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  1. #1
    ShawnP's Avatar
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    Default Flex Plate Supporting Sed Dormer????

    Hello,
    Looking for some insight into this little dilema.
    Home inspector called this flex plate a temporary support installed when the shed dormer was installed on the 2nd floor. It appears that this 2nd floor was designed to be finished when the house was built (walk up finished steps etc).

    Question: Can this flex plate be removed with no ill results?
    What additional collar ties are needed?
    (see pics)

    Specs:
    Roof Rafters 2x6 16" on center
    Floor Joists 2x8 16" on center
    Ridge Board is 1x6

    Gable rafters 2x8 16" on center
    Gable ties 2x6 16"
    Gable ridge board 2x8

    thanks in advance.
    Any suggestions appreciated.
    Shawn

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  2. #2
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    Default Re: Flex Plate Supporting Sed Dormer????

    Quote Originally Posted by ShawnP View Post

    Home inspector called this flex plate a temporary support installed when the shed dormer was installed on the 2nd floor.

    Shawn
    .
    Bet that's Not all He said.
    .

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  3. #3
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    Default Re: Flex Plate Supporting Shed Dormer????

    I've never heard of a "flex plate" and have no idea what he is referring to, but that huge-ridge-board-at-that-angle is not doing much at-that-angle.

    Jerry Peck, Construction / Litigation Consultant
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  4. #4
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    Default Re: Flex Plate Supporting Sed Dormer????

    Jerry,

    Thanks..I agree.
    I believe that huge ridge board was put in place during the construction of the shed dormer. I believe it was used to hold the rafters (opposite of the shed dormer) when the ridge board was removed during construction?
    The blocking on the floor makes me believe this arrangement was temporary while the shed dormer was being built as well?

    -Shawn


  5. #5
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    Default Re: Flex Plate Supporting Shed Dormer????

    I think the intent was for that at-an-angle ridge board to support the ridge, however, it should have been installed vertically instead of at an angle and the ends supported with posts sufficient to carry the load of all the rafter bearing on that ridge board, and then the posts would need to bear on sufficient walls/columns below to carry the load.

    To me, it just looks plain screwy (technical term ).

    I'm waiting for one of our experienced framers to post a better description of what it is, is for, and how it should have been done.

    Jerry Peck, Construction / Litigation Consultant
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  6. #6
    Jim Zborowski's Avatar
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    Default Re: Flex Plate Supporting Sed Dormer????

    What the heck is a flex plate? never heard that one used before.Are you sure this is an actual certified, trained home inspector?
    Jerry's right, that boards not doing much at an angle.


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    Default Re: Flex Plate Supporting Sed Dormer????

    If I knew what a flex plate was I might be able to answer the question. Never heard of it. I've built shed dormers and never had a need to install an angled 'ridge board support?' like that. Whether that board is temporary or not, I guess would depend on what/how the rafters are tied together above that board. Is that a vertical ridge board between the rafters; are the rafters sitting against each other or off-set? Essentially, is there anything to hold it all up if that angled board is removed. I can't tell from the pictures and I've built plenty.

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  8. #8
    A.D. Miller's Avatar
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    Default Re: Flex Plate Supporting Sed Dormer????

    Looking for some insight into this little dilema.
    Shawn: OMG, what a disaster area that is! I think I found the carpenters though . . .

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  9. #9
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    Default Re: Flex Plate Supporting Sed Dormer????

    Basically, you are all right, It looks like a temporary support while they cut the rafters transitioned to a final member. I wouldn't remove it as the top of the shed dormer is transferring load to the 1x ridge then to opposing rafters to "that beam" If you want to remove that beam a new beam needs to be placed vertical under the ridge and posted down to transfer the load appropriately. If you just remove it I believe the center top section of the shed dormer will sag in time.


  10. #10
    Phil Brody's Avatar
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    Default Re: Flex Plate Supporting Sed Dormer????

    BTW, a flex plate is a plate that connects an automobile engine to an automatic transmission, vernacular not present in construction to my knowledge.


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    Default Re: Flex Plate Supporting Sed Dormer????

    Where rafters meet the ridge AND are less than 3/12 then a ridge beam must be installed. A ridge beam shall be designed to span the length required to support the rafters.

