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  1. #1
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    Default What can happen with roof over.

    People ask about roofing over an existing board deck where the truss are not evenly spaced.
    Roof had plywood installed over old boards. Rather than tear down to truss they attached to the deck boards. As a result the nailing has pulled up and the plywood ends have curled up. Not to mention that the roof shingles are puckered up. This was a case of hit and run roofing.

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  2. #2
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    Default Re: What can happen with roof over.

    No offense, but how can you be sure it wasn't unavoidable wind damage?

    I see plywood or OSB over shiplap quite often, but it doesn't automatically cause failure like that.

    John Kogel, RHI, BC HI Lic #47455
    www.allsafehome.ca

  3. #3
    MARVIN TOWNSEN's Avatar
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    Default Re: What can happen with roof over.

    I dont see any attic vents, if there are not any that could cause it


  4. #4
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    Default Re: What can happen with roof over.

    Quote Originally Posted by MARVIN TOWNSEN View Post
    I dont see any attic vents, if there are not any that could cause it
    There could be soffit and gable vents ...

    Jerry Peck
    Construction/Litigation/Code Consultant - Retired
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  5. #5
    Ted Menelly's Avatar
    Ted Menelly Guest

    Default Re: What can happen with roof over.

    wood shingles are torn off everyday and plywood put over the skip sheathing the wood shingles used to be nailed to. Now, if they did not break the plywood on the skip sheathing or poorly nailed it to the sheathing or loosened many a 1x ripping the shingles off and did not secure it nailed/screwed properly before putting the plywood on .... in other words just did a screwed up job then it will look like your roof in the end.

    Done right there are never problems.


  6. #6
    James Duffin's Avatar
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    Default Re: What can happen with roof over.

    Never really thought about it but it seems like you would run the new plywood parallel to the original rafters in this application with the ends of the plywood breaking on the strips run perpendicular to the rafters.


  7. #7
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    Default Re: What can happen with roof over.

    Looks like that failing chimney chase will shortly take care of the rest of the undamaged roof covering.


  8. #8
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    Default Re: What can happen with roof over.

    Quote Originally Posted by Bob Wisnewski View Post
    Looks like that failing chimney chase will shortly take care of the rest of the undamaged roof covering.
    ??? I must be missing something. What is it you see with the chimney Bob?

    "It takes a big man to cry. It takes an even bigger man to laugh at that man". - Jack Handey

  9. #9
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    Default Re: What can happen with roof over.

    Nick,

    From what I can make out from the photo, looks likes there are some missing bricks???


  10. #10
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    Default Re: What can happen with roof over.

    On the right-hand side? If that's the area, it looks like the straps that are securing the antannae to the chimney. Kind of hard to tell with the size of the pic but you might be right with some being a bit deteriorated behind the straps. The top one looks to be the most suspect.

    "It takes a big man to cry. It takes an even bigger man to laugh at that man". - Jack Handey

  11. #11
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    Default Re: What can happen with roof over.

    Yes Nick, that is the area I was looking at. Sorry Garry, I know this was not the subject of your post.
    Bob


  12. #12
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    Default Re: What can happen with roof over.

    There was a lot of things wrong with the roof.
    Purpose of post is to just show a plywood roof over and why not to do it.
    There are times that you may get away with it but still is a bad idea/practice.
    General info, house 100 + yrs, no ventilation except for two windows, attic had finished ceiling.


  13. #13
    MARVIN TOWNSEN's Avatar
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    Default Re: What can happen with roof over.

    Quote Originally Posted by Garry Sorrells View Post
    There was a lot of things wrong with the roof.
    Purpose of post is to just show a plywood roof over and why not to do it.
    There are times that you may get away with it but still is a bad idea/practice.
    General info, house 100 + yrs, no ventilation except for two windows, attic had finished ceiling.
    I would argue that is the reason why you should do it properly


  14. #14
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    Default Re: What can happen with roof over.

    i see stains coming from chimney chase and somethnig strapped to chimney--not suppose to be.

    chas

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  15. #15
    Ted Menelly's Avatar
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    Default Re: What can happen with roof over.

    Quote Originally Posted by Garry Sorrells View Post
    There was a lot of things wrong with the roof.
    Purpose of post is to just show a plywood roof over and why not to do it.
    There are times that you may get away with it but still is a bad idea/practice.
    General info, house 100 + yrs, no ventilation except for two windows, attic had finished ceiling.
    Instead of the rafters being X apart from one another you has the 1x closely spaced. If the 1Xs are nailed down well the plywood will be secured far greater than the entire 8 foot length of the sides touching only several 2x. As far as the ends the are very secure as well due to the close spacing of the 1X

    Don't see how you can go wrong if all is secured properly. I think it actually tightens that roof up a whole lot more. It is similar to 1x3 strapping nailed to ceiling joists and then the drywall nailed to it. I believe the entire home tightens up more when done so.

    Not a bad practice at all

    Other than doing something wrong as in any installation of anything, If done right I just do not see why there would be any concern. Yours was simply done wrong or other problems arrose aftert the installation as is possible with any installation of anything.


  16. #16
    MARVIN TOWNSEN's Avatar
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    Default Re: What can happen with roof over.

    Quote Originally Posted by Ted Menelly View Post
    Instead of the rafters being X apart from one another you has the 1x closely spaced. If the 1Xs are nailed down well the plywood will be secured far greater than the entire 8 foot length of the sides touching only several 2x. As far as the ends the are very secure as well due to the close spacing of the 1X

    Don't see how you can go wrong if all is secured properly. I think it actually tightens that roof up a whole lot more. It is similar to 1x3 strapping nailed to ceiling joists and then the drywall nailed to it. I believe the entire home tightens up more when done so.

    Not a bad practice at all

    Other than doing something wrong as in any installation of anything, If done right I just do not see why there would be any concern. Yours was simply done wrong or other problems arrose aftert the installation as is possible with any installation of anything.
    I agree whole heartedly. I have a feeling improper venting played pretty big role also


  17. #17
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    Default Re: What can happen with roof over.

    It's my understanding that inadequate spacing between sheets of plywood can cause the plywood to buckle and that inadequate roof deck ventilation aggravates the condition.

    "the relentless pursuit of perfection"

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