woodland.

 

[bholler]

Installing wood stove and the chimney is only 11' tall from top of stove. When the liner is installed, their will be about 3' feet extending above the crown. It seems like a waste to cut this off and not utilize it.

Does anyone know if their is a SS steel tube/pipe available that would slip over the remainder of the liner? What Im thinking is, the tube would slip over the "outside" of the top plate and into the "inside" of the cap, between the cap and liner. It could be secured with screws at top and bottom and have a small cut out for the clamp fastener on the top plate. Having the liner inside the tube would add some structural integrity to the flue extension. Also, their would be an insulation advantage since their would be an airspace between the liner and tube. It may even be possible to add insulation in the space between liner and tube.

I realize their are flue extenders available in 18" and 24" lengths designed for the flex liner systems. But, these are a little pricey when you want to extend more then 2 feet.

If this is not availbale, are their any fabricators that may be interested in making this?

You want that extension to be insulated so you would need a transition plate to go from a liner to class a chimney.

Yeah, you can buy a 3 foot length of 7 inch dia rigid SS from Woodland.

Yes but they are un insulated and will quickly form creosote.

 

[RobbieB]

Where? In the 6 inch liner running inside the 7 inch?

 

[bholler]

Where? In the 6 inch liner running inside the 7 inch?

In side the liner which has no insulation on it above the top of the chimney it will cool quickly and form creosote. If you put a 7" pipe around that liner how do you kerp water creosote bugs etc out of the gap?

 

[ColdNorCal]

In side the liner which has no insulation on it above the top of the chimney it will cool quickly and form creosote. If you put a 7" pipe around that liner how do you kerp water creosote bugs etc out of the gap?

Yes, a 7" wont work. I found someone that can make it. He needs to make it in two pieces though as he can only work with 24" pieces. He would do a 24" then add a 12"+ section as needed. Waiting for a price. Unfortunately he is in Maine and shipping is costly.

Thought about adapter plate from flex liner to Class A pipe. When you add the adapter cost with Class A pipe and Class A cap, the cost is not appealing either.

btw- just finished replacing the original 45 year old crown. The overall height is closer to 11' 6" now

 

[bholler]

Yes, a 7" wont work. I found someone that can make it. He needs to make it in two pieces though as he can only work with 24" pieces. He would do a 24" then add a 12"+ section as needed. Waiting for a price. Unfortunately he is in Maine and shipping is costly.

Thought about adapter plate from flex liner to Class A pipe. When you add the adapter cost with Class A pipe and Class A cap, the cost is not appealing either.

btw- just finished replacing the original 45 year old crown. The overall height is closer to 11' 6" now

You may not like the price but that is how it should be done. Well what should have been done is add to the masonry before you did the crown but that is allot more work.

 

[ColdNorCal]

You may not like the price but that is how it should be done. Well what should have been done is add to the masonry before you did the crown but that is allot more work.

Considered adding some brick and made several calls for brick, clay flu liners and such. No one knew much about it in this area. Thought about the possibility of needing load calcs also. Not a good direction for many reasons. Work was not at the top of the list. Perhaps it should be though

Also, one reason the chimney stack is short is because the roof pitch is very mild. Despite the short stack height, it terminates over 2', no cap, above the highest ridge.

Can you please point me to a 6" Flex to Class A top plate adapter? I saw one last week and cant find it now.

 

[bholler]

Considered adding some brick and made several calls for brick, clay flu liners and such. No one knew much about it in this area. Thought about the possibility of needing load calcs also. Not a good direction for many reasons. Work was not at the top of the list. Perhaps it should be though

Also, one reason the chimney stack is short is because the roof pitch is very mild. Despite the short stack height, it terminates over 2', no cap, above the highest ridge.

Can you please point me to a 6" Flex to Class A top plate adapter? I saw one last week and cant find it now.

Most of the chimney manufacturers make them. We use olympia products.

 

[ColdNorCal]

Yeah, you can buy a 3 foot length of 7 inch dia rigid SS from Woodland.