    Looking at the pictures, it appears the rafters are less than 3/12. The other half is over 3/12 but I think you have to take the area where the dormer is and design it as a beam. The ridge beam would need to be supported according to engineered design. Maybe on each end....maybe every four feet...whatever the design calls for.

    In my opinion the beam is required to stay and is not temporary. It may need further evaluation IF they want to remove the braces. I'm with the others as far as the angle of the beam. If anything it is angled the wrong direction. It it were totally opposite of what it is now, I could see it supporting the 3/12 part...but then again, needs to be perpendicular to the joists.


  12. #12
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    Default Re: Flex Plate Supporting Sed Dormer????

    It may need further evaluation IF they want to remove the braces.
    Excuse me for disagreeing, temporary or not, this does not need evaluation, it needs to be removed and correctly reconstructed. This installation is totally wrong, flying in the face a whole laundry list of code citations. And did I mention that there was not one ounce of common sense being used by the installer? Let's not even broach the subject of best building practices.

    This attic would warrant at least two or three of my report pages. Hall of shame candidate if there ever was one.


  13. #13
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    Default Re: Flex Plate Supporting Sed Dormer????

    If the roof is 3/12 or more it doesn't need reconstructing. It doesn't need anything at that location. You could take everything out (beam/braces to beam) and be within code.


  14. #14
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    Default Re: Flex Plate Supporting Sed Dormer????

    Quote Originally Posted by Wayne Carlisle View Post
    If the roof is 3/12 or more it doesn't need reconstructing. It doesn't need anything at that location. You could take everything out (beam/braces to beam) and be within code.
    Wayne: LOL, LOL, LOL. OK, whatever you say.


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    Default Re: Flex Plate Supporting Shed Dormer????

    Quote Originally Posted by Phil Brody View Post
    BTW, a flex plate is a plate that connects an automobile engine to an automatic transmission, vernacular not present in construction to my knowledge.

    You mean the engine crank shaft to the torque converter, right?

    The engine is rigidly bolted to the transmission.

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    Default Re: Flex Plate Supporting Shed Dormer????

    Wayne,

    I disagree with you on that 3/12 issue. That would definitely not apply in this case as the shed roof for the dormer are not on a wall which is similar to the same wall as the opposing rafters are on, these are bearing on a totally independent wall, one which will not resist the offseting opposing forces.

    Thus, that ridge area for the shed roof rafters at the dormer would need a structural ridge (ridge beam) regardless.

    However, I also disagree with Aaron when he says ...

    Quote Originally Posted by A.D. Miller View Post
    Excuse me for disagreeing, temporary or not, this does not need evaluation, it needs to be removed and correctly reconstructed.
    That area needs to be reconstructed BEFORE that angled ridge beam is removed, otherwise you may well end up with the roof rafters laying on the attic floor.

    I do agree with Aaron on this part:

    This installation is totally wrong, flying in the face a whole laundry list of code citations. And did I mention that there was not one ounce of common sense being used by the installer? Let's not even broach the subject of best building practices.
    Maybe the problem is that the flex plate needs a torque converter bolted to it?

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  17. #17
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    Default Re: Flex Plate Supporting Sed Dormer????

    OK, here is where it says you don't need anything supporting the ridge if it is 3/12 or steeper.


    You cannot require something that is not within the relm of the code. Well I guess you can but it's just that...asking for something that's more than required.



    R802.3 Framing details.
    Rafters shall be framed to ridge
    board or to each other with a gusset plate as a tie. Ridge board
    shall be at least 1-inch (25 mm) nominal thickness and not less
    in depth than the cut end of the rafter. At all valleys and hips
    there shall be a valley or hip rafter not less than 2-inch (51 mm)
    nominal thickness and not less in depth than the cut end of the
    rafter. Hip and valley rafters shall be supported at the ridge by a
    brace to a bearing partition or be designed to carry and distribute
    the specific load at that point. Where the roof pitch is less
    than three units vertical in 12 units horizontal (25-percent
    slope), structural members that support rafters and ceiling
    joists, such as ridge beams, hips and valleys, shall be designed
    as beams.

    The original post states that the ridge meets the requiremnts without the beam. Now you would need to support the walls of the dormer but not the ridge.

