Two flues, one fireplace

[John Kogel]

This chimney has two flues, pretty normal. But what's odd is, they are both open to a normal sized wood-burning fireplace. Has anyone seen this? How would draft be affected? There would be a weaker draft, but twice the capacity for smoke.

The damper was stuck open. Big drafty hole in the wall, and it is pulling away from the house, too.

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[Gunnar Alquist]

Flue size is dependent on the opening at the front of the firebox. The mason may have not been able to get a single flue tile that was large enough.

[John Kogel]

Flue size is dependent on the opening at the front of the firebox. The mason may have not been able to get a single flue tile that was large enough.

Well that is the surprising part. The fireplace opening is no larger then any normal fireplace. You can see that it has a standard screen in front of it. The flue tiles are large enough that one flue would have been ample, IMO.

[Scott Patterson]

It looks like it does have a drafting issue. Just looking at the smoke stained rockwork on the front of the fireplace I would say that it is backdrafting pretty good. Without seeing the throat and smoke shelf area it is difficult to tell by the photos. I would just report it as unconventional and tell my client that unconventional items perform in unconventional ways! Without seeing a real fire in that fireplace and how it performs everything is going to be a guess.

[Vern Heiler]

I owned a house with exact fireplace. Stone face and two flues. On real cold days I would have to light several sheets of loose news paper just to get the draft started.

[John Kogel]

I owned a house with exact fireplace. Stone face and two flues. On real cold days I would have to light several sheets of loose news paper just to get the draft started.

Thanks Vern. Poor draft was my guess.
Was there any advantage to the double flue? Like Scott says, it goes against convention.

[Vern Heiler]

Thanks Vern. Poor draft was my guess.
Was there any advantage to the double flue? Like Scott says, it goes against convention.

None that I could tell. On windy nights sometimes it would blow a puff into the house. I was going to block off one but sold the house before I got around to it.

[Ashley Eldridge]

This chimney has two flues, pretty normal. But what's odd is, they are both open to a normal sized wood-burning fireplace. Has anyone seen this? How would draft be affected? There would be a weaker draft, but twice the capacity for smoke.

The damper was stuck open. Big drafty hole in the wall, and it is pulling away from the house, too.

Actually John, that is considered acceptable and recognized by most building authorities as a means of providing sufficient area to the flue (normally for larger fireplaces). The tiles should be in contact with each other at the bottom and supported by masonry on the remaining 3 sides.

Ashley Eldridge
Chimney Safety Institute of America
Director of Education
Chimney Safety Institute of America

[Vern Heiler]

Actually John, that is considered acceptable and recognized by most building authorities as a means of providing sufficient area to the flue (normally for larger fireplaces). The tiles should be in contact with each other at the bottom and supported by masonry on the remaining 3 sides.

Ashley Eldridge
Chimney Safety Institute of America
Director of Education
Chimney Safety Institute of America

Though it might be recognized as acceptable, mine sucked! Well, "didn't suck"!

Do you have a chart of the dimensions for flue size to fireplace size?

[Evan Wray]

The mason must have liked lots of draft on his fireplaces, he may have had a problem with draw in a heavily treed area previously. The real issues are the home owners heating dollars going up the chimney and the settling away from the house which may have stopped. Anyway just wanted to say hi to John K. I used to be a southern Van. Islander also. Merry green Christmas from the city of snow and ice.


Evan W. mason ,Internachi member.

[Ashley Eldridge]

This chimney has two flues, pretty normal. But what's odd is, they are both open to a normal sized wood-burning fireplace. Has anyone seen this? How would draft be affected? There would be a weaker draft, but twice the capacity for smoke.

The damper was stuck open. Big drafty hole in the wall, and it is pulling away from the house, too.

Though it might be recognized as acceptable, mine sucked! Well, "didn't suck"!

Do you have a chart of the dimensions for flue size to fireplace size?

