New s.s. metal chimney and cutting roof rafter?

Discussion in 'Building Construction' started by Bill, Sep 7, 2005.

  1. Bill

    Bill Guest

    I am installing a new wood stove (EPA Cert.), have mechanical permit, etc.

    And I have built my hearth pad (proper R-Value to code, etc.) and have
    located my wood stove on the hearth pad to manufacturer's specs. (Proper
    distance from walls, etc.) This is the *only* place the wood stove can go.
    The chimney is stainless steel 6" inside diameter and 8" outside diameter.
    I'm Using Selkirk - Metalbestos chimney parts.

    So guess what? The metal chimney going straight up will go right smack dab
    through a rafter (45 deg. roof slope - one of many 2 x 4's at 45 deg. angle
    supporting roof.)

    So I will need to cut the rafter....

    Questions....

    Can I cut the rafter, then add 2x 4's which transfer the support for that
    rafter to neighboring rafters?

    I read that there needs to be a 2 inch separation between wood and the
    metal chimney. If I do this where the chimney pops up through the roof,
    there will be a 2" air gap going from the attic to the vented roof jack
    (flashing). I am concerned about insects getting into the vent, then making
    a home in the attic. Can I place screen or something somewhere in this area
    (to keep insects out)?
    Bill, Sep 7, 2005
    #1
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  2. Bill

    RicodJour Guest

    Bill wrote:
    > I am installing a new wood stove (EPA Cert.), have mechanical permit, etc.
    >
    > And I have built my hearth pad (proper R-Value to code, etc.) and have
    > located my wood stove on the hearth pad to manufacturer's specs. (Proper
    > distance from walls, etc.) This is the *only* place the wood stove can go.
    > The chimney is stainless steel 6" inside diameter and 8" outside diameter.
    > I'm Using Selkirk - Metalbestos chimney parts.
    >
    > So guess what? The metal chimney going straight up will go right smack dab
    > through a rafter (45 deg. roof slope - one of many 2 x 4's at 45 deg. angle
    > supporting roof.)
    >
    > So I will need to cut the rafter....
    >
    > Questions....
    >
    > Can I cut the rafter, then add 2x 4's which transfer the support for that
    > rafter to neighboring rafters?
    >
    > I read that there needs to be a 2 inch separation between wood and the
    > metal chimney. If I do this where the chimney pops up through the roof,
    > there will be a 2" air gap going from the attic to the vented roof jack
    > (flashing). I am concerned about insects getting into the vent, then making
    > a home in the attic. Can I place screen or something somewhere in this area
    > (to keep insects out)?



    There's not a lot of extra strength in a 2x4, I would not want to add
    additional loads to the flanking rafters without reinforcing them.

    Buy an adjustable elbow or two, and run the chimney so it avoids the
    rafters altogether. It's a much easier and better way to do it.

    R
    RicodJour, Sep 7, 2005
    #2
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  3. Bill

    kevin Guest

    Get some more opinions, but I would think transfering the load
    shouldn't be a big deal as long as the spacing on your rafters is small
    enough. If so, I'd probably think about reinforcing the neighboring
    rafters with, say, a 6' length of 2x4, then making the chimney box
    right in the middle of the reinforced area using 2x4s to connect the
    three rafters together.
    kevin, Sep 7, 2005
    #3
  4. "Bill" <> wrote in message
    >
    > So guess what? The metal chimney going straight up will go right smack dab
    > through a rafter (45 deg. roof slope - one of many 2 x 4's at 45 deg.
    > angle
    > supporting roof.)
    >
    > So I will need to cut the rafter....


    There are ways of boxing around the stack, but it may be easier and cheaper
    to buy a couple of 45 degree elbows and zig around hte 2 x 4.
    Edwin Pawlowski, Sep 7, 2005
    #4
  5. Bill

    DanG Guest

    The traditional way to do this would be to double the rafter on
    each side of the one to be cut, install a header between these
    rafters to carry the cut rafter. You should support the load
    until all the connections are made, though the roof will probably
    carry it long enough to accomplish.

    If the rafters are 2x4, it must be a fairly old structure. What
    worries me is that they may be trusses. DO NOT CUT A TRUSS. Get
    further input and advice.

    (top posted for your convenience)
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    Keep the whole world singing . . . .
    DanG (remove the sevens)




    "Bill" <> wrote in message
    news:...
    >I am installing a new wood stove (EPA Cert.), have mechanical
    >permit, etc.
    >
    > And I have built my hearth pad (proper R-Value to code, etc.)
    > and have
    > located my wood stove on the hearth pad to manufacturer's specs.
    > (Proper
    > distance from walls, etc.) This is the *only* place the wood
    > stove can go.
    > The chimney is stainless steel 6" inside diameter and 8" outside
    > diameter.
    > I'm Using Selkirk - Metalbestos chimney parts.
    >
    > So guess what? The metal chimney going straight up will go right
    > smack dab
    > through a rafter (45 deg. roof slope - one of many 2 x 4's at 45
    > deg. angle
    > supporting roof.)
    >
    > So I will need to cut the rafter....
    >
    > Questions....
    >
    > Can I cut the rafter, then add 2x 4's which transfer the support
    > for that
    > rafter to neighboring rafters?
    >
    > I read that there needs to be a 2 inch separation between wood
    > and the
    > metal chimney. If I do this where the chimney pops up through
    > the roof,
    > there will be a 2" air gap going from the attic to the vented
    > roof jack
    > (flashing). I am concerned about insects getting into the vent,
    > then making
    > a home in the attic. Can I place screen or something somewhere
    > in this area
    > (to keep insects out)?
    >
    >
    DanG, Sep 7, 2005
    #5
  6. Bill

    Bill Guest

    "DanG" wrote in message
    >
    > ...If the rafters are 2x4, it must be a fairly old structure. What
    > worries me is that they may be trusses. DO NOT CUT A TRUSS.
    > Get further input and advice.
    >


    I did just that, got further advice. I took pictures of everything and took
    them to my building inspector...

    I told him I had the option of cutting the rafter if I wanted my chimney to
    go straight up from the wood stove, or using a 15 deg. or 30 deg. pair of
    elbows up in the attic (max bend recommended by the chimney manufacturer)
    to re-direct the chimney to come out between the rafters. I asked what to
    do?

    He said *DO NOT* cut the rafter!

    Then he came up with a third idea. He said he preferred a pair of 15 deg.
    elbows (not 30 deg.) and to place these elbows at the wood stove, not
    higher up, or in the attic. He said it was better to place elbows lower
    down rather than higher up.

    This will save me money as the pipe coming out of the stove is single wall
    and elbows at this location will be much less expensive than using Selkirk
    s.s. insulated chimney elbows in the attic.

    He also looked pleased that I was asking for advice in *advance* rather
    than going ahead and doing the wrong thing, then having to fix my mistakes
    after inspection.

    So thanks for the advice to "get more advice"! This will be a lot less
    work, less worry, and less cost. Can't beat that!
    Bill, Sep 10, 2005
    #6
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