Looked at the 6" top plate and rain cap this evening. And you are correct, a 7" would work. A small cut out at the bottom of the rigid would "probably" have to be made to clear the 6" top plate band clamp screw head that tightens the flex liner. Then another band clamp would be used to tighten the 7" rigid pipe to the 6" top plate collar. And the rain cap that came with the flex liner easily widens to accept a 7"+ pipe.

Adding a 18" section to the remainder of the liner with a 7" x 48" Rigid pipe encasing it, would provide a 15' 6" flue. And of course, this should be supported with a flue bracket. Although, everything I read says a flue support bracket is required for anything over 5 ft.

 

[bholler]

Looked at the 6" top plate and rain cap this evening. And you are correct, a 7" would work. A small cut out at the bottom of the rigid would "probably" have to be made to clear the 6" top plate band clamp screw head that tightens the flex liner. Then another band clamp would be used to tighten the 7" rigid pipe to the 6" top plate collar. And the rain cap that came with the flex liner easily widens to accept a 7"+ pipe.

Adding a 18" section to the remainder of the liner with a 7" x 48" Rigid pipe encasing it, would provide a 15' 6" flue. And of course, this should be supported with a flue bracket. Although, everything I read says a flue support bracket is required for anything over 5 ft.

That is a bad idea.

 

[ColdNorCal]

That is a bad idea.

Details?

 

[bholler]

Details?

Un insulated extension will collect tons of creosote even if you put it inside an uninsulated pipe. How are you going to keep creosote out from between the two? How will you keep bugs from nesting in there? Not to mention it is an unapproved modification to a ul listed system which voids that listing and violates code.

 

[ColdNorCal]

Un insulated extension will collect tons of creosote even if you put it inside an uninsulated pipe. How are you going to keep creosote out from between the two? How will you keep bugs from nesting in there? Not to mention it is an unapproved modification to a ul listed system which voids that listing and violates code.

Spoke with a forum vendor about the flex liner extensions they sell, non-insulated. He said, its better to have some extra creosote then poor draft. And that given the climate where I live creosote will not be a problem like other parts of the country.

A 6" pipe with a 7" over it can be insulated with a thin layer of rockwool. Even a small air gap provides some insulation.

Sealing the top and bottom with silicone, and perhaps a metal band inserted between the two at the top, will keep bugs and creosote out. The gap between the two is not very wide, 6 1/4" OD inside a 7" ID.

The only concerns I have with this are not blowing over, holding up for many years and not catching on fire.

When making the crown, I installed four inverted SS 1/4" bolts into the concrete to secure the top plate. This, with a flue support bracket, addresses any "blowing over" concerns. Everything will be SS, providing longevity. And being above the roof line and 11 feet above the stove, fire is only a problem when the house is on fire.

When I look at the UL option of a single non-insulated extension with a clamp to secure it, and they can be stacked to add height, it makes me comfortable with this design.

I haven't bought anything yet and as always, I sleep on these type of decisions.

 

[bholler]

Spoke with a forum vendor about the flex liner extensions they sell, non-insulated. He said, its better to have some extra creosote then poor draft. And that given the climate where I live creosote will not be a problem like other parts of the country.

A 6" pipe with a 7" over it can be insulated with a thin layer of rockwool. Even a small air gap provides some insulation.

Sealing the top and bottom with silicone, and perhaps a metal band inserted between the two at the top, will keep bugs and creosote out. The gap between the two is not very wide, 6 1/4" OD inside a 7" ID.

The only concerns I have with this are not blowing over, holding up for many years and not catching on fire.

When making the crown, I installed four inverted SS 1/4" bolts into the concrete to secure the top plate. This, with a flue support bracket, addresses any "blowing over" concerns. Everything will be SS, providing longevity. And being above the roof line and 11 feet above the stove, fire is only a problem when the house is on fire.

When I look at the UL option of a single non-insulated extension with a clamp to secure it, and they can be stacked to add height, it makes me comfortable with this design.

I haven't bought anything yet and as always, I sleep on these type of decisions.