Vern, the acceptable rule is that for square liners or those with less than a 2-to-1 ratio (meaning the width of the tile is no more than twice the depth) the flue should be 1/10th the area of the fireplace opening. If the flue has a greater ratio it should be 1/8th the area of the fireplace. For round flues the flue should be 1/12th the area of the fireplace opening.

One exception to that rule is the Rumford design. If the design features of that fireplace are followed the flue can be up to 1/20th the area of the fireplace opening. The simple formula for the Rumford is;
if x designates the depth, then the width is 2x and the height is 3x.

While the IRC specifies a minimum depth of a conventional firebox to be 20 inches, the Rumford can be as shallow as 12. The throat for the Rumford must be 12 inches above the lintel while traditional construction only requires 8 inches.

I hope that helps,

Ashley Eldridge
Chimney Safety Institute of America
Director of Education
Chimney Safety Institute of America

[Vern Heiler]

Vern, the acceptable rule is that for square liners or those with less than a 2-to-1 ratio (meaning the width of the tile is no more than twice the depth) the flue should be 1/10th the area of the fireplace opening. If the flue has a greater ratio it should be 1/8th the area of the fireplace. For round flues the flue should be 1/12th the area of the fireplace opening.

One exception to that rule is the Rumford design. If the design features of that fireplace are followed the flue can be up to 1/20th the area of the fireplace opening. The simple formula for the Rumford is;
if x designates the depth, then the width is 2x and the height is 3x.

While the IRC specifies a minimum depth of a conventional firebox to be 20 inches, the Rumford can be as shallow as 12. The throat for the Rumford must be 12 inches above the lintel while traditional construction only requires 8 inches.

I hope that helps,

Ashley Eldridge
Chimney Safety Institute of America
Director of Education
Chimney Safety Institute of America

Thanks Ashley, that's going in my referance folder.

[John Kogel]

I hope that helps,

Ashley Eldridge
Chimney Safety Institute of America
Director of Education
Chimney Safety Institute of America

Yes, thanks for the info. Since fireplaces are built from the ground up, the mason here knew his opening size before the flues went up, eh?

The mason must have liked lots of draft on his fireplaces, he may have had a problem with draw in a heavily treed area previously. The real issues are the home owners heating dollars going up the chimney and the settling away from the house which may have stopped.

I've posted a few more pics. What is your opinion of this fireplace?

Anyway just wanted to say hi to John K. I used to be a southern Van. Islander also. Merry green Christmas from the city of snow and ice.
Evan W. mason ,Internachi member.

We had a snow day at the end of November, cold one this year. I'd rather just watch it build up on the mountains. At least you guys can escape to the Mall.

[Evan Wray]

It's got a lot of issues some money is going to be need spent on it. Hopefully it has stopped settling ,don't see any damage on the inside. There are mud jacking companies in Edmonton don't recall seeing any on the Island. Good luck.

Evan Wray

[Ashley Eldridge]

Yes, thanks for the info. Since fireplaces are built from the ground up, the mason here knew his opening size before the flues went up, eh?
I've posted a few more pics. What is your opinion of this fireplace?
We had a snow day at the end of November, cold one this year. I'd rather just watch it build up on the mountains. At least you guys can escape to the Mall.

John, the mason should know what size the opening will be and have a clear vision of how the chimney will be built to support it. That includes a proper foundation and flue sizing. You clearly have some settling issues here. The chimney pulling away from the house is never a good sign. Overall it looks like minimalist construction to me based on the block construction. The foundation is the most likely suspect. Whe images show me the chimney, I suspect the fireplace and remaining construction details will show similarly marginal to poor design and construction, but that is where many of the defects will be visible, from inside the structure.

Ashley Eldridge
Chimney Safety Institute of America
Director of Education
Chimney Safety Institute of America

[John Kogel]

Thanks, guys. I described what you see here with lots of pics. There were other issues, electrical and plumbing. My clients walked away.

[Evan Wray]

Good decision