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Offset my chimney, or weaken my house?

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by annette, Dec 15, 2005.

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  1. annette

    annette Member

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    I finally went into my attic to check where my chimney will go. (Remember the installer visit, where he didn't need to check my attic, saying they could take care of any structure that was in the way?) It does not look good! Not only is the flue centerpoint about 2 inches away from a ceiling 2x4 and a rafter, it's also directly underneath some important-looking beam thing running the whole length of my house across the ceiling 2x4s. (I don't know house construction terms, so I'm just describing what I saw.) My house is a normal, rectangular ranch, with a wall along the long centerline. Then midway between the center wall and the outside wall, on either side, there are 2 or 3 2x4s nailed together, which sit on top of the ceiling 2x4s. That's the "beam thing."

    Before I visited the attic and realized that there's a rafter above, I'd only imagined cutting a ceiling 2x4, not interfering with rafters and roof support. Now I have this beam thing, AND a rafter, and I figure I should just offset my chimney. I really can't move my stove more than a couple of inches--the spot is really tight.

    Does anyone have an opinion one way or another? Should I take pictures, or do you know what I mean by my descriptions?

    Thanks a lot!

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  2. saichele

    saichele Minister of Fire

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    So the 'beam thing' runs down the long axis of the house, perpendicular to the ceiling joists, and is not directly over any wall? Is anything resting on top of it?

    Steve
  3. Corie

    Corie Minister of Fire

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    Just offset it if it seems like you're going to have to do THAT much structural modification.

    I've got two 15 degree bends in our chimney and we have a plenty strong draft.
  4. Rhone

    Rhone Minister of Fire

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    This "beam" you're talking about from my knowledge is one of two things. It's either where you ceiling joists connect to from either side, and normally has plates on it that latch into your ceiling joists, and if you ceiling joists try to seperate from that beam the plate and force of the ceiling joist on the other side cancels it.

    The second is a support beam, which usually spans over an open concept and is much larger. The support structure is normally in a wall but with open concepts there is no wall to put it in, so they lift it into the attic.

    I have to agree with Corie, no matter what you're probably better off NOT touching it and going around it.
  5. Corie

    Corie Minister of Fire

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    And, we live in a Raised Ranch, stove is in the basement. I have 16 feet of straight pipe, the two 15 degree offsets and 12" of pipe between the offsets. And our draft is fine. Just rest assured that using a couple bends is not going to destroy your draft.

    In fact, I had to put in a barometric damper for coal because our draft is still too strong.
  6. elkimmeg

    elkimmeg Guest

    Did you save my other responses from the past forum concerning this issue. Double wall 15 degree elbows are expensiv so try to post pictures I think I know what you are dealing with. One I am inspector my other job I am a builder remodeler. I think I can figure out a solution from the carpentry perspective and code compliant. Also measure the soacing between the ceiling members (joist) and rafters report and post pictures here
  7. annette

    annette Member

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    Thanks, everybody. I will go get the photos.

    Elk, I saved your posts, but once I saw all the wood in the way, I thought you must have been talking about something different and easier. The offsets sure are expensive, so it would be nice to find a way to keep my house structural but keep the chimney straight!
  8. annette

    annette Member

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    Here are photos and measurements:

    The ceiling "joists" (they're 2x4s) are 16" on center. So are the 2x4s of the roof. The angled guys (are those the rafters?) are 48" apart on center.

    Please excuse my messy attic, but I've had many other projects to work on! It's on "the list," though...



    General view of one side of the attic:

    Attached Files:

  9. annette

    annette Member

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    This shows the spot where the chimney needs to come up--just on this side of that upright:

    Attached Files:

  10. annette

    annette Member

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    Here is a close-up of the ceiling 2x4 and that beam thing (which is toenailed into the ceiling 2x4s):

    Attached Files:

  11. annette

    annette Member

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    And this is a closeup of the part of the roof that it would go through. Yes, that bit of 2x4 is coming off. Easier job for me, I guess:


    Let me know if you want more photos!