Well if the sales man said it would work i am sure it will be fine. I have see those single wall extensions in the feild they are a mess. Dod you ask if they tested it is your climate to know that it was fine? I am sorry to vent on you but it pisses me off when retailers have their sales people giving out bad info. Lots of them regularly say there is no need for insulation at all.

Again sorry rant over. What you are proposing may work but it is untested and will void your listing warantee and will not meet code. Not that most inspectors will know that though.

My question is what happens if that space gets full of creosote or if the insulation you put in there gets saturated with it? That could potentially be quite a bit of fuel for a fire.

Are you sure that single wall extension is ul listed? Most i have seen are not listed. But that one may be.

 

[ColdNorCal]

Well if the sales man said it would work i am sure it will be fine. I have see those single wall extensions in the feild they are a mess. Dod you ask if they tested it is your climate to know that it was fine? I am sorry to vent on you but it pisses me off when retailers have their sales people giving out bad info. Lots of them regularly say there is no need for insulation at all.

Again sorry rant over. What you are proposing may work but it is untested and will void your listing warantee and will not meet code. Not that most inspectors will know that though.

My question is what happens if that space gets full of creosote or if the insulation you put in there gets saturated with it? That could potentially be quite a bit of fuel for a fire.

Are you sure that single wall extension is ul listed? Most i have seen are not listed. But that one may be.

Your "rant" is much appreciated. Always good to listen and learn from others.

The creosote buildup between the pipes is something to seriously consider. Blocking the gap at the top can be addressed since it is rather small.

This is the flu extender. It is common, UL approved, and sold by several retailers. To be clear, the retailer below is not who I spoke with.

http://www.woodlanddirect.com/Flue-Extender?gclid=CjwKCAjwzoDXBRBbEiwAGZRIeMNkADLE7RX1tmgyMbDpoGZgl-_YdjL7Gv7vDjTcIPZY0JbAyp6VOBoCW4YQAvD_BwE#252Diameter:6"

 

[bholler]

Your "rant" is much appreciated. Always good to listen and learn from others.

The creosote buildup between the pipes is something to seriously consider. Blocking the gap at the top can be addressed since it is rather small.

This is the flu extender. It is common, UL approved, and sold by several retailers. To be clear, the retailer below is not who I spoke with.

http://www.woodlanddirect.com/Flue-Extender?gclid=CjwKCAjwzoDXBRBbEiwAGZRIeMNkADLE7RX1tmgyMbDpoGZgl-_YdjL7Gv7vDjTcIPZY0JbAyp6VOBoCW4YQAvD_BwE#252Diameter:6"

Yes it is listed to ul 1777 which only covers liners which are meant to go inside masonry chimneysnot out the top of them. I have to question if it is listed for the application they are selling it for.

 

[ColdNorCal]

Yes it is listed to ul 1777 which only covers liners which are meant to go inside masonry chimneysnot out the top of them. I have to question if it is listed for the application they are selling it for.

Interesting. Maybe they did not list all ratings? I dont know....

Other vendors advertise it as an chimney extension also. This is from two other vendors:

"Use this to extend a flue above the top of the chimney liner collarplate by 18". Must mount on a chimney liner collarplate of the same diameter chimney liner."

"Flue extender fits between rain cap and top plate"

 

[bholler]

Interesting. Maybe they did not list all ratings? I dont know....

Other vendors advertise it as an chimney extension also. This is from two other vendors:

"Use this to extend a flue above the top of the chimney liner collarplate by 18". Must mount on a chimney liner collarplate of the same diameter chimney liner."

"Flue extender fits between rain cap and top plate"

Yes i know many of the diy oriented vendors sell them but none of the pro ones do.

We will extend with single wall as a temporary test to see if it helps. If it does we then come back and extend it properly with a transition plate and a section of chimney.

In fact my own chimney has 18" of rigid liner sticking out the top right now. But that is only because we just bought it and i need to pour a crown this summer i will cut it to the right height at that point. And yes i had to clean the top mid season. No real buildup on the insulated section below.