    If you disagree, and basically the capitalized lol says you do, would you post the section of the code that requires it? Maybe you could teach me something. I am always willing to learn.



    Last edited by Wayne Carlisle; 01-20-2009 at 12:06 PM. Reason: Goota go...I'll catch up on this discussion tomorrow.

  18. #18
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    Default Re: Flex Plate Supporting Shed Dormer????

    Wayne,

    Before R802.3 is R802.2: (underlining is mine)
    - R802.2 Design and construction. The framing details required in Section R802 apply to roofs having a minimum slope of three units vertical in 12 units horizontal (25-percent slope) or greater. Roof-ceilings shall be designed and constructed in accordance with the provisions of this chapter and Figures R606.11(1), R606.11(2) and R606.11(3) or in accordance with AFPA/NDS. Components of roof-ceilings shall be fastened in accordance with Table R602.3(1).

    The entire section R802 is only for roofs having a slope of 3/12 or greater.

    The first part of that references Figures R606.11(1) and R606.11(2) which are for masonry construction. The latter part, the part after the "or" is for wood framing.

    If you look through there and at those figures, you will see that they are designing with rafters meeting at the ridge with opposing rafters, and with either ceiling joists or rafter ties used to tie the two walls the opposing rafters are bearing on.

    In the photos shown, there is nothing which ties the walls the opposing rafters together regarding the wall for the dormer and its rafters where it meets the other rafters.

    Thus, EVEN IF the shed roof rafters where 3/12 and greater - which is what I was referring to - a structural ridge (ridge beam) would be required as rafter ties would intruded into the space to be finished out.

    Thus, with a ridge beam being necessary - EVEN IF the roof were 5/12 - the ridge beam would need to be installed properly. Which is where Aaron was at.



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  19. #19
    Ron Bibler's Avatar
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    Default Re: Flex Plate Supporting Sed Dormer????

    THEY SHOULD START OVER!!!
    Got a match ?

    Best

    Ron


  20. #20
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    Default Re: Flex Plate Supporting Sed Dormer????

    Quote Originally Posted by Ron Bibler View Post
    THEY SHOULD START OVER!!!

    Got a match ?

    Best

    Ron
    Ron: You bet! But, just not the same "they" that built it.


  21. #21
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    Talking Re: Flex Plate Supporting Sed Dormer????

    Good point, Jerry. The heavy rotating mass bolted to the crankshaft oF an engine to which the clutch engages is called a flywheel on a manual transmission car. On an automatic, it is a lighter weight steel component with the starter ring welded to it to which the torque converter bolts. The reason it is called a flex plate isthat it allows a slight amount of for / aft movement thus preventing damage to the pump on an automatic transmission.
    I don't think the pictures look anything like that.


  22. #22
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    Default Re: Flex Plate Supporting Shed Dormer????

    Quote Originally Posted by Jim Zborowski View Post
    The heavy rotating mass



    I don't think the pictures look anything like that.

    Jim,

    Those photos do have a heavy rotating mass (that angled ridge beam) and is connected by long rods (the diagonal supporting studs) with pivot points at each end (the nail connections) ...

    ... all that is needed is a bump on the starter and that mass will surely rotate.



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  23. #23
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    Default Re: Flex Plate Supporting Sed Dormer????

    When I said they could take the whole mess out I was refering to the ridge beam and the weird braces supporting it. It appears to have the collar ties as required to tie the rafters together. The collar ties would need to stay to meet code. Who knows why they installed the whatever it is on an angle like that!

    I agree if they removed the collar ties then a ridge beam is required.


  24. #24
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    Default Re: Flex Plate Supporting Shed Dormer????

    The collar ties are too high to allow for removable of that ridge beam, rafter ties would be needed, and how would you install rafter ties from the shed roof to the main sloped roof opposing it?

    Jerry Peck, Construction / Litigation Consultant
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    Default Re: Flex Plate Supporting Sed Dormer????

    Jerry, what do you mean "the collar ties are too high to allow for removable of that ridge beam"?


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    Default Re: Flex Plate Supporting Sed Dormer????

    OK, my bad!!! Gotcha! It's not that you can't remove them because of their heigth but because there are no structural connection of the exterior walls (read rafter ties).


  27. #27
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    Default Re: Flex Plate Supporting Sed Dormer????