    Attached Files:

  12. elkimmeg

    elkimmeg Guest

    what you have is a trust system The one angle piece that starts at ceiling level can be removed by attaching a 2/4 on each side of of the adjacent joist. I wish I knew exactly where you were trying to go threw. This is not conventional framing. They used 2/4 where 2/6 should be used for roof rafters and ceiling joist. 2/4 were used because the trust system tringleates the load and spands, meaning cutting them out is a lot harder to replace the load shift. I mean 2 minutes looking, I can figure out your options. I cannot say for sure if one member can be cut out headed off , just looking at pictures and not still knowing the exact location. I did notice the metal clad wire looks like a 20 amp or 12 wire curcuit call bx wire.

    Mabe the cheapest way to advoid cutting framing members is ofsetting the single wall connector pipe before the stainless steel double wall pipe where those elbows definitely cost a bit more. I mean if you were a couple of towns away, I would look at it and figure a cost effective solution.
  13. elkimmeg

    elkimmeg Guest

    Where do you live? Do you get a fair amount of snow? I am thinking about the possible snow load on your roof
    What I am getting at, is to advise you the consequences, if your installers tell you no problem just cut it out.
    I do not have all the confidence in them, since they never took the time to actually look in the attic and see the framing members
  14. annette

    annette Member

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    Elk:

    I live in NW Indiana, and we get a decent amount of lake-effect snow. There's been 8 inches of snow sitting on the roof for a week. This is unusual for December, but does happen every year.

    As for where the flue will come up: in my third photo, look at the point where the beam and the bx and the upright and the black cable meet. The bit of brown insulation paper is basically the center point of the flue. (I thought I'd use Paint to make circles and markings, but it turns out I don't have it anymore. If you want, I'll go take a picture with a home-made arrow in it!) And looking at picture #4, the flue would go into the roof right where all those pieces of wood meet.

    I hope that helps,

    Annette
  15. woodpile

    woodpile Member

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    I like the idea of a single wall offset to get to the right position for a straight, unobstructed run up through the roof. How far below the ceiling must the insulated double wall pipe start?
  16. annette

    annette Member

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    I should have mentioned that I can't use single-wall, in order to have my stove as close to the wall as I want/need. I can still offset using double-wall, it's just more expensive. :(
  17. elkimmeg

    elkimmeg Guest

    how far from the ceiling? the black double wall connector pipe is the distance from combustiables that pipe is rated i If 9" or 6" and any where in between. Still cheaper using an offset elbow in that pipe instead of the stainless steel class A chimney pipe.

    Looking at the pictures again the upright 2/4 can be moved to the other side of the ceiling joist that would get that out of the way. It looks like your spacing of your roof rafters is at least 24" making it much more impertive to the transfere the weight required if one was cut. Move the upright 2/4 to the other side if needed but do not let the installers start cutting away.. the rafter and the cross menbers. With normal 2/6 16" on center cutting one and heading it of is ok. You do not have that and you need all the support. One cannot be cut unless major carpentry is also planned, to head and transere that weight load .

    In this case a 15 degree offset or two, if needed will be cheaper then the required corrective carpentry
  18. annette

    annette Member

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    Thanks for the answer, Elk. It seemed to me that offsetting would be easier than moving all that stuff. (But if I could have saved a couple hundred dollars without having to rebuild my house, I'd have done it!) Some of that structure looks like it really should stay tied in with the rest of the house. With other parts, like putting diagonals on either side of the one I want to remove (with a net gain of diagonals), it seems like moving it could have worked.

    I don't quite understand this comment of yours: "how far from the ceiling? the black double wall connector pipe is the distance from combustables that pipe is rated i If 9” or 6” and any where in between. " What do you mean? I have to have the double-wall pipe go up to the ceiling, so it's going to get pretty close! (I think the Class A starts at the ceiling, right?) I will need to do the offsets in the double-wall pipe, in order to avoid that tangle of wood.

    How much higher should I make my chimney to compensate for 2 offsets? Also, I think 45-degree offsets are the only ones available in double wall?

    Thanks again!
  19. annette

    annette Member

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    Well, sort of :)

    But you could tell by my highly technical nomenclature that I am not very experienced in altering the structure of houses! I figured I'd toss it out here in case someone could look at it and go "It's easy! You just..."
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