 

[ColdNorCal]

After more thought and per bholler suggestions, Im thinking of using a 6" x 36" insulated double wall pipe with a finishing collar inserted into the 6 inch flex liner.

I spoke with SBI and they said the minimum recommended flue height for my stove is 12 ft. With a 36" pipe added above the crown the flue height would be ~14 1/2 ft. If more draft is needed, another section can easily be added.

https://www.northlineexpress.com/sh...yUjB6Prh6qpyj9q5H6Kz4e37Oj2hPi74aAhwWEALw_wcB

https://www.northlineexpress.com/shasta-vent-6-inch-finishing-collar.html

https://www.northlineexpress.com/6-selkirk-storm-collar-206810.html

 

[TomasB]

Un insulated extension will collect tons of creosote even if you put it inside an uninsulated pipe. How are you going to keep creosote out from between the two? How will you keep bugs from nesting in there? Not to mention it is an unapproved modification to a ul listed system which voids that listing and violates code.

Bugs & insulation: perlite/vermiculite?

How are you going to keep creosote out from between the two?"

How would creosote build in between pipes. There is no smoke between the two? As well, perlite/vermiculite?

My only concern would be if somehow condensation would be occurring for some reason. But if packed, should not be an issue?

The one benefit of doing properly with transition plate (that costs ungodly several hundred dollars, what a rip-off!) and double wall insulation pipe is that when cleaning, you can remove double wall with cap thus eliminating a need to climb higher on the chimney, when cleaning is done from the roof.

 

[WoodChopper92]

After more thought and per bholler suggestions, Im thinking of using a 6" x 36" insulated double wall pipe with a finishing collar inserted into the 6 inch flex liner.

I spoke with SBI and they said the minimum recommended flue height for my stove is 12 ft. With a 36" pipe added above the crown the flue height would be ~14 1/2 ft. If more draft is needed, another section can easily be added.

https://www.northlineexpress.com/sh...yUjB6Prh6qpyj9q5H6Kz4e37Oj2hPi74aAhwWEALw_wcB

https://www.northlineexpress.com/shasta-vent-6-inch-finishing-collar.html

https://www.northlineexpress.com/6-selkirk-storm-collar-206810.html

Did you end up going with this solution? I am also trying to figure out a way to add 2 to 3 feet to the top of my chimney to extend total length. The brand of flu liner my installer put in doesn't have a transition plate, and they have been less than helpful.

 

[TomasB]

Did you end up going with this solution? I am also trying to figure out a way to add 2 to 3 feet to the top of my chimney to extend total length. The brand of flu liner my installer put in doesn't have a transition plate, and they have been less than helpful.

Did you end up going with this solution? I am also trying to figure out a way to add 2 to 3 feet to the top of my chimney to extend total length. The brand of flu liner my installer put in doesn't have a transition plate, and they have been less than helpful.

If you go with duravent, they will charge you an arm, leg, your left kidney and a first new born child for that. Stupid amount for the piece of plate.

Rather google for this:

Selkirk Sure-Temp 6" Anchor Plate​

Their dual wall quick connect pipes are reasonably priced, as well as caps.
Then the flashing goes on top of the plate. The cone (water divertor) is installed on the extension pipe, as well as the cap on top.
The beauty is that you can remove the extension by twisting, thus cleaning is easier.

In retrospective, that what I should have done. And I might still will if insulating with another wider diameter pipe won't satisfy me for some reason.

 

[WoodChopper92]

If you go with duravent, they will charge you an arm, leg, your left kidney and a first new born child for that. Stupid amount for the piece of plate.

Rather google for this:

Selkirk Sure-Temp 6" Anchor Plate​

Their dual wall quick connect pipes are reasonably priced, as well as caps.
Then the flashing goes on top of the plate. The cone (water divertor) is installed on the extension pipe, as well as the cap on top.
The beauty is that you can remove the extension by twisting, thus cleaning is easier.

In retrospective, that what I should have done. And I might still will if insulating with another wider diameter pipe won't satisfy me for some reason.

Thank you for these links! I will probably get this done next summer. Not a fan of crawling on a roof covered in snow