    Note the difference in COLLAR ties and RAFTER ties. Two different components for two different purposes.

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  28. #28
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    Default Re: Flex Plate Supporting Sed Dormer????

    So If I understand everything:

    The purlin (not flex plate) was installed prior to opening the roof up to install the shed dormer. It is currently only supporting the orginal rafters opposite the shed dormer. The original ridge board 1x6 was removed and replaced with a 2x8 along the ridge for the dormer. The shed dormer was built and the purlin was left in place. No idea why?

    Is their any additional info I can gather that would give those in "know" more insight in to my problem?
    Any good framers in the S.E. PA area?

    Thanks
    Shawn

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  29. #29
    ShawnP's Avatar
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    Default Re: Flex Plate Supporting Sed Dormer????

    So If I understand everything:

    The purlin (not flex plate) was installed prior to opening the roof up to install the shed dormer. It is currently only supporting the orginal rafters opposite the shed dormer. The original ridge board 1x6 was removed and replaced with a 2x8 along the ridge for the dormer. The shed dormer was built and the purlin was left in place. No idea why?

    Is their any additional info I can gather that would give those in "know" more insight in to my problem?
    Any good framers in the S.E. PA area?

    Thanks
    Shawn


  30. #30
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    Default Re: Flex Plate Supporting Sed Dormer????

    There are specifics for this type of installation. What we actually have here is a combination of a rafter/collar tie. On one side the joist are connected to a top plate, then run parallel with the rafters and then become a colar tie, because it (the joist) does not tie to a top plate. Here is a portion of the code that pertains to this situation.

    Where ceiling joists are not connected to the rafters at the
    top wall plate, joists connected higher in the attic shall be
    installed as rafter ties, or rafter ties shall be installed to provide
    a continuous tie. Where ceiling joists are not parallel to
    rafters, rafter ties shall be installed. Rafter ties shall be a
    minimum of 2-inch by 4-inch (51 mm by 102 mm) (nominal),
    installed in accordance with the connection requirements
    in Table R802.5.1(9),

    If you go to the "rafter span table" the following applies;
    a. The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on the bearing walls, such as rafter ties, is provided at that location.

    When ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the factors given below:
    H
    C/HR Rafter Span Adjustment Factor

    1/3 0.67
    1/4 0.76
    1/5 0.83
    1/6 0.90
    1/7.5 or less 1.00
    where:
    H
    C
    = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.

    H
    R
    = Height of roof ridge measured vertically above the top of the rafter support walls.

    So in my opinion the rafters opposite of the dormer would have to be upsized to accomodate the additional pressure according to the above posted code section.

    OR you could build a wall opposite of the dormer where the joists that are sitting on top of the dormer top plate tie into the rafters opposite of the dormer.

    OR you could have someone design a real beam that could be used as a ridge beam.




  31. #31
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    Default Re: Flex Plate Supporting Shed Dormer????

    You don't need a "good framer", you really need a "structural engineer" who can draw up what needs to be done and sign and seal that drawing. Doing it that way will protect not only your family but your butt as well.

    Then, after the work has been completed, have the structural engineer come out and make sure the work was done as they designed it, then issue a letter stating that the work was done in accordance with the engineering.

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  32. #32
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    Default Re: Flex Plate Supporting Sed Dormer????

    Hi Shawn,

    My question to you is what is your involvement? Are you the inspector or are you doing the repair?
    First, I don't believe this was meant to be a perminent fix as it shouldn't be. Second,why was it installed to begin with and a perminent fix not done?
    Speaking as a inspector only, you should not be offering solutions to this sort of problem.
    Save your self from potential litigation and refer this to a general contractor or structural engineer.
    Have you checked for shifting and other stress indicators related to the roof?
    Hopefully you are acting as an inspector only,
    Good Luck,

    Gary


  33. #33
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    Default Re: Flex Plate Supporting Sed Dormer????

    Gary,

    I am the lucky homeowner.
    Not going to be doing any of this myself.
    I am only going on what the Home Insp. told me.
    Not sure why it was done this way ...etc?
    I believe it was put in place to hold the opposing rafters while the shed dormer rafters were tied in to the new ridge board.
    The house needs a new roof down to the rafters....so I did not bother looking in to this little mess after the inspection....guess I should have!
    -Shawn


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